ABSTRACT
BACKGROUND: Sudden cardiac death in patients on a liquid protein diet has been suggested to be related to repolarization abnormalities. Although increased QT dispersion is also associated with sudden cardiac death, it has not been examined in the setting of weight loss using liquid protein diet. METHODS AND RESULTS: Sixty-three patients (mean age 42 years, 18 men) with a mean initial weight of 116 kg were randomly chosen from patients who had completed 26 weeks of liquid protein diet therapy. QT, corrected QT interval, QT dispersion and corrected QT dispersion were measured blindly along with serum albumin and electrolytes at the beginning and end of 26 weeks of liquid protein diet therapy. In 57 patients (89.5%) (group 1), QT dispersion shortened after weight loss while it was prolonged in 6 patients (10.5%) (group 2). The mean weight loss (group 1: 115+/-21 to 91+/-16 kg; group 2: 122+/-21 to 98+/-13 kg), and serum albumin and electrolyte levels before weight loss were the same in both groups. The decrease in QT dispersion in group 1 was due to increase in the minimum QT interval (350+/-22 v. 375+/-21 mis, p<0.01) after weight loss. However, the QT dispersion increase in group 2 was due to prolongation of the maximum QT interval (402+/-27 v. 441+/-19 ms, p<0.05) after weight loss. This suggests that shortening of the minimum QT interval causes the increased QT dispersion in obesity. Half the patients in group 2 showed a drop in the serum albumin level and 2 patients had an abnormally high phosphorous level at the end of the treatment. CONCLUSIONS: QT dispersion shortens in most patients (89.5%) using liquid protein diet for weight loss. However, increase of QT dispersion is seen in 10.5% of patients. The cause of increased QT dispersion in obesity (before weight loss) differs from that in patients after weight-loss using liquid protein diet. QT dispersion changes observed in this study may explain the risk of sudden cardiac death in these patients.