Application of the Bogossian formula for evaluation of the QT interval in pacemaker patients with stimulated left bundle branch block

BackgroundThe presence of left bundle branch block (LBBB) represents a particular challenge in properly measuring the QT interval. Here we demonstrate the applicability of the Bogossian formula in pacemaker patients with LBBB due to apical or nonapical right ventricular (RV) pacing and preserved left ventricular function.MethodsA total of 163 patients with a cardiac one- or two-chamber pacemaker were included in this prospective, multicentre observational study. Twelve-lead ECG recordings were obtained during both intrinsic rhythm and RV pacing with induced LBBB. The QT interval measured during LBBB was corrected using the Bogossian formula to obtain the modified QT (QTm). The QTmc interval was calculated with the Bazett formula, and this was compared with the QTc interval during intrinsic rhythm.ResultsEighty-three patients (789years; male n=83) with apical and eighty patients (71 +/- 13years; male n=80) with non-apical RV pacing were included in this study. In the apical group the QTmc was determined to be 444 +/- 39ms in paced rhythm and the QTc interval 413 +/- 36ms in intrinsic rhythm. In the non-apical group these values were 430 +/- 34ms in paced and 416 +/- 32ms in intrinsic rhythm.ConclusionThe Bogossian formula is a reliable tool for QTc interval evaluation in pacemaker patients with LBBB due to apical or non-apical RV pacing. However, an overestimation of 30ms should be included in the calculation.