O1005: Long-Term Risk of Mortality, Heart Transplant, and Heart Failure in Pediatric RCM vs. HCM

Background: Pediatric restrictive cardiomyopathy (RCM) is rare and associated with poor prognosis, whereas hypertrophic cardiomyopathy (HCM) is more common with a more variable course. We aimed to compare long-term outcomes between RCM and HCM in children using a large multicenter health record network.

Methods: We queried the TriNetX US Collaborative Network (68 HCOs) for pediatric patients (≤18 years) diagnosed with RCM or HCM between 2000 and 2025. The RCM cohort required a restrictive cardiomyopathy diagnosis and excluded secondary causes (amyloidosis, sarcoidosis, endocardial fibroelastosis), while the HCM cohort required a hypertrophic cardiomyopathy diagnosis with the same exclusions. Outcomes of interest were all-cause mortality, heart transplant (transplant-free survival), and incident heart failure during 15 years of follow-up (up to 5,500 days post-diagnosis). We compared cohorts using risk differences (RD), risk ratios (RR), and odds ratios (OD) (with 95% confidence intervals) and Kaplan–Meier survival curves (log-rank test). Patients with outcome events prior to the observation window were excluded.

Results: All-cause mortality was significantly higher in the RCM group compared to HCM (8.0% vs. 4.5%; RR 1.76, 95% CI 1.46–2.11, p< 0.001; OR 1.82, 95% CI 1.50–2.21), with a 15-year survival probability of 88.1% for RCM vs. 91.2% for HCM (p=0.003). Transplant-free survival was markedly lower in RCM than HCM (7.9% vs. 1.2%; RR 6.33, 95% CI 4.79–8.36, p< 0.001; OR 6.78, 95% CI 5.09–9.04)[Figure 1], with survival probability at 15 years of 88.0% vs. 96.1%, respectively (p < 0.001) [Figure 2]. Similarly, heart failure was more common in RCM than HCM (15.6% vs. 7.5%; RR 2.09, 95% CI 1.81–2.41, p< 0.001; OR 2.29, 95% CI 1.94–2.70), and 15-year heart failure–free survival was 72.9% for RCM vs. 78.9% for HCM (p < 0.001).

Conclusion: Pediatric RCM is associated with significantly worse outcomes than HCM. Children with RCM had higher mortality, a dramatically lower transplant-free survival, and a greater risk of heart failure compared to those with HCM. These findings highlight the aggressive natural history of RCM in childhood and the need for vigilant clinical monitoring and early consideration for advanced therapies (such as transplant) in this population.