Abstract 14706: Cardiac Phenotype in Children Undergoing Screening for Familial Hypertrophic Cardiomyopathy: Is it Time to Change Screening Guidelines?

Abstract

Introduction: Current hypertrophic cardiomyopathy (HCM) screening guidelines recommend that clinical and/or genetic screening of children with family history of HCM be initiated from age 10 years (European Society of Cardiology 2014) or 12 years (American Heart Association 2011) onward and earlier only in the presence of malignant family history, presence of symptoms and/or participation in competitive sports. We assessed the proportion of asymptomatic children undergoing HCM screening that developed HCM phenotype or major adverse cardiac events (MACE) prior to age 12 years. Methods: This was a single centre retrospective study of HCM kindreds referred for screening to our cardiomyopathy clinic. Index cases with HCM, and cases with secondary cardiomyopathy (metabolic, neuromuscular, syndromic) were excluded. Genotype and phenotype status at initial screening and last follow-up were analyzed. MACE was defined as occurrence of death, transplant, resuscitated cardiac arrest, implantation of ICD or myectomy. Results: From 2005-2014, 427 children were referred for cardiac screening secondary to a family history of HCM. Of these, 379 (88.8%) had first-degree relatives with HCM and 146 (34.1%) had a family history of sudden cardiac death. The median age at first screening was 7.4 years (range 1 day-17 years), and median follow-up duration was 3 years. 45% (13/29 tested) phenotype-positive children, and 53% (32/60 tested) phenotype-negative children has positive genetic testing. 27/427 (6.3%) were phenotype-positive (maximal LV wall thickness Z-score >2.0) at initial screening and an additional 13 (3%) became phenotype-positive during follow-up. The median age at positive phenotypic diagnosis of HCM was 8 years (range 5 days-17 years) with 24 children being <12 years old (5.6%). 11/427 (2.6%) suffered a MACE during follow-up. Median age at MACE occurrence was 10.9 years (range 6-15 years) with 6 children being <12 years old at occurrence of MACE (1.4%). Conclusion: Overall, more than 5% children being screened for HCM were phenotype-positive and 1.4% suffered a MACE before 12 years of age. These data suggest the importance of revising existing guidelines to recommend clinical and/or genetic screening of HCM of all family members independent of age.