QT INTERVAL PROLONGATION PREDICTS CARDIOVASCULAR MORTALITY IN AN APPARENTLY HEALTHY POPULATION

Background. In myocardial infarction patients, heart rate-adjusted QT interval (QT(c)), an electrocardiographic indicator of sympathetic balance, is prognostic for survival. Methods and Results. In a 28-year follow-up, the association between QT(c) and all-cause, cardiovascular, and ischemic heart disease mortality was studied in a population of 3,091 apparently healthy Dutch civil servants and their spouses, aged 40-65 years, who participated in a medical examination during 1953-1954. Moderate (QT(c), 420-440 msec) and extensive (QT(c), more than 440 msec) QT(c) prolongations significantly predict all-cause mortality during the first 15 years among men (adjusted respective relative risks [RRs], 1.5 and 1.7) and among women (RRs, 1.7 and 1.6). In men, cardiovascular (RRs, 1.6 and 1.8) and ischemic heart disease mortality (RRs, 1.8 and 2.1) mainly account for this association. In women, the association cannot be attributed specifically to cardiovascular and ischemic heart disease mortality. RRs for a subpopulation without any sign of heart disease at baseline are similar. The same is observed for QT(c) prolongation after light exercise, although in this situation most associations are not statistically significant, probably because of smaller numbers in the QT(c) prolongation categories. Conclusions. Our results suggest that QT(c) contributes independently to cardiovascular risk. If autonomic imbalance is an important mechanism, it might be speculated that changes in life-style (e.g., with regard to physical exercise and smoking) may have a preventive impact.