From the Guidelines
Echocardiographic signs of cardiac tamponade include right atrial collapse, diastolic RV collapse, and inferior vena cava plethora with decreased respiratory variation, as well as respiratory variation in mitral and tricuspid inflow velocities, which are crucial for prompt diagnosis and management of this life-threatening condition. The most sensitive sign of tamponade is cyclic compression, inversion or collapse of the right atrium, where chamber collapse in late diastole persisting into early ventricular systole occurs in the case of severely increased intrapericardial pressure 1. Diastolic RV collapse (inward diastolic motion of the RV free wall) occurs later, but is a more specific sign and is best appreciated from the parasternal or subcostal long-axis views 1. Some key echocardiographic findings that suggest a haemodynamically significant pericardial collection include:
- Right atrial collapse lasting more than one-third of the cardiac cycle
- Diastolic RV collapse
- Inferior vena cava dilation (>2.1 cm) with minimal respiratory variation (<50% collapse)
- Exaggerated respiratory variation in mitral inflow velocity (>25% decrease during inspiration) and tricuspid inflow velocity (>40% increase during inspiration) 1. These findings reflect the pathophysiology of tamponade, where accumulating pericardial fluid increases intrapericardial pressure, restricting cardiac filling and causing equalization of diastolic pressures across all cardiac chambers. Recognizing these echo signs is crucial for prompt diagnosis and management of this life-threatening condition, as treatment involves drainage of the pericardial fluid, preferably by needle pericardiocentesis, with the use of echocardiographic or fluoroscopic guidance, and should be performed without delay in unstable patients 1.
From the Research
Echo Signs of Tamponade
The echo signs of tamponade include:
- Pericardial effusion 2
- Diastolic right ventricular collapse (high specificity) 2, 3
- Systolic right atrial collapse (earliest sign) 2, 4
- Plethoric inferior vena cava with minimal respiratory variation (high sensitivity) 2
- Exaggerated respiratory cycle changes in mitral and tricuspid valve in-flow velocities as a surrogate for pulsus paradoxus 2, 4
- Early diastolic collapse of the right ventricle 4
- Late diastolic collapse of the right atrium 4
- Respiratory variation in mitral valve inflow (akin to pulsus paradoxus) 4
- Decreased early filling (E wave) of mitral valve inflow (related to loss of the y descent) 4
Echocardiographic Findings
Echocardiographic findings are crucial in the diagnosis of cardiac tamponade, as they can confirm the size, location, and other characteristics of the causal pericardial collection 4. The emergency physician must recognize and understand the core echocardiographic findings and associated pathophysiology that suggest pericardial tamponade 2.
Comparison of Echo Signs
Right ventricular diastolic collapse is more sensitive, specific, and predictive of cardiac tamponade than pulsus paradoxus 3. The sensitivity of right ventricular diastolic collapse is 93%, and its specificity is 100%, whereas pulsus paradoxus has a sensitivity of 79% and a specificity of 40% 3.