normal pericardium is a double - walled sac that contains the heart and the roots of the great vessels .
the pericardium is composed of two different layers ; an outer fibrous parietal pericardium and an inner visceral pericardium.1 ) the inner visceral pericardium is a serous - type membrane and is located immediately outside of the myocardium.2)3 ) the pericardium prevents sudden dilatation of the heart , especially the right chamber , and displacement of the heart and great vessels , minimizes friction between the heart and surrounding structures , and prevents the spread of infection or cancer from the lung or pleura .
the pericardium also contributes to diastolic coupling between the two ventricles.3)4 ) in between the parietal and visceral pericardium , there is a pericardial cavity filled with 10 - 50 cc of fluid , an ultrafiltrate of plasma that is produced by the visceral pericardium .
pericardial effusion can develop in patients with virtually any condition that affects the pericardium , including acute pericarditis and a variety of systemic disorders.1)5 ) the clinical causes of pericardial effusion are very diverse and include malignancies of other organs , pulmonary tuberculosis , chronic renal failure , thyroid disease , autoimmune disease , and iatrogenic and idiopathic causes ( table 1).5 - 7 ) the development of a pericardial effusion may have important implications for the prognosis ( as in patients with intrathoracic malignancy ) or diagnosis ( as in myopericarditis or acute pericarditis ) , or both ( as in dissection of the ascending aorta).6 ) when a pericardial effusion is initially or incidentally detected , a major concern for clinicians may be its etiology . in a majority of cases ,
the etiology of the effusion can be presumed from the underlying condition of the patient .
although the exact etiology of pericardial effusion can be identified by invasively - obtained pericardial fluid or tissue , an invasive procedure , like pericardiocentesis , is only indicated when the effusion is large or symptomatic , the effusion is accompanied by tamponade , or the cause of the effusion is questionable .
there is some discrepancy in the etiologies of pericardial effusion , requiring pericardiocentesis between countries or centers .
a review of many articles from throughout the world shows that the relative frequency of different etiologies is mainly affected by the decade , local epidemiology , hospital volume , and the diagnostic protocol.6)7 ) the etiology of pericardial effusion in korea and other countries is summarized in table 2.8 - 15 ) in korea , lung cancer and pulmonary tuberculosis are predominant causes of large pericardial effusion.8 - 10 ) sagrista - sauleda et al.13 ) reported that when an etiology is not apparent , the clinical indices , including the size of the effusion , the presence of inflammatory signs , and cardiac tamponade , may be useful in suggesting a possible etiologic category . for example , severe effusions without inflammatory signs or tamponade were significantly associated with chronic idiopathic pericardial effusion .
m - mode and 2-dimensional doppler echocardiography is the most effective technique , and is the gold standard for the diagnosis of pericardial effusion , because it is sensitive , specific , noninvasive , and easily made available at the bedside.16 ) pericardial effusion can be detected as an " echo - free space " on 2-dimensional echocardiography ( fig .
1).1 - 5 ) small collections of pericardial fluid , which can be physiologic ( 25 to 50 ml ) , may be visible during ventricular systole . when the amount of effusion is more than 50 ml , an echo - free space persists throughout the cardiac cycle .
when a pericardial effusion is detected by echocardiography , the next step is to assess the size of the effusion , its location , hemodynamic importance , and associated diseases.4)17 ) a pericardial effusion is not always uniformly distributed around the heart .
initially , small effusions are evident over the posterobasal left ventricle ; however , as the fluid volume increases , it gradually spreads anteriorly , laterally , and behind the left atrium .
ultimately , the separation becomes circumferential and appears as " swinging heart " , which is a sign of a large pericardial effusion and possibly cardiac tamponade.4 ) despite the fact that there is a large amount , the pericardial effusion does not surround the posterior portion of the heart .
therefore , the amplitude of the p wave is not changed , in spite of a large pericardial effusion or after pericardiocentesis ( fig . 2).18 ) several grading systems have been developed , based on the size of the pericardial effusion .
however , a generally accepted system is the effusion graded as minimal ( scanty ) , small , moderate , or large . for circumferential pericardial effusions , any pericardial effusion with less than 5 mm of pericardial separation in diastole ( corresponding to a fluid volume of 50 to 100 ml )
is defined as minimal ; 5 to 10 mm of separation as small ( corresponding to a fluid volume of 100 to 250 ml ) ; 10 to 20 mm of separation as moderate ( corresponding to a fluid volume of 250 to 500 ml ) ; and greater than 20 mm separation as large ( corresponding to a fluid volume greater than 500 ml ) ( fig .
