AGING INCREASES ISCHEMIA-REPERFUSION INJURY IN THE ISOLATED, BUFFER-PERFUSED HEART

Survival after acute myocardial infarction is decreased in elderly pat ients as compared with the overall adult population. Although several cardiac and noncardiac causes could contribute to the increased mortal ity rate, little is known regarding the relative susceptibility of agi ng myocardium to injury during ischemia and reperfusion. We hypothesiz ed that the elderly heart is intrinsically more susceptible to damage than the adult heart. The recovery of isolated, buffer-perfused rat he arts from elderly animals (Fischer 344 rats, 24 months of age) was com pared with that of adult hearts (6 months of age) obtained from the sa me strain. Hearts underwent 25 minutes of ischemia followed by 30 minu tes of reperfusion. Hemodynamic recovery was decreased in elderly (n = 5) as compared with adult (n = 5) hearts, including developed pressur e (% of preischemic baseline: elderly 31% +/- 4% vs adult 57% +/- 4%, p < 0.01), Elderly hearts also sustained greater tissue damage, with a markedly increased release of creatine kinase (elderly 2950 +/- 500 U vs adult 860 +/- 345 U, p < 0.01) during the 30-minute reperfusion pe riod. The release of total protein and lactate dehydrogenase, other ma rkers of myocyte injury, was also increased. Thus the elderly rat hear t is more susceptible than the adult rat heart to ischemia-reperfusion injury. Greater injury during ischemia and reperfusion in an experime ntal model of aged myocardium raises the possibility of a more rapid p rogression of ischemic damage in elderly patients suffering acute myoc ardial infarction.