reduced by diversion into the small cardiac vein and then to the coro-
the right coronary artery.
nary sinus.
Extracardiac anastomoses
Coronary sinus
Extracardiac anastomoses connect various coronary branches with other
Most cardiac veins drain into the wide coronary sinus, 2 or 3 cm long,
thoracic vessels, most commonly involving the bronchial and internal
lying in the posterior atrioventricular groove between the left atrium
thoracic arteries (Fig. 57.54). To a much lesser degree, anastomoses
and ventricle (see Fig. 57.4B; Fig. 57.59). The sinus opens into the right
between coronary arteries and pericardiacophrenic branches of the
atrium between the opening of the inferior vena cava and the right
internal thoracic, anterior mediastinal, intercostal and oesophageal
atrioventricular orifice. The opening may be guarded by an endocardial
arteries also exist. The posterior pericardium also receives a direct
fold (semilunar valve of the coronary sinus, Thebesian valve; see Fig.
supply from the bronchial arteries; extracardiac coronary anastomoses
57.13A); the fold may be absent or may cover the ostium of the sinus
involving bronchial arteries are typically found at the pericardial reflec-
completely. The tributaries of the coronary sinus are the great, small
tions, such as the points of entry of the venae cavae. The most common
and middle cardiac veins, the posterior vein of the left ventricle and the
anastomoses are with the circumflex branch of the left coronary artery
oblique vein (of Marshall) of the left atrium; all except the oblique vein
via the posterior pericardial reflections and reflect the close proximity
have orificial valves. Isolated absence of the coronary sinus has been
of the bronchial arteries within the pulmonary hila. In pathological
reported, with coronary venous drainage into the pulmonary trunk
conditions, notably those resulting in pericardial adhesions, it is
(Ogawa et al 2013).
also possible for extracardiac anastomoses to develop through trans-
pericardial vascularization.
Extracardiac communications also exist with coronary atrial


branches, especially the sinu-atrial nodal artery. The effectiveness of any
of these connections as collateral routes in coronary occlusion is not
Aorta
well quantified. Coronary arteriovenous anastomoses and numerous
connections between the coronary circulation and cardiac cavities, pro- Pulmonary trunk
ducing so-called ‘myocardial sinusoids’ and ‘arterioluminal vessels’, Superior vena
cava
have been reported, but their importance in coronary disease remains
uncertain. Left pulmonary veins
Coronary angiography Right pulmonary
Oblique vein of
veins
left atrium
Available with the Gray’s Anatomy e-book
Great cardiac vein
Coronary revascularization Right atrium
Left marginal vein
Available with the Gray’s Anatomy e-book
Inferior vein of
Coronary sinus
left ventricle
Coronary artery fistula Inferior vena
A coronary artery fistula is an abnormal connection that directly links cava
one or more coronary arteries to a heart chamber or to major thoracic
vessels without an interposed capillary bed. Small cardiac vein
Middle
Coronary artery fistulae are rare (Fig. 57.58); those that arise from cardiac vein
Right marginal vein
a coronary artery and then terminate in a chamber of the heart are
known as coronary cameral fistulae, while those terminating into a vein
are coronary arteriovenous fistulae. Fistulae may be congenital or may Fig. 57.59 The principal veins of the heart.


Heart
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Table 57.1 Patterns of cardiac collateral arteries Anterior interventricular artery
Grade Description
0 Total absence of any collateral arteries
1 Poorly developed collateral arteries with no prominent distal channel visualized by
angiography
2 Presence of moderate collateral arteries providing faint but delayed opacification of
a prominent distal channel
3 Good collateral arteries giving clear opacification of a prominent distal channel
4 Excellent collateralization giving full and brisk opacification of prominent distal
vessels
Clinical imaging (catheter angiography and colour Doppler ultra-
sound) has led to the development of a grading system to describe the
overall pattern of cardiac collateral arteries (Table 57.1).
Coronary angiography may be performed by introducing a catheter
through the femoral, radial or brachial arteries. The femoral artery is
punctured with a needle 3 cm below the inguinal ligament while the
leg is held adducted and slightly externally rotated. The exact position
is guided by palpation of the femoral arterial pulse, and the needle is
inserted at an angle of 45°. After arterial puncture, a fine guidewire is
inserted through the needle and fed into the artery. The catheter is then Circumflex coronary artery Lower lobe of left lung
inserted over the guidewire and manipulated via the iliac artery into the
Fig. 57.54 A left coronary angiogram in left lateral projection, showing a
aorta, up the aortic arch and into the ascending aorta. The brachial or
large, tortuous vessel (arrow) arising from the proximal circumflex branch
radial artery may be used for percutaneous access to the circulation.
of the left coronary artery and anastomosing with the bronchial artery,
Once the catheter is located in the ascending aorta, a variety of
which goes on to supply the lower lobe of the left lung. (With permission
guidewires may be used to enter the coronary vessels for selective arte-
from Stefas L, Assayag P, Aubry P, et al, Coronary to bronchial artery
riography and interventions. Angiography is performed with standard anastomosis with bronchial steal syndrome demonstrated by thallium-201


high-osmolality contrast medium with cineangiography. In selected myocardial tomoscintigraphy. Eur Heart J, 1990, 11, 275–279.)
patients, new-generation, low-osmolality contrast medium may also be
used. All the coronary arteries are catheterized and evaluated in a variety
of views to obtain a full evaluation of their anatomy and to determine
Cn
the location and degree of any stenoses (Figs 57.55–57.56). The ostium
of the left coronary artery arises from the left aortic sinus and is best
viewed in the direct frontal and left anterior oblique projections. The
SA
right anterior oblique view is useful in demonstrating the diagonal
branches and anterior interventricular (descending) coronary artery.
The right coronary artery originates from the right sinus of Valsalva and
is usually visualized in the right anterior oblique view. Pressure and
Rv
oxygen saturations can be measured via the catheter; changes in pres-
sure across valves allow the degree of stenosis to be measured. Coronary
blood flow and relative flow reserve can also be calculated. Significant Rm
stenosis may be treated initially by balloon angioplasty followed by
stent insertion. The balloon exerts pressure against the plaque in the
arterial wall, fracturing and splitting the plaque. The splinting effect of
the plaque and elastic recoil are reduced, resulting in an increase in the
PIA
arterial lumen. Stent insertion reduces the re-stenosis rate.
Fig. 57.55 A right coronary angiogram showing several branches of the
right coronary artery. Abbreviations: Cn, conal artery; PIA, posterior
(inferior) interventricular artery; Rm, right marginal artery; Rv, right
ventricular branches; SA, artery to the sinu-atrial node. (Courtesy of
M Loukas MD, PhD.)
LCA
Sp
AIA Latr
LCx
ObM
PIA
Fig. 57.56 A left coronary angiogram showing several branches of the left
coronary artery (LCA). Other abbreviations: AIA, anterior interventricular
artery; Latr, left atrial branch; LCx, left circumflex artery; ObM, obtuse
marginal; PIA, posterior (inferior) interventricular artery; Sp, septal


perforator. (Courtesy of M Loukas MD, PhD.)


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Fig. 57.57 A, A left coronary angiogram showing
a stent placement within the anterior
interventricular artery. B, After stent placement
(and once the contrast medium has filled the
coronary arterial tree), the anterior interventricular
artery shows no evidence of stenosis.
Abbreviations: AIA, anterior interventricular artery;
Stent Dg, diagonal branch; LCx, left circumflex artery.
(Courtesy of M Loukas MD, PhD.)
AIA LCx
Dg
A B
Atherosclerosis causing more than 60% stenosis of the terminal diam-
eter of the coronary arteries is likely to cause significant reduction in
myocardial perfusion. Patients with high-grade lesions, left main stem
coronary artery or triple-vessel disease with impaired left ventricular
function are usually considered for coronary artery bypass grafting. The
common grafts that are used are the internal thoracic (mammary) and
radial arteries. The left internal thoracic artery and radial artery grafts
have a greater patency rate than saphenous vein grafts. Approximately
15% of saphenous vein grafts occlude in 1 year and, from then on, at
an annual rate of 1–2% in the first 6 years and 4% thereafter; between
40% and 50% of saphenous vein grafts have occluded by 10 years,
whereas only about 10% of left internal thoracic or radial artery grafts
have occluded over this time. The common surgical approach is via a
midline sternotomy. If the internal thoracic artery is used as a donor
graft, it is divided distally (maintaining its proximal origin from the
subclavian artery) and anastomosed to the coronary artery distal to the A
stenosis. If radial artery grafts are used, they must be anastomosed both
proximal and distal to the coronary artery, to bridge the site of the
stenosis. In selected cases, minimally invasive direct coronary artery
bypass grafting is performed, but the approach is dependent on the
vessel being grafted. The anterior approach is via mini-thoracotomy
over the fourth intercostal space underneath the nipple for grafting the


mid-left anterior interventricular (descending) and diagonal branches.
The anterolateral approach is via an incision in the third intercostal
space from the mid-clavicular to anterior axillary lines and is used for
grafting early marginal branches of the circumflex system. The lateral
approach allows grafting of the circumflex vessels via a lateral thora-
cotomy measuring only 10 cm in size through the fifth or sixth inter-
costal spaces. Extrathoracic approaches that are occasionally used
include the subxiphoid approach for the distal right coronary artery and
posterior interventricular (descending) artery. Port access surgery allows
for full revascularization with cardiopulmonary bypass but obviates the
need for midline sternotomy. However, the vast majority of patients are B
treated with stent placement (Fig. 57.57).
Fig. 57.58 A coronary artery fistula in a 54-year-old woman with
palpitations. A, A CT image showing a tortuous left circumflex artery
(white arrows) that is dilated in comparison with the anterior
interventricular artery (black arrow). B, A volume-rendered CT image
shows the markedly tortuous left circumflex artery (arrows). (With
permission from Shriki JE, Shinbane JS, Rashid MA, Hindoyan A, Withey
JG, DeFrance A, Cunningham M, Oliveira GR, Warren BH, Wilcox A.
2012. Identifying, characterizing, and classifying congenital anomalies of
the coronary arteries. Radiographics 32:453–468.)


