Signs

• Right Atrial Collapse: Occurs during systole. This is the earliest and most sensitive sign.
• Right Ventricular Diastolic Collapse: The RV free wall "bows" inward during diastole. This is highly specific for tamponade.
• Plethoric IVC: The Inferior Vena Cava will be dilated (usually > 2 cm) with < 50% respiratory collapse (the "sniff test"). A collapsing IVC has a very high negative predictive value, meaning it effectively rules out tamponade.