Electrocardiographic QTc interval: short-term weight loss effects

Abstract

OBJECTIVE: Prolongation of the QTc interval is a risk factor for ventricular arrhythmias and sudden death. There is a correlation between body mass index (BMI) and QTc, with longer intervals observed in obese subjects. Dieting and weight loss on selected diets are also associated with prolongation of the QTc interval, although the mechanisms and risk factors of this syndrome are not clearly established. The aim of the current investigation was to determine if short-term weight loss over seven days while living on a metabolic ward in¯uences cardiac repolarization as indicated by QT interval duration. DESIGN AND SUBJECTS: The elctrocardiogram QT, RR, and QTc (QT/RR 0.5 ) intervals were assessed in 30 healthy obese (BMI b 27 kg/m 2 ) men and women ingesting a balanced 1120 kcal/d formula diet (23% kcal as fat and 52 g protein/d). RESULTS: Weight loss (3.9 AE 1.7 kg) over seven days had no measurable effect on the RR interval and there was a signi®cant (P 0.02) shortening of the QT interval (mean AE s.d., 0.395 AE 0.028±0.386 AE 0.027 s) and borderline signi®-cant (P 0.11) shortening of the QTc (0.411 AE 0.028±0.404 AE 0.025 s) interval. The QTc interval normalized in three subjects with prolonged baseline QTc ( b 0.44 s). A statistically signi®cant (P 0.007) reduction in systolic blood pressure early in the course of weight loss (day 2) accompanied the electrocardiographic changes. CONCLUSION: These results fail to support the development of cardiac repolarization abnormalities in obese patients who ingest a nutritionally balanced low calorie diet over seven days. A signi®cant reduction in QT interval duration and amelioration of abnormally prolonged baseline QTc intervals suggest improved cardiac repolarization with early weight loss.

Onset of decreased heart work is correlated with increased heart rate and shortened QT interval in high-carbohydrate fed overweight rats

“…The significant increases in both systolic and diastolic pressures together with increased end systolic and diastolic volumes suggest the induction of hypertension for compansation the decreased heart work and cardiac output in MetS D r a f t 17 rats. Another compensation mechanism may be induction of QT shortening during our experiments as initial response, instead of prolonged QT observed in obese patients (Pietrobelli et al 1997). Indeed, this prolongation could be almost normalized when patients had even short-term weight loss (Bai et al 2007;Pietrobelli et al 1997) It is well accepted that MetS is a risk factor for prolonged QT, which may further increase cardiovascular morbidity and mortality in these subjects.…”

“…Another compensation mechanism may be induction of QT shortening during our experiments as initial response, instead of prolonged QT observed in obese patients (Pietrobelli et al 1997). Indeed, this prolongation could be almost normalized when patients had even short-term weight loss (Bai et al 2007;Pietrobelli et al 1997) It is well accepted that MetS is a risk factor for prolonged QT, which may further increase cardiovascular morbidity and mortality in these subjects. A short QT-interval is defined as short QT syndrome, generally a genetic disease of the electrical system of the heart and mutations in the KCNH2, KCNJ2, and KCNQ1 genes.…”

QT Interval Shortening After Bariatric Surgery Depends on the Applied Heart Rate Correction Equation

“…An abnormal ventricular repolarization, which predisposes to sudden death upon cardiac arrhythmia [3], may contribute to the increased mortality risk since obesity has been found to be associated with a high prevalence of a prolonged QT interval in electrocardiographic (ECG) recordings [4]. Furthermore, weight loss, in particular when induced by bariatric surgery, has been found to reduce QT interval (QTc) length in many studies (for overview see Table 1) [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. However, the validity of this observation has been challenged by one previous study [9] that demonstrated that the significance of QTc shortening upon weight loss gets lost when the QT interval is corrected for heart rate (HR) by using Fridericia or Framingham correction equation instead of the most commonly used Bazett equation.…”

Association between Maximal Oxygen Uptake and the Heart Rate Corrected-QT Interval in Postmenopausal Overweight Women

“…Previous studies have reported that morbid obesity is also correlated with a prolonged QTc interval 11,12) . Several studies have observed that weight loss could improve the QTc in obese subjects [12][13][14] . These results suggest that the resolution of obesity by diet or exercise can therefore help to improve the autonomic nervous system, arrhythmia, LVH, prevention of cardiac sudden death and coronary artery disease.…”