Cardiac performance and myocardial blood flow in pigs with compensated right ventricular hypertrophy.

Abstract

Compensated right ventricular hypertrophy (RVH), defined by a greater than 100% RV weight increase compared to 17 normal animals, was created in 17 young pigs by pulmonary arterial banding. RVH was associated with significant elevations (p less than 0.001) in RV peak dP/dt, RV stroke work, RV minute work and RV rate-pressure product compared to normal animals matched by body weight. RV peak dP/dt showed a positive correlation (p less than 0.001) with RV peak systolic pressure in normals; however, this relationship was lost in banded animals since progressively higher RV pressures were not associated with concomitant increases in RV peak dP/dt, thus, suggesting an intrinsic difference between right and left ventricles when working at systemic arterial pressures. Time to RV peak dP/dt became progressively longer (p less than 0.05) as RV weight increased in the RVH animals. When indices of cardiac work were normalized for RV weight, the RVH group could not be distinguished from normals suggesting that the performance per unit weight of RV muscle in RVH was unchanged. Total RV blood flow, measured by radioactive microspheres, closely followed (p less than 0.001) increases in RV mass in banded animals. Blood flow . g-1 muscle in RV and septal right side were unaltered in RVH; however, regional perfusion of the left ventricle (p less than 0.001) and septal right side were unaltered in RVH; however, regional perfusion of the left ventricle (p less than 0.001) and septal left side (p less than 0.02) increased significantly. There were regional variations in RV perfusion which were maintained in compensated RVH; stress (isoprenaline infusion) caused significant increases in blood flow to all regions of the heart in normal and RVH animals (p less than 0.001), but relative regional distribution was maintained. Our observations suggest a relationship between myocardial work and blood flow in RVH such that RV perfusion . g-1 is elevated to meet haemodynamic requirements once RV regional work . g-1 become greater than normal.