Regional distribution of blood flow at the onset of right ventricular diastolic collapse during cardiac tamponade.

The onset of right ventricular diastolic collapse has been shown to be a very sensitive and specific sign of cardiac tamponade in both clinical and conscious canine studies, and is associated with a decline in cardiac output of about 20%. To determine if blood flow to critical regions was affected at the time of onset of right ventricular diastolic collapse, seven unanesthetized, chronically instrumented dogs were studied during cardiac tamponade induced by the intrapericardial infusion of warm saline solution. Aortic blood pressure, heart rate, and cardiac output (electromagnetic flowprobe) were recorded at baseline (drained pericardial space) and at the onset of right ventricular diastolic collapse as seen on two-dimensional echocardiography. Regional blood flow was measured with radionuclide-labeled microspheres. Despite the expected decline in cardiac output, there was no significant change in cardiac, renal, or cerebral cortical blood flow at the onset of right ventricular diastolic collapse. Therefore, this noninvasive marker of early cardiac tamponade begins before vital organ perfusion is compromised, thus strengthening its clinical value.