Heart
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Great cardiac vein The great cardiac vein begins at the cardiac apex, veritable venous plexus. Not only are adjacent veins often connected,
and ascends in the anterior interventricular groove to the atrioventricu- but connections also exist between tributaries of the coronary sinus and
lar groove, which it follows, passing to the left and posteriorly to enter those of the anterior cardiac veins. Abundant anastomoses occur at the
the coronary sinus at its origin (see Fig. 57.59). It receives tributaries apex and its anterior and posterior aspects. Like the coronary arteries,
from the left atrium and both ventricles, including the large left mar- cardiac veins connect with extracardiac vessels, particularly the vasa
ginal vein that ascends the left aspect (obtuse border) of the heart. It vasorum of the large vessels that are continuous with the heart.
usually courses superior to the arterial branches. The valve of Vieussens
normally guards the orifice of the great cardiac vein at its junction with Lymphatic drainage of the heart
the oblique vein; smaller diminutive valves may occur.
Cardiac lymphatic vessels form subendocardial, myocardial and sub-
Small cardiac vein The small cardiac vein lies in the posterior atrio-
epicardial plexuses. Efferents from the subepicardial plexuses form the
ventricular groove between the right atrium and ventricle, receiving
left and right cardiac collecting trunks; two or three left-sided trunks
blood from their posterior parts and opening into the atrial end of the
ascend the anterior interventricular groove, receiving vessels from both
coronary sinus (see Fig. 57.59). The right marginal vein passes right,
ventricles. On reaching the atrioventricular groove, they are joined by a
along the inferior cardiac margin (acute border), and sometimes joins
large vessel from the diaphragmatic surface of the left ventricle, which
the small cardiac vein in the atrioventricular groove, typically opening
first ascends in the posterior interventricular groove and then turns left
directly into the right atrium.
along the atrioventricular groove. The vessel formed by this union
ascends between the pulmonary artery and the left atrium, and usually
Middle cardiac vein The middle cardiac vein begins at the cardiac


ends in an inferior tracheobronchial node. The right trunk receives
apex and runs posteriorly in the inferior interventricular groove to end
afferents from the right atrium and the right border and diaphragmatic
in the coronary sinus near its atrial end (see Fig. 57.59). The vein is also
surface of the right ventricle. It ascends in the atrioventricular groove,
described as meeting the great cardiac vein at the apex, so forming,
near the right coronary artery, and then anterior to the ascending aorta,
together with the coronary sinus, a full venous circle.
and ends in a brachiocephalic node, usually on the left (Fig. 57.60).
(For further reading, see Loukas et al (2011).)
Inferior vein of the left ventricle The inferior vein of the left
ventricle (previously named as the posterior vein of the left ventricle)
lies on the diaphragmatic surface of the left ventricle, a little to the left INNERVATION
of the middle cardiac vein, and usually opens into the middle of the
coronary sinus, sometimes into the great cardiac vein (see Fig. 57.59).
Initiation of the cardiac cycle is myogenic, originating in the sinu-atrial
Rarely, the inferior vein of the left ventricle is absent, in which case the
node. It is harmonized in rate, force and output by autonomic nerves
left marginal vein drains most of the left ventricular wall.
that operate on the nodal tissues and their prolongations, on coronary
vessels and on the working atrial and ventricular musculature. All the
Oblique vein of the left atrium The diminutive oblique vein of
cardiac branches of the vagus (parasympathetic) and all the sympathetic
the left atrium descends obliquely on the posterior aspect of the left
branches (other than the cardiac branch of the superior cervical sym-
atrium to join the coronary sinus (see Fig. 57.59). It is continuous above
pathetic ganglion) contain both afferent and efferent fibres; the cardiac
with the ligament of the left vena cava; both structures are remnants of
branch of the superior cervical sympathetic ganglion is entirely efferent.
the left common cardinal vein.


Sympathetic fibres accelerate the heart and dilate the coronary arteries
Left marginal vein when stimulated, whereas vagal fibres slow the heart and cause coro-
The left (obtuse) marginal vein courses over the left oblique marginal nary arterial constriction.
surface of the heart, draining much of the left ventricular myocardium. Preganglionic cardiac sympathetic axons arise from neurones in the
It runs superficial to the marginal branch of the left coronary artery and intermediolateral column of the upper four or five thoracic spinal seg-
usually drains into the great cardiac vein, although may sometimes ments. Some synapse in the corresponding upper thoracic sympathetic
drain directly into the coronary sinus. ganglia, while others ascend to synapse in the cervical ganglia; postgan-
glionic fibres from these ganglia form the sympathetic cardiac nerves.
Anterior cardiac veins Preganglionic cardiac parasympathetic axons arise from neurones either
The anterior cardiac veins drain the anterior part of the right ventricle. in the dorsal vagal nucleus or near the nucleus ambiguus, and run in
Usually two or three, sometimes even five, they ascend in subepicardial vagal cardiac branches to synapse in the cardiac plexuses and atrial
tissue to cross the right part of the atrioventricular groove, passing deep walls. In humans (like most mammals), intrinsic cardiac neurones are
or superficial to the right coronary artery. They end in the right atrium, limited to the atria and interatrial septum, and are most numerous in
near the atrioventricular groove, separately or in variable combinations. the subepicardial connective tissue near the sinus and atrioventricular
A subendocardial collecting channel, into which all may open, has been nodes. The intrinsic ganglia are thought not to be simple nicotinic
described. relays, but may act as sites for the integration of extrinsic nervous inputs
and form complex circuits for the local neuronal control of the heart,
Right marginal vein
and perhaps even local reflexes.
The right marginal vein courses along the inferior (acute) cardiac
margin, draining adjacent parts of the right ventricle, and usually opens Cardiac plexus
separately into the right atrium, although it may join the anterior
cardiac veins or, less often, the coronary sinus. It is often grouped with


Nearing the heart, the autonomic nerves form a mixed cardiac plexus,
the small cardiac veins but it is larger in calibre, comparable to the
usually described in terms of a superficial component inferior to the
anterior cardiac veins or even wider.
aortic arch, lying between it and the pulmonary trunk, and a deep part
Small cardiac veins between the aortic arch and tracheal bifurcation. The cardiac plexus is
The existence of small cardiac (venae cordis minimae; Thebesian) veins, also described by regional names for its coronary, pulmonary, atrial and
opening into all cardiac cavities, has been confirmed but they are dif- aortic extensions (Fig. 57.61). Ganglion cells are largely confined to the
ficult to demonstrate. Their numbers and size are highly variable: vessels atrial tissues, with a preponderance adjacent to the sinu-atrial node, but
up to 2 mm in diameter open into the right atrium and ones as small some may also be found within the heart along the branches of the
as 0.5 mm in diameter open into the right ventricle, all with valveless plexuses. Their axons are considered to be largely, if not exclusively,
orifices. Numerous small cardiac veins have been identified in the right postganglionic parasympathetic. Cholinergic and adrenergic fibres,
atrium and ventricle but they are rarely found in the left side. Four types arising in or passing through the cardiac plexus, are distributed most
of Thebesian veins have been described: venoluminal veins drain profusely to the sinus and atrioventricular nodes; the supply to the atrial
directly into the cardiac chambers; venosinusoidal veins drain into and ventricular myocardium is much less dense. Adrenergic fibres
subendocardial sinusoids (which, in turn, drain into the cardiac cham- supply the coronary arteries and cardiac veins. Rich plexuses of nerves
bers); arterioluminal veins connect small arteries and arterioles directly containing cholinesterase, adrenergic transmitters and other peptides,
with the cardiac chambers; and arteriosinusoidal veins connect thin e.g. neuropeptide Y, are found in the subendocardial regions of all
arteries or arterioles with subendocardial sinusoidal spaces. chambers and within the valvular leaflets.


Cardiac venous anastomoses Superficial (ventral) part of the cardiac plexus The superficial
Widespread anastomoses occur at all levels of the cardiac venous circu- (ventral) part of the cardiac plexus lies inferior to the aortic arch and
lation, on a scale exceeding that of the arteries and amounting to a anterior to the right pulmonary artery. It is formed by the cardiac branch


HEART
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Right internal jugular vein Paratracheal lymph nodes Fig. 57.60 The cardiac
lymphatic system. (With
permission from Loukas,
M, Shah, S, Bhusnurmath
S, et al; A general outline
Left internal jugular vein
Right lymphatic duct of the cardiac lymphatic
system. In: The Cardiac
Lymphatic System,
Thoracic duct
Karunamuni, G (ed).
Springer. 2013.)
Right subclavian vein Left brachiocephalic vein
Right brachiocephalic vein
Posterior mediastinal
lymph nodes Posterior mediastinal
lymph nodes
Tracheobronchial
lymph nodes
Anterior mediastinal Anterior mediastinal
lymph nodes lymph nodes
Thoracic duct
Right sympathetic trunk Left sympathetic trunk Fig. 57.61 The cardiac plexus: its
source from the cervical parts of
the vagus nerves and sympathetic
Left vagus nerve trunks and its extensions, the
Right vagus nerve pulmonary, atrial and coronary
plexuses. Note the numerous
junctions between sympathetic and
Left recurrent laryngeal nerve
Right recurrent parasympathetic (vagal) branches
laryngeal nerve that form the plexus.
Left common carotid artery
Trachea
Oesophagus Left subclavian artery
Right recurrent laryngeal nerve Third thoracic sympathetic ganglion
Thoracic cardiac branch
of vagus nerve
Thoracic (sympathetic)
Brachiocephalic trunk cardiac branches
Thoracic cardiac branch
Thoracic (sympathetic) of vagus nerve
cardiac branches
Arch of aorta
Deep cardiac plexus
Superficial cardiac plexus
Left recurrent laryngeal nerve
Ligamentum arteriosum
Left pulmonary artery
Superior vena cava


