Identification and assessment of the pericardial space

Pericardial effusions are frequently seen in patients with critical illness and are often a key differential diagnosis in hemodynamic decompensation. Although identification of an anechoic space of a potential pericardial effusion can be performed with relative ease, a number of important steps are required to refute other false positives and determine its' significance.

​This section will review potential false positives, differentiating pleural vs pericardial, assessment of size and hemodynamic significance, in conjunction with clinical examination. Please come back soon as we will post a video tutorial.

​Pericardial vs pleural

This clip displays key differences between pericardial and pleural effusions on the PLAX view. The descending thoracic aorta is a key landmark, which is often used as a key feature to distinguish pericardial from pleural effusions. Other cardiac views (And even thoracic views) can help you differentiate whether it is strictly pericardial, pleural or both.

Pleural effusion

 The following clip demonstrates a large pleural effusion, which travels behind the thoracic aorta and outline the entire hemithorax. Notice a thin anechoic strip along the margins of the heart---this is the pericardium.

Potential false positive

Be aware that epicardial fat can be a potential false positive. Fat is typically of mixed echogenicity and moves with the heart dynamically.

Estimating size

 The size of a pericardial effusion can be measured by placing a caliper in the echo-free space between the parietal and visceral pericardium at end-diastole. Small and large effusions are likely to be unevenly distributed and measurements can vary widely depending on where the measurement is taken. Unfortunately, little evidence is able to guide measurement of the pericardial space in this instance.

RV diastolic collapse

Due to its thin, compliant walls RV collapse in diastole has a very high specificity for cardiac tamponade. Note that the RV should collapse in systole as this reflects RV systolic function.

IVC assessment

The IVC requires special consideration in assessment of a pericardial effusion. In tamponade, it is very likely to be dilated >2.2cm with minimal collapsibility as RV collapse favors an atrial to caval gradient. In fact, it is very unlikely to have pericardial tamponade in the presence of a flat, collapsing IVC (but can happen in rare/select circumstances).

Key considerations

Please keep in mind these key considerations as you assess any pericardial effusion. 

• Pericardial effusions are remarkably common, few will have tamponade
• Pulsus paradoxus is still one of the most helpful clinical findings to help make a diagnosis
• Size is much less relevant than hemodynamic effect--even small acute effusions can be symptomatic.
• Assessment of the IVC is critical--see above!

References

Klein AL, Abbara S, Agler DA, Appleton CP, Asher CR, Hoit B, et al. American society of echocardiography clinical recommendations for multimodality cardiovascular imaging of patients with pericardial disease: Endorsed by the society for cardiovascular magnetic resonance and society of cardiovascular computed tomography. J Am Soc Echocardiogr [Internet]. 2013;26(9):965-1012.e15. 
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 Labovitz AJ, Noble VE, Bierig M, Goldstein SA, Jones R, Kort S, et al. Focused cardiac ultrasound in the emergent setting: a consensus statement of the American Society of Echocardiography and American College of Emergency Physicians. J Am Soc Echocardiogr [Internet]. 2010 Dec;23(12):1225–30.

​Nagdev A, Stone MB. Point-of-care ultrasound evaluation of pericardial effusions: Does this patient have cardiac tamponade? Resuscitation. 2011;82(6):671–3. 

Olaru C, Dean A, Mulugeta L, Bewtra M, Panebianco N. Bedside echocardiography in the diagnosis of pericardial effusion with increased intrapericardial pressure. Acad Emerg Med. 2015;1):S345.