Cardiac tamponade is a clinical diagnosis and occurs when the accumulation of fluid in the pericardial space increases pericardial pressure and leads to progressive elevation of (and usually equalization of) intracardiac pressures, with subsequent limitation to ventricular diastolic filling and a decline in cardiac output. Postoperative tamponade is more frequent after valve surgery than after coronary artery bypass surgery and is more frequent with anticoagulant therapy. 2-D echocardiography with Doppler plays a major role in the identification and assessment of the hemodynamic significance of a large pericardial effusion. Echocardiography is sensitive, specific, and noninvasive. Computed tomography and magnetic resonance imaging often are less readily available and generally are not necessary. The chest radiograph may show an enlarged cardiac silhouette but will not differentiate tamponade from a noncompressive pericardial effusion. Rarely, the echocardiographic findings in tamponade reveal a moderate-to-large pericardial effusion, right atrial and right ventricular collapse, a plethoric vena cava, and, in approximately 25% of patients, the very specific finding of left atrial collapse. The mechanism of pulsus paradoxus, that is, bulging of the interventricular septum into the left ventricle, leading to a reduction in left ventricular volume and, correspondingly, a reduction in cardiac output, may be visible by echocardiogram.
- 2-D echocardiography with Doppler.
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