Cardiac tamponade occurs when increased intrapericardial pressure for any reason (e.g., blood, fluid, air) impedes venous filling of the right ventricle. Symptoms may include tachycardia, tachypnea, dyspnea, orthopnea, and diaphoresis. Beck’s triad of elevated central venous pressure (CVP), systemic hypotension with decreased pulse pressure, and distant/muffled heart sounds describes the classic clinical signs, but one or more findings is frequently absent. Electrocardiography may reveal decreased amplitude or electrical alternans. Ultimately, as intrapericardial pressure (IPP) dictates intracardiac chamber pressures, diastolic filling pressures equilibrate (i.e., CVP = PADP = PCWP = IPP, where PADP is the pulmonary artery diastolic pressure, and PCWP is the pulmonary capillary wedge pressure). The hemodynamics of tamponade physiology are uniquely susceptible to wide respiratory variations. In particular, pulsus paradoxus is an exaggeration of the normal physiologic decrease in systemic arterial blood pressure with spontaneous inspiration. In the post–cardiac surgery patient, compression may be isolated to a single chamber of the heart (e.g., due to loculated blood clot), making the classic signs and symptoms less useful; a high degree of clinical suspicion is required to make the diagnosis.

Increased availability has led to an increase in reliance on perioperative echocardiography for the diagnosis of cardiac tamponade. Echo findings may include presence of a pericardial effusion, right atrial collapse during systole, right ventricular collapse during diastole, and inferior vena caval plethora. Echocardiographic correlates of pulsus paradoxus may be seen, including respiratory variation in both left and right ventricular filling as evidenced either by Doppler inflow patterns or by variations in septal wall motion. Right atrial collapse lasting longer than one third of systole has a 94% sensitivity and 100% specificity for the diagnosis of tamponade. In the post–cardiac surgery patient, transthoracic imaging may be technically limited, necessitating a transesophageal study (Figure 277.1).