RELATIONSHIP BETWEEN PRESSURE-RATE PRODUCT AND MYOCARDIAL OXYGEN-CONSUMPTION OF NORMAL AND HYPERTROPHIC RIGHT VENTRICLES IN OPEN-CHEST DOGS

There are few reports on the relationship between right ventricular pe rformance and its myocardial oxygen consumption (RVMVO2). The present study was conducted to investigate the relationship between RVMVO2 and the mechanical performance of normal and hypertrophic right ventricle s in open-chest dogs. Right ventricular hypertrophy (RVH) was induced by producing chronic right ventricular pressure overload by banding th e pulmonary arteries of 8 puppies for 6 months. The experiment was per formed under basal conditions and after increasing the RVMVO2 in the e ight dogs with RVH as well as in 20 normal dogs. The RVMVO2 showed sig nificant positive relationships with right coronary (RCA) flow, right ventricular systolic pressure, and right ventricular pressure-rate pro duct (PRP) in both the normal right ventricle and RVH hearts. However, the slope between the PRP and RVMVO2 was significantly steeper in the normal right ventricle (RV) than in the hypertrophic RV. When the PRP was normalized for the thickness of the right ventricular free wall, the slope of the two regression lines merged into a single line of fit . These results suggest that the pressure-rate product can be used to predict myocardial oxygen demand not only in the normal RV but also in well-compensated, hypertrophic RV. Isoproterenol induced smaller incr eases in cardiac output in the dogs with RVH than in those with normal RV. It also appears that the cardiac output of the hypertrophic RV is less sensitive to beta-adrenoceptor stimulation than that of the norm al RV.