Heart
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of the left superior cervical sympathetic ganglion and the lower of the onwards to form part of the right coronary plexus. Fibres passing pos-
two cervical cardiac branches of the left vagus. A small cardiac ganglion terior to the pulmonary artery supply a few filaments to the right atrium
is usually present in this plexus immediately below the aortic arch, to and then continue into the left coronary plexus. The left half of the deep
the right of the ligamentum arteriosum. This part of the cardiac plexus part of the cardiac plexus is connected to the superficial part; it supplies
connects with the deep part, the right coronary plexus and the left filaments to the left atrium and left anterior pulmonary plexus, and
anterior pulmonary plexus. forms much of the left coronary plexus.
Deep (dorsal) part of the cardiac plexus The deep (dorsal) part Left coronary plexus The left coronary plexus is larger than the
of the cardiac plexus lies anterior to the tracheal bifurcation, superior right and is formed mainly by the prolongation of the left half of the
to the point of division of the pulmonary trunk and posterior to the deep part of the cardiac plexus and a few fibres from the right half. It
aortic arch. It is formed by the cardiac branches of the cervical and accompanies the left coronary artery to supply the left atrium and
upper thoracic sympathetic ganglia, the vagus and recurrent laryngeal ventricle.
nerves. The only cardiac nerves that do not join it are those that join
the superficial part of the plexus. The deep plexus consists of right and Right coronary plexus The right coronary plexus is formed from
left halves; the right typically surrounds the brachiocephalic trunk, and both superficial and deep parts of the cardiac plexus. It accompanies
the left surrounds the aortic arch. The more dorsal (deep) aspect is the right coronary artery to supply the right atrium and ventricle.
larger than its more ventral (superficial) aspect on both sides. Branches
from the right half of the deep part of the cardiac plexus pass both Atrial plexuses The atrial plexuses are derivatives of the right and


anterior and posterior to the right pulmonary artery. Fibres passing left continuations of the cardiac plexus along the coronary arteries.
anterior to the pulmonary artery are more numerous; they supply a few Their fibres are distributed to the corresponding atria, overlapping those
filaments to the right anterior pulmonary plexus before continuing from the coronary plexuses.
Bonus e-book images and table
Fig. 57.5 Acute cardiac tamponade due to F, Transposition of the great arteries at 21 ventricular artery coursing along the anterior
ruptured aortic dissection. weeks’ gestation. interventricular groove, and the left
circumflex artery coursing in the left
Fig. 57.6 A, The subxiphoid approach in Fig. 57.35 A, Cardiac magnetic resonance atrioventricular groove.
pericardiocentesis. B, A mid-sagittal section angiography in a patient with a normal
of a cadaver. C, A cross-section of the heart. B, A cardiac magnetic resonance Fig. 57.51 A posterior oblique volume-
lower part of the thorax to show the angiogram from a patient with transposition rendered image showing the left anterior
relationships of the pericardial cavity with of the great arteries. ventricular artery coursing along the anterior
adjacent structures. D, Bedside cardiac interventricular groove, and the left
ultrasound performed in a 62-year-old male, Fig. 57.38 Measurements of the width and circumflex artery coursing in the left
demonstrating a large pericardial effusion height of the sinu-atrial node and the atrioventricular groove.
consistent with cardiac tamponade. distances of nodal tissue to epicardium and
endocardium, measured in cadaveric tissue. Fig. 57.53 A dissection of a cadaveric
Fig. 57.7 The typical appearance of a heart in which a large part of the anterior
pericardial cyst. Fig. 57.39 Histological sections of the nodal interventricular artery is covered by a
body. myocardial bridge.
Fig. 57.8 Congenital absence of the
pericardium. Fig. 57.40 Histological sections showing the Fig. 57.54 A left coronary angiogram in left


features of (A) the atrioventricular (AV) node lateral projection, showing a large, tortuous
Fig. 57.11 The fundamental differences and (B) the penetrating atrioventricular vessel arising from the proximal circumflex
between describing the heart according to bundle. branch of the left coronary artery and
the conventional (A) or the attitudinally anastomosing with the bronchial artery,
correct (B) orientation. Fig. 57.43 The right coronary sinus, which goes on to supply the lower lobe of
revealing a coronary orifice for the right the left lung.
Fig. 57.15 An inferior view of a cadaveric coronary artery and a coronary orifice for
heart, demonstrating an exaggerated the conal artery. Fig. 57.55 A right coronary angiogram
Eustachian valve occupying a significant showing several branches of the right
portion of the lumen of the inferior vena Fig. 57.44 A variation of the anulus of coronary artery.
cava. Vieussens.
Fig. 57.56 A left coronary angiogram
Fig.57.16 Chiari’s network. Fig. 57.46 Normal ECG-gated CT anatomy showing several branches of the left
of the right coronary artery and its branches. coronary artery.
Fig. 57.31 A histological section through
one of the coronary aortic sinuses to Fig. 57.47 Normal ECG-gated multidetector Fig. 57.57 A, A left coronary angiogram
demonstrate the way in which ventricular row CT anatomy of the right coronary artery showing a stent placement within the
muscle supports the transition from the and its branches. anterior interventricular artery. B, After stent
fibroelastic wall of the sinus to the tissues of placement (and once the contrast medium
the leaflet. Fig. 57.48 Normal ECG-gated multidetector has filled the coronary arterial tree), the
row CT anatomy of the right coronary artery anterior interventricular artery shows no
Fig. 57.34 A, Tricuspid atresia at 21 weeks’ and its branches. evidence of stenosis.
gestation. B, An atrioventricular septal
defect at 20 weeks’ gestation. C, Fig. 57.49 Normal ECG-gated multidetector Fig. 57.58 A coronary artery fistula in a


Hypoplastic left heart syndrome at 32 row CT anatomy of the left coronary artery 54-year-old woman with palpitations.
weeks’ gestation. D, Hypoplastic left heart and its branches.
syndrome at 32 weeks’ gestation. E, Table 57.1 Patterns of cardiac collateral
Tetralogy of Fallot at 33 weeks’ gestation. Fig. 57.50 An anterior oblique volume- arteries.
rendered image showing the left anterior


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Kortelainen ML 1997 Adiposity, cardiac size and precursors of coronary Sánchez-Quintana D, Pizarro G, López-Mínguez JR et al 2013 Standardized
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violent deaths. Int J Obes Relat Metab Disord 21:691–7. Transl Res 6:124–44.
Loukas M, Abel N, Tubbs RS et al 2011 The cardiac lymphatic system. Clin Spicer DE, Anderson RH 2013 Methodological review of ventricular
Anat 24:684–91. anatomy – the basis for understanding congenital cardiac malforma-
Loukas M, Bilinsky E, Bilinsky S et al 2014a The anatomy of the aortic root. tions. J Cardiovasc Transl Res 6:145–54.
Clin Anat 27:748–56. Uysal F, Bostan OM, Semizel E et al 2014 Congenital anomalies of coronary
Loukas M, Groat C, Khangura R et al 2009 The normal and abnormal arteries in children: the evaluation of 22 patients. Pediat Cardiol
anatomy of the coronary arteries. Clin Anat 22:114–28. 35:778–84.


CHAPTER
58
Great vessels
pulmonary trunk atretic, small or even normal in size, making diagnosis
MAJOR BLOOD VESSELS
challenging. A diminished pulmonary flow is supplied through a patent
ductus arteriosus (Smith and McKay 2004), and a concomitant ven-
The major blood vessels are the pulmonary trunk, the thoracic aorta tricular septal defect may permit outflow from the right ventricle. Surgi-
and its branches, and the superior and inferior venae cavae and their cal repair is necessary to allow adequate oxygenation throughout the
tributaries. body.
In truncus arteriosus, a single arterial trunk exits the heart and sub-
sequently divides into the pulmonary trunk and the aorta. Early neo-
ARTERIES
natal life is possible because there is usually a coexisting ventricular
septal defect; expedited surgical repair is necessary to avoid congestive
Pulmonary trunk
heart failure, failure to thrive and death.
Right and left pulmonary arteries
The pulmonary trunk, or pulmonary artery, conveys deoxygenated
blood from the right ventricle to the lungs. About 5 cm in length and The pulmonary arteries are described on page 959.
3 cm in diameter, it is the most anterior of the cardiac vessels and arises
from the pulmonary anulus surrounding the subpulmonary infundibu- Thoracic aorta
lum at the base of the right ventricle, superior and to the left of the
supraventricular crest. It slopes posterosuperiorly, at first anterior to the
Ascending aorta
ascending aorta and then to its left; at the level of the fifth thoracic
vertebra, inferior to the aortic arch at the left of the midline, it divides The ascending aorta is typically 5 cm long. It originates at the base of
into right and left pulmonary arteries, of almost equal size. The bifurca- the left ventricle, level with the inferior border of the third left costal
tion of the pulmonary trunk lies anteroinferior and to the left of the cartilage, and ascends obliquely, curving anteriorly and to the right, and
tracheal bifurcation and its associated inferior tracheobronchial lymph passing from posterior to the left half of the sternum to the level of the


nodes and deep cardiac plexus. In the fetus, at the level of the bifurca- superior border of the second left costal cartilage. In children, the diam-
tion, the pulmonary artery is connected to the aortic arch by the ductus eter of the thoracic aorta correlates most closely with body surface area
arteriosus. (Kervancioglu et al 2006, Kaiser et al 2008).
Relations The pulmonary artery is entirely within the pericardium, Relations The ascending aorta lies within the fibrous pericardium,
enclosed with the ascending aorta in a common tube of visceral peri- enclosed in a tube of serous pericardium together with the pulmonary
cardium. The fibrous pericardium gradually disappears within the trunk (see Figs 57.3, 57.4A–C). The infundibulum, initial segment of
adventitia of the pulmonary arteries. Anteriorly, it is separated from the the pulmonary trunk and right appendage are anterior to its lower
sternal end of the left second intercostal space by the pleura, left lung part. Superiorly, it is separated from the sternum by the pericardium,
and pericardium. Posterior relations are the ascending aorta and left right pleura, anterior margin of the right lung, loose areolar tissue and
coronary artery initially, then the left atrium. The ascending aorta ulti- the thymus or its remnants. The left atrium, right pulmonary artery and
mately lies on its right. The appendage and coronary artery lie on each principal bronchus are posterior. The superior vena cava and right
side of its origin. The superficial cardiac plexus lies between the pulmo- atrium, the former partly posterior, are to the right. The left atrium and,
nary bifurcation and the aortic arch. The tracheal bifurcation, lymph more superiorly, the pulmonary trunk are to the left. At least two aort-
nodes and nerves are superior, bilateral and to the right. icopulmonary bodies lie between the ascending aorta and the pulmo-
nary trunk. The inferior aorticopulmonary body is near the heart and
Variations and congenital conditions The pulmonary trunk is anterior to the aorta, and the middle aorticopulmonary body is near


a relatively constant structure and there are minimal variations in the right side of the ascending aorta.
healthy individuals. Congenital anomalies include pulmonary atresia The aortopulmonary window is a space between the pulmonary
and truncus arteriosus. artery and aortic arch, bordered by the ascending aorta anteriorly, the
The coronary arteries usually originate from within the aortic sinuses, descending aorta posteriorly, the mediastinal pleura laterally and the
but occasionally may arise from ectopic locations. Most commonly, an left principal bronchus medially (Deutsch and Savides 2005) (Fig.
ectopic left coronary artery arises from the pulmonary trunk or one of 58.3). It contains lymph nodes, fatty tissue, the ligamentum arteriosum
its branches (Bland–White–Garland syndrome). This potentially fatal and the left recurrent laryngeal nerve.
condition requires urgent surgical correction because the myocardium
Aortic arch
is supplied with pulmonary blood instead of systemic blood (Loukas
et al 2009). Infantile symptoms include pallor, fatigue, irritability, weak The aortic arch continues from the ascending aorta (see Figs 57.3,
cry, cough, dyspnoea, and signs of ischaemia and cardiac failure pre- 57.4A–C). Its origin, slightly to the right, is level with the superior
cipitated by feeding, bowel movements or crying. The electrocardio- border of the right second sternocostal joint. The arch first ascends
gram may reveal deep narrow Q waves, left ventricular hypertrophy and diagonally and posteriorly to the left over the anterior surface of the
left axis deviation. Radiologically, cardiomegaly is present with left trachea, then posteriorly across its left side, finally descending to the
ventricular and left atrial enlargement. Colour flow imaging can identify left of the fourth thoracic vertebral body, continuing as the descending
the anomalous origin of the left coronary artery. The pulmonary trunk thoracic aorta. It terminates level with the sternal end of the left second
may also give rise to the right coronary artery, the left interventricular costal cartilage and so lies wholly within the superior mediastinum. It
(anterior descending) coronary artery, or even both coronary arteries. curves around the hilum of the left lung, and extends superiorly to the


