comparative morphological implications. Anat Sci Int 86:30–49. evaluate with selective intercostal or lumbar angiography. MR and CT
An exploration of the future implications of autonomic cardiac nervous angiography allowed its clear visualization by providing detailed depiction of
system (ACNS) preservation in cardiovascular surgery. Morphological the vascular anatomy from the aorta to the anterior spinal artery.


Mediastinum
993.e1
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RETPAHC
REFERENCES
Asghar A, Syed YM, Nafis FA 2012 Polymorphism of Hassall’s corpuscles the first thoracic spinal nerve. These ‘Kuntz’s nerves’ join the lower part of
in thymus of human fetuses. Int J Appl Basic Med Res 2:7–10. the brachial plexus without passing through the stellate ganglion, explaining
Cho HM, Lee DY, Sung SW 2005 Anatomical variations of rami communi- the incomplete sympathetic blockade of the upper extremities in stellate
cantes in the upper thoracic sympathetic trunk. Eur J Cardiothorac Surg ganglion blockade.
27:320–4. Miller FH, Fitzgerald SW, Donaldson JS 1993 CT of the azygoesophageal
Deso S, Ludwig B, Kabutey NK et al 2012 Lymphangiography in the diag- recess in infants and children. Radiographics 13:623–34.
nosis and localization of various chyle leaks. Cardiovasc Intervent Mountain CF, Dresler CM 1997 Regional lymph node classification for lung
Radiol 35:117. cancer staging. Chest 111:1718–23.
A description of the unparalleled abilities of lymphangiography (LAG)
Raica M, Encică S, Motoc A et al 2006 Structural heterogeneity and immuno-
highlighting the added benefit of post-LAG CT imaging in the diagnosis and
histochemical profile of Hassall corpuscles in normal human thymus.
localization of chyle leaks. The retained utility of LAG is demonstrated
Ann Anat 188:345–52.
despite the development of conventional CT, MRI and nuclear medicine
imaging. Segni M, di Nardo R, Pucarelli I et al 2011 Ectopic intrathyroidal thymus in
children: a long-term follow-up study. Horm Res Paediatr 75:258–63.
Doerr CH, Miller DL, Ryu JH 2001 Chylothorax. Semin Respir Crit Care Med
Sklair-Levy M, Agid R, Sella T et al 2000 Age-related changes in CT attenu-
22:617.
ation of the thymus in children. Pediatr Radiol 30:566–9.


An explanation of how injury or disease of the thoracic duct or its major
tributaries can lead to a chylous effusion, diagnosed by fluid assaying for van de Wal-Visscher E, Nieuwenhuijzen GA, van Sambeek MR et al 2011
triglyceride content and lipid electrophoreses for chylomicrons. Conservative Type B aortic dissection resulting in acute oesophageal necrosis. Ann
management options include observation, treatment of the underlying Vasc Surg 25:837.
disease, strict medium-chain triglyceride diet or total parenteral nutrition, Varga I, Uhrinova A, Toth F et al 2011 Assessment of the thymic morpho-
thoracocentesis, tube thoracostomy with chemical pleurodesis or thoracic duct metry using ultrasound in full-term newborns. Surg Radiol Anat 33:
embolization. Surgical management includes pleurectomy, talc poudrage, 689–95.
pleuroperitoneal shunting or repair/ligation of the thoracic duct.
Weerkamp F, de Haas EF, Naber BA et al 2005 Age-related changes in the
Garly ML, Trautner SL, Marx C et al 2008 Thymus size at 6 months of age cellular composition of the thymus in children. J Allergy Clin Immunol
and subsequent child mortality. J Pediatr 153:683–8, 688.e1–3. 115:834–40.
Gofeld M, Faclier G 2006 Bilateral pain relief after unilateral thoracic per- Wemyss-Holden SA, Launois B, Maddern GJ 2001 Management of thoracic
cutaneous sympathectomy. Can J Anaesth 53:258–62. duct injuries after oesophagectomy. Br J Surg 88:1442–8.
Han BK, Babcock DS, Oestreich AE 1989 Normal thymus in infancy: sono- Wind GG, Valentine RJ 2013 Carotid arteries. In: Anatomic Exposures in
graphic characteristics. Radiology 170:471–4. Vascular Surgery. Philadelphia: Wolters Kluwer, Lippincott Williams &
Wilkins; Ch. 1, pp 23–50.
Henry L, Durrant TE, Anderson GJ 1992 Pericapillary collagen in the human


thymus: implications for the concept of the ‘blood-thymus’ barrier. Anat Yang GS, Bishop WP, Smith BJ et al 2005 Radiographic and endoscopic
181(Pt 1):39–46. measurements of esophageal length in pediatric patients. Ann Otol,
Rhinol Laryngol 114:587–92.
Kawashima T 2011 Anatomy of the cardiac nervous system with clinical and
comparative morphological implications. Anat Sci Int 86:30–49. Yoshioka K, Niinuma H, Ohira A et al 2003 MR angiography and CT
An exploration of the future implications of autonomic cardiac nervous angiography of the artery of Adamkiewicz: noninvasive preoperative
system (ACNS) preservation in cardiovascular surgery. Morphological assessment of thoracoabdominal aortic aneurysm. RadioGraphics 23:
studies are described from macroscopic, clinical and evolutionary anatomical 1215–25.
viewpoints, together with their applications in improving surgical technique An exploration of how the artery of Adamkiewicz must be identified in
and for future evaluation in regenerative medicine. patients with thoracoabdominal aortic aneurysm to aid surgical planning
and to avoid postoperative paraplegia. It is difficult and very dangerous to
Kuntz A 1927 Distribution of the sympathetic rami to the brachial plexus: evaluate with selective intercostal or lumbar angiography. MR and CT
its relation to sympathectomy affecting the upper extremity. Arch Surg angiography allowed its clear visualization by providing detailed depiction of
15:871–7. the vascular anatomy from the aorta to the anterior spinal artery.
A description of the significant number of individuals in whom the
intrathoracic somatic branches from the second thoracic spinal nerve join


CHAPTER
57
Heart
under increased ventricular end-diastolic pressure; formation of a
PERICARDIUM
barrier to spread of infection; facilitation of atrial filling by promoting
negative pericardial pressure during ventricular systole; and, in associa-
The pericardium contains the heart and the juxtacardiac parts of its great tion with the pleural fluid, the formation of a system that automatically
vessels. It consists of two components – the fibrous and the serous applies compensating hydrostatic pressures to the cardiac periphery
pericardia – with a normal combined thickness of 1–2 mm, as fre- when accelerating forces act.
quently seen on cross-sectional imaging (Figs 57.1–57.2). The fibrous
pericardium is a sac made of tough connective tissue, completely sur-
rounding and unattached to the heart. It develops through a sequential FIBROUS AND SEROUS PERICARDIUM
process of cavitation of the embryonic body wall by expansion of the
secondary pleural cavity; its lateral walls are thus clothed by parietal Fibrous pericardium
mediastinal pleura. The serous pericardium consists of two layers, one
inside the other; the inner (visceral) serosal layer adheres to the heart The fibrous pericardium is a roughly conical, compact, collagenous
and forms its outer covering, known as the epicardium, whereas the cardiac cloak composed mainly of three collagen layers, cross-woven at
outer (parietal) serosal layer adheres to the internal surface of the 120° to each other, which limits stretch and ensures a physical barrier
fibrous pericardium. These two serosal surfaces are apposed and sepa- to disease.
rated by a film of fluid, which allows independent movement of the A three-point ‘cardiac seat belt’ anchors the pericardium securely,
inner membrane and its adherent heart, constituting two parietovisceral maintaining the intrathoracic cardiac disposition. Pericardial anchoring
lines of serosal reflection. The separation of the two membranes of the is obtained by superior continuity with the great vessel adventitia and
serous pericardium creates a narrow pericardial cavity that provides pretracheal fascia, inferior attachment to the central diaphragmatic


complete cleavage between the heart and its surroundings, allowing tendon and a small adjacent muscular area to its left, together with
freedom of cardiac motion and shape change. anterior attachment to the posterior sternal surface via the superior and
The multifunctionality of the pericardium has been suggested to inferior sternopericardial ligaments (the extent of these ‘ligaments’ is
include facilitation of secure intrathoracic cardiac stability (via the ster- very variable; the superior is often undetectable).
nopericardial ligaments and from the fusion of fibrous pericardium Anteriorly, the fibrous pericardium is separated from the thoracic
with the central diaphragmatic tendon and great vessel adventitia; see wall by the lungs and pleural coverings. However, in a small area behind
below); friction reduction between the heart and the mediastinal struc- the lower left half of the body of the sternum and the sternal ends of
tures; limitation of cardiac distension and chamber dilation with pre- left fourth and fifth costal cartilages, the pericardium is in direct contact
vention of hypertrophy; uniform cardiac distribution of pericardial with the thoracic wall. Until it regresses, the lower end of the thymus
cavity hydrostatic pressure, preventing ventriculoatrial regurgitations is also anterior to the upper pericardium. The principal bronchi,
oesophagus, descending thoracic aorta and posterior parts of the media-
stinal surface of both lungs are all posterior relations. Laterally are the
pleural coverings of the mediastinal surface of the lungs. The phrenic
neurovascular bundle descends bilaterally between the fibrous pericar-
dium and mediastinal pleura. Inferiorly, the pericardium is separated
Fig. 57.1 The effect of section thickness on visualization of normal
pericardium. Multidetector CT image of the chest obtained from a
dual-source scanner (Somatom Definition Flash; Siemens, Erlangen,
Germany) with 1.0 mm collimation. Non-ionic contrast material (120 ml)
was injected at a rate of 5 ml/sec. In this image with a section thickness
of 10 mm, the pericardium appears as a thin, curvilinear structure
(arrows). The pericardium is typically best visualized along the right side


of the heart because of surrounding fat. With increasing section thickness, Fig. 57.2 Normal pericardium. T1-weighted fast spin-echo magnetic
maximal pericardial thickness (measured along the right ventricle) resonance image (MRI) (1.4 × 2.0 mm resolution) in horizontal long-axis
increases from 0.9 mm to 1.0 and 1.6 mm by using section thicknesses plane, in which the pericardium appears as a thin, curvilinear hypointense
of 3 mm and 10 mm, respectively. (With permission from Bogaert J, structure (arrows), best visible when surrounded by fatty tissue. (With
Francone M. 2013. Pericardial disease: value of CT and MR imaging. permission from: Bogaert J, Francone M. 2013. Pericardial disease: value
994 Radiology 267:340–356.) of CT and MR imaging. Radiology 267:340–356.)


