Introduction
Pericardial effusion can develop during any of the processes discussed in the preceding paragraphs. The speed of accumulation determines the physiologic importance of the effusion. Because the pericardium stretches, large effusions (> 1000 mL) that develop slowly may produce no hemodynamic effects. Smaller effusions that appear rapidly can cause tamponade. Tamponade is characterized by elevated intrapericardial pressure (> 15 mm Hg), which restricts venous return and ventricular filling. As a result, the stroke volume and pulse pressure fall, and the heart rate and venous pressure rise. Shock and death may result.

Clinical Findings

A. Symptoms and Signs
Pericardial effusions may be associated with pain if they occur as part of an acute inflammatory process or may be painless, as is often the case with neoplastic or uremic effusion. Dyspnea and cough are common, especially with tamponade. Other symptoms may result from the primary disease.

A pericardial friction rub may be present even with large effusions. In Cardiac tamponade, tachycardia, tachypnea, a narrow pulse pressure, and a relatively preserved systolic pressure are characteristic. Pulsus paradoxus - a greater than 10 mm Hg decline in systolic pressure during inspiration due to further impairment of left ventricular filling - is the classic finding, but it may also occur with obstructive lung disease. Central venous pressure is elevated, and edema or ascites may be present; these signs favor a more chronic process.

B. Laboratory Findings
Laboratory tests tend to reflect the underlying processes.

C. Diagnostic Studies
Chest x-ray can suggest effusion by an enlarged cardiac silhouette with a globular configuration but may appear normal. The ECG often reveals nonspecific T wave changes and low QRS voltage. Electrical alternans is present uncommonly but is pathognomonic. Echocardiography is the primary method for demonstrating pericardial effusion. Tamponade presents a characteristic picture of inadequate ventricular filling (diastolic collapse of the right ventricle or right atrium). The echocardiogram readily discriminates pericardial effusion from congestive heart failure. MRI also demonstrates pericardial fluid and lesions. Diagnostic pericardiocentesis or biopsy is often indicated for microbiologic and cytologic studies; a pericardial biopsy may be performed relatively simply through a small subxiphoid incision.

Treatment

Small effusions can be followed clinically and with the aid of echocardiograms. When tamponade is present, urgent pericardiocentesis is required. Removal of a small amount of fluid often produces immediate hemodynamic benefit, but complete drainage with a catheter is preferable. Continued drainage may be indicated.

Additional therapy is determined by the nature of the primary process. Recurrent effusion in neoplastic disease and uremia, in particular, may require partial pericardiectomy.

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