Mitochondrial and myocardial performance. Response to ischemia and reperfusion

The relationships between cardiac bioenergy metabolism and myocardial function were examined in a model of global myocardial ischemia and reperfusion. The respiratory activity of distinct populations of subsarcolemmal and interfibrillar mitochondria was correlated with max dP/dt (an index of myocardial contractility with respect to time). Max dP/dt was significantly reduced to 27% of the preischemic value following two hours of cardioplegia-protected, warm, global, ischemia in dogs during the cardiopulmonary bypass period. Reperfusion resulted in improved myocardial function such that by 60 minutes of reperfusion, max dP/dt returned to baseline. Significant declines in both state 3 respiratory rates and respiratory control indexes for subsarcolemmal and interfibrillar mitochondria were noted following the ischemic interval. Mitochondrial function similarly returned to baseline values following 60 minutes of reperfusion. These data demonstrate a close association between mitochondrial and myocardial activity.