Pericardium
995
75
RETPAHC
from the liver and gastric fundus by the diaphragm. The aorta, superior between the thickness of this fat layer and obesity in children (Ozdemir
vena cava and the pulmonary arteries and veins all receive extensions et al 2010).
of the fibrous pericardium but the inferior vena cava traversing the
central tendon has no such covering. Pericardial reflections The reflections of the serosal layer are
arranged as two complex ‘tubes’; the aorta and pulmonary trunk are
Serous pericardium enclosed in one, and the venae cavae and four pulmonary veins lie in
the other. The perivenous tube is an inverted J; the cul-de-sac within its
The serous pericardium is a closed sac within the fibrous pericardium curve posterior to the left atrium is termed the oblique sinus. The trans-
and has visceral and parietal layers. The parietal layer forms the internal verse sinus is a passage between the two pericardial ‘tubes’ (Fig. 57.3);
surface of the fibrous pericardium. The visceral layer, or epicardium, the aorta and pulmonary trunk are anterior (Fig. 57.4A,C), and the atria
covers the heart and great vessels, and is reflected into the parietal layer, and their great veins are posterior (Fig. 57.4B,D).
which lines the internal surface of the fibrous pericardium. The visceral
layer of the serous pericardium is a single layer composed of ciliated Pericardial space and fluid The pericardial cavity is the space
mesothelial cells on a thin subserosal layer of connective tissue abun- formed between the parietal and visceral layers of the serous pericar-
dant in elastic fibres, blending with the fibrous pericardium at the dium. The pericardial cavity covers the proximal part of the great vessels
parietal membrane and with the interstitial myocardial tissue at the and the vast majority of the heart, extending between the left atrium
visceral membrane. The serosal cilia increase the surface area for fluid and the descending thoracic aorta; the left pleural space extends poste-


production and resorption, in addition to reducing friction between the rior to the descending aorta. The pericardial cavity normally contains
opposing pericardial layers. The cardiac subserosal layer contains fat, approximately 15–20 ml of serous plasma ultrafiltrate.
especially along the ventricular side of the atrioventricular and inter-
ventricular grooves and the inferior cardiac border. The main coronary
vessels and their larger branches are embedded in this fat; the amount VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
is related to the general extent of body fat and gradually increases with
age. The amount of epicardial adipose tissue may be a cardiometabolic Approximately 80% of the pericardial blood supply is derived from the
risk factor, with increasing thickness linked to metabolic syndrome and right and left internal thoracic arteries by way of their pericardiaco-
diabetes mellitus. A significant correlation has been demonstrated phrenic branches. Inferiorly, the pericardium is supplied by small
Thymic vein
Trachea
Left recurrent laryngeal nerve
Inferior thyroid vein Left brachiocephalic vein
Vagus nerve Left common carotid artery
Left subclavian artery
Right brachiocephalic
vein Aortic arch
Phrenic nerve
Internal thoracic vein
Pericardiacophrenic
artery and vein
Brachiocephalic trunk Left lung
Superficial cardiac plexus
Superior vena cava
Vagus nerve
Parietal pleura,
Ligamentum arteriosum
mediastinal part
Left recurrent laryngeal nerve
Right lung
Left pulmonary
artery
Bifurcation
Transverse
of pulmonary
pericardial sinus Right pulmonary trunk
artery
Postcaval recess
Right superior
pulmonary vein
Right inferior
pulmonary vein Left superior
pulmonary vein
Left inferior
pulmonary vein
Fatty folds
Parietal pleura, Oblique pericardial
diaphragmatic part sinus
Inferior vena cava
Fibrous pericardium
Serous pericardium,
parietal layer
Fig. 57.3 Interior of the serosal pericardial sac after section of the large vessels at their cardiac origin and removal of the heart, anterior view. Refer to


the text for additional named recesses of the general serous pericardial cavity and its transverse sinus. (With permission from Waschke J, Paulsen F
(eds), Sobotta Atlas of Human Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright 2013.)


Heart
995.e1
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RETPAHC
The arrangement of the oblique and transverse sinuses, along with
that of the main ‘principal’ cavity, is further affected by the development
of complex three-dimensional pericardial recesses between adjacent
structures, grouped according to the siting of their orifices or ‘mouths’.
From the principal pericardial cavity, the postcaval recess projects
towards the left, behind the atrial termination of the superior vena cava,
limited superiorly by the right pulmonary artery and inferiorly by the
superior right pulmonary vein, with its mouth opening superolaterally
to the right. The right and left pulmonary venous recesses each project
superomedially on the posterior surface of the left atrium between the
superior and inferior pulmonary veins on each side, indenting the side
walls of the oblique sinus. The superior aortic recess extends from the
transverse sinus; via its inferior mouth, it ascends posterior to, then to
the right of, the ascending aorta and ends at the level of the sternal
angle. The inferior aortic recess, also extending from the transverse
sinus, is a diverticulum that descends from a superiorly located mouth
to run between the inferior ascending part of the aorta and the right
atrium. The left pulmonary recess, with its mouth under the vena caval
fold, passes to the left between the inferior aspect of the left pulmonary
artery and the superior border of the superior left pulmonary vein. The
right pulmonary recess lies between the inferior surface of the proximal
part of the right pulmonary artery and the superior border of the left
atrium.
A triangular fold of serous pericardium is reflected from the left
pulmonary artery to the subjacent superior left pulmonary vein as the
fold of the left superior vena cava. It contains a fibrous ligament, a
remnant of the obliterated left common cardinal vein (left duct of
Cuvier), which descends anterior to the left pulmonary hilum from the
superior part of the left superior intercostal vein to the posterior surface
of the left atrium, where it is continuous with the oblique vein of the
left atrium. The left common cardinal vein may persist as a left superior
vena cava, which then replaces the oblique vein of the left atrium and


empties into the coronary sinus. When both common cardinal veins
persist as a double superior vena cava, the transverse anastomosis
between them, which normally forms the left brachiocephalic vein, may
be small or absent. When there is a left superior vena cava, it is joined
by the left superior intercostal vein. Knowledge of these recesses and
sinuses is important in the avoidance of misdiagnosis as lymphaden-
opathy or aortic dissection and in surgical control of the great vessels.


HEART
996
7
NOITCES
A Left common carotid artery
Brachiocephalic trunk
Left subclavian artery
Aortic arch
Superior vena cava Ligamentum arteriosum
Pulmonary trunk
Right pulmonary artery
Serous pericardium, Serous pericardium,
parietal layer parietal layer
Left appendage (auricle) C
Right appendage
Great cardiac vein
(auricle)
Infundibulum
Left coronary artery,
(conus arteriosus)
circumflex branch
Left coronary
Right atrium artery, anterior
interventricular branch
Anterior
Small cardiac vein interventricular vein
Left ventricle
Right coronary artery
Right ventricle
Serous pericardium,
visceral layer (epicardium)
Serous pericardium, parietal layer
B
Vertebral vein
Left subclavian artery
Right brachiocephalic vein
Left common carotid artery
Left brachiocephalic vein
Aortic arch
Brachiocephalic trunk
Posterior intercostal arteries
Azygos vein
Descending aorta
Ascending aorta
Ligamentum arteriosum
Superior vena cava
Left pulmonary artery
Bifurcation of D
Pericardium pulmonary trunk
Right pulmonary artery
Pulmonary trunk
Left pulmonary veins Right pulmonary veins
Left appendage (auricle)
Great cardiac vein
Left atrium
Left coronary artery,
circumflex branch
Sinus of venae cavae
Inferior veins Serous pericardium,
of left ventricle parietal layer
Serous pericardium,
visceral layer Left atrial veins
(epicardium)
Right atrium
Sulcus terminalis cordis
Left ventricle
Inferior vena cava
Coronary sinus
Coronary sulcus
Right coronary artery, inferior
interventricular branch
Middle cardiac vein Right ventricle
Fig. 57.4 The heart and great vessels. A, Anterior view. B, Posteroinferior view. C,D, Corresponding three-dimensional reconstructions from multislice
computed tomography (CT) scanning. (A,B, With permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th ed, Elsevier,
Urban & Fischer. Copyright 2013.)


Heart
997
75
RETPAHC
branches from the intercostal and superior phrenic arteries. The poste-
rior portion of the pericardium is supplied from small mediastinal Obtuse margin
branches that are derived either directly from the descending aorta or
from its oesophageal or bronchial branches. The veins are tributaries of
the azygos system, internal thoracic and superior phrenic veins.
Most lymph drainage of the pericardium is to the thoracic and the
right lymphatic ducts; bilateral upper mediastinal and parasternal
internal thoracic lymph nodal groups also receive efferents. Overall, a
double layer of pericardial lymphatic vasculature exists: one contacting
and surrounding the parietal pericardium, the other present in the fat
a
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n
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e
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a
po
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e
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e
a
y
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e
e
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r
r
t
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r
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-
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cardial nodes located at the pericardio-diaphragmatic junction. Drain-
age from the lateral pericardium is more variable. Inferiorly, it drains
towards the phrenic nerves and the pericardiacophrenic vessels as they
reach the diaphragm; superiorly, it drains into the tracheobronchial
and paratracheal lymph nodes. The posterior pericardium, including Diaphragmatic
the posterior aspect of the cupula and extending as far as the pulmo-


nary veins, drains superiorly to the superior and inferior tracheobron-
chial lymph nodes. The portion of the pericardium that adheres to the
diaphragm drains via short channels to the lymph nodes at the right
border of the inferior vena caval opening in the central diaphragmatic
Acute margin
tendon.
Fig. 57.9 A cadaveric heart, removed from the body and placed in an
attitudinally appropriate position, then viewed from the apex of the left
INNERVATION
ventricle. The ventricular mass takes the form of a squashed cone with
anterior, inferior and posterior borders. The labels show the location of
Pain from parietal pericardium is mainly transmitted by the phrenic these borders relative to the thoracic structures, and illustrate the acute
nerves, while pain from serous pericardium is mediated via sympathetic and obtuse angles between the borders. (With permission from Anderson
fibres that arise from the cervical, upper thoracic and stellate ganglia R, Loukas M. 2009. The importance of attitudinally appropriate
and travel to the aortic and cardiac plexuses. The pericardium also description of cardiac anatomy. Clin Anat 22:47–51.)
receives vagal fibres via the oesophageal plexus and left recurrent laryn-
geal nerve (see Fig. 57.61). Pericardial pain is typically sharp, severe and
substernal, typically exacerbated by lying back or on the left side and
relieved by leaning forwards, occasionally radiating to the superior structures are virtually in line, but inclined forwards and to the left at
border of trapezius. 45° to the sagittal plane. The planes of the mitral and tricuspid valves
are vertical and not precisely co-planar; they are broadly at right angles
to the septal plane. The right atrium, therefore, is not only to the right,
CARDIAC TAMPONADE but also anterior and inferior to the left atrium, and it is partly anterior
to the left ventricle. The right ventricle forms most of the anterior aspect
of the ventricular mass (see Fig. 57.12); only its inferior end is to the
Available with the Gray’s Anatomy e-book
right of the left ventricle, while its upper left extremity (pulmonary


