Dispersion of the QT Interval as a Predictor of Cardiac Death in Patients with Coronary Heart Disease

Abstract

Abnormal dispersion of the QT interval (QTd), measured as interlead variability of QT, may reflect a regional variation in duration of ventricular action potential and, hence, of cardiac electrical instability. In this retrospective study, we analyzed the effect of QTd on survival and its relation to other known predictors of subsequent cardiac death (CD) and sudden cardiac death (SCD) in 162 patients with coronary heart disease (CHD). QTd was calculated as the difference between the highest and lowest values measured in each of the 12 ECG leads (Qtmax - QTmin). Seventeen CDs occurred, including nine SCDs, during a 25 +/- 11 month follow-up. There were significant differences in CD (P < 0.001 in log-rank test) and in SCD (P < 0.01). The 1- and 3-year survivals were 87.5% and 76.5% in patients with QTd > 0.060 seconds versus 98% and 93.5% in patients with QTd < 0.060 seconds, respectively. Additionally, a stepwise Cox regression analysis revealed that increased QTd was an independent risk factor of CD and SCD. A cut-off value of 60 ms for QTd had a 53% sensitivity and 79% specificity in discriminating patients who are at risk of CD. The positive and negative prognostic values were 23% and 93%, respectively. Our findings support the hypothesis that increased QTd has a prognostic value in the stratification of patients with CHD independent of other known risk factors.