This study is from our very own Stephen Alerhand!
The characteristic findings of pericardial tamponade on bedside ultrasound include:
- Pericardial effusion
- Diastolic right ventricular collapse (high specificity)
- Systolic right atrial collapse (earliest sign)
- Plethoric inferior vena cava with minimal respiratory variation (high sensitivity)
- Exaggerated respiratory cycle changes in mitral and tricuspid valve in-flow velocities as a surrogate for pulsus paradoxus
Why does this matter?
Pericardial tamponade is a potential life-threatening condition that can be difficult to diagnose. Diagnosis is often challenging and is usually based upon history, physical exam, and cardiac imaging. Definitive diagnosis is confirmed with clinical response to pericardial fluid drainage. Point-of-care ultrasound (POCUS) in the Emergency Department (ED) can be an extremely useful adjunct for both diagnosis and treatment of pericardial tamponade.
POCUS Making Waves for Diagnosis of Pericardial Effusion
This was a review that succinctly summarized the echocardiographic findings of pericardial tamponade and potential pearls and pitfalls of POCUS evaluation.
See figure 10 from the article below for a high yield summary and pocket primer for ultrasound findings of pericardial tamponade:
Other key points from the review are listed below:
- Rate of fluid accumulation is more important than the actual effusion size
- Beware of false positives such as a pleural effusion (posterior to descending aorta on parasternal long axis [PLAX] view) or pericardial fat pad (echoic “stippled appearance” structure in the anterior atrioventricular groove that appears to move in concert with the myocardium)
- Can be seen in PLAX, parasternal short axis (PSAX), apical 4-chamber (A4C), or subxiphoid (SX) views, but best seen in PLAX or SX view
Diastolic Right Ventricular Collapse
- High specificity (75-90%) but low sensitivity (48-60%) for tamponade
- Best seen in PLAX, A4C, or SX views
Systolic Right Atrial Collapse
- Earliest echocardiographic sign of pericardial tamponade because pressure is lower in right atrium than ventricle
- Variable sensitivity and specificity depending on duration of chamber collapse
- The absence of both right atrial systolic and right ventricular diastolic collapse has a 90% negative predictive value for tamponade.
- Best seen in A4C or SX view
Plethoric Inferior Vena Cava
- A dilated, plethoric IVC with minimal respiratory variation (defined as diameter > 2.1 cm and <50% inspiratory reduction) has high sensitivity for tamponade (95-97%) but low specificity (~40%)
Doppler Surrogate of Pulsus Paradoxus
- Tamponade physiology will produce an approximately 25% decrease in mitral valve in-flow velocity and 40% increase in tricuspid valve inflow velocity with inspiration
- Best seen and measured in the A4C view with doppler
Do not miss this rap on detecting tamponade with POCUS by The EMC. It is unbelievably good!
This emDocs post from Stephen Alerhand, the author of the study, provides great information on when a pericardial effusion becomes tamponade and POCUS.
What echocardiographic findings suggest a pericardial effusion is causing tamponade? Am J Emerg Med. 2019 Feb;37(2):321-326. doi: 10.1016/j.ajem.2018.11.004. Epub 2018 Nov 17.
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