orifice) is to the left and superior relative to the aortic valve. The left
atrium forms most of the posterior aspect of the heart, whereas the left
CONGENITAL ANOMALIES OF THE PERICARDIUM ventricle is only prominent inferiorly, running along the left margin to
reach the apex. The atria are essentially right of and posterior to their
respective ventricles. These general dispositions are of the greatest
Available with the Gray’s Anatomy e-book
importance in planning or interpreting radiographs, CT and MRI studies,
cardiac angiograms and echocardiograms (Fig. 57.10).
The right heart, while forming the right aspect or ‘border’, follows a
HEART
gentle curve and covers most of the anterior aspect of the left heart
(except for a left-sided strip including the apex). Thus the right heart
The heart has a complicated, spiral, three-dimensional organization forms the largest part of the anterior surface, its outflow tract ascending
that is markedly skewed when compared with the planes of the body. until it terminates on the left side of the outflow tract from the left
Established anatomical orientation terms have been historically applied ventricle. The sites of the tricuspid and pulmonary valves are widely
to the heart based on early embryological development before axial separated and on different planes, and the sectionally crescentic flat
rotation of the cardiovascular tube. This, together with the traditional cavity of the right ventricle splays out between them. Conversely, the
study of isolated whole or dissected hearts outside the body, hinders left heart (except the left-sided strip mentioned above) is largely poste-
intuitive understanding of the descriptive relations of in vivo and surface rior in position and, when viewed from the front, is obscured by the
cardiac anatomy. The following description emphasizes such difficulties chambers of the right heart. The inlet to the left ventricle, which con-
in order to circumvent certain misconceptions, before proceeding to an tains the mitral valve, is very close to its outlet (the aortic valve), the
account of more detailed structure. The oblique position of the heart two being embraced by the wide tract linking inlet and outlet compo-
in the thorax may be conceptualized by comparing it to a rather nents of the right ventricle. The planes of the left ventricular orifices,


deformed pyramid, with the base facing posteriorly and to the right, although relatively inclined, are more nearly co-planar than those of
and the apex anteriorly and to the left. A line from the apex to the the right. The left ventricular cavity is narrow and conical, and its tip
approximate centre of the base projected posterolaterally emerges near occupies the cardiac apex.
the right mid-scapular line. Some surfaces of the cardiac ‘pyramid’ are
flat and others more or less convex, these aspects merging along rather
ill-defined ‘borders’. Precise definitions of surfaces and intervening GENERAL ORGANIZATION
‘borders’ are therefore difficult. In the account that follows, the official
Terminologia Anatomica (2011) and more generally used terms from The heart is a fused pair of valved muscular pumps circulating blood
clinical practice are given as alternatives. in series through systemic (‘left’ heart) and pulmonary (‘right’ heart)
The heart is described as having a base and apex; its surfaces are circulations (see Fig. 57.4). The fibromuscular framework and conduc-
designated as sternocostal (anterior), diaphragmatic (inferior), and right tion tissues of these physiologically separate pumps are structurally
and left (pulmonary) (Fig. 57.9). Its borders are termed upper, inferior interwoven. Despite the functional disposition in series, the two
(‘acute’ margin or border) and left (‘obtuse’ margin or border). The right pumps are topographically described in parallel. Of the four cardiac
surface is sometimes called a ‘border’, despite its extent. Although the chambers, the two atria receive venous blood as weakly contractile
heart is placed obliquely in the thorax, the atrial and ventricular septal reservoirs for final filling of the two ventricles, which then provide the


Heart
997.e1
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RETPAHC
Cardiac tamponade is external compression of the heart, usually caused
by accumulation of fluid in the pericardial space (pericardial effusion)
(Fig. 57.5). This causes compression of the right atrium, reducing
venous return and therefore cardiac output. It may be secondary to
trauma, proximal extension from a dissecting aortic aneurysm, cardiac
surgery or central venous catheter insertion. Patients develop hypoten-
sion, chest tightness, dyspnoea and possibly eventual shock. The typical
signs of a cardiac tamponade include three elements (Beck’s triad): a
small quiet heart (due to fluid within the pericardial cavity), falling
atrial pressure (decreased stroke volume) and rising jugular venous
pressure (impaired cardiac venous return). Emergency treatment
involves first relieving the tamponade by percutaneous pericardial aspi-
ration (pericardiocentesis; see below), possibly followed by surgery to
address the underlying cause. The volume of fluid may not be propor-
tional to the degree of physiological circulatory impairment. Echocar-
diography is an important tool in diagnosis and is also useful in guiding
percutaneous pericardial aspiration. Surgery is via a subxiphoid incision
or a left anterior thoracotomy.
Pericardiocentesis
Pericardiocentesis is the aspiration of fluid from the pericardial cavity
in cases of cardiac tamponade and for relief of symptomatic pericardial
effusion. In addition, this technique can be used for the diagnosis of
neoplastic effusions and purulent pericarditis, and for introducing cyto- Fig. 57.5 Acute cardiac tamponade due to ruptured aortic dissection. An
lytic agents into the pericardial space. Ultrasound-guided parasternal axial CT image acquired 60 seconds after contrast agent administration
pericardiocentesis has become the preferred elective procedure. With shows a large, high-attenuation pericardial effusion corresponding to
acute traumatic cardiac tamponade, the subxiphoid approach is used massive haemopericardium. Weakening of the aortic wall with subsequent


and aspiration of as little as 10–20 ml of blood may greatly improve rupture has led to massive extravasation of contrast agent into the
cardiac output. A complete and controlled parasternal drainage avoids pericardial sac. (Image courtesy of GF Gualdi MD, and C Valentini MD,
DEA Policlinico Umberto I, Rome, Italy, with permission from Bogaert J,
the diaphragm and phrenic nerve. Apical and abdominal approaches
Francone M 2013 Pericardial disease: value of CT and MR imaging.
may also be used (Fig. 57.6).
Radiology 267:340–356.)
Congenital anomalies of the pericardium include pericardial cysts and
diverticula, and absence of the pericardium.
be located anywhere in the pericardium, and are three times more
Pericardial cysts and diverticula common in males. It has been suggested that failure of pericardial
A pericardial cyst is a congenitally encapsulated cyst with no pericardial development results from premature atrophy of the cardinal vein and
communication, which forms when a portion of pericardium is pinched hence poor nourishment of the left pleuropericardial membrane. The
off during early development. Pericardial cysts are most often incidental most common defect is complete absence of the left side of the peri-
and are located at the right cardiophrenic angle or sulcus, where they cardium. When this occurs, lung tissue is interposed between the main
present as a well-defined ovoid expansion of the right inferolateral pulmonary artery and aorta. Bulging of the left atrial appendage through
cardiac border on a chest film, usually round or elliptical, thin-walled the defect will cause ischaemic necrosis and compression of the left
and sharply defined with fluid attenuation on CT or homogenously coronary artery, and the heart rotates to the left. Complete absence of
high signal on fluid-sensitive MR sequences. the pericardium is usually asymptomatic. Partial defects may cause
A pericardial diverticulum is a rare condition that corresponds to a complications such as herniation of cardiac structures (Fig. 57.8).
herniation through a defect in the parietal pericardium that communi- Congenital pericardial defects are associated with other congenital


cates with the pericardial cavity. It typically occurs at the same place as abnormalities such as bronchogenic cysts, ventricular and atrial septal
a pericardial cyst and should be suspected when a complete wall cannot defects, patent ductus arteriosus, mitral stenosis, bicuspid aortic valve,
be identified in all parts of the lesion (Fig. 57.7). pulmonary arteriovenous malformations, diaphragmatic hernia, mid-
line closure defects or bronchopulmonary sequestration (Hutchison
Congenital absence of the pericardium
2009). Pentalogy of Cantrell is a rare congenital abnormality consisting
Congenital absence of the pericardium is rare. The condition encom- of absence of the diaphragmatic portion of the pericardium; midline
passes defects ranging from a small foramen to absence of the entire closure defects, including sternal and abdominal wall defects; anterior
pericardium. The majority of defects occur on the left side but they can diaphragmatic defect; and congenital heart defects.


HEART
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A
Sternum
Right ventricle
Pericardial cavity
Direction of
needle insertion
Syringe angled 45˚ from surface of skin Cardiac apex
Diaphragm
Pericardial cavity Right ventricle
Liver
Lung RCA Sternum AIA
Needle direction
B
C
Liver Right atrium Left ventricle
RV LV
D
Fig. 57.6 A, The subxiphoid approach in pericardiocentesis. The needle is inserted into the angle between the xiphisternum and the left costal margin at
about 45° to the anatomical transverse plane. B, A mid-sagittal section of a cadaver. The broken arrow shows the direction of the pericardiocentesis
needle. C, A cross-section of the lower part of the thorax to show the relationships of the pericardial cavity with adjacent structures. The broken arrow
shows the direction of the pericardiocentesis needle. Abbreviations: AIA, anterior interventricular artery; RCA, right coronary artery. D, Bedside cardiac
ultrasound performed in a 62-year-old male, demonstrating a large pericardial effusion consistent with cardiac tamponade (red asterisk). The broken red
line shows the extended pericardial cavity. An 18-gauge 3.5 inch needle was attached to a 60 ml syringe and advanced between the xiphoid process
and left costal margin at a 45° angle, directed towards the left shoulder (arrow). The white line demarcates the borders of the right ventricular apical wall
and right ventricular cavity (RV); the yellow line depicts the left ventricular apical wall and left ventricular cavity (LV). (With permission from Loukas M,
Walters A, Boon JM, Welch TP, Meiring JH, Abrahams PH. 2012. Pericardiocentesis: a clinical anatomy review. Clin Anat 25:872–881.)


Heart
997.e3
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RETPAHC
A B
Fig. 57.7 The typical appearance of a pericardial cyst.
A, A PA chest radiograph showing a sharply defined
opacity at the apex of the heart. B, An axial contrast-
enhanced CT image showing the presence of a well-
defined, ovoid, fluid-filled structure (attenuation: 3 HU) in
broad contact with the pericardium. C, A cyst with low
signal intensity on a T1-weighted spin-echo MR image
(1.4 × 2.0 mm in-plane resolution), horizontal long axis
plane. (With permission from Bogaert J, Francone M.
C 2013. Pericardial disease: value of CT and MR imaging.
Radiology 267:340–356.)
A B
Fig. 57.8 Congenital absence of the pericardium. A, Axial and B, coronal T1-weighted spin-echo MR images (1.4 × 2.0 in-plane resolution) showing
pronounced left-sided rotation and displacement of the heart, filling the anterior portion of the left hemithorax. The pericardial defect is usually difficult to
visualize, but large defects such as this can be suspected on the basis of the abnormal location of the heart in the absence of other predisposing
factors. (Images courtesy of Luigi Lovato MD, S. Orsola Malpighi Hospital, Bologna, Italy. With permission from Bogaert J, Francone M. 2013. Pericardial
disease: value of CT and MR imaging. Radiology 267:340–356.)


