Age-dependent changes in myocardial susceptibility to ischemic injury.

We studied the relation between age and the heart's ability to tolerate ischemia. Groups of 5-7 isolated Langendorff perfused hearts from neonatal (5 days old), immature (11-44 days old), and adult (54 days old) rats, were subjected to 60 minutes of global ischemia and 60 minutes of reperfusion at 37 degrees C. Pre-ischemic left ventricular developed pressure was 54 +/- 1, 56 +/- 2, 59 +/- 4, 80 +/- 3, 91 +/- 9, 91 +/- 8, 94 +/- 3, 101 +/- 10, 107 +/- 8 and 132 +/- 4 mmHg in the 5, 11, 14, 18, 23, 26, 33, 40, 44, and 54 day old groups, respectively. Left ventricular developed pressure recovered to 65 +/- 13, 69 +/- 4, 103 +/- 14, 84 +/- 10, 81 +/- 3, 59 +/- 11, 42 +/- 10, 34 +/- 6, 34 +/- 6 and 25 +/- 7% respectively. Ischemia-induced contracture was greater in adult hearts and the time-to-onset and the time-to-peak contracture decreased with increasing age. Leakage of creatine kinase after ischemia correlated poorly with the recovery of contraction. Left ventricular end-diastolic pressure, at the end of 60 minutes of reperfusion, increased in an age-dependent manner from a pre-ischemic value which was set at 2-8 mmHg to 14 +/- 4, 22 +/- 2, 21 +/- 5, 27 +/- 3, 47 +/- 16, 52 +/- 7, 71 +/- 7, 81 +/- 9, 73 +/- 5, and 82 +/- 8 mmHg in the 5, 11, 14, 18, 23, 26, 33, 40, 44, and 54 day old groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)