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PERICARDIAL EFFUSION

Pericardial effusions are usually seen as an anechoic rim around the myocardium bordered by the bright white of the pericardium (1). Malignant effusions, purulent effusions and haematoma formation may lead to echogenic material within the fluid. 

Anechoic pericardial effusion

Anechoic pericardial effusion

echogenic material within the pericardial space

If you see echogenic material in a pericardial effusion, always look at the aorta for dilatation and a dissection flap. A pericardial effusion with clot is commonly associated with type A dissections (2).

The volume of the effusion can be estimated from the width of the largest fluid pocket. Keep in mind though that off axis imaging and loculated effusions may be over/underestimated in this way (3,4). Typical values for pericardial effusion volumes are:  trivial (seen only in systole), mild (<10 mm), moderate (10-20 mm), and severe (>20 mm) (5).

The important thing to remember in all this is the fact that the pericardium is elastic and will stretch over time. So the volume of fluid in the pericardium (except for very large effusions) does not usually predict the risk of tamponade. A very acute accumulation of fluid will cause tamponade at a smaller volume than a slow accumulation fluid (6). 

Pressure volume curves showing the effect of the rate of development of pericardial fluid volume on tamponade physiology: Blue line (rapid fluid accumulation) and red line (slow fluid acculmulation)

PITFALLS

The most common pitfall is to call the normal epicardial fat pad a pericardial effusion. This is usually only seen anterior to the RV in PLAx and more commonly in people with a high levels of visceral fat. There may not be a direct association with obesity (7). There are case reports of circumferential fat pads (8). Note, Epicardial fat is between the myocardium and the pericardium; pericardial fat is outside the parietal pericardium. 

The epicardial fat pad can be distinguished from an effusion by the following common features:

1. usually only anterior to RV 

2. Not anechoic, has echogenic strands

3. Does not usually cause features of tamponade

PLAx Epicardial and pericardial fat pad

LEFT PLEURAL EFFUSION

In PLAx, a left pleural effusion can sometimes look like a loculated inferior effusion. The way to distinguish the two is to look at the descending aorta in PLAx. The inferior pericardium passes anterior to the anterior wall of the descending aorta. A pericardial effusion will therefore be anterior to the aorta, A pleural effusion will have the aorta within the fluid. Further, examining the heart in multiple views will show that the fluid is ouside the heart.

L Pleural effusion in PLAx, aorta within the fluid (Note: there is trace fluid within the pericardium as well)

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REFERENCES

1. Ceriani, E., Cogliati, C. Update on bedside ultrasound diagnosis of pericardial effusion.Intern Emerg Med 11, 477-480 (2016). https://doi.org/10.1007/s11739-015-1372-8

2. Hiratzka LF, Bakris GL, Beckman JA, Bersin RM, Carr VF, Casey DE Jr, Eagle KA, Hermann LK, Isselbacher EM, Kazerooni EA, Kouchoukos NT, Lytle BW, Milewicz DM, Reich DL, Sen S, Shinn JA, Svensson LG, Williams DM; ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM guidelines for the diagnosis and management of patients with Thoracic Aortic Disease. Circulation. 2010 Apr 6;121(13):e266-369.

3. D'Cruz I, Prabhu R, Cohen HC, Glick G. Potential pitfalls in quantification of pericardial effusions by echocardiography. Br Heart J. 1977 May;39(5):529-35. doi: 10.1136/hrt.39.5.529. PMID: 861096; PMCID: PMC483270.

4. Maisch B, Seferovic PM, Ristic AD, Erbel R, Rienmuller R, Adler Y, et al. Guidelines on the diagnosis and management of pericardial diseases executive summary, the task force on the diagnosis and management of pericardial diseases of the European Society of Cardiology. Eur Heart J (2004) 25:587-610.10.1016/j.ehj.2004.02.00

5. DeMaria DM, Waring AA, Gregg DE, Litwin SE. Echocardiographic Assessment of Pericardial Effusion Size: Time for a Quantitative Approach. J Am Soc Echocardiogr. 2019 Dec;32(12):1615-1617.

6. Spodick DH. Acute pericarditis: current concepts and practice. JAMA (2003) 289:1150-3.10.1001/jama.289.9.1150

7. Iacobellis G, Willens HJ. Echocardiographic epicardial fat: a review of research and clinical applications. J Am Soc Echocardiogr. 2009 Dec;22(12):1311-9; quiz 1417-8. doi: 10.1016/j.echo.2009.10.013. PMID: 19944955.

8. Pressman G, Verma N. Pericardial fat masquerading as tumor. Echocardiography. 2010 Feb;27(2):E18-20. doi: 10.1111/j.1540-8175.2009.01063.x. PMID: 20380671.