QTc interval evaluation in patients with right bundle branch block or bifascicular blocks

Abstract

Background The right bundle branch block (RBBB) and the bifascicular blocks affect QRS duration in the right precordial leads, which are usually used for QT interval determination. Up to now, there is no clear recommendation how to determine QT interval in patients with RBBB or bifascicular block. Hypothesis The hypothesis of the present study was to evaluate the feasibility of a simple formula for RBBB and bifascicular block correction, thereby making it easier to determine the QTc interval. Methods In patients with intrinsic QRS duration <120 ms, artificial RBBB with either left posterior (LPFB) or left anterior fascicular block (LAFB), created by left ventricular pacing maneuvers, were corrected using the Bogossian formula (QTm) and afterward were heart rate corrected (QTmc). Heart rate correction was performed using different heart rate formulas in comparison to each other. The QTmc intervals were compared in each patient with the QTc interval during intrinsic rhythm. Results A total of scheduled 71 patients were included in this prospective multicenter observational comparative study. Compared to intrinsic QTc interval, the mean ΔQTmc interval by combination of the Bogossian and the Hodge formulas was −3 ± 24 ms in RBBB + LPFB (P = .44) and −6 ± 25 ms in RBBB + LAFB (P = .15). The Bogossian formula showed a significant deviation from the actual QTc interval with both the Bazett and the Fridericia formulas. Conclusion In combination with the Hodge formula, the Boggosian formula delivered the best results in comparing the true QTc interval in narrow QRS with the QTmc interval in the presence of a bifascicular block.

QTc evaluation in patients with bundle branch block

“…In this prospective multicenter observational study, 71 patients were included. The mean difference between intrinsic QTc and corrected QTc during RBBB was −3 ± 24 ms and − 6 ± 25 ms for RBBB with left posterior and left anterior hemiblock, respectively [26] , thus demonstrating the applicability of the LBBB formula in patients with RBBB.

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“…*applicability of this formula in RBBB was shown in a following publication [26] . **further assessment performed in four following publications [22] , [23] , [25] , [26] . ***further assessment performed in the same publication [20] .…”

“…The estimation of the QT interval in the presence of BBB is significantly more complex at extreme heart rates (i.e., heart-rates other than 60 bpm and especially in bradycardia or tachycardia). This was a relevant aspect in the Publications of Rautaharju, Tang and Erkapic [14] , [20] , [26] . In the Study of Rautahrju et al, rate- and gender-adjusted JT interval was in focus during the formula investigation.…”

“…Erkapic et al investigated the applicability of the Bogossian-formula to assess the QT interval in patients with RBBB. Based on a similar method of design as for the development of the LBBB-formula, the appropriate use during RBBB was further investigated [26] . In particular, during left-sided EP procedures an artificial RBBB (with left anterior or left posterior hemiblock) was induced by left ventricular pacing.…”

“…A fast heart rate resulted in an increasing difference between intrinsic and modified QTc. Recently, in the manuscript evaluating the LBBB-formula in RBBB-QRS-complexes, the authors applied three different heart rate correction formulas (Bazett, Fridericia, and Hodges) after QT-correction (due to QRS width) [26] . This comparison revealed that the smallest deviation was achieved by the Hodges-formula, intermediate deviation by the Fridericia-formula and the greatest deviation by Bazett’s formula.…”