Intracellular kinetics of the activator calcium of rat heart after ischemic arrest and cardioplegia: quantitative comparison of right and left ventricles.

The effects of plain ischemia (34 degrees C) and the protective role of hypothermia (20 degrees C) alone or in combination with cardioplegia (St Thomas' Hospital [STH] or glucose-potassium-nifedipine [GPN]) on the intracellular kinetics of the activator calcium of cardiac muscle were quantified and compared from the interval-force behaviour (mechanical restitution) of right and left ventricles of the perfused rat heart. Plain ischemia caused a major depression in the restitution of force of contraction of both ventricles, deranged the mixed linear-exponential functions by significantly increasing the time constants of the fitted mechanical restitution curves (MRC) and altered the control right/left ventricle interval-force relationship. The right ventricle was found to be more susceptible to ischemic damage than the left ventricle, and its inotropic reserve was virtually abolished by 1 h of plain ischemia. Hypothermic preservation during ischemia improved the mechanical restitution, salvaged the inotropic reserve and optimized right/left ventricle interval-force relationship, but the time constants of the fitted MRCs were still prolonged. However, both the cardioplegic formulations were equally effective in normalizing the time constants of the fitted curves. In general, right ventricle functions were better preserved by STH cardioplegia and left ventricle functions were better preserved by GPN cardioplegia. Cardioplegic interventions did not further improve the ventricular inotropic reserve compared with hypothermic preservation. Additional beneficial effects of cardioplegic formulations were directed towards stabilizing the linear-exponential functions and hence restitution of force of contraction.(ABSTRACT TRUNCATED AT 250 WORDS)