Coronary reserve and right ventricular function in awake newborn lambs with persistent right ventricular hypertension

Right ventricular function curves as measured by right ventricular stroke work were normal in all control lambs, whereas three of five lambs with banded pulmonary arteries had relatively flat curves. Left ventricular function was similarly normal in the control group as compared to a near zero slope function curve in the banded group. Regional myocardial blood flow to the septum and right and left ventricles was similar in control and banded lambs. At rest right ventricular coronary vascular resistance was lower in the banded than in the control group and decreased in both groups during both isoproterenol and dextran stress states. In general, both groups had a similar ratio of right to left ventricular oxygen supply to demand ratio. These results show first that there is minimal, if any, biventricular functional reserve in lambs with persistent right ventricular hypertension, and second, that there is substantial coronary vascular reserve in both normal and banded groups. Speculation: Although both right and left ventricular function are impaired in neonatal lambs with persistent right ventricular hypertension, the etiology is unclear. We have demonstrated right ventricular coronary vascular reserve in this group; however, we did not test for further reserve in the dextran stress state, and therefore cannot be certain that coronary blood flow was not maximal in the dextran state and hence ventricular function impaired by inadequate oxygen supply.