Comparison of left and right ventricular blood flow responses during arterial pressure reduction in the autonomically blocked dog: evidence for right ventricular autoregulation.

The effect of reducing systemic arterial pressure with an arteriovenous fistula on left and right ventricular myocardial blood flow was studied in 17 anaesthetised, open chest, autonomically blocked dogs. Global and regional myocardial blood flows were measured with radioactive microspheres. As mean arterial pressure was reduced from 133 mmHg to 78 mmHg left ventricular myocardial blood flow and the left ventricular inner to outer flow ratio decreased progressively. By contrast, right ventricular myocardial blood flow remained constant (range 78-81 ml.min-1.100 g-1) whereas right ventricular vascular resistance fell linearly (from 235 to 130 kPa.litre-1.min.100 g-1). The inner to outer right ventricular free wall flow ratio (range 1.04-1.10) and blood flow to the right side of the interventricular septum also did not change significantly. It is concluded that the right ventricular myocardium shows effective autoregulation of total and regional tissue blood flow during changes in coronary perfusion pressure.