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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Effusions in General
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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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 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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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
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Cardiac Tamponade - Physiology
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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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
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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 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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Doppler Findings in Tamponade
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