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

Background: 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.

Methods: 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.

Results: Irrespectively of the used correction formula, QTc interval length was reduced after the surgery (QTc -31 ± 18 ms; QTc -12 ± 15 ms; QTc -14 ± 15 ms; QTc -9 ± 15 ms; all Ps < 0.001), but QTc reduction was significantly greater than the reduction in QTc calculated upon the other three equations (all Ps < 0.001). Moreover, changes in QTc (P < 0.001) but not in QTc, QTc and QTc (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 QTc, QTc and QTc values (all Ps < 0.05) preoperatively, whilst changes in QTc interval length after the surgery were not consistently associated to concurrent changes in metabolic traits.

Conclusions: 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.