title: QT Interval Shortening After Bariatric Surgery Depends on the Applied Heart Rate Correction Equation.
abstract: A shortening of electrocardiographic QT interval has been observed in obese subjects after weight loss, but previous results may have been biased by inappropriate heart rate (HR) correction.
  
  
  
  Electrocardiography (ECG) recordings of 49 (35 females) severely obese patients before and 12 months after Roux-en-Y gastric bypass (RYGB) surgery were analysed. QT interval (QTc) was calculated by using four different equations, i.e. Bazett, Fridericia, Framingham and Hodges.
  
  
  
  Irrespectively of the used correction formula, QTc interval length was reduced after the surgery (QTcBazett-31 ± 18 ms; QTcFridericia-12 ± 15 ms; QTcFramingham-14 ± 15 ms; QTcHodges-9 ± 15 ms; all Ps < 0.001), but QTcBazettreduction was significantly greater than the reduction in QTc calculated upon the other three equations (all Ps < 0.001). Moreover, changes in QTcBazett(P < 0.001) but not in QTcFridericia, QTcFraminghamand QTcHodges(all Ps > 0.05) were significantly correlated with concurrent changes in HR. Multivariate regression analyses revealed a significant independent association of serum insulin levels with QTcFridericia, QTcFraminghamand QTcHodgesvalues (all Ps < 0.05) preoperatively, whilst changes in QTc interval length after the surgery were not consistently associated to concurrent changes in metabolic traits.
  
  
  
  Our data show that the extent of weight loss-associated QTc interval shortening largely depends on the applied HR correction equation and appears to be overestimated when the most popular Bazett's equation is used.
authors.affiliation: Department of Medicine/Physiology, University of Fribourg, Fribourg, Switzerland.
authors.forename: Erik K
authors.initials: EK
authors.lastname: Grasser
authors.affiliation: eSwiss Medical and Surgical Center, Interdisciplinary Obesity Center, St. Gallen, Switzerland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Ernst
authors.affiliation: eSwiss Medical and Surgical Center, Interdisciplinary Obesity Center, St. Gallen, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Thurnheer
authors.affiliation: eSwiss Medical and Surgical Center, Interdisciplinary Obesity Center, St. Gallen, Switzerland. bernd.schultes@eswiss.center.
authors.forename: Bernd
authors.initials: B
authors.lastname: Schultes
mesh_terms: D000328:Adult; D004562:Electrocardiography; D005260:Female; D015390:Gastric Bypass; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D009767:Obesity, Morbid / Q000503:physiopathology* / Q000601:surgery*
keywords: Bazett’s formula; Cardiac hyperpolarization; Morbid obesity; Prolonged QTc; Roux-en Y gastric bypass