. however , even the diffused and circumferential effusion dimensions of the echo - free space may be different in the views examined ; therefore , it is more correct and easier to measure and annotate the dimension of the effusion and to report where it has been evaluated ( e.g. , 12 mm in the left ventricular lateral wall in the apical four - chamber view ; 10 mm along the right atrium in the subcostal view ) .
this methodology not only facilitates the definition of effusion size , but also allows follow - up studies by detecting changes in the amount of pericardial fluid after therapy.17 ) except for the epicardial fat , the abnormal masses attached on the epicardial surface or floating in the pericardial space must also be reported .
it may be an infiltrative metastatic mass , inflammatory fibrin strands , pus , or a blood clot ( fig .
other imaging modalities , such as computed tomography ( ct ) or magnetic resonance imaging ( mri ) , may be used to identify the characteristics of pericardial effusion and tamponade in the presence of a technically - limited echocardiographic study.6)7)19 ) however , the clinical utility of ct and mri is questioned because of the high positive predictive value of echocardiography with potential safety concerns in acutely ill patients .
currently , these modalities have adjunctive roles to echocardiography , especially in situations that show atypical hemodynamics , presence and severity of tamponade are doubtful , or when there are other unexplained conditions.19 ) for instance , in the case of pericardial effusion associated with intrathoracic malignancies , such as lung , breast , or esophageal cancer , chest ct might be useful for understanding the disease progression at a glance .
cardiac tamponade is a life - threatening , slow or rapid compression of the heart due to the pericardial accumulation of fluid , pus , blood , clots , or gas as a result of effusion , trauma , or rupture of the heart.20)21 ) the normal pericardium can stretch to accommodate increases in the pericardial volume .
once the pericardium has been stretched to its limit , by accumulating effusion , ongoing accumulation of pericardial fluid into a closed space increases the intrapericardial pressure . when the intra - pericardial pressure becomes high enough to impede cardiac filling , cardiac function
therefore , the definition of cardiac tamponade is the state when the heart is compressed due to fluid accumulation and increased intrapericardial pressure , resulting in cardiogenic shock and circulatory collapse.20 ) in the physiology of tamponade development , a complex interaction of factors influences the ultimate physiologic consequences of pericardial effusion , in any given patient .
these factors include the pericardial pressure / volume relationship , the rapidity of fluid accumulation , underlying cardiac pathology ( particularly hypertrophy and shunts ) , and systemic volume status .
it is well understood that small acute pericardial effusions ( occurring most commonly post - intervention or traumatically ) can lead to dramatic tamponade physiology when fluid accumulates rapidly ; whereas , moderate - sized or even large pericardial effusions that accumulate slowly can be well tolerated , hemodynamically ( fig .
5).20)21 ) therefore , large pericardial effusions or the swinging motion of the heart is not always present in cardiac tamponade . on the contrary
, a localized compressing effusion may lead to dramatic hemodynamic consequences without producing classical echocardiographic indications of tamponade.4)22 ) the most common cause of cardiac tamponade reported is malignancy , which is involved in > 50% of all tamponade cases .
especially lung cancer was involved in > 70% of cardiac tamponade of malignant origin.21 ) although cardiac tamponade is considered a clinical diagnosis , clinical findings like dyspnea , hypotension , tachycardia , elevated jugular venous pressure , and pulsus paradoxus , are known to have limited sensitivity and specificity.20 )
echocardiography is the most useful diagnostic tool for evaluating patients with cardiac tamponade , and it should be performed without delay in patients if suspected.1)23 ) the most characteristic echocardiographic findings that suggest cardiac tamponade is diastolic collapse of the free walls of the right atrium , and/or the right ventricle.1)7)24 ) any cardiac chamber can be collapsed , but it usually occurs on the right - sided chambers because both the right atrium and right ventricle are compliant and low pressure chambers.1 ) right atrial compression for more than one third of the cardiac cycle ( late diastole ) is highly sensitive and specific for cardiac tamponade ( fig .
6a).1)7)22)25)26 ) right ventricular compression in early diastole is less sensitive for the presence of cardiac tamponade than ra diastolic collapse , but is very specific for cardiac tamponade ( fig .
6b).1)7)27 - 30 ) rv collapse may not occur when the rv is hypertrophied or when its diastolic pressure is greatly elevated .
left atrial chamber collapse can be seen in about 25% of patients with hemodynamic compromise , and is very specific for cardiac tamponade .
left ventricular collapse is less common , since the wall of the left ventricle is more muscular , but can be seen under special conditions , such as localized postsurgical tamponade or severe pulmonary hypertension .
reciprocal changes in the left and right ventricular volumes occur with respiration in cardiac tamponade .
doppler echocardiography has been used to estimate respiratory variation in mitral and tricuspid diastolic inflow velocity . in accordance with pulsus paradoxus ,
a more exaggerated respiratory variation in inflow velocity , representing an inspiratory decrease in peak mitral inflow velocity 30% , and an inspiratory increase of peak tricuspid inflow velocity 50% , would suggest an increased ventricular interdependence and presence of cardiac tamponade ( fig .
