Comparisons in clinical outcomes for pediatric patients diagnosed with hypertrophic cardiomyopathy
J Conway, M Butzner, J Godown, E Papademetriou, X Liu, S Shreay, A DalalAbstract
Background
Pediatric hypertrophic cardiomyopathy (HCM) is associated with substantial morbidity and mortality. Phenotype-specific differences in outcomes between obstructive HCM (oHCM) and nonobstructive HCM (nHCM) remain incompletely characterized for children and adolescents. We evaluated these associations in a real-world cohort of pediatric patients with HCM in the United States.
Methods
Retrospective cohort study of pediatric patients (<18 years) with HCM (2016–2024) using Symphony medical and pharmacy claims data. Patients were classified as oHCM or nHCM using ICD-10 diagnosis codes and followed from index diagnosis until death, health plan disenrollment, or end of study. The primary outcome was a cardiovascular composite end point which included atrial fibrillation/flutter, supraventricular or ventricular tachyarrhythmia, ventricular fibrillation/tachycardia, sudden cardiac arrest, heart failure, heart transplant, implantable cardioverter defibrillator, pacemaker, implantable loop recorder, wearable cardioverter defibrillator, ventricular assist device, or septal myectomy. Analyses were conducted using Kaplan–Meier methods, with between-group comparisons assessed using the log-rank test.
Results
Among 6,093 children with HCM, 1,452 (24%) had oHCM (mean age 11.0 ± 5.1 years; 66.9% male; mean length of follow up 69.1 ± 30.4 months) and 4,641 (76%) had nHCM (mean age 10.5 ± 5.3 years; 64.3% male; mean length of follow up 56.5 ± 29.7 months). Among the 6,093 patients with HCM, 1,378 (95%) patients with oHCM and 4,341 (94%) patients with nHCM had no prior record of a cardiac event (6-months prior to index diagnosis). During follow up (Figure), 529 (38.4%) oHCM patients and 750 (17.3%) nHCM patients experienced a cardiovascular composite event (p<0.0001). Patients with oHCM had more frequent events of implantable cardioverter-defibrillator implantation (16.1% vs 4.1%), heart failure (17.8% vs 9.4%), sudden cardiac arrest (5.9% vs 3.1%), ventricular fibrillation (4.9% vs 1.9%), ventricular tachycardia (9.9% vs 2.7%; all p<0.001), and supraventricular tachycardia (5.8% vs 3.7%; p= 0.003), compared to nHCM patients, respectively. Septal myectomy occurred in 93 patients (6.4%) with oHCM over the follow up period.
Conclusions
Pediatric patients with HCM experience substantial clinical burden. Obstructive HCM was associated with a higher cumulative risk of cardiovascular events compared with nonobstructive HCM. These findings demonstrate clinically relevant heterogeneity in pediatric HCM and may inform risk mitigation strategies.Figure. Composite Cardiovascular EventsFor image description, please refer to the figure legend and surrounding text.