Echocardiography - Effusions

8/14/2019 Echocardiography - Effusions

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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


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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 anotherchamber

This linking of volumes forms the basis for thephysiology of pulsus paradox and findings seen intamponade


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Fluid Accumulation Rates

Space is limited, so a significant accumulation of fluidreduces total volume the 4 chambers can contain at anyone time may result in hemodynamic compromise

Hemodynamic compromise related to intrapericardialpressure, which in turn is related to volume ofpericardial fluid and compliance/distensibility ofpericardium


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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


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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


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Detecting & Quantifying Fluid

2D echo most commonly used

Commonly visuallyquantified as:

Minimal, small, moderate or large

Further characterized as free or loculated

Should always report on presence or absence of

hemodynamic compromise


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Effusions in General

Tend to be more prominent in dependent area

Frequently appears maximal in the posterior AV groove


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Short axis and apical views can help you determine the

circumferential nature


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Definitions

Small effusions as much as 1cm fo posterior echo-free

space with or without fluid accumulation elsewhere


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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


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May be localized or loculated rather than

circumferential

Not uncommon after cardiac surgery or trauma where

inflammation results in an unequal distribution of fluidin the pericardial space


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Pericardial vs. Pleural Fluid

Left pleural effusions result in echo free space posteriorto the heart when pt is supine or left lateral

Can be confused with pericardial effusions

Recall pericardial reflections surround the pulmonaryveins this tends to limit the potential space behind theLA

Fluid appearing exclusively behind the LA more likely to

be pleural


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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


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Cardiac Tamponade - Physiology

Normal intrapericardial pressure ranges from -5 to +5cm 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 resultsin a linked variation in filling of the right & leftventricles


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Cardiac Tamponade - Inspiration

During inspiration, intrathoracic & intrapericardial

pressure decrease

Increased flow into right heart and decreasedflow out

of pulmonary veins

Result is augmented RV filling and stroke volume with a

compensatory decrease in LV stroke volume in early

inspiration


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Cardiac Tamponade - Expiration

Intrathoracic & intrapericardial pressure increase

Mild decrease in RV diastolic filling withsubsequent increase in LV filling

This cyclic variation of left & right ventricularfilling is sufficient to create mild changes instroke volume and BP with the respiratory cycle

Normal respiratory variation in stroke volume

results in no more than 10 mmHg decrease insystemic arterial pressure with inspiration


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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


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Intrapericardial pressure can equal or exceednormal filling pressures of the heart thusbecomes the determining factor for the passive

intracardiac pressuresRA, LA, RV diastolic, PADP, PCWP

With elevation of intrapericardial pressureabove normal filling pressure, the diastolic

pressure in all 4 chambers equalizes and isdetermined by the intrapericardial pressurethe hallmark of tamponade


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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 tobe associated with intrapericardial pressure elevation

so the swinging heart and pressure elevation is indirect

rather than direct evidence of elevated pressure


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Echo Features of Tamponade

More specific signs of elevated intrapericardial pressureand hemodynamic compromise:

Diastolic RV outflow collapse

Exaggerated RA collapse in atrial systole

Remember these are indirect evidence that pericpressure is high and the substrate for tamponade islikely present


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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%


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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


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Normally vena caval flow occurs in both systole& diastole nearly continuous

With elevated intrapericardial pressure, the

diastolic vena caval flow is truncated and mostof the flow occurs during ventricular systole

Hepatic vein flow may also reflect theexaggerated respiratory phase dependency ofRV filling

These are confirmatory findings, not diagnostic


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Some order to these findings

Typically, the earliest feature to be noticed is exaggeratedrespiratory variation oftricuspid inflow

Exaggeration of mitral inflow is usually next

Abnormal RA collapse typically occurs at lower levels ofintrapericardial pressure elevation than does RV outflowtract collapse

RV free wall collapse is seen only later in the developmentof elevated pericardial pressures

Echocardiography - Effusions

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