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

The prevalence of left bundle branch block (LBBB) is significantly higher in the heart failure (HF) population compared to the general population. LBBB is more often associated with structural heart disease especially dilated cardiomyopathy (DCM) of a non-ischemic origin. In isolation, LBBB is not a cause of specific clinical concern and does not affect prognosis. However, in the presence of structural heart disease, LBBB is an independent predictor of cardiovascular mortality and HF events suggesting that long-standing LBBB may be the cause of HF. In addition, guideline directed medical treatment (GDMT) in DCM patients with LBBB is less effective or associated with worsening symptoms. Conversely, cardiac resynchronization therapy (CRT) has shown beneficial outcomes in DCM patients with LBBB. It reverses LV dysfunction and protects against HF events, which suggests the possibility of a specific type of LBBB-induced CM characterized by LV dilatation and depressed LV systolic function in the absence of any other known aetiology. Despite the evidence, current medical literature does not consider LBBB-induced CM as a clinical entity but a complication of CM or structural heart disease. Since LBBB-induced CM requires early treatment with CRT instead of after three months of GDMT, diagnosis of LBBB-induced CM is important to guide the choice of optimal treatment (CRT). The present review summarizes the current published evidence on LBBB-induced CM and identifies gaps in knowledge that may benefit from additional research.