HEART
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The basic rules of cardiac anatomy dictate that structures within the tion. Another example is the papillary muscles that support the leaflets
heart should be described relative to the bodily coordinates rather than of the mitral valve. These were conventionally described as being
to the heart itself. In other words, the structures within the heart should anterolateral and posteroseptal, reflecting the fact that the heart was
be described as the rest of the body when viewed in the anatomical placed on its apex in order to describe its component parts. However,
position. An important concept to apply is recognition of the diaphragm- examination in left anterior oblique orientation, as for the inferior
atic surface as being inferior, and the left atrium as being posterior. A interventricular artery, shows that, in reality, the so-called posteroseptal
typical example of not applying this concept is the posterior interven- muscle is anterior to its partner, despite the fact that the latter is
tricular artery. In cardiological and older anatomical texts, this artery is currently described as being anterolateral. Similarly, the posterior
described as being posterior and descending, whereas in reality it is interventricular sulcus is situated inferiorly rather than posteriorly
neither, since it is interventricular and inferior. Moreover, blockage of (Fig. 57.11; see Figs 57.9, 57,10).
the artery is well recognized as producing inferior myocardial infarc-
Superior Superior
Anterior Anterior
Posteroseptal Inferoseptal
papillary muscle papillary muscle
Posterior Posterior
A Posterior interventricular artery B Inferior interventricular artery Inferior
Fig. 57.11 The fundamental differences between describing the heart according to the conventional (A) or the attitudinally correct (B) orientation. (With
permission from Anderson R, Spicer D, Hlavacek A, Hill A, Loukas M. 2013. Describing the cardiac components–attitudinally appropriate nomenclature. J
Cardiovasc Transl Res. 6:118–123.)


HEART
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The ‘left heart’ starts at the left atrium, which receives all the pulmo-
nary inflow of oxygenated blood and some coronary venous inflow. It
contracts to fill the left ventricle through the left atrioventricular orifice,
guarded by its mitral valve. Left ventricular contraction rapidly increases
the pressure in the apical trabecular component, closing the mitral valve
and opening the aortic valve, enabling the ventricle to eject via the left
ventricular outflow tract into the aortic sinuses and the ascending aorta,
and thence to the entire systemic arterial tree, including the coronary
arteries. This vast vascular bed presents a high peripheral resistance that,
with large metabolic demands (especially the sustained requirements
of the cerebral tissues), explains the more massive structural organiza-
tion of the ‘left heart’. The ejection phase of the left ventricle is shorter
than that of the right but its fluctuations in pressure are very much
greater.
The heart is therefore, by necessity, a functionally and structurally
markedly asymmetrical pair of combined pumps, with both ventricles
designed to deliver the same volume with each contraction into two
very different resistive series circulations.
A
Cardiac size, shape and external features
Aorta Pulmonary Left atrial Left ventricle
valve appendage
The heart is a hollow, fibromuscular organ of a somewhat conical or
pyramidal form, with a base, apex and a series of surfaces and ‘borders’.
Enclosed in the pericardium, it occupies the middle mediastinum
between the lungs and their pleural coverings (see Fig. 57.3). It is placed
obliquely behind the body of the sternum, adjoining costal cartilages
and ribs. Approximately one-third of the mass lies to the right of the
midline. An average adult heart is 12 cm from base to apex, 8–9 cm at
its broadest transverse diameter and 6 cm anteroposteriorly. Its weight
varies from 280 to 340 g (average 300 g) in males and from 230 to
280 g (average 250 g) in females. Cardiac weight is 0.45% of body


weight in males and 0.40% in females. The difference in weight between
males and females appears after the age of 12 years (Kortelainen 1997).
Adult weight is achieved between the ages of 17 and 20 years. The heart
reaches 50% of its adult dimensions at birth, 75% by 5 years and 90%
by 12 years (Nidorf et al 1992).
Grooves on the cardiac surface
The division of the heart into four chambers produces boundaries that
are visible externally as grooves (sulci). Some are deep and obvious,
and contain prominent structures. Others are less distinct, even barely
perceptible, and are sometimes obscured, in part, by the major struc-
tures that cross them.
The extensive interatrial groove (of Waterston) separates the two
atria. The lateral limits are defined by the borders of the atria. The atrio-
B ventricular (coronary) groove separates the atria from the ventricles and
contains the main trunks of the coronary arteries. It descends obliquely
to the right on the sternocostal surface, separating the right atrium (and
Right atrium Right ventricle its auricle or appendage) from the oblique right margin of the right
ventricle and its infundibulum. Superiorly, its left part is obliterated by
Fig. 57.10 A cast of the so-called right and left chambers of the heart,
the crossing of the pulmonary trunk, and posterior to this, the aorta
cast in blue and red, respectively. A, The cast superimposed on a chest from which the coronary arteries originate. Continuing to the left, the
radiograph from a normal individual. The broken line indicates the midline
groove curves around the ‘obtuse’ margin and descends to the right,
of the body. The long axis of the heart extends from the right shoulder
separating the atrial base from the diaphragmatic surface of the ventri-
towards the left hypochondrium. The adult heart is usually positioned
within the mediastinum such that one-third is to the right of the midline cles (see Fig. 57.4). This diaphragmatic part of the atrioventricular


and two-thirds to the left. B, The cast enlarged to show the chambers groove then curves around the ‘acute’ margin at its lower right end to
that form the various borders of the frontal cardiac silhouette. (With become confluent with the sternocostal part. Thus, the groove passes
permission from: Anderson R, Loukas M. 2009. The importance of from superior on the left to inferior on the right, with the diaphragm-
attitudinally appropriate description of cardiac anatomy. Clin Anat atic part being a little to the left of the sternocostal. A section that
22:47–51.) includes the atrioventricular groove is at 45° to the sagittal plane and
at a greater but variable angle to the transverse and coronal planes. It
approximately traverses the lines of attachment of the atrioventricular
powerful expulsive contraction that forces blood into the main arterial
valves and, even less precisely, those of the aortic and pulmonary
trunks.
valves. A line at right angles to the centre of this plane will descend
The ‘right heart’ starts at the right atrium, which receives the supe-
anteriorly and leftwards to the cardiac apex. Internally, the ventricles
rior and inferior venae cavae and the main myocardial venous inflow
are separated by the septum; its mural margins correspond to the ante-
via the coronary sinus. This systemic venous blood traverses the right
rior and inferior (diaphragmatic) interventricular grooves. The anterior
atrioventricular orifice, guarded by the tricuspid valve, to enter the
groove, seen on the sternocostal cardiac surface, is near and almost
inlet component of the right ventricle. Contraction of the ventricle,
parallel to the left ventricular obtuse margin. On the diaphragmatic
particularly its apical trabecular component, closes the tricuspid valve
surface, the groove is closer to the midpoint of the ventricular mass.
and, with increasing pressure, ejects the blood through the muscular
The interventricular grooves extend from the atrioventricular groove to
right ventricular outflow tract into the pulmonary trunk and then
the apical notch on the acute margin, the latter a little to the right of
through the relatively low-resistance pulmonary vascular bed. Changes
the true cardiac apex.


in pressure, time relations and valvular events are described below.
Many structural features of the ‘right heart’, including its overall geo-
Cardiac base, apex, surfaces and borders
metry, myocardial architecture, and the construction and relative
strengths of the tricuspid and pulmonary valves, accord with this low
resistance, being associated with comparatively low changes in Posterior aspect of the heart The true cardiac base is somewhat
pressure. quadrilateral, with curved lateral extensions. It faces posteriorly and to


Heart
999
75
RETPAHC
the right, separated from the thoracic vertebrae (fifth to eighth in the atrium. The left atrium is largely hidden by the ascending aorta and
recumbent, sixth to ninth in the erect posture) by the pericardium, right pulmonary trunk. Only a small part of the left atrial appendage projects
pulmonary veins, oesophagus and aorta. It is formed mainly by the left forwards to the left of the pulmonary trunk. Of the ventricular region,
atrium, and only partly by the posterior part of the right atrium (see about one-third is made up by the left and two-thirds by the right
Fig. 57.4B,D). It extends superiorly to the bifurcation of the pulmonary ventricle. The site of the septum between them is indicated by the ante-
trunk and inferiorly to the posterior part of the atrioventricular groove, rior interventricular groove. The sternocostal surface is separated by the
which contains the coronary sinus and coronary arterial branches. It is pericardium from the body of the sternum, the sternocostal muscles
limited to the right and left by the rounded surfaces of the correspond- and the third to sixth costal cartilages. Because of the bulge of the heart
ing atria, separated by the shallow interatrial groove. The point of junc- to the left, more of this surface is behind the left costal cartilages than
tion of the atrioventricular, interatrial and posterior (inferior) the right. It is also covered by the pleural membranes and the thin
interventricular grooves is termed the cardiac crux. Two pulmonary anterior edges of the lungs, except for a triangular area at the cardiac
veins on each side open into the left atrial part of the base, whereas the incisure of the left lung. The lungs and their pleural coverings are vari-
superior and the inferior venae cavae open into the upper and lower able in their degree of cardiac overlap.
parts of the right atrial basal region. The area of the left atrium between
the openings of right and left pulmonary veins forms the anterior wall Inferior, diaphragmatic surface of the heart Largely horizon-


of the oblique pericardial sinus (see Fig. 57.3). This description of the tal, the inferior surface of the heart gently slopes anteroinferiorly
anatomical base reflects the usual position of the heart in the thorax. towards the apex (see Fig. 57.4B,D). It is formed by the ventricles
Some confusion is produced by other current usages of the term ‘base’, (chiefly the left) and rests mainly on the central tendon but also,
often applied to the segment of the atrioventricular and ventriculoarte- apically, on a small area of the left muscular part of the diaphragm. It
rial junctions seen after dissections through the atrioventricular groove. is separated from the anatomical base by the atrioventricular groove,
This area is better termed the base of the ventricles. In clinical practice, and is traversed obliquely by the posterior (inferior) interventricular
auscultation in or near the parasternal parts of the second intercostal groove.
spaces is often described as occurring at the ‘clinical base’, to make the
contrast with the ‘clinical apex’. Such descriptions, while less than Left surface of the heart Facing posterosuperiorly to the left, the
perfect anatomically, will almost certainly persist. left surface consists almost entirely of the obtuse margin of the left
ventricle, but a small part of the left atrium and its left atrial appendage
Anatomical apex of the heart This is the apex of the conical left contribute superiorly. Convex and widest superiorly, where it is crossed
ventricle, which is directed anteroinferiorly and to the left. It is over- by the atrioventricular groove, it narrows to the cardiac apex. It is sepa-
lapped by the left lung and pleura. The apex is located most commonly rated by the pericardium from the left phrenic neurovascular bundle,
behind the fifth left intercostal space, near or a little medial to the mid- and by the left pleura from the deep concavity of the left lung.
clavicular line.
Right surface of the heart The right surface is rounded and formed
Anterior, sternocostal surface of the heart Facing forwards by the right atrial wall. It is separated from the mediastinal aspect of


and upwards, the anterior surface has an acute right and a more gradual the right lung by the pericardium and pleural coverings. Its convexity
left convexity (Fig. 57.12). It consists of an atrial area superior and to merges inferiorly into the short intrathoracic part of the inferior vena
the right, and a ventricular part inferior and to the left of the atrioven- cava and above into the superior vena cava. The sulcus terminalis is a
tricular groove. The atrial area is occupied almost entirely by the right prominent landmark separating the systemic atrial venous sinus from
Paratracheal nodes
Inferior thyroid vein
Anterior mediastinal nodes
Internal thoracic artery and vein
Axillary artery and vein
Vagus nerve Brachial plexus
Right phrenic nerve
Left phrenic nerve
Pericardiacophrenic
Anterior mediastinal nodes
artery and vein
Right main bronchus Recurrent laryngeal nerve
Ligamentum arteriosum
Superior tracheobronchial lymph
nodes Superior tracheobronchial
lymph nodes
Left superior pulmonary vein
Right pulmonary artery
Left pulmonary artery
Right pulmonary vein
Left inferior pulmonary vein
Inferior tracheobronchial lymph
nodes
Inferior tracheobronchial
Node of ligamentum lymph nodes
arteriosum
Superior diaphragmatic nodes
Superior diaphragmatic
lymph nodes
Fig. 57.12 The heart, great vessels and the lungs in situ. The manubrium sterni has been retracted cranially, the thymus has been completely removed
and the pericardium has been partially removed. The hilum of the lung has been dissected to expose the tracheobronchial lymph nodes. (With
permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright 2013.)