6c).1)7)31)32 ) dilatation of the inferior vena cava ( ivc ) and < 50% reduction in the diameter of the dilated ivc during inspiration , so called ivc plethora , reflecting a marked elevation in the central venous pressure is frequently seen in patients with cardiac tamponade.1)7)33 ) ivc plethora was associated with pulsus paradoxus and was present in 92% of those with pericardial effusion , who required pericardial drainage .
collapse of the right - sided chambers is a sensitive indicator of tamponade , but abnormalities in cardiac filling are a more specific finding of tamponade.34 ) although cardiac tamponade may be diagnosed , using the above findings , clinicians should be aware that echocardiography has some limitations for diagnosis and follow - up of cardiac tamponade .
for example , severe hypovolemia or large pleural effusions can cause diastolic chamber collapse . additionally , disease states that increase right - sided cardiac pressures , such as pulmonary hypertension or pulmonary thromboembolism , may prevent diastolic chamber collapse.35 ) cardiac tamponade
is not an " all - or - none " phenomenon , but rather a spectrum of findings.6 ) therefore , for the final diagnosis of cardiac tamponade , clinicians should correlate the echocardiographic signs of tamponade ( rv collapse , ra collapse , respiratory alteration of mitral and tricuspid flow , and ivc plethora ) with the symptoms and signs of clinical tamponade ( dyspnea , tachycardia , jugular venous distension , pulsus paradoxus , hypotension , and shock).6 )
percutaneous needle pericardiocentesis has been the most useful therapeutic procedure for the early management of large , symptomatic pericardial effusion or cardiac tamponade , and it continues to be used as a diagnostic procedure in some patients with asymptomatic pericardial effusion , such as chronic idiopathic effusion.7)17)36)37 ) before , during , and after the percutaneous pericardiocentesis , transthoracic echocardiography guidance is essential.36)38 ) if the pericardiocentesis is performed at bedside without echocardiographic guidance , the risk of threatening complications like bleeding or shock have been reported to be as high as 20% . in contrast , echocardiographic guidance increases the success rate of pericardiocentesis by reducing these complications.7)11 ) in korea , the success rate of echocardiography - guided pericardiocentesis was about 99%.8)9 ) when deciding to perform pericardiocentesis , many clinical and echocardiographic factors must be comprehensively considered .
these factors include the amount and location of the effusion , hemodynamics on echocardiography , sufficient margins of the echo free space so as to prevent laceration , clinical indication and urgency , underlying etiologies , and bleeding tendency . recently , halpern et al.39 ) suggested a " pericardial effusion scoring index " for deciding whether to perform pericardiocentesis .
the scoring index consists of 3 components obtained at initial presentation ; effusion size on echo , echocardiographic assessment of hemodynamics , and etiology of effusion .
authors reported that percutaneous pericardiocentesis could be performed when the score was 4 or above .
1 ) check clinical indications and medical history , such as taking anti - platelet or anti - coagulation drugs , and get a consent form.2 ) positioning and echocardiographic imaging 
 a ) position the patient in the semi - fowler position in bed.b ) perform 2d echocardiographic imaging at the apical view ( fig .
7c ) to gain insight into the effusion.40)41 ) 
 3 ) determination of puncture site 
 a ) choose sites with the biggest echo - free space for safe needle entry , and mark it using a pen or nail tip on the site ( fig .
4 ) preparation of puncture site 
 a ) prepare all requisite tools for the centesis on the table ( fig .
7f).b ) cover the patient with a surgical drape and the patient 's eyes with an eye patch to reduce tension and anxiety ( fig .
5 ) pericardiocentesis 
 a ) perform a preliminary exploration with the local anesthetic needle ( 21 gauge ) to confirm the direction of the needle approach and to feel the nature of the effusion.b ) put the puncture needle ( 18 gauge ) to the tip of the puncture syringe.c ) gently insert and advance the puncture needle from the skin of the puncture site toward the heart in the breath holding state .
the puncture needle must maintain the direction that was determined during the preliminary exploratory test ( fig .
7i).d ) feel the " pop " moment at the puncture and observe negatively drained fluid in the syringe ( fig .
