Usefulness of QTc interval on the discharge electrocardiogram for predicting survival after acute myocardial infarction.

The corrected QT (QTc) interval was measured on the discharge electrocardiogram of 457 consecutive patients who had survived the first 28 days after a first acute myocardial infarction (AMI). The patients were followed for 4 years. The QTc interval was not related to long-term survival after the acute phase of AMI. Sixteen percent of the patients had a QTc interval above the normal upper limit of 440 ms. Of them, 71% survived 4 years and 77% with a shorter QTc interval survived (p = 0.31). When mortality per 100 patient-years was calculated for different QTc intervals, with 10 ms accuracy, no consistent relation between the 2 variables was seen. Results that indicate a strong relation between QTc-interval prolongation and sudden death after AMI should be reevaluated. The QTc interval is not a useful prognostic tool after AMI.