HEART
1000
7
NOITCES
the appendage; it curves approximately along the junction of the ster- into its dome, and the inferior vena cava into its inferoposterior part
nocostal and right surfaces, corresponding to the position of the termi- (see Fig. 57.4A,B). An extensive muscular pouch, the appendage,
nal crest. projects anteriorly to overlap the right side of the ascending aorta; it is
a broad, triangular, pyramidal structure and has a wide junction with
Upper border of the heart This is atrial (mainly the left atrium). the venous component of the atrium (see Fig. 57.4A,C). The junction
Anterior to it are the ascending aorta and the pulmonary trunk (see between the venous part (sinus venosus) and the atrium proper is
Fig. 57.3). At its extremity, the superior vena cava enters the right marked externally by a shallow groove, the sulcus terminalis, extending
atrium. between the right sides of the openings of the two venae cavae. The
sulcus terminalis corresponds, internally, to the terminal crest (crista
Right border of the heart Corresponding to the right atrium, the terminalis), which is the site of origin of the extensive pectinate muscles
profile of the right border is slightly convex to the right as it approaches that arise serially at right angles from the crest. Posteriorly, the vertical
the vertical. interatrial groove descends to the crux. Anteriorly, the right atrium is
related to the anterior part of the mediastinal surface of the right lung,
Inferior border of the heart Also known as the acute margin of from which it is separated by pleura and pericardium. Laterally, the
the heart, the inferior border is sharp, thin and nearly horizontal. It atrium is also related to the mediastinal surface of the right lung, but
extends from the lower limit of the right border to the apex and is anterior to its hilum and separated from it by the pleura, right phrenic
formed mainly by the right ventricle, with a small contribution from nerve and pericardiacophrenic vessels and pericardium. Posteriorly and


the left ventricle near the apex. to the left, the interatrial septum and the surrounding infolded atrial
walls separate the atria (the mural infolding is indicated by an extensive
Left border of the heart Also known as the obtuse margin, the left interatrial groove). Posteriorly and to the right are the right pulmonary
border separates the sternocostal and left surfaces. It is round and veins. Medially are the ascending aorta and, to a limited extent, the
mainly formed by the left ventricle but, to a slight extent superiorly, is pulmonary trunk and its bifurcation.
formed by the left atrial appendage. It descends obliquely, convex to
Internal features
the left, from the appendage to the cardiac apex.
The interior surface of the right atrium can be divided into three regions:
the smooth-walled venous component located posteriorly leads anteri-
Right atrium
orly to the vestibule of the tricuspid valve and to the appendage (Figs
57.13–57.14). The wall of the vestibule is smooth but its junction with
General and external features
the appendage is ridged all around the atrioventricular junction by
The right atrium is both anterior and to the right of the left atrium (see pectinate muscles. The smooth-walled systemic venous sinus receives
Fig. 57.4), and extends inferior to it. Its walls form the right superior the openings of the venae cavae and coronary sinus; it originates from
sternocostal surface, the convex right (pulmonary) surface and a little the sinus venosus of the embryonic heart. The trabeculated appendage
of the right side of the anatomical base. The superior vena cava opens is derived from the embryonic atrium proper. The superior and inferior
A Pulmonary trunk Fig. 57.13 A, The interior of the
heart, revealed by incising it along
Ascending aorta Left coronary artery (orifice)
its right, and part of the lower,
Superior vena cava Sinus of pulmonary trunk surfaces. The rest of the heart has
been turned over to the left. B, The
Pulmonary valve, triangle of Koch, defined by the
Opening of superior vena cava left adjacent leaflet
tendon of Todaro, orifice of the
Aortic sinus coronary sinus and the septal leaflet


of the tricuspid valve. (A, With
Right atrium Aortic valve, permission from Waschke J, Paulsen
left coronary leaflet
F (eds), Sobotta Atlas of Human
Sinu-atrial node
Anatomy, 15th ed, Elsevier, Urban &
Opening of coronary sinus
Fischer. Copyright 2013.)
Supraventricular crest
Opening of inferior
vena cava
Right bundle
Atrioventricular bundle
Valve of inferior vena cava
Atrioventricular node
Valve of coronary sinus
Anterior papillary muscle
Right ventricle
Tricuspid valve,
anterosuperior leaflet
B Triangle of Koch Atrioventricular bundle
Tendon of Todaro
Orifice of coronary sinus
Septal leaflet of tricuspid valve


Heart
1001
75
RETPAHC
Venous Superior Right atrial Terminal Anterosuperior Pectinate The right atrium and its appendage are separated from the venous
component vena cava auricle crest leaflet muscles sinus by the crista terminalis, a smooth, C-shaped muscular ridge that
originates from the upper part of the septal surface and, passing anterior
to the orifice of the superior vena cava, skirts its right margin to reach
the right side of the orifice of the inferior vena cava. It marks the site
of the right venous valve of the embryonic heart, corresponding exter-
nally to the terminal groove. The sinu-atrial (sinus) node is located in
the superior part of the groove, inferolateral to the orifice of the superior
vena cava (see Fig. 57.13). The mean length of the crest is 51 ± 9 mm
and its thickness from epicardium to endocardium at the junction of
the superior vena cava with the posterior atrial wall is 5.5 ± 1.3 mm. The
pectinate muscles (musculi pectinati) are almost parallel muscular
ridges that extend anterolaterally from the terminal crest, reaching into
CFB
the appendage where they form several trabeculations. The largest and
most prominent pectinate muscle, forming the bridge of the sulcus
Todaro
t se pr um rii un mal )is
.
Tin ht ee r sn epal tl ay l, wis
a
lt lh pe
r
et sa ee nn ti sa thsa eg i ft ot sa sl ais o( vs ae lc io s,n ad
n
c or ve ast
l
do er ps re ep sst iu om
n
CS
superior and to the left of the orifice of the inferior vena cava. Its floor
is the primary atrial septum (septum primum). The rim of the fossa
(limbus) is prominent. Often said to represent the edge of the so-called
septum secundum, in reality the muscular borders of the fossa are no
more than infoldings of the atrial walls, incorporating extracardiac
adipose tissue. It is most distinct anterosuperiorly to the fossa, usually
deficient inferiorly. Some hearts display an excessive amount of extrac-


ardiac adipose tissue within the fold, raising a marked elevation of the
superior rim of the fossa (intervenous tubercle of Lower). A small slit
Fossa Inferior Triangle Hinge of Interior Septal
is sometimes found at the upper margin of the fossa, ascending beneath
ovalis vena cava of Koch tricuspid valve leaflet leaflet
the rim to communicate with the left atrium. This represents failure of
Fig. 57.14 The internal features of the right atrium. The superior and obliteration of the fetal foramen ovale, which remains patent in up to
inferior venae cavae have been dissected, exposing the venous one-third of all normal hearts. Anteroinferior in the right atrium is the
component of the right atrium and the fossa ovalis. The dotted line large, oval vestibule leading to the orifice of the tricuspid valve. A trian-
indicates the triangle of Koch, demarcated by the orifice of the coronary
gular zone (of Koch) is defined between the attachment of the septal
sinus (CS) and its valve, the Thebesian valve; the anterior extension of the
leaflet of the tricuspid valve, the anteromedial margin of the ostium of
Eustachian valve, the tendon of Todaro, to the central fibrous body (CFB);
the coronary sinus, and the palpable round, collagenous subendocar-
and the septal leaflet of the tricuspid valve. (Courtesy of M Loukas MD,
dial tendon of Todaro (see Figs 57.13–57.14). Koch’s triangle is a
PhD.)
landmark of particular surgical importance, indicating the site of the
atrioventricular node and its atrial connections. Anterosuperior to the
venae cavae, together with the coronary sinus, open into the venous insertion of the tendon of Todaro, the septal wall is formed by the atrio-
component. ventricular component of the membranous septum, intervening
The superior vena cava returns blood from head, neck and upper between the right atrium and subaortic outlet of the left ventricle (Fig.
limb through an orifice that faces anteroinferiorly and has no valve; it 57.17). The bulging atrial wall anterosuperior to the membranous


also receives blood from the chest wall and the oesophagus via the septum, the aortic mound (torus aorticus), marks the location of the
azygos system. non-coronary aortic sinus with its enclosed valvular leaflet.
The inferior vena cava is larger than its superior counterpart. It drains
blood from all structures below and including the diaphragm into the Right ventricle
lowest part of the atrium near the septum. Anterior to its orifice, and
found along its lateral or right margin, is the flap-like Eustachian valve,
The right ventricle extends from the right atrioventricular (tricuspid)
a fold of endocardium that encloses a few muscular fibres and is of
orifice nearly to the cardiac apex. It then ascends to the left to become
varying size (see Fig. 57.13; Fig. 57.15). When traced inferiorly, it forms
the infundibulum, or conus arteriosus, reaching the pulmonary orifice
the Eustachian ridge, which runs into the sinus septum (see below),
and supporting the leaflets of the pulmonary valve. Topographically, the
continuous with the valve of the coronary sinus. The lateral part of the
ventricle possesses an inlet component that supports and surrounds the
valve becomes continuous with the lower end of the terminal crest. The
tricuspid valve; a coarsely trabeculated apical component; and a mus-
Eustachian valve is large during fetal life, when it serves to direct richly
cular outlet or infundibulum that surrounds the attachments of the
oxygenated blood (from the placenta) from the right atrium through
pulmonary valve leaflets.
the foramen ovale of the interatrial septum into the left atrium. The
valve varies markedly in size in postnatal life; it is sometimes cribriform External features
or filamentous but often absent. The convex anterosuperior surface of the right ventricle makes up a large
The coronary sinus opens into the venous atrial component between part of the sternocostal aspect of the heart, and is separated from the
the orifice of the inferior vena cava, the fossa ovalis and the vestibule thoracic wall only by the pericardium (see Fig. 57.1). The left pleura