7j).e ) stop the advancing puncture needle and hold the needle with your fingers to prevent further advancement . insert a smooth tip guidewire through a back - hole in the syringe , sufficiently into the pericardial space ( fig .
7n ) , insert a double lu men indwelling catheter over the guidewire into the pericardial space ( fig .
7o).h ) remove the guidewire with the remaining indwelling catheter in the pericardial space.i ) confirm the success of the procedure by manual drainage with a syringe ( fig .
7q ) or a saline bubble test with echocardiography . the patient 's reduced or relieved symptoms soon after the drainage , even by a small amount , is additional evidence of success.j ) suture the catheter on the skin and continue to drain the effusion into a bottle ( fig .
1 ) check clinical indications and medical history , such as taking anti - platelet or anti - coagulation drugs , and get a consent form .
2 ) positioning and echocardiographic imaging 
 a ) position the patient in the semi - fowler position in bed.b ) perform 2d echocardiographic imaging at the apical view ( fig .
7c ) to gain insight into the effusion.40)41 ) 
  a ) position the patient in the semi - fowler position in bed .
7c ) to gain insight into the effusion.40)41 ) 3 ) determination of puncture site 
 a ) choose sites with the biggest echo - free space for safe needle entry , and mark it using a pen or nail tip on the site ( fig .
a ) choose sites with the biggest echo - free space for safe needle entry , and mark it using a pen or nail tip on the site ( fig .
4 ) preparation of puncture site 
 a ) prepare all requisite tools for the centesis on the table ( fig .
7f).b ) cover the patient with a surgical drape and the patient 's eyes with an eye patch to reduce tension and anxiety ( fig .
b ) cover the patient with a surgical drape and the patient 's eyes with an eye patch to reduce tension and anxiety ( fig . 7
5 ) pericardiocentesis 
 a ) perform a preliminary exploration with the local anesthetic needle ( 21 gauge ) to confirm the direction of the needle approach and to feel the nature of the effusion.b ) put the puncture needle ( 18 gauge ) to the tip of the puncture syringe.c ) gently insert and advance the puncture needle from the skin of the puncture site toward the heart in the breath holding state .
the puncture needle must maintain the direction that was determined during the preliminary exploratory test ( fig .
7i).d ) feel the " pop " moment at the puncture and observe negatively drained fluid in the syringe ( fig .
7j).e ) stop the advancing puncture needle and hold the needle with your fingers to prevent further advancement . insert a smooth tip guidewire through a back - hole in the syringe , sufficiently into the pericardial space ( fig .
7n ) , insert a double lu men indwelling catheter over the guidewire into the pericardial space ( fig .
7o).h ) remove the guidewire with the remaining indwelling catheter in the pericardial space.i ) confirm the success of the procedure by manual drainage with a syringe ( fig .
7q ) or a saline bubble test with echocardiography . the patient 's reduced or relieved symptoms soon after the drainage , even by a small amount , is additional evidence of success.j ) suture the catheter on the skin and continue to drain the effusion into a bottle ( fig .
a ) perform a preliminary exploration with the local anesthetic needle ( 21 gauge ) to confirm the direction of the needle approach and to feel the nature of the effusion .
b ) put the puncture needle ( 18 gauge ) to the tip of the puncture syringe .
c ) gently insert and advance the puncture needle from the skin of the puncture site toward the heart in the breath holding state . the puncture needle must maintain the direction that was determined during the preliminary exploratory test ( fig .
d ) feel the " pop " moment at the puncture and observe negatively drained fluid in the syringe ( fig .
e ) stop the advancing puncture needle and hold the needle with your fingers to prevent further advancement . insert a smooth tip guidewire through a back - hole in the syringe , sufficiently into the pericardial space ( fig .
7n ) , insert a double lu men indwelling catheter over the guidewire into the pericardial space ( fig .
i ) confirm the success of the procedure by manual drainage with a syringe ( fig .
7q ) or a saline bubble test with echocardiography . the patient 's reduced or relieved symptoms soon after the drainage , even by a small amount , is additional evidence of success .
j ) suture the catheter on the skin and continue to drain the effusion into a bottle ( fig .
there are 3 approaches to needle entry during pericardiocentesis ; left parasternal , subxyphoid , and left apical.37)41 ) among these , the left parasternal approach seems to be preferred in the era of echocardiography - guided pericardiocentesis , because the left parasternal view provides a more direct route to the largest echo free space and better safety than other approaches . using the left parasternal approach ,
the puncture needle is inserted close to the sternum , usually in the left 5th or 6th intercostal space .
