Corrected QT-interval during one year follow-up after an acute myocardial infarction.

One hundred and one unselected patients less than 66 years of age who had had a myocardial infarction were investigated with exercise ECG and technetium resting left ventricular ejection fraction (LVEF) within one month of the myocardial infarction (MI), and at 6 months and 12 months. QTc was measured at rest (QTcrest) and at maximal exercise (QTcwork). In patients with QTcwork less than QTcrest LVEF was found to be lower (mean 0.42) and QTcrest longer (mean 0.467 s) than in patients with QTcwork greater than QTcrest. In this latter group LVEF was 0.50 (mean value) (P less than 0.001) and QTcrest 0.426 s (mean value) (P less than 0.001). A negative correlation was found between LVEF and QTcrest, r = -0.35, P less than 0.001. A negative correlation was also found between QTcwork-QTcrest (i.e. the change in QTc during maximal exercise) and QTcrest, r = -0.69, P less than 0.001. In patients with QTcrest greater than 0.480 s at the first investigation, the one-year mortality was 50%, compared with 9% in patients with QTcrest less than 0.480 s (P = 0.0002). It is concluded that in post-MI patients, QTcrest reflects the condition of the left ventricular myocardium, a prolonged QTcrest being found with impaired myocardial function.