Dynamic changes of QT interval and QT dispersion in non-Q-wave and Q-wave myocardial infarction

QT interval and QT dispersion both prolong early postinfarction. Non-Q wave (NQMI) and Q-wave myocardial infarction (QMI) differ in the extent of tran smural necrosis, which may influence these measures of myocardial repolariz ation. This study compared dynamic changes in QT interval and QT dispersion early postinfarction between NQMI and QMI. In 40 patients with NQMI and 69 patients with QMI. maximum QTc (QTc(max)) and QT dispersion (QTD) were mea sured during the first 4 days postinfarction. Infarct size was assessed dai ly by using the Selvester BRS score. In both infarct types, QTc(max) and QT D were prolonged on day 1 of infarction, peaking over the nest 2 days befor e returning toward baseline by day 4. NQMI patients had significantly longe r QTc(max) and QTD by days 2 to 3 when compared with QMI patients. Multivar iable linear regression identified "infarct type x QRS score" as the only i ndependent predictor of QTc(max) (R-2 = .32, P < .0001) and QTD (R-2 = .19, P < .0001) on day 2. In conclusion, dynamic changes of QTc(max) and QTD oc cur in both infarct types. Large NQMI is associated with gl eater prolongat ion of QTc(max) and QTD, which may be due to greater M cell uncoupling and exposure when compared with QMI.