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Decoding electrocardiographic predictors of left ventricular mechanical remodeling in patients with left bundle branch block

Introduction – Left bundle branch block (LBBB) occurrence is uncommon in the general population (~1-3%), but is more prevalent among patients with congestive heart failure (~30%), and portends worse prognosis1-3. The impact of LBBB on left ventricular (LV) systolic function can range from minimal to dramatic reduction of ejection fraction. The delay in electrical activation subsequently triggers dyssynchronous contraction of the LV opposing walls, leading to ventricular remodeling and elevated LV filling pressures. This is turn results in electrical and mechanical left atrium (LA) remodeling. The left ventricular activation time (LVAT) and P-wave terminal force in lead V1 (PTFV1) have been correlated with cardiac resynchronization response. However, the relationship between these electrocardiographic markers and LV mechanical remodeling has not been evaluated. Aims – The aim of this study is to investigate the relationship between LVAT and PTFV1 recorded on ECG and the LV mechanical remodeling evaluated by the left ventricular end-diastolic diameter (LVEDd) in patients with LBBB. Methods – We have conducted a retrospective, observational study on 155 consecutive patients diagnosed with LBBB admitted in our clinic between January 2017 and December 2019 with NYHA class I-IV, regardless of the left ventricle ejection fraction (LVEF). Biventricular electrical activation in LBBB was performed by measuring the right and left ventricular activation times (RVAT, LVAT) and electrical activation of the LA was analyzed by measuring P-wave terminal force in lead V1 (PTFV1). Results – In our cohort, LVEDd is statistically significantly correlated with LVAT and PTFV1, with a higher Pearson correlation coefficient for LVAT compared to PTFV1. In multivariate analysis LVAT and PTFV1 are independent predictors of LVEDd. Conclusion – This study suggests that LV mechanical remodeling in patients with LBBB can be predicted by the delayed electrical activation of the LV and the magnitude of P-wave negative terminal forces in V1.