Consider Pulsus Alternans as a Sign of Impending Tamponade
Melissa Camp MD
Cardiac tamponade occurs when fluid accumulates in the pericardial space and leads to impaired diastolic filling due to increased pericardial pressure. The pericardium is relatively inelastic and in the acute setting an accumulation of 100 to 200 cc of fluid can cause tamponade physiology. In intensive care unit patients the most common scenarios involving tamponade include after cardiothoracic surgery, after central line placement with inadvertent puncture of the superior vena cava or right atrium, and after blunt or penetrating chest trauma. Of note, following cardiothoracic surgery, tamponade may also result from a small clot compressing the filling of the heart.
Signs and Symptoms
Early signs of tamponade include tachycardia and elevated central venous pressure, followed by hypotension and decreased cardiac output. Beck’s triad describes the classic findings of jugular venous distention, muffled heart sounds, and hypotension. If a pulmonary artery catheter is present, the equalization of filling pressures may be evident with right atrial pressure = right ventricular end-diastolic pressure = pulmonary artery diastolic pressure = pulmonary artery wedge pressure = left ventricular end diastolic pressure. It should be noted that pressure equalization may not be evident postcardiac surgery because the pericardium has invariably been opened. Pulsus paradoxicus, the decrease in systolic blood pressure of greater than 10 to 15 mm Hg on inspiration, is also observed in tamponade. Pulsus paradoxicus is a result of systemic venous return during inspiration causing rapid right ventricular filling, which compresses and impairs left ventricular filling.