Typically, there is a large development of collateral vessels in the heart midlevel of the manubrium of the sternum.
(Figs 58.1–58.2). The shadow of the arch is easily identified in frontal chest radio-
Pulmonary atresia is caused by a complete obstruction of pulmonary graphs; its left profile is sometimes called the aortic ‘knuckle’ or ‘knob’
outflow and may be due to an absence or defect of the pulmonary (see Fig. 56.16). There may also be an ‘aortic nipple’ (the shadow of
valvular leaflets. It is associated with a blind-ending pulmonary trunk the adjacent left superior intercostal vein crossing posteroanteriorly to
1024 that causes right ventricular hypoplasia. Reduced flow may render the its left). The aortic arch is best visualized in left anterior oblique views


Great vessels
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RETPAHC
Pulmonary valve Left coronary artery orifice Anterior interventricular artery
Tricuspid valve
Fig. 58.1 A case of a left anterior interventricular artery arising from the
pulmonary trunk. (Courtesy of Professor Loukas. With permission from
Loukas M, Groat C, Khangura R, Owens DG, Anderson R. The normal
and abnormal anatomy of the coronary arteries. Clinical Anatomy. 2009;
22: 114–128.)


GREAT vEssEls
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7
NOITCEs
A
A PA
PA
A B
A
PPAA
A
PA
*
C D
A
PA
Fig. 58.2 Bland–White–Garland syndrome in a 29-year-old woman. A, A
preoperative anterior oblique volume-rendered (VR) image shows a dilated
right coronary artery (arrow) and the anterior interventricular artery with
multiple collateral vessels at the right ventricular wall (arrowheads).
B–C, Preoperative VR images (cardiac chambers removed with manual
editing) clearly demonstrate the anomalous origin of the left coronary artery
(long arrow) from the pulmonary trunk, along with multiple collateral
vessels within the interventricular septum (short arrows in B) and the
dilated right coronary artery (short arrow in C). D–E, Postoperative VR
images, obtained after ligation of the original os of the left coronary artery
from the pulmonary trunk and creation of an anastomosis between the left
internal thoracic artery (short white arrows) and the left coronary artery
* (long white arrow), demonstrate a decrease in the size of the right coronary
artery (black arrow) and markedly diminished collateral vessels in the
interventricular septum and right ventricular wall (*). Abbreviations: A, aorta;
PA, pulmonary artery. (With permission from Kim SY, Seo JB, Do KH, et al
2006 Coronary artery anomalies: classification and ECG-gated multi
E detector row CT findings with angiographic correlation. Radiographics
26:317–33; discussion 333–4.)


Major blood vessels
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AP window Pneumomediastinum and aortic nipple
Available with the Gray’s Anatomy e-book
Variations of the arch The summit of the arch is usually about
2.5 cm inferior to the sternal notch but may diverge from this. In the
infant, it is closer to the superior border of the sternum; the same is
often the case in senescence as a result of vascular ectasia/unfolding.
In a right-sided aortic arch, the aorta curves over the right pulmonary
hilum and descends to the right of the vertebral column; this is usually
associated with transposition of the thoraco-abdominal viscera. Less
often, after arching over the right hilum, the aorta may pass posterior
to the oesophagus to gain its position (this is not accompanied by
visceral transposition). The presence of a right-sided arch is of relevance
to the paediatric surgeon who is planning repair of oesophageal atresia
in neonates.
The aorta may divide into ascending and descending trunks, the
former dividing into three branches to supply the head and upper
limbs. It may divide near its origin, producing a double aortic arch; the
two branches soon reunite and the oesophagus and trachea usually pass
through the interval between them. If the aorta, ductus arteriosus or
descending aorta entraps the oesophagus and/or trachea, this is referred
A to as a vascular ring.
AP window Branches and variations Three branches arise from the convex
aspect of the arch: the brachiocephalic trunk, left common carotid and
left subclavian arteries (see Figs 57.3–57.4). They may branch from the
beginning of the arch or the superior part of the ascending aorta. The
distance between these origins varies, the most frequent being approxi-
mation of the left common carotid artery to the brachiocephalic trunk.
Other branches may arise from the aortic arch, including the inferior
thyroid, thyroidea ima, thymic, left coronary and bronchial arteries
(Bergman et al 1988).
Coarctation of the aorta The aortic lumen is occasionally partly
or completely obliterated, either above (preductal or infantile type),


opposite or just beyond (postductal or adult type), the entry of the
ductus arteriosus. In the preductal type, the length of coarctation is
variable, aortic arch hypoplasia is common, and the left subclavian and
even the brachiocephalic trunk may be involved. Severe forms of infan-
tile coarctation and its extreme form (aortic interruption) may be patent
B ductus arteriosus-dependent, as there is no time for effective collateral
circulation to develop. Prostaglandin infusion prior to transfer, and
surgery at a tertiary centre often provide a very good mid- to long-term
Fig. 58.3 The aortopulmonary (AP) window. A, A posteroanterior (PA)
outlook for such infants.
chest radiograph. B, A coronal computed tomography (CT) scan
The postductal type of coarctation has been attributed to abnormal
reconstruction.
extension of the ductal tissue into the aortic wall, stenosing both
vessels as the duct contracts after birth. This form may permit years of
on angiography and with equivalent computed tomography (CT) normal life, allowing the development of an extensive collateral circu-
reconstruction planes; the pulmonary trunk and its left branch may be lation to the aorta distal to the stenosis (Figs 58.6–58.7). High vascu-
discerned nestling inferiorly in its concavity. The diameter of the arch larity of the thoracic wall is important and clinically characteristic;
initially matches that of the ascending aorta but is significantly reduced many arteries arising indirectly from the aorta proximal to the coarcta-
distal to the origin of the great vascular branches. The aortic isthmus, a tion segment anastomose with vessels connected with it distal to the
small stricture at the border with the descending thoracic aorta, may block, and all of these vessels become greatly enlarged. Thus, in the
be followed by a dilation; in the fetus, the isthmus lies between the anterior thoracic wall, the thoraco-acromial, lateral thoracic and sub-
origin of the left subclavian artery and the opening of the ductus scapular arteries (from the axillary artery), the suprascapular artery


arteriosus. (from the subclavian artery) and the first and second posterior inter-
costal arteries (from the costocervical trunk) anastomose with other
Relations The left mediastinal pleura is anterior and to the left of the posterior intercostal arteries, and the internal thoracic artery and its
arch. Deep to the pleura, the arch is crossed, in anteroposterior order, terminal branches anastomose with the lower posterior intercostal and
by the left phrenic nerve, left lower cervical cardiac branch of the vagus inferior epigastric arteries.
nerve, left superior cervical cardiac branch of the sympathetic trunk and Posterior intercostal arteries are always involved, and enlargement
the left vagus nerve (see Figs 57.3, 57.61). As the left vagus nerve crosses of their dorsal branches may eventually groove (‘notch’) the inferior
the arch, its recurrent laryngeal branch hooks below the vessel, to the margins of the ribs. The radiographic shadow of the enlarged left sub-
left and behind the ligamentum arteriosum, then ascends on the right clavian artery is also increased. Enlargement of the scapular vessels and
of the arch. The left superior intercostal vein ascends obliquely anteri- anastomoses may lead to widespread interscapular pulsation (easily
orly on the arch, superficial to the left vagus nerve, deep to the left appreciated with the palm of the hand, and sometimes heard on
phrenic nerve. The left lung and pleura separate all these from the auscultation).
thoracic wall. Posterior and to the right are the trachea and the deep
cardiac plexus, the left recurrent laryngeal nerve, oesophagus, thoracic Aortic aneurysm formation Degeneration of the aortic tunica
duct and vertebral column. Superiorly, the brachiocephalic trunk, left media and intimal dissection play a major role in the pathogenesis of
common carotid and subclavian arteries arise from its convexity, and aneurysms affecting the ascending aorta and arch. Smooth muscle cells
are crossed anteriorly near their origins by the left brachiocephalic vein. are lost and elastic fibres degenerate, producing cystic spaces in the


The pulmonary bifurcation, left principal bronchus, ligamentum arte- media, which then fill with mucoid material. The loss of these structural
riosum, superficial cardiac plexus and the left recurrent laryngeal nerve cells leads to weakening of the wall with progressive dilation. Ageing
are all inferior. The concavity of the aortic arch, best viewed from the and hypertension are major predisposing factors to cystic medial degen-
left, is the upper curved limit through which structures gain access to, eration and there is a strong link with cigarette smoking. Thoracic aortic
or leave, the hilum of the left lung. aneurysms are categorized by their location. A particular pattern of


Great vessels
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Pneumomediastinum is an encompassing term that describes the pres- Aortic arch Superior intercostal vein/aortic nipple
ence of air in the mediastinum. It may arise from a wide range of
pathological conditions or physiological states, e.g. penetrating trauma,
ruptured major airways or oesophagus, hyperventilation or distressed
ventilation such as acute asthma, periparturition or diabetic ketoacido-
sis. The ‘aortic nipple’ is the radiographic term used to describe a lateral
nipple-like projection from the aortic knuckle seen in a small number
of individuals that corresponds to the end-on appearance of the left
superior intercostal vein coursing anteriorly. It may be mistaken radio-
logically for lymphadenopathy or an intrapulmonary nodule/neoplasm.
Despite their relative independence, the aortic nipple is defined by new
contours in cases of pneumomediastinum, taking on an ‘inverted aortic
nipple’ appearance (Fig. 58.4). In this position, the inverted aortic
nipple may facilitate radiographic discrimination of pneumomediasti-
num from similar conditions. An aortic nipple has been shown to
precede pathological conditions such as venous obstruction in the supe-
rior and inferior vena cavae or left brachiocephalic vein, and has been
identified in conditions where venous flow through the left superior
intercostal vein is increased (e.g. portal hypertension and certain con-
genital venous anomalies).
There are several variants of this arrangement, of which the most
common are as follows: a right-sided aortic arch and upper portion of
the descending aorta pass anterior to the oesophagus and trachea, and
the ductus arteriosus passes posterior to the oesophagus into an aortic
diverticulum; a right-sided aortic arch and the upper portion of the
descending aorta pass anteriorly, and the ductus arteriosus is inserted
Pneumomediastinum Pleura
into the left subclavian artery, which arises as a fourth branch from the
aortic arch; a left-sided descending aorta is attached to a left-sided Fig. 58.4 A PA chest radiograph, anteroposterior view, showing the


