Predictive value of QT interval correction formulas for all-cause mortality in patients with left bundle branch block

BACKGROUND: QT prolongation is recognized as a prognostic marker associated with poor clinical outcomes and is frequently observed in patients with left bundle branch block (LBBB). However, the identification of QT prolongation in LBBB patients remains challenging. Although multiple QT correction formulas have been specifically developed for LBBB, the prognostic significance and predictive value of these corrected QT intervals in LBBB patients have not been conclusively established. METHODS AND RESULTS: This retrospective cohort study consecutively enrolled LBBB patients from 2011 to 2021. The exclusion criteria comprised patients with persistent atrial fibrillation/flutter, atrioventricular block, right ventricular pacing, atypical LBBB morphology and malignant tumor. Comprehensive data collection included electrocardiographic parameters, biochemical profiles, and clinical characteristics for all-cause mortality analysis. Five established QT correction (QTc) formulas (Rautaharju, Yankelson, Wang, Bogossian, and Colunga) were applied to calculate QTc intervals in LBBB patients. During a median follow-up time of 5.1 ± 2.9 years, the overall mortality rate was 21.50% (106/493), with differential rates observed between cardiology (18.32%, 74/404) and non-cardiology (35.96%, 32/89) subgroups. Multivariable regression analysis identified age, left ventricular ejection fraction, diabetes mellitus, and coronary artery disease as significant predictors of all-cause mortality following adjustment. Cardiac resynchronization therapy demonstrated consistent protective effects across all five analytical models constructed by each QTc formula. Furthermore, prolonged QTc interval calculated using all 5 formulas was significantly associated with increased mortality risk in multivariable analyses. Among the correction formulas, the Rautaharju formula exhibited superior predictive performance for all-cause mortality (AUC = 0.812, cut-off = 416.59 ms). CONCLUSION: In this retrospective cohort, patients with LBBB demonstrate substantially elevated mortality rates, particularly in non-cardiology populations, necessitating heightened clinical attention. While our findings demonstrate a robust association between QTc prolongation and all-cause mortality. Among the formulas evaluated, our study identifies the Rautaharju formula as the preferred tool for risk stratification in LBBB patients.