A cohort study of childhood hypertrophic cardiomyopathy

OBJECTIVES: The study analyzed factors, including treatment, affecting disease-related death in patients with hypertrophic cardiomyopathy (HCM) presenting in childhood. BACKGROUND: Previous smaller studies suggest that mortality is higher in patients with HCM presenting in childhood compared with presentation in adulthood, but these studies have all originated from selected patient populations in tertiary referral centers, and reported no significant protection by treatment. METHODS: Retrospective comparisons of mortality were done in total cohort of patients presenting to three regional centers of pediatric cardiology. There were 66 patients (25 with Noonan's syndrome) with HCM presenting at age <19 years; mean follow-up was 12.0 years. RESULTS: Among risk factors for death were congestive heart failure (p = 0.008), large electrocardiogram voltages (Sokolow-Lyon index p = 0.0003), and degree of septal (p = 0.004) and left ventricular (p = 0.028) hypertrophy expressed as percent of 95th centile value. The only treatment that significantly reduced the risk of death on multifactorial analysis of variance was high-dose beta-adrenoceptor antagonist therapy (propranolol 5 to 23 mg/kg/day or equivalent; p = 0.0001). Nineteen out of 40 patients managed conventionally (no treatment, 0.8 to 4 mg/kg of propranolol, or verapamil) died, median survival 15.8 years, with no deaths among 26 patients on high-dose beta-blockers (p = 0.0004); survival proportions at 10 years were 0.65 (95% confidence interval 0.49-0.80) and 1.0, respectively (p = 0.0015). Survival time analysis shows better survival in the high-dose beta-blocker group compared with the "no specific therapy" group (p = 0.0009) and with the conventional-dose beta-blocker group (p = 0.002). Hazard ratio analysis suggests that high-dose beta-blocker therapy produces a 5-10-fold reduction in the risk of disease-related death. CONCLUSIONS: High-dose beta-blocker therapy improves survival in childhood HCM.