Background: Hypertrophic cardiomyopathy (HCM), with an estimated prevalence of 1 in 500, is hereditary and often remains asymptomatic and undiagnosed. Although potentially treatable, HCM is a leading cause of sudden cardiac death among adolescents and young adults. While previous HCM-related mortality estimates were extrapolated from cohort studies, this study applies two definitions to death certificate data to estimate national mortality rates and identify at-risk groups.
Methods: Death certificates of 12-35 year olds with HCM-related deaths in 1999-2013 were obtained from the National Vital Statistics System. Two definitions were applied: 1) specific—underlying-cause-of-death (UCD) ICD-10 code for HCM (I42.1, I42.2); and 2) sensitive—deaths that met the specific definition; had a UCD code for cardiomyopathy, unspecified (I42.9); or had a contributing cause code of I42.1, I42.2, or I42.9 and a HCM-related UCD (Figure). Deaths with external injury (V01-Y89) or congenital (Q00-Q99) codes were excluded. Ratios comparing rates by age (12-19, 20-35), gender (male, female), time (1999-2003, 2004-2008, 2009-2013), and race (non-Hispanic (NH) white, NH black) were calculated.
Results: During 1999-2013, 2,735 specific and 8,390 sensitive HCM-related deaths occurred among 12-35 year olds. Mortality rates were 1.84 and 5.64 per million, respectively. Mortality rates were higher in 20-35 vs 12-19 year olds (specific mortality ratio 1.69, sensitive mortality ratio 5.66); males vs females (5.09, 2.55), and NH blacks vs NH whites (2.66, 3.24), and decreased over time (Figure).
Discussion: The HCM-related mortality estimates and at-risk groups (e.g. males, blacks) described here are consistent with findings from previous studies. HCM-related deaths are potentially avoidable through implementation of screening and treatment interventions; however, ideal screening parameters have not been identified. Ongoing surveillance can inform screening improvement efforts and assess for continued rate decreases.