Massive left ventricular hypertrophy (LVH) is a risk factor for sudden cardiac death in children with hypertrophic cardiomyopathy (HCM), but its natural history is poorly understood. This analysis from two large international registries (SHaRe and IPHCC) compares children with HCM with and without massive LVH — defined as maximal wall thickness ≥30 mm or a z-score ≥+20 before age 18 — using serial wall-thickness measurements and composite outcomes for major ventricular arrhythmia events (sudden cardiac death, aborted sudden cardiac death or appropriate ICD therapy) and heart failure. The study characterises the course and risk profile of this severe phenotype to support risk stratification and treatment decisions such as ICD implantation.
BACKGROUND:Massive left ventricular hypertrophy (LVH) is a risk factor for sudden cardiac death in children with hypertrophic cardiomyopathy (HCM), but little is understood about its natural history.METHODS:Patients with pediatric-onset HCM identified from 2 registries (SHaRe [Sarcomeric Human Cardiomyopathy Registry] and IPHCC [International Paediatric Hypertrophic Cardiomyopathy Consortium]) with or without massive LVH were compared. Massive LVH was defined as absolute maximal left ventricular wall thickness (MLVWT) ≥30 mm or MLVWTzscore ≥+20 at <18 years of age. Data from SHaRe and IPHCC include encounters from January 1960 through March 2024 and January 1970 through March 2024, respectively. Demographic, clinical, and serial MLVWT data were collected. Composite outcomes included major ventricular arrhythmia event (sudden cardiac death, aborted sudden cardiac death, or appropriate implantable cardioverter defibrillator therapy); heart failure (HF) event (left ventricular ejec