this approach is associated with possibly a higher risk of pneumothorax than with the subxyphoid approach.41)42 ) the puncture needle during the subxyphoid approach is inserted at an angle between the xiphisternum and left costal margin , towards the left shoulder at a 15 to 30 degree angle to the skin.20 ) this approach has been performed when echocardiography is not available , in the cardiac catheterization room with ecg monitoring , or in emergent situations .
this route is extrapleural and avoids the coronary , pericardial , and internal mammary arteries .
injuries to the pleura , liver , or stomach , irritation to the diaphragm and phrenic nerve resulting in bradycardia and shock , and higher procedure - related mortality have been reported with this approach than with others.7)41 ) in the left apical approach , the puncture needle is inserted into the intercostal space outside of the left nipple , where the left ventricular apical beating is touched , and is toward the right shoulder . during this approach , the apex
can easily be pierced , and evoke ventricular fibrillation ; thus , it is not indicated in emergent situations and must be performed under the guidance of echocardiography.41 ) the choice of direction of approach must be decided by an experienced clinician , after considering if there is a safe enough margin of echo free space , the patient 's position , and clinical situation .
a major complication of percutaneous pericardiocentesis includes laceration of the heart and coronary arteries , hemothorax and pneumothorax , ventricular tachyarrhythmia , and vasovagal response.7 ) during pericardiocentesis , clinicians must be attentive to the important anatomic structures in the way of the puncture needle approach , including the internal thoracic arteries ( located 0.5 to 2 cm lateral to the sternal edge ) , intercostal vessels ( inferior border of the rib ) and nerves , phrenic nerve in the diaphragm , pleura , lung parenchyma , and free wall of the right or left ventricle.41 ) aortic dissection is a major contraindication of pericardiocentesis .
relative contraindications include uncorrected coagulopathy , anticoagulant therapy , and thrombocytopenia < 50000/mm , and small , posterior , and loculated
effusions.7 ) surgical drainage , rather than percutaneous pericardiocentesis is preferred in the following situations : traumatic hemopericardium , purulent pericarditis , recurrent malignant effusion , loculated effusion in the posterior side of the heart , a need for pericardial biopsy with drainage for diagnosis , and coagulopathy or thrombocytopenia.43 - 45 )
pericardial effusion can develop in patients with virtually any condition that affects the pericardium , including acute pericarditis , malignancies , pulmonary tuberculosis , chronic renal failure , thyroid disease , autoimmune disease , or iatrogenic and idiopathic causes .
the causes of large pericardial effusions , requiring invasive pericardiocentesis or pericardiotomy , vary according to the times , status of the countries , and the location , size , and facilities of the hospital . especially in korea ,
transthoracic echocardiography is the most important tool for the diagnosis , grading , pericardiocentesis procedure , and follow up for pericardial effusion .
clinicians should understand the tamponade physiology , especially cardiac tamponade that can develop without large pericardial effusion or swinging heart .
in addition , clinicians should correlate the echocardiographic findings of tamponade , such as right ventricular collapse , right atrial collapse , respiratory variation in the mitral and tricuspid flow , and ivc plethora , with the signs of clinical tamponade , such as hypotension or pulsus paradoxus .
pericardiocentesis is lifesaving for cardiac tamponade , and indicated in cases where there is a large volume of pericardial effusion .
 pericardial effusion can develop from any pericardial disease , including pericarditis and several systemic disorders , such as malignancies , pulmonary tuberculosis , chronic renal failure , thyroid diseases , and autoimmune diseases . 
 the causes of large pericardial effusion requiring invasive pericardiocentesis may vary according to the time , country , and hospital . 
 transthoracic echocardiography is the most important tool for diagnosis , grading , the pericardiocentesis procedure , and follow up of pericardial effusion . 
 cardiac tamponade is a kind of cardiogenic shock and medical emergency . 
 clinicians should understand the tamponade physiology , especially because it can develop without large pericardial effusion . 
 in addition , clinicians should correlate the echocardiographic findings of tamponade , such as right ventricular collapse , right atrial collapse , and respiratory variation of mitral and tricuspid flow , with clinical signs of clinical tamponade , such as hypotension or pulsus paradoxus . 
 percutaneous pericardiocentesis has been the most useful procedure in many cases of large pericardial effusion , cardiac tamponade , or pericardial effusion of unknown etiology . 
 the procedure should be performed with the guidance of echocardiography . 
Introduction
Etiologies of Pericardial Effusion
Transthoracic Echocardiography for Pericardial Effusion
Cardiac Tamponade
Echocardiographic Findings of Cardiac Tamponade
Echocardiography Guided Pericardiocentesis
Conclusions