Left Ventricular Pacing-Associated Cardiomyopathy Revealing Myocardial Vulnerability in Congenital Complete Heart Block.

BACKGROUND: Mechanisms underlying cardiac manifestations of immune-mediated congenital complete heart block (CCHB) remain unclear. Dilated cardiomyopathy (DCM) in immune-mediated CCHB has been associated with RV pacing, whereas reports of LV pacing-associated DCM are lacking. CASE SUMMARY: A girl with immune-mediated CCHB showed endocardial fibroelastosis (EFE) at 20 weeks of gestation before heart block developed at 22 weeks. After LV basal-lateral pacing, she developed DCM with LV dyssynchrony. Cardiac resynchronization therapy (CRT) improved LV function and induced reverse remodeling. CONCLUSIONS: Myocardial injury may precede conduction system involvement in immune-mediated CCHB. Subclinical immune-mediated myocardial vulnerability and pacing-related dyssynchrony may contribute to DCM progression.