QT Interval Correction In Left Bundle Branch Areas Pacing (LBBAP)

Abstract

Background

LBBAP results in greater electrical resynchronization than right ventricular apical pacing. The literature exploring the impact of LBBAP on QT interval is sparse, and may have impacts on anti-arrhythmic drug monitoring.

Objective

Establish differences in QT interval during native conduction (NC) and LBBAP following atrioventricular junction ablation to minimize confounding through fusion pacing.

Methods

Retrospective chart review of 34 consecutive patients who underwent LBBAP and subsequent AVJ. RR interval, QRS duration (QRSd), and QT intervals were measured from standard 12-lead ECG during native conduction and following LBBAP and AVJ. Linear regression models were used to estimate QT as a function of RR and correction of QTc as a function of change in QRSd.

Results

QRSd (ms) in the NC and LBBAP groups was 113±32 vs.135±18 (p<0.01), respectively. Mean difference in QRSd with LBBAP was 22±35ms compared to NC. QT interval (ms) in the NC and LBBAP groups was 394±55 vs. 436±34 (p<0.01), respectively. Mean QTc (ms, Bazzette's) in the NC and LBBAP groups was 478±43 vs. 504±38, respectively. Mean difference in QTc following LBBAP was 26±47ms compared to NC. QTc^NC could be modeled as QTc^NC = QTc^LBBAP - 0.792(QRSd^LBBAP-QRSd^NC) - 8.72. With mean difference QRSd of 22ms, this simplifies to QTc^NC = QTc^LBBAP - 26.14.

Conclusion

LBBAP significantly increases QRSd and QT intervals from native rhythm. Differences in linear regression between RR and QTc between LBBAP and NC can be explained changes in QRSd. Larger studies are required to improve the accuracy of the model.