Q-T interval changes in acute transmural myocardial infarction.

The serial Q-T interval changes were studied in 29 survivors of acute transmural anteroseptal (11 patients), extensive anterior (10 patients), and inferior (8 patients) myocardial infarctions admitted 4 to 48 hours after the acute episode. Q-T prolongation evidenced by abnormal Q-T ratio was a constant and almost universal feature detected in 28 (97.06%) patients. The maximum Q-T prolongation was observed on an average about 36 hours after the onset of acute episode. Patients with anterior myocardial infarction had significantly higher Q-T ratios than inferior myocardial infarction group. There was a rapid decline towards normal in anteroseptal and inferior myocardial infarction groups in which it settled during initial six days, whereas, in extensive anterior myocardial infarction group, it took a longer time beyond six days to settle. The normalization of Q-T interval did not correspond to settling down of the elevated ST segment. Patients having ventricular tachyarrhythmias (VT and frequent VPBS) (14) had significantly higher Q-T ratios than those without arrhythmias. Further, the Q-T ratio was significantly higher in patients with VT (4) than in those with frequent VPBs (10). Alterations in Q-T ratio were not related to severity or extent of infarction and occurrence of heart failure. It is concluded that prolongation of electrical systole (Q-T interval) is a constant phenomenon after acute transmural myocardial infarction, magnitude and time course of its alterations being related to location of infarct and its electrical complications. It does not seem to have any correlation with mechanical complications of infarction.(ABSTRACT TRUNCATED AT 250 WORDS)