Influence of acute right ventricular dysfunction on cardiac tamponade.

Echocardiographic and hemodynamic data were measured in nine closed chest dogs during graded cardiac tamponade (pericardial pressure 5, 10, 15 mm Hg) before and after production of diffuse acute ischemic right ventricular dysfunction. Right ventricular dysfunction was produced by intracoronary injection of nonradioactive microspheres (mean diameter +/- SD 54 +/- 4 microns) and caused a significant increase in right atrial pressure (7.6 +/- 1.4 vs. 1.6 +/- 1 mm Hg, p less than 0.001) and cross-sectional areas of both the right atrium (8.3 +/- 0.3 vs. 5.6 +/- 0.2 cm2, p less than 0.001) and right ventricle (8.8 +/- 0.4 vs. 5.7 +/- 0.4 cm2, p less than 0.001). Right atrial and ventricular collapse required a significantly larger pericardial effusion and pericardial pressure after right ventricular infarction than before. Mean aortic pressure had fallen 1.9 +/- 2% and 6.5 +/- 6.9% at the time of right atrial collapse (p = NS before vs. after right ventricular dysfunction) and 3 +/- 4.1% and 20.1 +/- 20.8% at the time of right ventricular collapse (p less than 0.03) before and after right ventricular dysfunction, respectively. In the presence of ischemic right ventricular dysfunction, echocardiographic signs of cardiac tamponade are less sensitive and occur later in the hemodynamic progression of cardiac tamponade. Pulsus paradoxus with cardiac tamponade was not prevented by coexisting ischemic right ventricular dysfunction.