Ischemic threshold and myocardial stunning in the aging heart

The aging heart appears to be more susceptible to ischemia-reperfusion inju ry than the adult heart. There is no evidence of an age-related difference in the threshold of myocardial ischemia and myocardial stunning. We studied the effects on mechanical, hemodynamic, and metabolic parameters of graded reduction of coronary perfusion pressure from 66 to 29 mmHg in isolated an d perfused hearts from adult and senescent rats. Cardiac function was also assessed during recovery following ischemic period. In both adult and senes cent hearts developed pressure and +dP/dt linearly decreased and end-diasto lic pressure linearly increased with decreasing perfusion pressure. However , all mechanical parameters were more severely impaired in senescent than i n adult hearts at 37 mmHg and 29 mmHg perfusion pressure, respectively (p < 0.01 vs. adult). At 29 mmHg, in both adult and senescent hearts lactate pr oduction similarly increased whereas creatine kinase leakage did not differ from controls. Developed pressure recovered more slowly in senescent than in adult hearts (p < 0.001) in the absence of cellular damage and in the pr esence of restoration of coronary flow. Lactate production observed at the same step of coronary perfusion pressure suggests that the ischemic thresho ld is similar in adult and senescent hearts. The slow recovery of myocardia l contractility after the ischemic period observed in senescent hearts sugg ests an age-related increase in myocardial stunning. (C) 1999 Elsevier Scie nce Inc. All rights reserved.