The hemodynamic response of the right ventricle following acute and chronic partial obstruction of the main pulmonary artery in dogs.

In eight adult dogs the main pulmonary artery was constricted to elevate the right ventricular peak systolic pressure to 50% of the peak aortic pressure at rest. The response of the right ventricle was assessed immediately, at 30 minutes and at six months. The right ventricle responded to acute systolic loading by complete compensation. After 30 minutes there was a reduction in the right ventricular outflow tract resistance. The cardiac output, heart rate and aortic pressure were maintained. The right ventricular systolic ejection period, end-diastolic pressure, peak pressure time, mean systolic pressure, right ventricular-main pulmonary artery mean systolic gradient, right ventricular work index, systolic work and outflow tract resistance were all increased.The right ventricle in the dog was shown to have an immediate capacity to compensate for systolic loading and retains this capacity for long periods of time. The ability to increase work is accomplished by adaptations in right ventricular physiology which increase right ventricular mean systolic pressures and prolong the right ventricular ejection period.