Differences in the recovery of right and left ventricular function after ischaemic arrest and cardioplegia

Abstract

Differential susceptibility of right (RV) and left (LV) ventricles to plain ischaemia and the contribution of cardioplegia in reducing the ischaemic damage was evaluated in a sheep model of cardiopulmonary bypass. Sheep (n = 16) were equally divided for the two protocols of the study. Each sheep served as its own control. RV and LV functions were studied and compared by plotting ventricular function curves (Starling and Sarnoff). The mathematical centre of mass (COM) for each curve was computed by a polynomial regression program. The COM values of the contractility indices [stroke volume (SV), stroke work (SW)] represented ventricular heterometric reserve. RV and LV heterometric reserve was significantly (P less than 0.01) reduced after 1 h plain ischaemia, and quantitatively this change was more for RV than for LV (P less than 0.05). As compared to LV, a significantly greater reduction in RVSW was brought about by a significantly (P less than 0.01) greater reduction in RVSV, because there were no significant differences between the post-ischaemic recovery in the RV and LV afterloads. Cardioplegic protection nearly normalized filling pressure and contractility (SV, SW) of both ventricles, but major differences were observed in the recovery of compliance. Recovery in the RV compliance exceeded the control values, and quantitatively the recovery in RVSW was slightly more than in LVSW. The results of this study indicate that the RV suffers more damage from plain ischaemic arrest and hence benefits more from the cardioplegic protection.