A Study of QT Interval of Healthy Individuals and its Determinants in the Indian Setting

Abstract

Background & Objectives: This study aimed at determining the simultaneous impact of socioeconomic status, lifestyle factors like daily exercise, serum potassium and lipid profile on QTc interval in healthy subjects. Method: A facility-based cross-sectional study was conducted during July-Dec 2009 in a tertiary care hospital. Data on heart rate corrected QT interval (QTc), age, gender, socio-economic status, body mass index, habit of daily exercise, smoking and alcohol status, serum potassium, and lipid profile were obtained in 153 apparently healthy subjects. Results: The QTc interval increased significantly with advancing age (r = 0.180, p = 0.026) and higher socio-economic status (r = - 0.183, p = 0.023). Males (245.97 ± 1.72, mean ± SEM, P < 0.0001) had significantly shorter QTc interval than females (257.72 ± 2.22) and subjects with daily habit of exercise had significantly shorter QTc interval than their counterparts (P < 0.008). QTc did not correlate at significant level with serum potassium or lipid profile in univariate regression analysis. A backward stepwise multivariable regression analysis showed that heart rate (P < .0001), gender (P < .001) and age (P < .003) independently predicted QTc interval and daily habit of exercise was a weak (P = .106) predictor of QTc. Interpretation & Conclusions: QTc interval is prolonged with increasing age, faster heart rate and female gender. Screening of these individuals for detection of the risk of cardiac arrhythmias may be useful for reducing cardiovascular morbidity.