QT interval change with age in an overtly healthy older population

Background: Prolonged QT interval on the surface electrocardiogram (ECG) is renown to be associated with arrhythmias, coronary heart disease, and sudden cardiac death. Increased QT dispersion has also been related to arrhythymias which are more frequent in the elderly. Hypothesis: This study investigated the relationship between aging, QT interval, and QT dispersion. Methods: Normal resting ECGs were recorded from 96 healthy subjects (73 women, age range 40-102 years). No subject had symptoms or signs of heart disease and none was on medication affecting cardiac function. All had normal heart size on chest x-ray and normal electrolytes. Using a digitizing board, the RR and QT intervals were measured on each lead of each ECG, excluding only the leads in which the T wave was not visible. Mean RR, mean QT interval, and heart rate-adjusted QTc interval (standard Bazet's formula) were obtained from these measurements. Further, QT dispersion was calculated for each ECG as (1) the difference between the maximum and minimium QT interval, and (2) as the coefficient of variance of QT interval of all measurable leads. Results: A significant correlation between aping and prolonged QTc was noted in the total population (r = 0.43, p < 0.05), as well as in men (r = 0.4, p<0.05) and women (r 0.23, p<0.05) separately. There was no association between QT dispersion and increasing age regardless of the method of calculation (r = -0.04, r = -0.08 respectively, both MS). Conclusion: The rate-adjusted QT interval is prolonged with increasing age and may contribute to the increased risk of ventricular arrhythmias and cardiac mortality in elderly patients.