QTc Interval Prolongation with Increasing Body Mass Index

Yoo, Young Hoon; Kang, Hee Sung; Roh, Yong Kyun

Abstract

BACKGROUND
Prolongation of the QTc interval is a risk factor for ventricular tachycardia, ventricular fibrillation, especially torsades de pointes, and sudden death. It is associated with increasing age, female sex, some of antiarrhythmic drugs, tricyclic antidepressants, and conditions such as hypokalemia, hypothermia, subarachnoid hemorrhage, congenital long QT syndrome. Earlier studies reported lengthening of the QTc interval with increasing body mass index (BMI) and intra-abdominal fat. But no such reports exist in Korea. Therefore, we determined the relationship between BMI and the QTc interval. METHODS: The study population consisted of 372 persons who undertook periodic health examination in a university hospital between September and December 1998. BMI and standard 12-lead electrocardiogram were measured in all subjects. Excluding 4 patients who had arrhythmia where QTc interval could not be calculated, the QT interval was measured in the electrocardiogram of 368 subjects. The QT interval was measured in the leads that showed the longest interval for three consecutive beats and then were averaged. Correlation between the calculated QTc interval and BMI was examined. The QTc interval difference according to sex and obesity was also analyzed. RESULTS: Among 368 subjects, there were 197 men (54%) and 171 women (46%). The mean ages were 44.5 years for men and 47.6 for women. The BMI was 23.8 3.13 (mean SD). Obese subjects with BMI above 27 kg/m2 totalled 61 (17%), including 31 men and 30 women. The QTc interval was 399 25 msec (mean SD), and the subjects showed prolonged QTc intervals of 24 (12 men and 12 women). There was a statistically significant correlation between BMI and QTc interval (r=0.135, P=0.0094), and the obese subjects were found to have a longer QTc interval than the nonobese controls. Women also had a longer QTc interval than men. CONCLUSION: There was a significant correlation between BMI and QTc interval, and longer QTc interval was observed in obese patients. The QTc interval should be considered when analyzing electrocardiogram of obese patients.