Cardiac tamponade is the pathologic increase in intrapericardial volume and pressure that impairs diastolic filling and CO. It is often classified as a form of "obstructive shock," which is clinically characterized by hemodynamic compromise with signs of elevated filling pressures and other evidence of great vessel obstruction or cardiac compression. Other causes of obstructive shock include pulmonary embolism, tension pneumothorax, dynamic ventricular inflow or outflow obstruction (eg, from asymmetrical septal hypertrophy, hyperdynamic mid-cavitary ventricular obstruction, or cardiac myxoma), and effusive constrictive pericarditis. An unusual cause of cardiac tamponade is a large pleural effusion, which can cause clinical and echocardiographic findings of cardiac tamponade in the presence of a small "low-pressure" pericardial effusion. Animal studies show that increasing intrapleural fluid and pleural pressure is transmitted to the pericardial sac, which then compresses the heart. In this situation, only thoracentesis will relieve cardiac tamponade.

Cardiogenic shock, and RV failure in particular, can have similar signs and symptoms to cardiac tamponade, including jugular venous distension, pulsus paradoxus, dyspnea, and hypotension. The presence of fever, especially in inflammatory pericarditis and cardiac tamponade, can confound the diagnosis. However, sepsis typically presents as hyperdynamic, vasodilatory shock, whereas cardiac tamponade is notable for low SV and vasoconstriction.

References

• Saito Y, Donohue A, Attai S, et al. The syndrome of cardiac tamponade with "small" pericardial effusion. Echocardiography. 2008;25:321-327.
• Traylor JJ, Chan K, Wong I, et al. Large pleural effusions producing signs of cardiac tamponade resolved by thoracentesis. Am J Cardiol. 2002;89:106-108.
• Vaska K, Wann LS, Sagar K, et al. Pleural effusion as a cause of right ventricular diastolic collapse. Circulation. 1992;86:609-617.