ductus arteriosus anterior to the oesophagus, and a right-sided arch classic ‘aortic nipple’ in a patient with pneumomediastinum. A label is
added on the left to delineate the nipple-like appearance of the left
passes posteriorly; the right superior portion of the descending aorta
superior intercostal vein more clearly. (Courtesy of Professor Loukas. With
wraps around the oesophagus and the ductus arteriosus is right-sided;
permission from Walters A, Cassidy L, Muhleman M, Peterson A, Blaak C,
or the right upper portion of the aorta wraps around the oesophagus
Loukas M. Pneumomediastinum and the aortic nipple: the clinical
and the ductus arteriosus is left-sided (Bergman et al 1988).
relevance of the left superior intercostal vein. Clinical Anatomy 2013;
The right common carotid and subclavian arteries may arise sepa-
27:757–63.)
rately, in which case the latter often branches from the left end of the
arch distal to the left subclavian artery, and usually passes posterior to
the oesophagus as an aberrant right subclavian artery. When this artery
arises from a dilated portion of the descending aorta, the diverticulum Right common carotid artery Trachea RtRSA Oesophagus
of Kommerell, it is known as the lusoria artery (Fig. 58.5). It may
become aneurysmal and cause fatal haemorrhage during endoscopy. It
may form a vascular ring around the oesophagus and trachea, present-
ing in the neonate as a feeding disorder with failure to thrive.
The left vertebral artery may arise between the left common carotid
and the subclavian arteries.
A rare avian form has been reported in which the right common
carotid and subclavian arteries arise from the aortic arch, and the left
common carotid and subclavian arteries arise from the descending
aorta (Bergman et al 1988). Another rare avian form with two brachio-
cephalic trunks, the right trunk originating both common carotid arter-
ies, and the left trunk originating both subclavian arteries, has been
reported. Another rare order of the aortic branches is (in order from


right to left): the right subclavian artery, left subclavian artery, followed
by the right common carotid, and left common carotid arteries close
together – almost forming a common carotid trunk.
The aortic arch may also curve behind the oesophagus and trachea,
instead of in front, with variations in the aortic branches as well.
Another rare avian form reported is with both carotid arteries originat-
ing from the same stem, and a left subclavian artery originating from
the arch, while the right subclavian artery arises from the descending
aorta. One or more of the ductus arteriosi may remain patent.
Very rarely, external and internal carotid arteries arise separately, the Left common Right and left Left subclavian
common carotid artery being absent on one or both sides, or both carotid artery vertebral arteries artery
carotid arteries and one or both vertebral arteries may be separate Fig. 58.5 A dissection showing a left aortic arch that gives rise to a
branches. When a ‘right aorta’ occurs, the arrangement of its three common vertebral trunk and a retrotracheal right subclavian artery
branches is reversed and the common carotid arteries may have a single (RtRSA), also known as a lusoria artery. (Courtesy of Professor Loukas
trunk. Other arteries may branch from it: most commonly, one or both with permission from Loukas M, Louis RG Jr, Gaspard J, Fudalej M,
bronchial arteries and the thyroidea ima artery. Tubbs RS, Merbs W. A retrotracheal right subclavian artery in association
Associations also exist between thoracic aortic aneurysm and other with a vertebral artery and thyroidea ima. Folia Morphol (Warsz). 2006
connective tissue diseases such as homocysteinuria and Ehlers–Danlos Aug;65(3):236–41.)
syndrome. A genetic relation is seen in familial thoracic aortic aneurysm
syndrome (Baliga et al 2007). Rarely, aneurysms may occur as a result
of Takayasu’s arteritis, or infections within the aortic wall.


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Fig. 58.6 A cardiac magnetic resonance (MR) angiograph showing
three-dimensional reconstruction of a native aortic coarctation (arrow) in
an adult with extensive collateral flow. Note the marked dilation of the left
subclavian artery, supplying most of the collateral vessels, and mild aortic
arch hypoplasia. (Courtesy of Dr Raad Mohiaddin, Royal Brompton
Hospital, London.)
Fig. 58.7 The collateral circulation at MR angiography and phase-contrast
velocity-encoded cine MRI. The MR angiogram shows the intercostal
(short arrows) and internal thoracic (medium arrow) arteries, obtained in
a patient with a haemodynamically significant aortic coarctation (long
arrow). Note that the arteries appear enlarged. (With permission from Hom
JJ, Ordovas K, Reddy GP. Velocity-encoded cine MR imaging in aortic
coarctation: functional assessment of hemodynamic events.
Radiographics 2008 Mar–Apr;28(2):407–16.)


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aortic root involvement is seen in those with Marfan’s syndrome, diaphragm. The vertebral column and hemiazygos veins are posterior.
known as anulo-aortic ectasia (Baliga et al 2007). Descending aortic Posterior to the right are the azygos vein and thoracic duct, and inferi-
aneurysms are generally caused by atherosclerosis (90%); the remainder orly, the right pleura and lung; the pleura and lung are to the left. The
result from mycotic disease or trauma. oesophagus with its plexus of nerves is located laterally and to the right
Some aortic aneurysms are incidental findings on chest films or CT in the upper thorax, anteriorly in the lower thorax and descends to a
studies. Symptomatic cases present with breathlessness, unbearable left anterolateral position when it reaches the diaphragm. To a limited
chest and back pain, hoarse voice, cough and haemoptysis. Early diasto- degree, the descending aorta and oesophagus are mutually spiralized.
lic murmurs caused by aortic regurgitation may be audible. Repair is Occasionally, the aorta enters the diaphragm to the left and behind the
carried out in patients with symptoms or fusiform dilation measuring oesophagus (Berdjas and Turina 2011).
more than 5 cm in diameter.
Aneurysms may also occur in an aberrant right subclavian artery and Surface anatomy The descending thoracic aorta may be projected
may or may not involve the diverticulum of Kommerell, leading to as a 2.5 cm broad band from the sternal end of the second left costal
dysphagia and even tracheal compression. Inadvertent rupture may cartilage to a median position 2 cm above the transpyloric plane at the
occur during endoscopy because of its retro-oesophageal position. first lumbar vertebra.
Aortic dissection Branches
The thoracic aorta provides visceral branches to the pericardium,
Available with the Gray’s Anatomy e-book lungs, bronchi and oesophagus, and parietal branches to the thoracic
wall.
Aortopulmonary paraganglia Pericardial branches A few small vessels are distributed to the
posterior aspect of the pericardium.


Aortopulmonary paraganglia (aortic bodies) belong to the branchio-
meric category of paraganglia. They are chemoreceptors and respond to Bronchial arteries Bronchial arteries vary in number, size and
changes in arterial gas concentrations such as lowered pO, increased origin. There is usually only one right bronchial artery; it arises from
2
pCO and increased hydrogen ion concentration. These microscopic either the third posterior intercostal or the upper left bronchial artery,
2
structures occur in several locations within the thorax: coronary para- and runs posteriorly on the right principal bronchus. Its branches
ganglia lie between the ascending aorta and pulmonary trunk, either supply these structures, the pulmonary areolar tissue and the broncho-
anteriorly or posteriorly, adjacent to the aortic root; pulmonary para- pulmonary lymph nodes, pericardium and oesophagus. The left bron-
ganglia lie in the groove between the ductus arteriosus and the pulmo- chial arteries, usually two, arise from the thoracic aorta – the upper near
nary artery; and subclavian–supra-aortic paraganglia lie between either the fifth thoracic vertebra, the lower below the left principal bronchus
the right subclavian and right common carotid arteries or the left sub- – and run posterior to the left main bronchus; their branches are dis-
clavian and left common carotid arteries, or caudal to the left subclavian tributed as on the right.
artery, adjacent to the aortic arch.
Oesophageal branches Two or three bronchial arteries supply the
Brachiocephalic trunk (artery) thoracic portion of the oesophagus. In addition, two or three oesopha-
geal arteries that arise either anteriorly or from the right side of the aorta
supply the distal oesophagus (Norton et al 2008).
The brachiocephalic (innominate) artery (trunk), the largest branch of
the aortic arch, is 4–5 cm in length (see Fig. 57.4A,B). It arises from the
Mediastinal branches Numerous small vessels supply lymph
convexity of the arch posterior to the centre of the manubrium of the
nodes and areolar tissue in the posterior mediastinum.


sternum, and ascends posterolaterally to the right, at first anterior to
the trachea, then on its right. The brachiocephalic and left common
Phrenic branches Superior phrenic arteries arise from the lower
carotid arteries often share a common origin (Osborn 1998). It divides
thoracic aorta and are distributed posteriorly to the superior diaphrag-
into the right common carotid and subclavian arteries level with the
matic surface, anastomosing with the musculophrenic and pericardi-
upper border of the right sternoclavicular joint.
acophrenic arteries.
Relations Sternohyoid and sternothyroid, thymic remnants, left
Posterior intercostal arteries The posterior intercostal arteries
brachiocephalic and right inferior thyroid veins, crossing its root,
and their branches are described on page 943.
and sometimes the right cardiac branches of the vagus nerve, all sepa-
rate the brachiocephalic trunk from the manubrium. Posterior are the
Subcostal arteries Subcostal arteries are the last paired branches of
trachea (superiorly) and the right pleura (inferiorly). The right vagus
the thoracic aorta, in series with the posterior intercostal arteries and
nerve is posterolateral before passing lateral to the trachea. On its right
inferior to the twelfth ribs. Each runs laterally anterior to the twelfth
side are the right brachiocephalic vein and the upper part of the supe-
thoracic vertebral body and posterior to the splanchnic nerves, sympa-
rior vena cava and pleura, and on its left side are thymic remains, the
thetic trunk, pleura and diaphragm. The right subcostal artery is also
origin of the left common carotid artery, the inferior thyroid veins and
posterior to the thoracic duct and azygos vein, while the left is posterior
the trachea.
to the accessory hemiazygos vein. Each artery enters the abdomen at
the lower border of the twelfth rib, accompanied by the twelfth thoracic
Branches The brachiocephalic trunk usually has only terminal
(subcostal) nerve, lying posterior to the lateral arcuate ligament and
branches, the right common carotid and subclavian arteries. Occasion-


kidney, and anterior to quadratus lumborum. The right artery courses
ally, a thymic or bronchial branch, or a thyroidea ima artery arise from
posterior to the ascending colon, and the left courses posterior to the
it. The thyroidea ima artery is a small and inconstant artery that may
descending colon. Piercing the aponeurosis of transversus abdominis,
arise from the aorta, right common carotid, subclavian or internal
each subcostal artery proceeds between this and internal oblique, and
thoracic arteries; it ascends on the trachea to the thyroid isthmus, where
anastomoses with the superior epigastric, lower posterior intercostal
it terminates.
and lumbar arteries. Each has a dorsal branch, distributed like those of
the posterior intercostal arteries.
Descending thoracic aorta
Aberrant artery A small artery sometimes leaves the descending
The descending aorta is the segment of the thoracic aorta that is con- thoracic aorta on its right near the right bronchial artery origin. It
fined to the posterior mediastinum (see Figs 56.1–56.2, 56.6–56.7B, ascends to the right behind the trachea and oesophagus, and may anas-
56.13–56.14A, 56.19D,E). It begins level with the lower border of the tomose with the right superior intercostal artery. It is a vestige of the
fourth thoracic vertebra, continuous with the aortic arch, and ends right dorsal aorta and, occasionally, it is enlarged as the first part of a
anterior to the lower border of the twelfth thoracic vertebra in the aortic right subclavian artery.
hiatus. At its origin, it is left of the vertebral column; as it descends, it
reaches and terminates in the midline. Aortic rupture in trauma Rupture of the ascending aorta is usually
associated with a high immediate mortality (Baliga et al 2007). Blunt
Relations Anterior to the descending thoracic aorta, from superior to aortic rupture commonly occurs in road traffic accidents and has a 20%


inferior, are the left pulmonary hilum, the pericardium separating it survival rate. There is usually a transverse tear involving the tunica
from the left atrium, oesophagus and the vertebral portion of the intima and tunica media of the aortic wall; systemic circulatory pressure


