Hypertrophy of surviving myocytes overlying the infarct in human old myocardial infarctions with abnormal Q waves.

Abstract The time course of hypertrophy of surviving myocytes overlying the infarct after the onset was examined and the hypertrophy was analyzed in relation to the transmural extent of infarct in 34 autopsied hearts with Q wave infarction. The 34 hearts were divided into 4 groups according to the length of time between the onset of infarction and death. This was less than 5 days in group 1 ( n = 10), 20–30 days in group 2 ( n = 7), 40–60 days in group 3 ( n = 7), and 12–24 months in group 4 ( n = 10). To clarify the regional hypertrophy of myocytes overlying the infarct, the size of the surviving myocytes in the outer third of the left ventricular wall in the 1-cm wide central zone of the infarct was compared with that of the myocytes in the outer third of the left ventricular wall without infarction (control wall) in the same heart. To exclude factors which stimulate the hypertrophy of the whole left ventricle, the ratio of the myocyte diameter in the infarcted wall to that in the control wall was examined. It was 1.0 ± 0.0 (mean ± SD) in group 1, 1.0 ± 0.1 in group 2, 1.2 ± 0.1 in group 3, and 1.3 ± 0.1 in group 4. The ratio was significantly higher in group 3 than in groups 1 and 2, and was highest in group 4. In group 4, the corrected percentage transmural extent of infarct indicating the original transmural extent of infarct at the acute stage was 63 + 8%, and this transmural extent correlated positively with the ratio of myocyte diameter. It was concluded that the hypertrophy of surviving myocytes becomes detectable more than one month after the onset of infarction, probably due to compensation for increased local wall stress after the loss of myocytes.