Cardiac tamponade is the compression of the heart as a result of fluid within the pericardial sac. It usually is caused by blunt or penetrating trauma to the chest. A penetrating wound of the heart is associated with a high mortality rate. Cardiac tamponade also may follow diagnostic cardiac catheterization, angiographic procedures, and pacemaker insertion, which can produce perfo-rations of the heart and great vessels. Pericardial effusion with fluid compressing the heart also may develop from metastases to the pericardium from malignant tumors of the breast, lung, and mediastinum and may occur with lymphomas and leukemias,renal failure, TB, and high-dose radiation to the chest.