Dyssynchrony-Induced Cardiomyopathy in Children: Mechanisms, Diagnosis, and Contemporary Management.

Abnormal ventricular activation can be a reversible contributor to ventricular dysfunction in children, yet dyssynchrony often reflects secondary myocardial disease rather than a causal mechanism. Dyssynchrony‑induced cardiomyopathy is best defined as ventricular dysfunction arising after sustained electrical activation abnormality, accompanied by concordant mechanical dyssynchrony and adverse remodeling, lacking a more compelling alternative etiology, and improving after correction of the electrical substrate. Pediatric evidence for causality is strongest for chronic right ventricular pacing, ventricular pre‑excitation, and selected patients with high premature ventricular contraction burdens, whereas in congenital heart disease, systemic right ventricular physiology, Fontan circulation, genetic cardiomyopathy, anthracycline exposure, and neuromuscular disorders, dyssynchrony is typically intertwined with loading abnormalities, scar, fibrosis, or primary myocardial pathology. Diagnosis requires integrating electrical data with ventricular remodeling, atrioventricular valve regurgitation, strain patterns, and cardiac magnetic resonance tissue characterization, recognizing that no single cutoff applies across ages or morphologies. Catheter ablation and pacing‑site revision can yield reverse remodeling in selected causal substrates, while evidence for cardiac resynchronization therapy and conduction system pacing remains observational and heterogeneous. This review summarizes a causal framework, evidence hierarchy, and substrate‑specific approach to evaluating and managing dyssynchrony‑induced cardiomyopathy in children.