Which of the following statements about cardiac tamponade is/are correct?

E. When the diagnosis is made, treatment must be instituted rapidly and may include pericardiocentesis, creation of a pericardial window, and identification and treatment of the underlying cause.

DISCUSSION: Development of tamponade symptoms depends on the rate of accumulation of fluid. As little as 100 to 200 ml. accumulating rapidly may cause symptoms, whereas a slowly developing pericardial effusion of over 1 liter may remain asymptomatic. Pulsus paradoxus is not specific for tamponade; it may occur in patients with severe congestive heart failure, chronic obstructive pulmonary disease, hypovolemia, acute pulmonary embolism, or shock. Electrocardiographic findings of low QRS voltage and nonspecific ST T-wave changes are common in this condition, but electrical alternans, often considered pathognomonic of cardiac tamponade, is present in only a small number of patients. Trauma victims with tamponade frequently lack one or more of the elements of Beck's triad; for example, associated hypovolemia may lead to low or normal jugular venous distention. Since cardiac tamponade is life threatening, therapy designed to drain the pericardial fluid must be provided quickly and the underlying cause must be established and controlled.