FOWLER and GABEL TABLE 1 Hemodynamic effects of regional cardiac tamponade Right Left Ao

We studied the hemodynamic effects of surgically induced regional cardiac tamponade in anesthetized dogs. Tamponade restricted to either the right or the left ventricle was compared with tamponade of either ventricle and both atria. Intrapericardial pressures were elevated to approximately 20 mm Hg. With tamponade of the right ventricle alone, aortic pressure rose from 161 + 3.8 to 164 + 3.4 mm Hg (p > .05) and cardiac output fell from 149.4 + 16.1 to 134.9 + 11.9 ml/kg/min (p > .05). However, tamponade of the right ventricle plus both atria decreased mean aortic pressure from 152.5 ± 3.6 to 115.9 ± 8.7 mm Hg (p < .01) and cardiac output fell from 1 18 +14.8 to 38.9 ± 4.8 ml/kg/ min (p < .01). With tamponade of the left ventricle alone, aortic mean pressure changed significantly from 158.5 + 6.1 (control) to 148.9 ± 5.0 mm Hg (tamponade) (p < .05) and cardiac output was 135.5 -+ 28.3 (control) and 11l1 24.7 ml/kg/min (tamponade) (p > .05). However, when the atria were included, mean aortic pressure fell significantly more from 155.5 ± 5.4 to 105.5 + 10.4 mm Hg (p < .01) and cardiac output fell from 142.2 ± 16 to 47.8 + 6.4 ml/kg/min (p < .01). Atrial pressure rose when the atria were included, but not with tamponade of the left ventricle alone. Right but not left atrial pressure rose slightly with isolated right ventricular tamponade. We conclude that the principal hemodynamic effects of cardiac tamponade are not the result of compression of either the right or the left ventricle, but are the consequence of compression of the atria and/or the venae cavae and the pulmonary veins. Circulation 71, No. 1, 154-157, 1985. THE HEMODYNAMIC effects of cardiac tamponade are generally believed to result from compression of the cardiac ventricles, which limits diastolic cardiac filling.'-3 However, an earlier theory stated that tamponade limited the circulation by compressing the systemic veins within the pericardial sac, thus restricting venous return to the right atrium.4 This question was studied by Isaacs et al.' and they found no diastolic pressure gradient between the venae cavae and right atrium or pulmonary veins and left atrium. They thus concluded that compression of the great veins did not contribute to the reduced diastolic filling of the heart during tamponade. However, despite the above-mentioned findings, the hemodynamic effects of regional cardiac tamponade have not been investigated. Accordingly, we studFrom the Division of Cardiology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati. Address for correspondence: Noble 0. Fowler. M.D.. Cardiology Division, University of Cincinnati Medical College, 231 Bethesda Ave., Cincinnati, OH 45267. Received July 20, 1984; revision accepted Oct. 11, 1984. ied the effect of tamponade of the right or left ventricle individually in anesthetized dogs. We then examined the effect of combined tamponade of either ventricle and both atria. This investigation showed that tamponade of the right or left ventricle alone had little hemodynamic effect; only when the atria (and great veins) were included were the usual hemodynamic effects of cardiac tamponade demonstrated.