QT interval and QT dispersion before and after diet therapy in patients with simple obesity.

To evaluate whether a disordered QT interval and its dispersion in obese patients, if any, may be improved by therapeutic weight reduction, 36 obese patients admitted to our university hospital were examined over a 5-year period from April 1, 1992 to March 31, 1997. Participants included 18 males and 18 females whose mean age +/- SD was 28 +/- 9 and 33 +/- 14 years, respectively, and whose mean body mass index +/- SD was 35 +/- 5 and 38 +/- 6 kg/m2, respectively. Thirty-six control patients were matched in age and gender with the obese patients. All the obese patients were treated with behavioral therapy together with very-low-calorie conventional Japanese diet (VLCD: 370 kcal/day). A standard 12-lead electrocardiogram (ECG) revealed longer maximum (445 +/- 32 msec, mean +/- SD) and minimum (388 +/- 29 msec) heart rate corrected QT intervals (QTc intervals) in the obese group than in the control group (P < 0.0001 for each). QTc dispersion, defined as the difference between maximum and minimum QTc intervals derived from 12-lead ECG, was greater in the obese group (57 +/- 19 msec) than in the control group (32 +/- 13 msec) (P < 0.0001). Both the maximum and minimum QTc intervals in the obese patients were shortened, respectively, to 434 +/- 28 msec and 377 +/- 29 msec (P < 0.05 for each) with no significant change in either QTc dispersion, QRS voltage, or QRS duration following weight reduction. The coefficient value from the linear regression line between QT interval and RR interval in the obese group was less than in the control group. Together, the results show that obesity per se causes both a prolongation of QTc interval and an increase in QTc dispersion, and that weight reduction improves the prolonged QTc interval observed in obese patients.