Left bundle branch block-induced left ventricular remodeling and its potential for reverse remodeling

Abstract

With the emergence of cardiac resynchronization therapy (CRT) as a powerful tool to reverse left ventricular dysfunction in patients with left bundle branch block (LBBB), there is increasing awareness that LBBB-induced dyssynchrony may be a primary cause of heart failure with reduced ejection fraction (HFrEF). Current guidelines for implanting CRT require at least 3 months of guideline-directed medical therapy (GDMT) before device implantation in the hopes that medications will reverse cardiomyopathy and obviate the need for device therapy. However, no randomized controlled trial demonstrating efficacy of medications ever stratified outcomes by patients with conduction abnormalities. Consequently, CRT, not GDMT, may be a more effective first-line therapy for patients with LBBB and HFrEF. This review evaluates the evidence for LBBB-induced cardiomyopathy, examines the rationale for GDMT in this population, and presents the evidence for direct implantation of CRT. It is likely that many patients would benefit from earlier intervention with CRT, though about 25% of patients with LBBB and HFrEF may respond to GDMT.

Reverse Remodeling and Current Medical Therapy in Heart Failure with Reduced Ejection Fraction

“…Previous randomized control trials for medical therapies showed that in patients with HFrEF, beta-blockers, ACE-Is or ARBs improved LVEF from 2 to 12% over the course of 5-20 months. 8) Ivabradine demonstrated significant LV reverse remodeling at 8-month follow-up compared with placebo (2.7% increased LVEF, P < 0.001, −5.8 mL/m 2 reduced LVESV Index, P < 0.001, and −5.5 mL/m 2 reduced LVEDV Index, P = 0.002) in the SHIFT echocardiographic substudy. 9) The clinical efficacy of CRT therapy was also associated with LV reverse remodeling.…”

“…In the echocardiographic substudy of MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial-CRT), left bundle branch block (LBBB) and non-ischemic etiology of cardiomyopathy were significant predictors of super-responders to CRT, who were defined as top quartile responders in LVEF (191 of the total of 752 patients experienced essentially EF improvement " 14.5%) 12 months after CRT implantation. 8,10) Among these 752 patients who survived and received 12-month follow-up, 55 patients (7.3%) who achieved LVEF normalization (LVEF > 50%) and 594 patients (79.0%) who showed mild recovery (LVEF 36-49%) at the 12-month follow-up had low risk of ventricular tachyarrhythmia, HF or death compared with the non-responder group (LVEF !35%). 11) Article p.281…”

The importance of electrocardiographic follow‐up in heart failure

“…could be of interest. The importance of repeated ECGs in patients with HFrEF is additionally emphasized by the findings that delayed implantation of CRT might result in less response to CRT as summarized in a recent review, 14 although the underlying evidence for this notion is relatively poor. Thus, the most important clinical consequences of the paper by Kristensen et al 1 .…”

Left bundle branch block-induced cardiomyopathy: A review and pooled analysis of pathophysiology, diagnosis and clinical management

“…The recent history of CRT reflects the increasing understanding of the reversible harm induced by LBBB. In patients with systolic HF, the direct contribution of LBBB to LV dysfunction is substantial demonstrated by reverse remodelling and improvement in LVEF in most patients receiving CRT [44][45][46][47][48]. Two large multi-centre randomized trials -MADIT-CRT [49] and Resynchronization Defibrillation for Ambulatory Heart Failure Trial (RAFT) [50] demonstrated CRT to be a powerful intervention for the reduction of the combined end-point of HF hospitalization or death with beneficial effect limited to HF patients with LBBB.…”