Effect of Weight Loss After Bariatric Surgery on Left Ventricular Mass and Ventricular Repolarization in Normotensive Morbidly Obese Patients

To assess the effect of weight loss on ventricular repolarization in morbidly obese patients, 39 normotensive subjects whose baseline body mass indexes were ≥40 kg/m2 before weight loss from bariatric surgery were studied. All patients were free of underlying organic heart disease, heart failure, and conditions that might affect ventricular repolarization. Twelve-lead electrocardiography and transthoracic echocardiography were performed just before surgery and at the nadir of postoperative weight loss. The corrected QT interval (QTc) was derived using Bazett's formula. QTc dispersion was calculated by subtracting the minimum from the maximum QTc on the 12-lead electrocardiogram. Echocardiographic left ventricular (LV) mass was indexed to height2.7. The mean body mass index decreased from 42.8 ± 2.1 to 31.9 ± 2.2 kg/m2 (p <0.0005). For the entire group, weight loss was associated with significant reductions in mean QTc (from 428.7 ± 18.5 to 410.5 ± 11.9 ms, p <0.0001) and mean QTc dispersion (from 44.1 ± 11.2 to 33.2 ± 3.3 ms, p <0.0005). Mean QTc and QTc dispersion decreased significantly with weight loss in patients with LV hypertrophy but not in subjects without LV hypertrophy. Multivariate analysis identified pre–weight loss LV mass/height2.7 as the most important predictor of pre–weight loss QTc and QTc dispersion and also identified weight loss–induced change in LV mass/height2.7 as the most important predictor of weight loss–induced changes in QTc and QTc dispersion. In conclusion, LV hypertrophy is a key determinant of QTc and QTc dispersion in normotensive morbidly obese patients. Regression of LV hypertrophy associated with weight loss decreases QTc and QTc dispersion.