Augmentation of pulmonary blood flow after right ventricular bypass.

We have studied pulmonary hemodynamics after right ventricular bypass in dogs. Manipulations of pulmonary vascular resistance and transpulmonary blood pressure difference (delta Pp) made it possible to increase pulmonary blood flow. Decreasing resistance by raising arterial pH from 7.25 to 7.38 increased flow by 24.9%. Infusion of homologous blood to increase right atrial pressure from 10 to 30 mm Hg lowered resistance 41.5% and raised flow 183%. Left ventricular bypass (left atrium to aorta) lowered left atrial pressure, increased arteriovenous pressure gradient by 41.4%, and raised flow 32.8%. These experiments support earlier clinical observations of the importance of low pulmonary vascular resistance and of good left ventricular function both in selection of patients and in postoperative management after right ventricular bypass. Attention to the principles we discuss may permit right ventricular bypass operation in some patients who would not be operable by current criteria.