Great vessels
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Aortic dissection occurs as a result of degeneration of the tunica media Aortic dissections are classified as types I, II, IIIa and IIIb (De Bakey
of the aortic wall and is associated with senescence, persistent hyperten- classification), or types A and B (Stanford classification). Dissections
sion or collagen vascular diseases such as Marfan’s syndrome. Many that are proximal to the left subclavian artery, with or without distal
patients with aortic dissection have a pre-existing aneurysm. Other extension, are classified as type I, II or A. Type I may involve the entire
associations include aortic coarctation, Turner’s syndrome, cocaine aorta, whereas type II involves the ascending aorta only. Dissections
abuse (<1%) and trauma during surgical procedures. There is a higher that are distal to the left subclavian artery are classified as type IIIa
prevalence in men than women; after the age of 75, however, there is (involve the distal aorta up to the diaphragm), IIIb (extend below the
no sex difference (Baliga et al 2007). In a classic aortic dissection, an diaphragm) or B. These cases present acutely with severe retrosternal,
intimal tear may occur, producing a split into the tunica media that neck or interscapular chest pain. Depending on the extent of the dis-
creates a false lumen (Fig. 58.8). If another tear occurs, connection can section, they may be associated with neurological signs, diarrhoea or
be made once again with the true lumen (the double-barrel aorta). leg weakness. Extension into the pericardium causes cardiac tamponade
Additional aetiopathologies include penetrating atherosclerotic ulcera- and circulatory collapse. Diagnosis is established by echocardiography
tion, where an atherosclerotic plaque ruptures into the aortic tunica and on contrast-enhanced CT or magnetic resonance imaging (MRI).
media, and aortic intramural haematoma, where the vasa vasorum Medical management is possible for descending aortic dissections,
haemorrhage into the wall of the aorta (Baliga et al 2007). while surgical repair is essential for ascending aortic or aortic arch
dissection.
A B
C D E


Fig. 58.8 A Stanford type A aortic dissection. A–B, Axial images taken through the thorax. A, Dissection flap involvement of the aortic root and
descending aorta. B, The dissection flap in the aortic arch. C–E, A type A aortic dissection in a different patient. C–D, Sagittal reformatted images
through the thorax and upper abdomen obtained at different levels from 64-slice multi-detector CT demonstrating intimal flap involvement of the
ascending thoracic aorta. Note the extension of the dissection flap into aortic branch vessels (arrow). E, A sagittal maximum-intensity projection image
showing dissection flap involvement of both the ascending and descending aorta. (With permission from McMahon MA, Squirrell CA. Multidetector CT of
Aortic Dissection: A Pictorial Review. Radiographics. 2010 Mar;30(2):445–60.)


Major blood vessels
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RETPAHC
may cause the formation of a false aneurysm. Rupture of the isthmus VEINS
region of the descending aorta is more common probably because it
marks the junction between the mobile and fixed portions of the aorta. Brachiocephalic veins
Other sites include the ascending aorta proximal to the origin of the
brachiocephalic trunk, the aortic arch and the abdominal aorta. Rupture
The right and left brachiocephalic veins join to form the superior
is likely to be the result of a number of factors, including torsion, shear
vena cava.
and stretching forces, possibly compounded by hydrostatic pressure.
Right brachiocephalic vein
Aortic atherosclerosis or calcification Echocardiography, par-
The right brachiocephalic vein is about 2.5 cm long. It arises posterior
ticularly trans-oesophageal, allows very detailed assessment of proximal
to the sternal end of the right clavicle and descends almost vertically to
aortic atherosclerosis implicated in systemic embolic events and strokes.
join the left brachiocephalic vein, forming the superior vena cava pos-
The extent of turbulent flow may be documented. MRI may also allow
terior to the inferior border of the first right costal cartilage, near the
an accurate assessment of the composition and size of atherosclerotic
right sternal border. It is anterolateral to the brachiocephalic trunk and
plaques and flow dynamics, permitting assessment of the risk of plaque
right vagus nerve; the right pleura, phrenic nerve and internal thoracic
rupture and thrombus formation.
artery are initially posterosuperior, becoming lateral inferiorly (see Fig.
29.14). Its tributaries are the right vertebral, internal thoracic and infe-
Subclavian arteries rior thyroid veins, and sometimes the first right posterior intercostal
veins.
Right subclavian artery
Left brachiocephalic vein
The right subclavian artery arises from the brachiocephalic trunk, origi-
nating posterior to the upper border of the right sternoclavicular joint The left brachiocephalic vein is about 6 cm long, over twice the length


(see Fig. 51.2). It ascends superomedial to the clavicle and posterior to of the right. It arises posterior to the sternal end of the left clavicle,
scalenus anterior, then descends laterally to the outer border of the first anterior to the cervical pleura, and descends obliquely to the right,
rib, where it becomes the axillary artery. posterior to the superior half of the manubrium sterni, reaching the
sternal end of the first right costal cartilage where it joins the right
Left subclavian artery brachiocephalic vein to form the superior vena cava (see Fig. 29.14). It
is separated from the left sternoclavicular joint and manubrium by
In the majority of individuals, the left subclavian artery originates inde-
sternohyoid and sternothyroid, the thymus or its remnants, and areolar
pendently from the aortic arch after the origins of the brachiocephalic
tissue; terminally, it is overlapped by the right pleura. It crosses anterior
and left common carotid arteries (see Fig. 57.4). It rises into the neck
to the left internal thoracic, subclavian, brachiocephalic and common
lateral to the medial border of scalenus anterior, crosses posterior to
carotid arteries, left phrenic and vagus nerves, and the trachea. The
this muscle and then descends towards the outer border of the first rib,
aortic arch is inferior to it. Its tributaries are the left vertebral, internal
where it becomes the left axillary artery. A common origin occasionally
thoracic, inferior thyroid and superior intercostal veins, and sometimes
exists between the left subclavian and vertebral arteries. Rarely, there are
the first left posterior intercostal, thymic and pericardial veins.
bilateral brachiocephalic trunks, which subsequently divide on both
In children, the length and diameter of the left brachiocephalic vein
sides into common carotid and subclavian arteries.
are closely related to height; the diameter reaches adult dimensions at


Relations In the thorax, the left subclavian artery is related anteri- the age of 10 years (Figs 58.9–58.10) (Sanjeev and Karpawich 2006).
orly to the left common carotid artery and left brachiocephalic vein,
Superior vena cava
from which it is separated by the left vagus, cardiac and phrenic
nerves. More superficially, the anterior pulmonary margin, pleura,
sternothyroid and sternohyoid lie between the vessel and the upper The superior vena cava returns blood to the heart from the tissues above
left area of the manubrium of the sternum. On the left side of the the diaphragm. It is approximately 7 cm in length, and is formed by the
oesophagus, the thoracic duct and longus colli are posterior. The left junction of the brachiocephalic veins posterior to the lower border of
subclavian artery is in contact posterolaterally with the left lung and the first right costal cartilage. It descends vertically, posterior to the first
pleura. The trachea, left recurrent laryngeal nerve, oesophagus and and second intercostal spaces, and drains into the upper right atrium
thoracic duct are medial. Laterally, the artery grooves the mediastinal posterior to the third right costal cartilage. Its inferior half is within the
surface of the left lung and pleura, which also encroach on its anterior fibrous pericardium, which it pierces level with the second costal carti-
and posterior aspects. lage. Covered anterolaterally by serous pericardium (from which a ret-
rocaval recess projects), it is slightly convex to the right (see Figs 57.3,
57.4A,B, 57.12, 29.14). The superior vena cava is valveless. In children,
Common carotid arteries
the length and diameter of the superior vena cava are also closely related
to height; the diameter reaches adult dimensions at the age of 10 years
The right and left common carotid arteries differ in their length and (see Figs 58.9–58.10) (Sanjeev and Karpawich 2006).
origin. The right is exclusively cervical and arises from the brachio-


cephalic trunk posterior to the right sternoclavicular joint. The left Relations The anterior margins of the right lung and pleura are ante-
originates directly from the aortic arch immediately posterolateral to rior and the pericardium intervenes below; these structures separate the
the brachiocephalic trunk and therefore has both thoracic and cervical superior vena cava from the right internal thoracic artery, first and
parts. second intercostal spaces, and second and third costal cartilages. The
trachea and right vagus nerve are posteromedial, the right lung and
Right common carotid artery
pleura are posterolateral, and the right pulmonary hilum is posterior.
The right common carotid artery and its relations are described in The right phrenic nerve and pleura are immediate right lateral relations
Chapter 29. and the brachiocephalic trunk and ascending aorta lie to the left, the
aorta overlapping the superior vena cava (see Fig. 55.7).
Left common carotid artery
The left common carotid artery (see Figs 57.4, 29.7) ascends until level Tributaries Tributaries of the superior vena cava are the azygos vein
with the left sternoclavicular joint, where it enters the neck. Its thoracic and small veins from the pericardium and other mediastinal structures
portion is 20–25 mm long and it lies first anterior to the trachea, then (see Fig. 56.7A).
inclines to the left. The further course of the artery is described in
Chapter 29. Superior vena cava obstruction Superior vena cava obstruction
is characterized by headaches, facial and neck venous congestion, and
Relations Sternohyoid and sternothyroid, the anterior parts of the left oedema, reflecting impaired venous drainage of the head, neck and
pleura and lung, the left brachiocephalic vein and the thymic remnants arms, and of the collateral circulation, resulting in chest wall telangiecta-
are anterior and separate the left common carotid artery from the sia. Several of the symptoms may subside with recumbency, or may be
manubrium. The trachea, left subclavian artery, left border of the aggravated by standing up. The obstruction may be either partial or


oesophagus, left recurrent laryngeal nerve and thoracic duct are poste- complete, and may occur suddenly or gradually. It is usually caused by
rior. To the right are the brachiocephalic trunk (inferior) and the mediastinally invasive right upper lobe primary bronchogenic carci-
trachea, inferior thyroid veins and thymic remains (superior). To the noma or by metastatic involvement of the right paratracheal lymph
left are the left vagus and phrenic nerves, left pleura and lung. nodes.


