Echocardiography: Pericardial Effusions & Cardiactamponade: David M. Whitaker, Md

Echocardiography: Pericardial Effusions & CardiacTamponade David M. Whitaker, MD

Pericadial Anatomy 2 layers  visceral and parietal Most diseases involve both, even though the parietal layer is most commonly called the pericardium Normally 5-10 mL buffering fluid in space Extends up to great vessels and reflects around the pulmonary veins In disease free states – rarely visualized

Pericardial Purpose Restrains 4 chambers in a relatively confined volume. Thus the total volume of all 4 chambers is limited Changes in volume of one chamber must be reflected in a change in volume in the opposite direction in another chamber This “linking” of volumes forms the basis for the physiology of pulsus paradox and findings seen in tamponade

Fluid Accumulation Rates Space is limited, so a significant accumulation of fluid reduces total volume the 4 chambers can contain at any one time  may result in hemodynamic compromise Hemodynamic compromise related to intrapericardial pressure, which in turn is related to volume of pericardial fluid and compliance/distensibility of pericardium

Fluid Accumulation Rates An effusion which accumulates slowly may become large with little to no hemodynamic compromise Smaller effusions which accumulate rapidly may cause deterioration

Detecting & Quantifying Fluid Can use all traditional techniques M-mode  echo free space anterior and posterior No accurate way to quantitate volume in M-mode Isolated echo free space in anterior side may not be fluid – could be mediastinal fat, fibrosis, thymus or other tissue

Detecting & Quantifying Fluid 2D echo most commonly used Commonly visually quantified as:  Minimal, small, moderate or large

Further characterized as free or loculated Should always report on presence or absence of hemodynamic compromise

Effusions in General Tend to be more prominent in dependent area Frequently appears maximal in the posterior AV groove

Effusions in General Short axis and apical views can help you determine the circumferential nature

Definitions Small effusions – as much as 1cm fo posterior echo-free space with or without fluid accumulation elsewhere

Definitions Moderate – 1-2 cm of echo free space Large – greater than 2cm of max separation Different labs may have slightly different cut points for definition

Effusions in General May be localized or loculated rather than circumferential Not uncommon after cardiac surgery or trauma where inflammation results in an unequal distribution of fluid in the pericardial space

Pericardial vs. Pleural Fluid Left pleural effusions result in echo free space posterior to the heart when pt is supine or left lateral Can be confused with pericardial effusions Recall pericardial reflections surround the pulmonary veins – this tends to limit the potential space behind the LA Fluid appearing exclusively behind the LA more likely to be pleural

Pericardial vs. Pleural Fluid A more reliable distinguishing factor is location of fluid filled space in relation to descending aorta The pericardial reflection typicall anterior, so fluid appearing posterior to the aorta likely to be pleural. Fluid anterior likely pericardial This, of course, is in the PLAX view

Cardiac Tamponade - Physiology Normal intrapericardial pressure ranges from -5 to +5 cm H2O and fluctuates with respiration Recall the constraining effect the pericardium has on the combined volume of all 4 chambers Respiratory variation in intrapericardial pressure results in a “linked” variation in filling of the right & left ventricles

Cardiac Tamponade - Inspiration During inspiration, intrathoracic & intrapericardial pressure decrease Increased flow into right heart and decreased flow out of pulmonary veins Result is augmented RV filling and stroke volume with a compensatory decrease in LV stroke volume in early inspiration

Cardiac Tamponade - Expiration Intrathoracic & intrapericardial pressure increase Mild decrease in RV diastolic filling with subsequent increase in LV filling This cyclic variation of left & right ventricular filling is sufficient to create mild changes in stroke volume and BP with the respiratory cycle Normal respiratory variation in stroke volume results in no more than 10 mmHg decrease in systemic arterial pressure with inspiration

Cardiac Tamponade - Physiology Increased fluid  further increased intrapericardial pressure affecting right heart filling Overall effect is to limit total blood volume allowable within the 4 chambers This exaggerates the respiratoyr dependent ventricular volume interaction

Cardiac Tamponade - Physiology Intrapericardial pressure can equal or exceed normal filling pressures of the heart – thus becomes the determining factor for the passive intracardiac pressures  RA, LA, RV diastolic, PADP, PCWP

With elevation of intrapericardial pressure above normal filling pressure, the diastolic pressure in all 4 chambers equalizes and is determined by the intrapericardial pressure  the hallmark of tamponade

Echo Features of Tamponade Always remember that tamponade is a clinical diagnosis Echo findings may suggest a hemodynamic abnormality that may be the substrate for tamponade, but echo abnormalities alone do not establish the diagnosis

Echo Features of Tamponade One of earliest features is swinging heart Swinging is just a marker of large effusion A large effusion is more likely than a small effusion to be associated with intrapericardial pressure elevation – so the swinging heart and pressure elevation is indirect rather than direct evidence of elevated pressure

Echo Features of Tamponade More specific signs of elevated intrapericardial pressure and hemodynamic compromise:  Diastolic RV outflow collapse  Exaggerated RA collapse in atrial systole

Remember these are indirect evidence that peric pressure is high and the substrate for tamponade is likely present

Doppler Findings in Tamponade Exaggerated phasic variation in flow can be documented with doppler Normally, peak velocity of mitral inflow varies by 15% or more with respiration Tricuspid inflow by 25% or more Variation in peak velocity and VTI of aortic and pulmonary flow profiles are typically less than 10%

Doppler Findings in Tamponade With a hemodynamically significant effusion, respiratory variation in filling is exaggerated above these thresholds So, respiratory variation in outflow tract velocities and VTI is likewise exaggerated These doppler findings are the corollary to pulsus paradoxus

Doppler Findings in Tamponade Normally vena caval flow occurs in both systole & diastole – nearly continuous With elevated intrapericardial pressure, the diastolic vena caval flow is truncated and most of the flow occurs during ventricular systole Hepatic vein flow may also reflect the exaggerated respiratory phase dependency of RV filling These are confirmatory findings, not diagnostic

Doppler Findings in Tamponade Some order to these findings  Typically, the earliest feature to be noticed is exaggerated respiratory variation of tricuspid inflow  Exaggeration of mitral inflow is usually next  Abnormal RA collapse typically occurs at lower levels of intrapericardial pressure elevation than does RV outflow tract collapse  RV free wall collapse is seen only later in the development of elevated pericardial pressures