Background: Restrictive cardiomyopathy (RCM) has been associated with poor prognosis in childhood. The goal of the present analysis was to use the Pediatric Cardiomyopathy Registry to analyze outcomes of childhood RCM, with a focus on the impact of phenotype comparing pure RCM with cases that have additional features of hypertrophic cardiomyopathy (HCM).
Methods and results: We analyzed the Pediatric Cardiomyopathy Registry database (1990-2008; N=3375) for cases of RCM. Cases were defined as pure when RCM was the only assigned diagnosis. Additional documentation of HCM at any time was used as the criterion for RCM/HCM phenotype. RCM accounted for 4.5% of cases of cardiomyopathy. In 101 (66%), pure RCM was diagnosed; in 51 (34%), there was a mixed phenotype. Age at diagnosis was not different between groups, but 10% of the pure RCM group was diagnosed in infancy versus 24% of the RCM/HCM group. Freedom from death was comparable between groups with 1-, 2-, and 5-year survival of RCM 82%, 80%, and 68% versus RCM/HCM 77%, 74%, and 68%. Transplant-free survival was 48%, 34%, and 22% and 65%, 53%, and 43%, respectively (P=0.011). Independent risk factors at diagnosis for lower transplant-free survival were heart failure (hazard ratio 2.20, P=0.005), lower fractional shortening z score (hazard ratio 1.12 per 1 SD decrease in z score, P=0.014), and higher posterior wall thickness in the RCM/HCM group only (hazard ratio 1.32, P<0.001). Overall, outcomes were worse than for all other forms of cardiomyopathy.
Conclusions: Transplant-free survival is poor for RCM in childhood. Survival is independent of phenotype; however, the RCM/HCM phenotype has significantly better transplant-free survival.
Clinical trials registration: URL: http://www.clinicaltrials.gov. Unique Identifier: NCT00005391.