Great vessels
1027.e1
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RETPAHC
A
B
C
D
Fig. 58.9 Sites of measurement of the left brachiocephalic (innominate)
vein and superior vena cava at angiography. Key: A, distal
brachiocephalic vein; B, mid-brachiocephalic vein; C, brachiocephalic–
superior vena cava junction; D, mid-superior vena cava. (Redrawn with
permission from Sanjeev S, Karpawich PP. Superior vena cava and
innominate vein dimensions in growing children: an aid for interventional
devices and transvenous leads. Pediatr Cardiol. 2006
Jul–Aug;27(4):414–9.)
18
16
14
12
10
Fig. 58.10 Diameters of the distal brachiocephalic (innominate) vein
(dis-INN), mid-brachiocephalic vein (mid-INN), brachiocephalic–superior
vena cava junction (INN-SVC) and mid-superior vena cava (mid-SVC) in
children of varying ages. (Redrawn with permission from Sanjeev S,
Karpawich PP. Superior vena cava and innominate vein dimensions in
growing children: an aid for interventional devices and transvenous leads.
Pediatr Cardiol. 2006 Jul–Aug;27(4):414–9.)
)mm(
sretemaiD
<2 yr
3–4 yr
5–8 yr
8
8–9 yr
6
10–12 yr
4
2
0
Dis-INN Mid-INN INN-SVC Mid-SVC


GREAT vEssEls
1028
7
NOITCEs
Haemorrhagic intrathoracic goitre, mediastinitis (either benign, malig- and central area of the central tendon of the diaphragm at the level of
nant or fibrous), mediastinal haematoma, constrictive pericarditis, the eighth and ninth thoracic vertebrae, and drains into the inferopos-
mediastinal cyst, thrombosis of the superior vena cava and sarcoidosis terior part of the right atrium (see Fig. 55.1, 57.4B). The thoracic part
are less common aetiologies. Radiographic findings might include wid- is very short, and is partly inside and partly outside the pericardial sac.
ening of the upper mediastinum on the frontal film or obliteration of The extrapericardial part is separated from the right pleura and lung by
the retrosternal space on the lateral film. Other correlative findings may the right phrenic nerve, and the intrapericardial part is covered, except
include pulmonary or mediastinal masses, lymphadenopathy, enlarged posteriorly, by inflected serous pericardium. The abdominal course of
or obliterated azygos venous system, pleural effusion or rib notching. the inferior vena cava is described in Chapter 62.
This is usually considered to be an oncological emergency and symp-
toms are often completely and promptly relieved by insertion of a Collateral venous channels In obstruction of the upper inferior
vascular stent via the common femoral vein or by radiotherapy to the vena cava, the azygos and hemiazygos veins and vertebral venous plex-
affected region after a tissue diagnosis is established. uses are the main collateral channels that maintain venous circulation.
They connect the superior and inferior venae cavae and communicate
Variations of the brachiocephalic veins and superior with the common iliac vein by the ascending lumbar veins and with
vena cava many tributaries of the inferior vena cava.
Available with the Gray’s Anatomy e-book Variations Broadly speaking, the inferior vena cava may be congeni-
tally interrupted, duplicated, left-sided or even absent.
Inferior vena cava
The inferior vena cava returns blood to the heart from infradiaphrag-
matic tissues. It passes through the diaphragm between the right leaf
Bonus e-book images


Fig. 58.1 A case of a left anterior trunk and a retrotracheal right subclavian Fig. 58.9 Sites of measurement of the left
interventricular artery arising from the artery, also known as a lusoria artery. brachiocephalic (innominate) vein and
pulmonary trunk. superior vena cava at angiography.
Fig. 58.6 A cardiac magnetic resonance
Fig. 58.2 Bland–White–Garland syndrome in angiograph showing three-dimensional Fig. 58.10 Diameters of the distal
a 29-year-old woman. reconstruction of a native aortic coarctation brachiocephalic (innominate) vein mid-
in an adult with extensive collateral flow. brachiocephalic vein, brachiocephalic–
Fig. 58.4 A PA chest radiograph, superior vena cava junction and
anteroposterior view, showing the classic Fig. 58.7 The collateral circulation at MR mid-superior vena cava in children of
‘aortic nipple’ in a patient with angiography and phase-contrast velocity- varying ages.
pneumomediastinum. encoded cine MR imaging.
Fig. 58.5 A dissection showing a left aortic Fig. 58.8 A Stanford type A aortic
arch that gives rise to a common vertebral dissection.


Great vessels
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The brachiocephalic veins may enter the right atrium separately, the Embryologically, if the right subcardinal vein fails to anastomose
right vein descending like a normal superior vena cava. During embryo- with the hepatic sinusoids, the hepatic segment of the inferior vena cava
logical development, if the cardinal vein does not become obliterated, fails to develop. When this occurs, the hemiazygos or azygos veins,
it will persist as a left-sided superior vena cava. A left superior vena cava which both originate from the cranial supracardinal veins, return blood
may have a slender connection with the right and then cross the left to the heart. Azygos continuation of the inferior vena cava, character-
side of the aortic arch to pass anterior to the left pulmonary hilum ized by a prominent azygos vein, is an entity of which the paediatric
before turning to enter the right atrium. It replaces the oblique vein of surgeon should be aware when undertaking repair of oesophageal
the left atrium and coronary sinus, and receives all the tributaries of atresia and tracheo-oesophageal atresia in neonates. The azygos vein,
the coronary sinus. The left brachiocephalic vein sometimes projects which is commonly ligated and divided during this procedure, should
above the manubrium (more frequently in childhood), and crosses the be spared because ligation of this vessel in neonates with azygos con-
suprasternal fossa in front of the trachea. A left-sided superior vena cava tinuation of the inferior vena cava leads to intraoperative circulatory
may cause difficulties when placing a cardiac catheter, pacing or defibril- collapse and death. Double inferior vena cava (right side usually domi-
lating electrodes because the angle between the left superior vena cava nant) is a result of the persistence of all or any segments of the subcar-
and the left subclavian vein is much more acute than that between the dinal veins. One of the most common variations is a left-sided inferior
subclavian and a normal left brachiocephalic vein. Its calibre may also vena cava, which is formed if the right supracardinal vein regresses and


be smaller than that of the right. Even if insertion of a catheter into a the left supracardinal vein persists. There may also be a duplication of
left superior vena cava is possible, the angle at which the catheter enters the inferior vena cava, which typically occurs below the renal veins, and
the right atrium causes difficulty when attempting to place it into the is the result of persistence of the left lumbar and thoracic supracardinal
right ventricle and pulmonary trunk; this generally leaves the catheter veins and left suprasubcardinal anastomosis as well as malformation of
tip against the coronary sinus, making it difficult to obtain blood right subcardinal–hepatic anastomosis. Abnormalities associated with
samples. In the majority of persistent left superior venae cavae, blood duplication of the inferior vena cava include: congenital heart disease,
drains into the right atrium via the coronary sinus. When this does not congenital absence of the right kidney, cloacal extrophy, renal ectopia
happen, the coronary sinus is absent, and the persistent left superior with abdominal aneurysm, right retrocaval ureter, left retrocaval ureter
vena cava drains directly into the atrium. Cyanosis reflects a persistent and congenital absence of the iliac anastomosis, abnormal left arm
right-to-left shunt and affected individuals have a higher risk for para- drainage and transcaval ureter.
doxical embolism. Radiographically, there is a paramediastinal bulge In situs inversus with dextrocardia, the inferior vena cava passes
before the aortic arch. Electrocardiograms show a left P-wave axis. Diag- inferiorly along the left side instead of the right (as opposed to situs
nosis can be confirmed by cardiac catheterization and angiography. inversus with levocardia, in which the inferior vena cava remains on
Persistent left superior vena cava may be associated with extracardiac the right side). In situs ambiguus, otherwise known as heterotaxy, the
conditions such as VACTERL association (vertebral defects, anal atresia, major organs are arranged ambiguously within the body. Prominent
cardiac malformations, tracheo-oesophageal fistula with oesophageal azygos veins with interrupted inferior vena cava are associated with


atresia, radial and renal dysplasia, and limb anomalies); trisomy 21; heterotaxy (Punn and Olson 2010). Situs ambiguus with polysplenia is
22q11; CHARGE association (coloboma, heart defects, choanal atresia, associated with an absence of portions of the inferior vena cava on the
mental retardation, genital and ear anomalies); and 45 XO karyotype right side (with continuation through the azygos or hemiazygos vein),
(Turner’s syndrome). transposition of the inferior vena cava to the left side, or duplication of
If the superior vena cava is duplicated, the right superior vena cava the inferior vena cava with one on the right and one on the left. Situs
may drain into the right atrium and the left superior vena cava into the inversus with asplenia is similar to that of polysplenia, in that the infe-
left atrium. Although double superior vena cava is largely asympto- rior vena cava may be absent with azygos continuation or with the
matic, it is usually (along with a sole left-sided superior vena cava) inferior vena cava to the left of the midline. In situs inversus totalis,
associated with congenital cardiac anomalies, such as pulmonary steno- transposition of the inferior vena cava consists of a right-sided inferior
sis, coarctation of the aorta, tetralogy of Fallot and atrial septal defects. vena cava. The inferior vena cava may have an abnormally high inser-
tion into the right atrium. Congenital agenesis of the inferior vena cava
may occur and may be completely asymptomatic because venous drain-
age of the lower limbs occurs through anastomosed channels of the
azygos and hemiazygos veins. That said, this condition may be associ-
ated with a higher risk for deep vein thrombosis.