of the atrioventricular opening (see Fig. 57.13). It is often guarded by and, to a lesser extent, the anterior margin of the left lung are interposed
a thin, semicircular Thebesian valve that covers the lower part of the above and to the left. The inferior surface is flat and is related mainly,
orifice. The upper limb of this valve joins the Eustachian valve and its with the interposition of the pericardium, to the central tendon and a
muscular extension, the Eustachian ridge. It also joins a tendinous small adjoining muscular part of the diaphragm. The left and posterior
structure, the tendon of Todaro, running from this commissure into the wall is the ventricular septum, slightly curved and bulging into the right
sinus septum, which is the septum between the coronary sinus and ventricle so that, in sections across the cardiac axis, the outline of the
the fossa ovalis. The tendon of Todaro runs forwards to insert into the right ventricle is crescentic. The wall of the right ventricle is relatively
central fibrous body and is one of the landmarks of the triangle of Koch thin (3–5 mm), the ratio of the thickness of the two ventricular walls
(see below). The ostium of the coronary sinus forms a prominent land- usually being 1 : 3.
mark in the right atrium. The sinus itself lies within the left atrioven-
Internal features
tricular groove (see Fig. 57.4B,D) and is the conduit for return of most
of the venous blood from the heart, although some veins drain directly The inlet and outlet components of the ventricle, supporting and sur-
to the atrial chambers. The coronary sinus starts at the confluence of rounding the leaflets of the tricuspid and pulmonary valves, respec-
the oblique vein of the left atrium and the great cardiac vein, and tively, are separated in the roof of the ventricle by the prominent
receives the middle and small cardiac veins close to its junction with supraventricular crest (crista supraventricularis) (see Fig. 57.13A; Fig.
the right atrium. Several small venous ostia, draining the minimal atrial 57.18). The crest is made up predominantly by the inner heart curva-


veins, are found scattered around the atrial walls. They return a small ture, bounded on the epicardial aspect by the rightward margin of the
fraction of blood from the heart, and are most numerous on the septal transverse sinus. The crest is a thick, muscular, highly arched structure,
aspect. The anterior cardiac veins and, sometimes, the right marginal extending obliquely anteriorly and to the right from a septal limb high
vein may enter the atrium through larger ostia. on the interventricular septal wall to a mural or parietal limb on the


Heart
1001.e1
75
RETPAHC
Right atrium Pulmonary trunk Sulcus terminalis
Superior vena cava Aorta Right atrium
Superior
Anterior
Posterior
Inferior
FO
Inferior vena cava Eustachian valve Pm
Fig. 57.15 An inferior view of a cadaveric heart, demonstrating an
exaggerated Eustachian valve occupying a significant portion of the
lumen of the inferior vena cava. (With permission from Loukas M, Sullivan
A, Tubbs R, Weinhaus A, Derderian T, Hanna M. 2010. Chiari’s network:
review of the literature. Surg Radiol Anat. 32:895–901.)
Superior Posterior
Occasionally, a reticulated network, Chiari’s network, originates Inferior Anterior
from the Eustachian valve and connects to different parts of the right
atrium, including the coronary sinus. It results from incomplete resorp-
Inferior vena cava Chiari’s network
tion of the right valve of the embryonic sinus venosus (Fig. 57.16).
Often clinically insignificant, Chiari’s network has been associated Fig. 57.16 Chiari’s network. There are multiple attachment sites around
with the pathogenesis of thromboembolic disease, endocarditis, the opening of the inferior vena cava and inferiorly towards the coronary
arrhythmias, cardiac flow obstructions, heart murmurs, infective endo- sinus (the reflected part of the right atrium covers the distal attachment to
the coronary sinus). Abbreviations: FO, fossa ovalis; Pm, pectinate
carditis, cardiac tumours and entrapment of catheters on percutaneous
muscles. (With permission from Loukas M, Sullivan A, Tubbs R, Weinhaus
intervention.
A, Derderian T, Hanna M. 2010. Chiari’s network: review of the literature.
The prominent sub-Thebesian recess is located posterior to the Eus-
Surg Radiol Anat. 32:895–901.)
tachian valve and posteroinferior to the ostium of the coronary sinus.
The area between the Eustachian and tricuspid valves inferior to the
ostium of the coronary sinus (the cavotricuspid isthmus) is the target


of catheter-directed ablation procedures, the treatment of choice for
atrial flutter (Sánchez-Quintana et al 2013).


HEART
1002
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NOITCES
Aortic valve, left coronary leaflet Fig. 57.17 A dissection opening the
ventricles, viewed from the front. (With
Aortic valve, permission from Waschke J, Paulsen F
Left atrium
non-adjacent leaflet (eds), Sobotta Atlas of Human
Anatomy, 15th ed, Elsevier, Urban &
Ascending aorta
Fischer. Copyright 2013.)
Aortic leaflet
Mitral valve
Aortic sinus Mural leaflet
Right auricle
Right coronary artery
Interventricular septum, Pericardium
membranous part
Superolateral papillary muscle
Tricuspid valve,
inferior leaflet
Tricuspid valve,
Inferoseptal papillary muscle
septal leaflet
Pericardium
Anterior papillary muscle
Inferior papillary muscle
Interventricular septum, muscular part
Right coronary artery Subpulmonary infundibulum
Pulmonary trunk Supraventricular crest
Medial papillary muscle
Aorta
Septomarginal trabeculation
Superior vena cava
Septoparietal trabeculations
Venous
component
Anterior
pM ao pd ile lar ra yt o mr ub sa cn ld
e
V
e
Fossa ovalis stib
ule
Inferior papillary muscle
Inferior vena cava Tricuspid valve
Thebesian valve
Eustachian valve
Coronary sinus Sub-Thebesian recess
Fig. 57.18 A ‘window dissection’ of a cadaveric heart, prepared by removing the anterosuperior wall of the right atrium and ventricle, to expose their
internal features. The Eustachian valve separates the inferior vena cava from the sub-Thebesian recess. The Thebesian valve guards the entry into the
coronary sinus. The smooth circumferential area of atrial wall that surrounds the orifice of the tricuspid valve is the vestibule. Note the location of the
supraventricular crest and septomarginal trabeculation. The body of the septomarginal trabeculation continues as an important muscular strand, the
moderator band, to the anterior papillary muscle and the parietal wall of the right ventricle. (Specimen courtesy of M Loukas MD, PhD.)


anterolateral right ventricular wall. The posterolateral aspect of the crest caused by a myriad of endocardial, lined, irregular muscular ridges and
provides a principal attachment for the anterosuperior leaflet of the protrusions collectively known as trabeculae carneae. These protrusions
tricuspid valve. The septal limb of the crest may be continuous with, or and intervening grooves impart great variation in wall thickness; the
embraced by, the septal limbs of the septomarginal trabeculation. The protrusions vary in extent from mere ridges to trabeculations, fixed at
inlet and outlet regions extend apically into and from the prominent both ends but otherwise free. Other conspicuous protrusions are the
coarsely trabeculated component of the ventricle. The inlet component papillary muscles, which are inserted at one end on to the ventricular
itself is also trabeculated, whereas the outlet component (infundibu- wall and are continuous at the other end with collagenous cords, the
lum) has predominantly smooth walls. The trabeculated appearance is chordae tendineae (tendinous cords), inserted on the free edge of the


Heart
1003
75
RETPAHC
atrioventricular valves. One protrusion in the right ventricle, the septo- leaflets. The connective tissues around the orifice of the atrioventricular
marginal trabeculation or septal band, is particularly prominent, rein- valves separate the atrial and ventricular myocardial masses completely,
forcing the septal surface where, at the base, it divides into limbs that except at the point of penetration of the atrioventricular bundle; they
embrace the supraventricular crest. Towards the apex, it supports the vary in density and disposition around the valvular circumference.
anterior papillary muscle of the tricuspid valve and, from this point, Extending from the right fibrous trigone component of the central
crosses to the parietal wall of the ventricle as the moderator band (the fibrous body is a pair of curved, tapered, subendocardial tendons, or
name reflects an earlier idea that septomarginal trabeculation prevented ‘prongs’ (fila coronaria), which partly encircle the circumference. The
overdistension of the ventricle). The role of the moderator band as part latter is completed by more tenuous, deformable fibroblastic sulcal
of the conduction system of the heart involves the right atrioventricular areolar tissue. Although the extent of fibrous tissue varies with sex and
bundle, as conduction cardiomyocytes move towards the apex of the age, the tissue within the atrioventricular junction around the tricuspid
ventricle before entering the anterior papillary muscle. The moderator orifice is always less robust than similar elements found at the attach-
band may be short/thick, long/thick, short/thin, long/thin: it is occa- ments of the mitral valve. The topographical ‘attachment’ of the free
sionally absent. A further series of prominent trabeculations, the septo- valvular leaflets in the tricuspid valve does not wholly correspond to
parietal trabeculations, extend from its anterior surface and run on to the internal level of attachment of the fibrous core of the valve to the
the parietal ventricular wall. The smooth-walled outflow tract, or junctional atrioventricular connective tissue. The line of attachment of


infundibulum, ascends to the left, superior to the septoparietal trabecu- the leaflet is best appreciated in the heart when examined grossly, this
lations and inferior to the arch of the supraventricular crest to the feature being more readily discerned clinically.
pulmonary orifice (Spicer and Anderson 2013).
Tricuspid valve leaflets
Tricuspid valve
When they are closed, it is usually possible to distinguish the three
The atrioventricular valvular complex, in both ventricles, consists of the leaflets in the tricuspid valve on the basis of the zones of apposition
orifice and its associated anulus, the leaflets, the supporting chordae between them: hence the name. The leaflets are located anterosuperi-
tendineae of various types and the papillary muscles. Harmonious orly, septally and inferiorly, corresponding to the marginal sectors of
interplay of all of these, together with the myocardial mass, depends the atrioventricular orifice named in conjunction. The inferior leaflet is
on the conduction tissues and mechanical cohesion provided by the often described as being posterior, but when assessed in the attitudi-
cardiac skeleton. All parts change substantially in position, shape, angu- nally correct anatomical position, the leaflet is positioned inferiorly
lation and dimensions during the cardiac cycle (see Fig. 57.20). (Anderson and Loukas 2009). Each leaflet is a reduplication of endo-
cardium enclosing a collagenous core, continuous marginally and on
Tricuspid valvular orifice its ventricular aspect with diverging fascicles of chordae tendineae (see
The tricuspid valve orifice is best seen from the atrial aspect. It measures, below) and basally confluent with the anular connective tissue. In
on average, 11.4 cm in circumference in males and 10.8 cm in females. passing from the free margin to the inserted margin, all leaflets of the
There is a clear line of transition from the atrial wall or septum to the atrioventricular valves display rough, clear and basal zones. The rough
lines of attachment of the valvular leaflets. Its margins are not precisely zone is relatively thick, opaque and uneven on its ventricular aspect


