Impact of postoperative left bundle branch block on left ventricular remodeling following transapical beating-heart septal myectomy

Abstract

Objectives: The study objectives were to evaluate the incidence of postoperative left bundle branch block and its impact on left ventricular remodeling in patients with obstructive hypertrophic cardiomyopathy after transapical beating-heart septal myectomy.

Methods: This study included 286 patients with obstructive hypertrophic cardiomyopathy who underwent transapical beating-heart septal myectomy without preoperative conduction abnormalities or permanent pacemaker implantation. Clinical data, laboratory tests, electrocardiography, and echocardiography were compared between postoperative new-onset left bundle branch block and non-left bundle branch block groups, both presurgery and 6 to 12 months postsurgery. The effect of postoperative left bundle branch block on left ventricular remodeling was evaluated using mid septal strain-based staging classification. Multivariate logistic regression based on minimized Akaike information criterion was performed to detect the predictors for the adverse left ventricular remodeling after transapical beating-heart septal myectomy. A composite outcome of heart failure hospitalization, new-onset atrial fibrillation, stroke, thrombosis, permanent pacemaker implantation, and all-cause mortality was assessed.

Results: Postoperatively, 180 patients (63%) developed persistent new-onset left bundle branch block compared with 106 patients (37%) who did not. Compared with the non-left bundle branch block group, the new-onset left bundle branch block group exhibited longer QRS duration and peak strain dispersion after transapical beating-heart septal myectomy. However, global longitudinal strain was not different between the 2 groups postoperatively (P = .146). Septal strain-based staging in the new-onset left bundle branch block group showed 14% normal, 60% left bundle branch block 1, 16% left bundle branch block 2, and 10% left bundle branch block 3. Stage left bundle branch block 3 had worse global longitudinal strain and a more pronounced delay in electrical activity after transapical beating-heart septal myectomy. Stage left bundle branch block 3 was associated with a higher incidence of heart failure hospitalization during a median follow-up of 22 (interquartile range, 18-25) months. Preoperative global longitudinal strain and QRS duration were independent predictors of stage left bundle branch block 3.

Conclusions: Although 63% of patients with obstructive hypertrophic cardiomyopathy develop left bundle branch block after transapical beating-heart septal myectomy, the effects on left ventricular mechanical activity mainly fall into stages left bundle branch block 1 and left bundle branch block 2, with most new-onset left bundle branch block cases showing significant left ventricular reverse remodeling similar to those without left bundle branch block. Preoperative poor global longitudinal strain and prolonged QRS duration predict stage left bundle branch block 3 and adverse left ventricular remodeling after transapical beating-heart septal myectomy.

Keywords: left bundle branch block; reverse remodeling; strain pattern analysis; transapical beating-heart septal myectomy.