GREAT vEssEls
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NOITCEs
REFERENCES
Baliga RR, Neinaber CA, Isselbacher EM et al 2007 Aortic Dissection and Norton JA, Barie PS, Bollinger RR et al 2008 Surgery: Basic Science and
Related Syndromes. Ann Arbor, MI: Springer. Clinical Evidence (2nd ed). New York: Springer.
Berdjas D, Turina MI 2011 Operative Anatomy of the Heart. Berlin: Springer. Osborn AG 1998 Diagnostic Cerebral Angiography. Philadelphia: Lippin-
Bergman RA, Thompson SA, Afifi AK et al 1988 Compendium of Human cott, Williams & Wilkins.
Anatomic Variation. Baltimore: Urban & Schwarzenberg. Punn R, Olson I 2010 Anomalies associated with a prominent azygos vein
Deutsch J, Savides TJ 2005 Normal Thoracic Anatomy in Digital Human on echocardiography in the pediatric population. J Am Soc Echocardi-
Anatomy and Endoscopic Ultrasonography. Hamilton, ON: BC Decker. ogr 23:282–5.
Kaiser T, Kellenberger CJ, Albisetti M et al 2008 Normal values for aortic Sanjeev S, Karpawich PP 2006 Superior vena cava and innominate vein
diameters in children and adolescents–assessment in vivo by contrast- dimensions in growing children: an aid for interventional devices and
enhanced CMR-angiography. J Cardiovasc Magn Reson 10:56. transvenous leads. Pediatr Cardiol 27:414–19.
Kervancioglu P, Kervancioglu M, Tuncer CM 2006 Echocardiographic study Smith A, McKay R 2004 A Practical Atlas of Congenital Heart Disease.
of aortic root diameter in healthy children. Saudi Med J 27:27–30. London: Springer.
Loukas M, Groat C, Khangura R et al 2009 The normal and abnormal
anatomy of the coronary arteries. Clin Anat 22:114–28.


COMMENTARY
Technical aspects and applications of
7.1
diagnostic radiology
Jonathan D Spratt
Magnetic resonance imaging tions for the treatment of reperfusion injury and research into the
physiology of solid tumours and angiogenesis. There is every reason to
believe that continued efforts to push the envelope of high-field-
Magnetic resonance imaging (MRI) produces images by first magnet-
strength applications will open new vistas in what appears to be a
izing a patient in the bore of a powerful magnet and then broadcasting
never-ending array of potential clinical applications.
short pulses of radiofrequency (RF) energy at 46.3 MHz that resonate
T1 weighted images best accentuate fat and other soft tissues,
mobile protons (hydrogen nuclei) in the fat, protein and water of the
whereas fluid is low-signal; these images are nicknamed the ‘anatomy
patient’s soft tissues and bone marrow. The protons produce RF echoes
weighting’ amongst radiologists who publish or teach anatomy. T2
when their resonant energy is released; their density and location can
weighted images reveal fluid as high signal as well as fat. Fat suppression
be exactly correlated into an image matrix by complex mathematical
sequences using T2 ‘fat sat’ (T2FS) or short tau inversion recovery (STIR)
algorithms.
are very sensitive in highlighting the soft tissue or bone marrow oedema
The spinning proton of the hydrogen nucleus acts like a tiny bar
that almost invariably accompanies pathological states such as inflam-
magnet, aligning either with or against the magnetic field, and produc-
mation or tumours. Contrast-enhanced images with gadolinium, when
ing a small net magnetic vector. RF energy from various types of coil,
used with T1 fat saturation (T1FS) sequences, also exquisitely highlight
either built into the scanner or attached to specific body parts, generates
hypervascularity, particularly that associated with tumours and inflam-
a second magnetic field perpendicular to the static magnetic field that
mation, especially in pathologies where the blood–brain barrier is com-
rotates or ‘flips’ the protons away from the static magnetic field. When
promised. Metallic artefact reduction sequences (MARS) are superior in
the RF pulse is switched off, the protons flip back (relax) to their origi-
imaging periprosthetic soft tissues after joint replacement or other


nal position of equilibrium, emitting the RF energy they had acquired
orthopaedic metalwork implantation.
into the antenna around the patient. This information is then ampli-
fied, digitized and spatially encoded by the array processor.
MR tractography
MRI systems are graded according to the strength of the magnetic
field they produce. Routine high-field systems are those capable of
producing a magnetic field strength of 3–7 T (Tesla), using a supercon- MRT is a three-dimensional modelling technique used to represent
ducting electromagnet immersed in liquid helium. Open magnets for neural tracts visually using data collected by DTI or, more recently, by
claustrophobic patients and limb scanners use permanent magnets of HARDI, with results presented in two- and three-dimensional images
0.2–0.75 T. For comparison, Earth’s magnetic field varies from 30 to (Nucifora et al 2007).
60 µT. MRI does not present any recognized biological hazard. Patients In addition to the long tracts that connect the brain to the rest of
who have any form of pacemaker or implanted electro-inductive device, the body, there are complicated neural networks formed by short con-
ferromagnetic intracranial aneurysm clips, certain types of cardiac valve nections among different cortical and subcortical regions, their exist-
replacement or intraocular metallic foreign bodies must never be exam- ence revealed by histochemistry and postmortem biological techniques.
ined because there is a high risk of death or blindness. Many extracra- Central nervous system tracts are not identifiable by direct examination,
nial vascular clips and orthopaedic prostheses are now ‘MRI-friendly’ CT or conventional MRI scans, explaining the paucity of their descrip-
but may cause local artefacts; newer sequences exist to reduce artefact. tion in neuroanatomy atlases and the poor understanding of their
Loose metal items, ‘MR-unfriendly’ anaesthetic equipment and credit functions.
cards must be excluded from the examination room. Pillows contain- The MRI sequences used look at the symmetry of water diffusion in
ing metallic coiled springs have been known nearly to suffocate the brain. Bundles of fibre tracts make the water diffuse asymmetrically
patients, and heavy floor buffing equipment has been found wedged in a ‘tensor’, the major axis parallel to the direction of the fibres. There


in the magnet bore because domestic staff had been suboptimally is a direct relationship between the number of fibres and the degree of
informed. anisotropy. DTI assumes that the direction of least restriction corre-
New methods of analysing normal and pathological brain anatomy sponds to the direction of white matter tracts. Diffusion MRI was intro-
are now at the forefront of research. These are MR spectroscopy (MRS); duced in 1985. In the more recent evolution of the technique into
functional MRI (fMRI); diffusion tensor imaging (DTI); high angular diffusion tensor MRI (DTI), the relative mobility of the water molecules
resolution diffusion imaging (HARDI) for MR tractography (MRT, see from the origin is modelled as an ellipsoid rather than a sphere. This
below); and molecular MRI (mMRI), which has taken on a new direc- allows full characterization of molecular diffusion in the three dimen-
tion since the description of the human genome. sions of space and the formation of tractograms. Barriers cause uneven
MRS assesses function within the living brain. It capitalizes on the anisotropic diffusion. In white matter, the principal barrier is the myelin
fact that protons residing in differing chemical environments possess sheath, whereas bundles of axons provide a barrier to perpendicular
slightly different resonant properties (chemical shift). For a given diffusion and a path for parallel diffusion along the orientation of the
volume of brain, the distribution of these proton resonances can be fibres. Anisotropic diffusion is expected to be increased overall in areas
displayed as a spectrum. Discernible peaks can be seen for certain neu- of high mature axonal order. Conditions where barriers offered by the
rotransmitters: N-acetylaspartate varies in multiple sclerosis, stroke and myelin sheaths or the axons are disrupted, e.g. in trauma, tumours and
schizophrenia while choline and lactate levels have been used to evalu- inflammation, reduce anisotropy and yield DTI data used to seed
ate certain brain tumours. various tractographic assessments of the brain (p. 391). Data sets may
fMRI depends on the fact that haemoglobin is diamagnetic when be rotated continuously into various planes in order to appreciate the
oxygenated but paramagnetic when deoxygenated. These different structure better; colour may be assigned based on the dominant direc-


signals can be weighted to the smaller vessels, and hence closer to the tion of the fibres. A leading clinical application of MRT is in the
active neurones, by using larger magnetic fields. mMRI uses biomarkers presurgical mapping of eloquent regions. Intraoperative electrical stim-
that interact chemically with their surroundings and alter the image ulation (IES) provides a clinical gold standard for the existence of
according to molecular changes occurring within the area of interest, functional motor pathways that can be used to determine the accuracy
potentially enabling early detection and treatment of disease and basic and sensitivity of fibre-tracking algorithms.
pharmaceutical development and quantitative testing. Intersecting tracts or partial volume averaging of adjacent pathways
High-field-strength magnets give significant improvement in spatial with different fibre orientations are the reasons why DTI does not accu-
resolution and contrast. MR images of the microvasculature of the live rately describe the microstructure in complex white matter voxels that
human brain that allow close comparison with the detail seen in his- contain more than one fibre population, e.g. in the centrum semiovale,
tological slides have been acquired at 8 T. This has significant implica- where major white matter tracts such as the pyramidal tract, the e67


Technical aspecTs and applicaTions of diagnosTic radiology
e68
7
noiTces
superior longitudinal fasciculus and the corpus callosum intersect. This radiation dose to the target organ. For example, 99mtechnetium or
has hindered preoperative mapping of the pyramidal tract in brain 123iodine may be used to detect thyroid disease, but certain thyroid
tumour patients. HARDI permits more accurate delineation of pathways diseases or thyroid cancer may be treated solely or in part with 131iodine.
within complex regions of white matter. The q-ball reconstruction of The difference in the agent used depends on the type and energy levels
HARDI data provides an orientation distribution function (ODF) that of the radiation particle that the radioisotope emits.
can be used to determine the orientations of multiple fibre populations Radionuclides used in nuclear medicine are often chemically bound
contributing to a voxel’s diffusion MR signal, mapping fibre trajectories to a complex called a tracer. The way the body handles a tracer may
through regions of complex tissue architecture in a clinically feasible differ in disease or pathological processes. For example, the tracer used
timeframe. in bone imaging is methylene-diphosphonate (MDP) bound to 99mtech-
netium. MDP attaches to hydroxyapatite in bone; altered bone physiol-
ogy, such as occurs in a fracture, metastatic bone disease or arthritic
Ultrasound
change, produces an increase in biochemical bone activity and an accu-
mulation of MDP that is seen as a focal ‘hot spot’ of the radiopharma-
Uniquely, ultrasound images do not depend on the use of electromag- ceutical on a bone scan.
netic wave forms. The properties of high-frequency sound waves (lon- 99mTechnetium is the major workhorse radioisotope of nuclear medi-
gitudinal waves) and their interaction with biological tissues are cine. It can be eluted from a molybdenum/technetium generator stored
responsible for the production of ‘echograms’ (Desser and Jeffrey 2001). within a nuclear medicine department, allowing for easy access. It has a
A sound wave of appropriate frequency (diagnostic range 3.5–20 MHz) short half-life (6 hours), which allows for ease of medical imaging