in a single plane. It is almost vertical but at 45° to the sagittal plane where most chordae tendineae are attached; its atrial aspect makes
and slightly inclined to the vertical, such that it ‘faces’ (on its ventricular contact with the comparable surface of the adjacent leaflets during full
aspect) anterolaterally to the left and somewhat inferiorly (Fig. 57.19). valve closure. The clear zone is smooth and translucent, receives few
Roughly triangular, its margins are described as anterosuperior, inferior chordae tendineae and has a thinner, fibrous core. The basal zone,
and septal, corresponding to the lines of attachment of the valvular extending 2–3 mm from the circumferential attachment of the leaflets,
is thicker from increased connective tissue, vascularized and innervated.
It contains the insertions of the atrial myocardium. The anterosuperior
leaflet is the largest component of the tricuspid valve, attached chiefly
to the atrioventricular junction on the posterolateral aspect of the
supraventricular crest, and extending along its septal limb to the mem-
1 1
branous septum ending at the anteroseptal commissure. One or more
notches often indent its free margin. The attachment of the septal leaflet
passes from the inferoseptal commissure on the inferior ventricular wall
across the muscular septum, then angling across the membranous
2 2
septum to the anteroseptal commissure. The septal leaflet defines one
of the borders of the triangle of Koch, thereby aiding location of the
A P atrioventricular node at the apex of this triangle, and ensuring avoid-
P
3 3 ance during tricuspid valve surgery (see Figs 57.13, 57.17). The inferior
leaflet is wholly mural in attachment and guards the diaphragmatic
surface of the atrioventricular junction, its limits being the inferoseptal
A and anteroinferior commissures. The zone of apposition between the
4 M 4 inferior and the anterosuperior leaflets is supported by the septal papil-
lary muscle of the conus.
T Opening of the tricuspid valve
5 5 Despite its name, the tricuspid valve acts more like a bicuspid valve


T because its smallest septal leaflet is fixed between the atrial and ven-
M tricular septa. The remainder of the tricuspid anulus is muscular. During
diastole, the anulus dilates with right ventricular relaxation and the
6 6 large anterior and posterior leaflets move away from the plane of the
anulus into the right ventricle. During systole, the anulus constricts as
the right ventricle contracts and the two major leaflets move like sails
about a relatively immobile septal leaflet and the septum itself
7 7 (Fig. 57.20).
Chordae tendineae (tendinous cords)
The chordae tendineae are fibrous collagenous structures that support
Fig. 57.19 The relation of the sternocostal surface and valves of the heart
the leaflets of the atrioventricular valves. Sometimes, false chordae
to the thoracic cage. The right heart is blue, the arrow denoting the inflow
connect the papillary muscles to each other or to the ventricular wall
and outflow channels of the right ventricle; the left heart is treated
or septum, or pass directly between points on the wall or septum, or
similarly in red. The positions, planes and relative sizes of the cardiac
valves are shown. The position of the letters A, P, T and M indicate the both. Their numbers and dimensions vary in the right ventricle; approx-
aortic, pulmonary, tricuspid and mitral auscultation areas of clinical imately 40% of these false cords contain conduction cardiomyocytes.
practice, respectively. Note that, for the purpose of illustration, the orifices The true chordae usually arise from small projections on the tips or
of the aortic, mitral and tricuspid valves are shown with some separation margins of the apical third of papillary muscles, although they some-
between them, whereas, in reality, the leaflets of the three valves are in times arise from the papillary muscle bases or directly from the ven-
fibrous continuity (see Fig. 57.24). tricular walls and septum. They attach to various parts of the ventricular


HEART
1004
7
NOITCES
aspects or the free margins of the leaflets. True chordae are classified ventricular aspect) of the zones of apposition between leaflets and to
into first-, second- and third-order types, according to the distance of the ends of adjacent leaflets. Rough-zone chordae arise from a single
the attachment from the margins of the leaflets; the scheme has little stem that usually splits into three components that attach to the free
functional or morphological merit. Fan-shaped chordae have a short margin, the ventricular aspect of the rough zone and to some intermedi-
stem from which branches radiate to attach to the margins (or the ate point on the leaflet, respectively. Free-edge chordae are single,
thread-like and often long, passing from either the apex or the base of
120 a papillary muscle into a marginal attachment, usually near the mid-
point of a leaflet or one of its scallops. Deep chordae pass beyond the
100
margins and, branching to various extents, reach the more peripheral
Aorta
Pressure 80 rough zone or even the clear zone. Basal chordae are round or ribbon-
(mmHg) like, long and slender, or short and muscular; they arise from the
60
in left side smooth or trabeculated ventricular wall and attach to the basal compo-
of heart 40 nent of a leaflet.
Left atrium
20
Left venticle Papillary muscles
Pressure 0 The two major papillary muscles in the right ventricle are located in
(mmHg) 20 Pulmonary artery anterior and inferior positions. A third, smaller muscle lies medially,
in right side 0 Right atrium together with several smaller, variable muscles attached to the ventricu-
of heart Right ventricle lar septum. The anterior papillary muscle is the largest, its base arising
Atrium Ventricle from the right anterolateral ventricular wall inferior to the anteroinfe-
Mechanical Left Ejection Stipple marks isometric rior commissure of the inferior leaflet, also blending with the right end
activity Right Ejection contraction and relaxation of the septomarginal trabecula. The inferior, papillary muscle, often
bifid or trifid, arises from the myocardium inferior to the inferoseptal
Sequence of commissure. The septal (medial) papillary muscle of the conus, the


valve motion muscle of Lancisi, is almost always present and is the most superior and
largest of the small septal papillary muscles. It arises from the posterior
Closure of 1 5 Closure of septal limb of the septomarginal trabeculation and locates the right
mitral valve aortic valve
bundle branch within the right ventricle. All the major papillary
6 Closure of muscles supply chordae to adjacent components of the leaflets they
Closure of 2 pulmonary support (see Figs 57.17, 57.18). A feature of the right ventricle is that
tricuspid valve valve the septal leaflet is tethered by individual chordae tendineae directly to
the ventricular septum; such septal insertions are never seen in the left
7 Opening of ventricle. When closed, the three leaflets fit snugly together, the pattern
tricuspid
of the zones of apposition confirming the trifoliate arrangement of the
valve
Opening of 3 tricuspid valve.
pulmonary valve
8 Opening of Pulmonary valve
mitral valve
Opening of 4 The pulmonary valve, guarding the outflow from the right ventricle,
aortic valve surmounts the infundibulum and is situated at some distance from the
other three cardiac valves (Figs 57.21, 57.23). Its general plane faces
superiorly to the left and slightly posteriorly. It has three semilunar
Phonocardiogram
First heart Second heart leaflets, attached by convex edges partly to the infundibular wall of the
sound sound right ventricle and partly to the origin of the pulmonary trunk. The line
R
Electrocardiogram P T of attachments is curved, rising at the periphery of each leaflet near their
Q S zones of apposition (the commissures) and reaching the sinutubular
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 ridge of the pulmonary trunk (Fig. 57.24). Removal of the leaflets
Time (seconds) reveals that the fibrous semilunar attachments enclose three crescents
Fig. 57.20 A summary of some of the principal events that occur in of infundibular musculature within the pulmonary sinuses, whereas


the cardiac cycle and that are mentioned at various points throughout three roughly triangular segments of arterial wall are incorporated
this chapter. Systole begins at the onset of the first heart sound (see within the ventricular outflow tract beneath the apex of each commis-
phonocardiogram) and ends at the onset of the second heart sound, sural attachment. Thus there is no proper circular ‘anulus’ supporting
when diastole begins, and this cycle repeats itself. the leaflets of the valve, and the fibrous semilunar attachment is an
Pulmonary trunk Fig. 57.21 The base of the ventricles, after
removal of the atria and the pericardium,
Non-adjacent Left coronary leaflet exposing the coronary arteries and cardiac veins.
leaflet Contrast the planes and positions of the aortic
Pulmonary valve Right adjacent Right coronary leaflet Aortic valve and pulmonary valves, and with Figure 57.23.
leaflet
(With permission from Waschke J, Paulsen F
Left adjacent
(eds), Sobotta Atlas of Human Anatomy, 15th ed,
leaflet Non-adjacent leaflet
Elsevier, Urban & Fischer. Copyright 2013.)
Anterior interventricular branch
Right coronary artery
Left coronary artery
Circumflex branch Right fibrous trigone
Left fibrous trigone Right fibrous ring
Great cardiac vein
Atrioventricular bundle
Left fibrous ring
Valve of coronary sinus
Right marginal branch
Left marginal branch
Middle cardiac vein
Opening of coronary sinus
Right coronary artery,
Inferior interventricular vein
inferior interventricular branch


Heart
1005
75
RETPAHC
essential requisite for snug closure of the nodules and lunules of the of the anatomical base of the heart and is approximately quadrangular,
leaflets during ventricular diastole (see below). receiving the terminations of (usually) two pulmonary veins from each
It is difficult to name the leaflets and corresponding sinuses of the lung, forming the anterior wall of the oblique pericardial sinus (see Fig.
pulmonary valve and trunk precisely according to the coordinates of 57.3). This surface ends at the shallow vertical interatrial groove that
the body because the valvular orifice is obliquely positioned. Termino- descends to the cardiac crux.
logia Anatomica (2011) refers to anterior, posterior and septal leaflets on The left atrial appendage is characteristically longer, narrower and
the basis of their fetal position but this changes with development, more hooked than the right, and is a finger-like extension with more
becoming anterior, right and left, respectively, in the adult. Each leaflet deeply indented margins. It is constricted at its atrial junction and all
is an endocardial fold with a variably developed intervening substantial its contained pectinate muscles are much smaller than their right coun-
fibrous core that traverses both the free edge and the semilunar attached terparts. The left atrium lacks a crista terminalis, and the muscle bundles
border. The latter is particularly thickened at its deepest central part in the appendage are arranged in a whorl-like fashion rather than being
(nadir) of the base of each leaflet, and therefore never forms a simple in an array. The tip of the appendage has a variable position lying over
complete fibrous ring. The free margin of each leaflet contains a central the pulmonary trunk and anterior interventricular artery, pointing pos-
localized collagenous thickening, the nodule of Arantius. Perforations teriorly towards the aorta (Fig. 57.22). Its narrow morphology renders
within the leaflets close to the free margin and near the commissures the left atrial appendage a potential site for deposition of thrombi.
are frequently present and are of no functional significance. Each semi- The four pulmonary veins open into the superior posterolateral


