Prevalence of Hypertrophic Cardiomyopathy | Journal Scan
Has the prevalence of hypertrophic cardiomyopathy (HCM) been underestimated?
The authors compared the prevalence of HCM described by the Coronary Artery Risk Development in Young Adults (CARDIA) data on which the currently quoted prevalence of HCM was based, and the potential prevalence based on a contemporary cohort that included older patients and genotyping.
Since the CARDIA study published the prevalence of HCM in 1995, more than 11 genes have been identified, which primarily encode over 1,500 cardiac sarcomere and sarcomere-related single nucleotide mutations. The CARDIA cohort study was a biracial cohort of 4,111 unrelated people ages 23-35 years, randomly selected from the general population in community-based urban centers and census tracts. In 2012, Seidman and colleagues described the frequency of pathogenic mutations in a community-based cohort that included 3,600 participants ages 30-84, 1,637 unrelated individuals in the offspring cohort of the Framingham Heart Study, and 1,963 unrelated individuals from the Jackson Heart Study cohort. The CARDIA study phenotyped patients using an echocardiogram, while the Seidman study performed genotyping. By screening for the eight main HCM-causing sarcomere protein genes, Seidman and colleagues were able to identify at least one rare nonsynonymous sarcomere variant in 11.2% of the general population, of which 0.6% were considered pathogenic. Based on this, the minimum prevalence of HCM gene carriers could be estimated as high as 1 in 200. Genetic testing has allowed for the identification of patients who are at risk, but who are not yet clinically affected (genotype +/phenotype-); therefore, earlier studies were not able to identify this subgroup. Other sources of underestimation of HCM prevalence stem from exclusion of certain age groups and family members. In addition, newer imaging modalities, such as cardiac magnetic resonance imaging, may enhance the identification of HCM.
The ability to perform genetic testing for HCM has allowed the detection of HCM carriers and the determination of the prevalence of pathogenic genes. Based on this, the true prevalence of HCM is likely higher than 1 in 500. The authors suggest a revised estimate of the combined prevalence of clinically expressed HCM and gene carriers.
The current estimate of prevalence for HCM does not include gene carriers or account for the impact of potentially pathogenic genes. Combining the prevalence of clinically affected patients and gene carriers will increase the estimated prevalence of HCM and may serve to raise awareness, but should be considered with caution as the natural history of the carrier state is not yet resolved, and identification of carriers may lead to unnecessary tests, therapies, and lifestyle changes.
Keywords: Cardiomyopathy, Hypertrophic, Carrier State, Cohort Studies, Coronary Vessels, Echocardiography, Genetic Testing, Genotype, Magnetic Resonance Imaging, Mutation, Nucleotides, Phenotype, Prevalence, Sarcomeres, Heart Failure
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