lunar leaflet is contained within one of the three sinuses of the pulmo- surfaces of the left atrium, two on each side (see Figs 57.3, 57.4B). This
nary trunk. typical arrangement is present in 20–60% of the population. A common
variation includes the presence of a short or long left common venous
Opening of the pulmonary valve trunk and multiple pulmonary veins on the right (Fig. 57.25). The right
During diastole, all three leaflets of the pulmonary valve are tightly pulmonary veins travel posterior to their respective venae cavae. Their
apposed. The pulmonary valve is difficult to visualize at echocardio- orifices are smooth and oval, the left pair frequently opening via a
graphy and usually only the posterior leaflet is visible when the valve common channel. Interpulmonary ridges are usually found between
is closed; atrial systole may cause a slight posterior movement of the ipsilateral orifices; the most prominent is located between the openings
valve leaflets. The pulmonary valve opens passively during ventricular of the left atrial appendage and left superior pulmonary vein. The ridges
systole and then closes rapidly at the end of systole (see Fig. 57.20). are infoldings of the left atrial wall and contain adipose tissue, atrial
arteries and nerve bundles. At the site of the pericardial reflection, the
atrial musculature extends into the pulmonary veins, forming myocar-
Left atrium
dial sleeves that are thickest in the inferior wall of the superior pulmo-
nary veins and the superior walls of the inferior pulmonary veins. They
General, external and internal features
lie external to the venous tunica media and internal to the epicardium/
Although smaller in volume than the right, the left atrium has thicker adventitia and are often the site of focal electrical activity that initiates
walls (3 mm on average). It possesses a venous component that receives atrial fibrillation. Atrial myocardial bridges and crossing strands are
the right and left superior and inferior pulmonary veins, a vestibule and often present, connecting the left superior and inferior pulmonary
an appendage. Its cavity and walls are formed largely by the proximal veins.
parts of the pulmonary veins that are incorporated into the atrium Several epicardial fat pads on the pulmonary venous component


during development. Its extensive body is a remnant of the initial atrial house the superior left, posterolateral, left inferior and posteromedial
component of the primary heart tube. The left atrium is roughly cuboi- ganglionated cardiac intrinsic nerve plexuses (typically four). Minimal
dal, extending posterior to the right atrium and separated from it by cardiac veins (venae cordis minimae) return blood directly from the
the obliquely positioned septum. The right atrium is therefore antero- myocardium to the left atrial cavity. The left atrial aspect of the septum
lateral to the right part of the left atrium. The left part is concealed has a characteristically rough appearance, bounded by a crescentic,
anteriorly by the initial segments of the pulmonary trunk and aorta: superiorly concave ridge that marks the site of the foramen ovale. The
part of the transverse pericardial sinus lies between it and these arterial smooth circumferential area of atrial wall that surrounds the orifice of
trunks. Anteroinferiorly, and to the left, it adjoins the base of the left the mitral valve is the vestibule (see Fig. 57.25A, Fig. 57.26). The mus-
ventricle at the orifice of the mitral valve. Its posterior aspect forms most culature between the ostium of the inferior pulmonary vein and the
Ligamentum arteriosum Fig. 57.22 The anterior or sternocostal surface of the
Aortic arch
heart. (With permission from Waschke J, Paulsen F
(eds), Sobotta Atlas of Human Anatomy, 15th ed,
Serous pericardium, parietal layer
Superior vena cava Elsevier, Urban & Fischer. Copyright 2013.)
Serous pericardium, Left pulmonary artery
parietal layer
Pulmonary trunk
Right pulmonary artery
Ascending aorta
Left coronary artery
Transverse
Left atrium, left appendage
pericardial sinus
Great cardiac vein
Right coronary artery
Left coronary artery,
circumflex branch
Right appendage
Infundibulum (conus
Right atrium arteriosus)
Left coronary artery,
anterior interventricular branch
Right ventricular veins
Atrial branch
Anterior interventricular
vein
Right marginal branch
Apex of heart


Notch of cardiac apex


HEART
1006
7
NOITCES
Arch of aorta
Right pulmonary artery
Pulmonary trunk
Ascending aorta
Tendon of infundibulum
(conus ligament) Ostia of coronary arteries
Fibrous attachment of
pulmonary valve leaflets
Fibrous attachment of aortic valve:
Left coronary leaflet
Left fibrous trigone
Right coronary leaflet
Non-adjacent leaflet
Subaortic curtain
and leaflet extension
Line of aortic leaflet,
Tendon of Todaro
mitral valve
Membranous part of septum
MITRAL VALVE ANULUS
Atrioventricular node
Fila coronaria Line of septal leaflet, tricuspid valve
Sulcal connective tissue TRICUSPID VALVE ANULUS
Fila coronaria
Sulcal connective
tissue
Mitral and aortic ‘anuli’
Right fibrous trigone
Tricuspid and pulmonary ‘anuli’ (central fibrous body)
Tendon of the infundibulum
Fig. 57.23 Principal elements of the fibrous skeleton of the heart. For clarity, the view is from the right posterosuperior aspect. Perspective causes the
pulmonary anulus to appear smaller than the aortic anulus, whereas, in fact, the reverse is the case. Consult the text for an extended discussion.
(Copyright of The Royal College of Surgeons of England. Reproduced with permission.)
anulus of the mitral valve is the left atrial or mitral isthmus, and is an The effect of obesity on the heart is apparent as early as the second year
area where the vestibule of the left atrium directly opposes the wall of of life. Obese children aged 2 years have a greater left ventricular mass
the great cardiac vein, coronary sinus and circumflex coronary artery. compared with normal weight controls (de Jonge et al 2011).
Internal features
Left ventricle
The left ventricle has an inlet region guarded by the mitral valve (ostium
venosum), an outlet region guarded by the aortic valve (ostium arterio-
General and external features
sum) and an apical trabecular component. The left atrioventricular
The left ventricle is constructed in accordance with its role as a powerful orifice admits atrial blood during diastole, the flow being directed


pump for the high-pressured systemic arterial circulation. Variously towards the cardiac apex (Fig. 57.28). After closure of the mitral leaflets
described as half-ellipsoid or cone-shaped, it is longer and narrower and throughout the ejection phase of systole, blood is expelled from
than the right ventricle, extending from its base in the plane of the the apex through the aortic orifice. In contrast to the orifices within the
atrioventricular groove to the cardiac apex. Its long axis descends ante- right ventricle, those of the left ventricle are in close contact with
riorly and to the left. In transverse section, at right angles to the axis, fibrous continuity between the leaflets of the aortic and mitral valves
its cavity is oval or nearly circular, with walls three times thicker (the ‘subaortic curtain’) (Fig. 57.29); the inlet and outlet turn sharply
(8–12 mm) than those of the right ventricle (Fig. 57.27). It forms part round this fibrous curtain. The anterolateral wall is the muscular ven-
of the sternocostal, left and inferior (diaphragmatic) cardiac surfaces. tricular septum, the convexity of which completes the circular outline
Except where obscured by the aorta and pulmonary trunk, the base of of the left ventricle (see Fig. 57.27). Towards the aortic orifice, the
the ventricular cone is superficially separated from the left atrium by septum becomes the thin and collagenous interventricular component
part of the atrioventricular groove with the coronary sinus within in of the membranous septum, an oval or round area below and conflu-
its posterior aspect (see Fig. 57.4B,D). The anterior and posterior ent with the fibrous triangle separating the right and the non-coronary
(inferior) interventricular grooves indicate the lines of mural attach- leaflets of the aortic valve. Between the inferior limits of the free
ment of the ventricular septum and the limits of the ventricular territo- margins of the leaflets of the mitral valve and the ventricular apex, the
ries. The sternocostal surface of the ventricle curves bluntly into its left muscular walls exhibit deeper, finer and more intricate trabeculae


surface at the obtuse margin. carneae than those of the right ventricle, characteristically more devel-
The shape of the left ventricle changes from elliptical in the neonatal oped nearer the apex, and becoming smoother as the superior septal
period to the round adult shape later in infancy (Azancot et al 1983). surface is reached.


Heart
1007
75
RETPAHC
A
Commissural ring
(sinutubular junction)
LAA
Aortic wall
within ventricle
(interleaflet triangle) LUPV
e
V rine gn t ari ncu dl o jua nr cte tir oia nl
O
LLPV
estibul
MV
V
Ventricle within sinus
Basal ring
A
B
LAA
Sinutubular Haemodynamic ventriculoarterial
junction junction (semilunar)
Commissure LUPV
os
LLPV
Artery as part
Arterial of ventricle ule
wall estib MV
V
Ventricle
Ventricle as part
of aorta
B GCV
Anatomical ventriculoarterial
junction (circular) Fig. 57.25 Sagittal sections showing the left side of the left atrium in a
cadaveric heart. A, The oesophagus (O) passing behind the posterior left
atrial wall and a broad left-lateral ridge (double-headed arrow). The left
upper (LUPV) and left lower (LLPV) pulmonary veins enter the left atrium
C Pulmonary trunk Sinutubular junction
Non-adjacent leaflet via a short common stem. Other abbreviations: LAA, left atrial appendage;
Right coronary Left coronary Ventriculoarterial MV, mitral valve. B, The section passes through the os of the left atrial
leaflet leaflet junction appendage and the infolding of the ridge. The triangle indicates the carina
or interpulmonary ridge between the upper and lower pulmonary veins.
The great cardiac vein (GCV) runs underneath the left atrial wall. (With
permission from Ho SY, McCarthy KP, Faletra FF. 2011. Anatomy of the
left atrium for interventional echocardiography. Eur J Echocardiogr
12:11–15.)
Hypertrophy of heart muscle
Available with the Gray’s Anatomy e-book
Mitral valve
The general comments already made for the tricuspid valve also apply
to the mitral valve. Thus it has an orifice with a supporting anulus,
leaflets and a variety of chordae tendineae and papillary muscles.
Muscular septum Mitral valve Left fibrous trigone
Mitral valvular orifice


Right fibrous trigone
Central fibrous body
Membranous septum The mitral orifice is a well-defined transitional zone between the atrial
wall and the leaflet bases, being smaller than the tricuspid orifice (mean
Fig. 57.24 A, The structure of the aortic root is best conceptualized in
circumference is 9.0 cm in males and 7.2 cm in females). The approxi-
terms of a three-pronged coronet; there are at least three rings within this
mately circular orifice is almost vertical and at 45° to the sagittal plane
coronet but none supports the entirety of the attachments of the valvular
in diastole, but with a slight anterior tilt. Its ventricular aspect faces
leaflets (compare with C). B, The leaflets have been resected at their
anterolaterally to the left and a little inferiorly towards the left ventricu-
attachment to the aortic wall. Note the relationship of the leaflet insertions
lar apex. It is almost co-planar with the tricuspid orifice but postero-
and the ventriculoarterial junction. C, The root of the aorta has been cut
open and distended, in order to show the insertion of the semilunar superior to it, whereas it is posteroinferior and slightly to the left of the
leaflets. Note the zone of fibrous continuity between the leaflets of the aortic orifice. The mitral, tricuspid and aortic orifices are intimately
aortic and mitral valves and their relationship to the fibrous trigones, and connected at their central fibrous body. When the mitral valve leaflets
the semilunar attachment of the leaflets (compare with B). (Redrawn with close, they form a single zone of coaptation, termed the commissure.
permission, courtesy of Professor RH Anderson, Institute of Child Health, The anulus of the valve is not a simple fibrous ring but is made up of
University College, London.) fibrocollagenous elements of varying consistency, from which the
fibrous leaflet cores take origin; the variable consistency is essential to
allow the major changes in anular shape and dimensions during the
cardiac cycle that are needed for optimal valvular efficiency. The area of