Genetics of Unexplained Sudden Cardiac Death in Adult Caucasian and African American Individuals Living in the State of Maryland

Background Unexplained-sudden cardiac death (SCD) describes SCD with no cause identified after a comprehensive autopsy and toxicologic examination. Genetic testing helps to diagnose inherited cardiac diseases in unexplained-SCD, however, the relationship between pathogenic or likely pathogenic (P/LP) variants of inherited cardiomyopathies and primary electrical disorders (PED) and risk of unexplained-SCD in adults living the United States has never been systematically examined. Methods We performed sequencing of 29 cardiomyopathy and 39 arrhythmia genes in 413 African-Americans and Caucasians (≥18 years-old) who died of unexplained-SCD (median age; 41 years-old, 37% females, 50% African-Americans) and whose hearts were found to have no gross pathological finding upon referral to our institution for pathologic consultation from the State of Maryland Medical Examiner. We examined P/LP variants in these genes to study the association between presence of these variants and unexplained-SCD. Results 143/413 (34.6%) subjects had variants considered P/LP for cardiomyopathy and/or PED (i.e. Brugada Syndrome (BrS), long QT syndrome (LQTS), and arrhythmogenic right ventricular dysplasia (ARVD)). In total, 102 (24.7%) subjects harbored 86 P/LP variants for cardiomyopathies and 60 (14.5%) subjects carried 76 P/LP variants for PED. The following pathogenic variants were identified: 68 P/LP variants for hypertrophic cardiomyopathy (HCM) in 79/413 (19.1%) subjects, 18 P/LP variants for dilated cardiomyopathy (DCM) in 22/413 subjects (5.3%), and 76 P/LP variants in 60/413 (14.5%) for PED. There were greater than 121.0- and 138.5-fold median enrichments (431.4- and 200.0-fold cumulative enrichments) in these cardiomyopathy and arrhythmia variants in victims of unexplained SCD versus the general population, respectively. Among these P/LP positive carriers, combinations of conditions were found, including 14/413 (2.4%) having both HCM and PED variants, and 5/413 (1.2%) with DCM and PED variants. African Americans (AA) and Caucasians were equally likely to harbor P/LP variants (32.7% versus 36.6%, p=0.5), but AA had a higher frequent variants of unknown significance. Conclusions This study represents the largest examination reported on the association between cardiomyopathy and arrhythmia P/LP genetic variants and unexplained-SCD in adults with no gross abnormality on rigorous pathological examination. Nearly one-third of those with unexplained-SCD were carriers of P/LP variants. Our findings with respect to both the association of unexplained SCD with cardiomyopathy genes and race-specific genetic variants suggest new avenues of study for this poorly understood entity. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study is supported by the CVPath Institute Research Fund. ### Author Declarations All relevant ethical guidelines have been followed and any necessary IRB and/or ethics committee approvals have been obtained. Yes All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Not Applicable Any clinical trials involved have been registered with an ICMJE-approved registry such as ClinicalTrials.gov and the trial ID is included in the manuscript. Not Applicable I have followed all appropriate research reporting guidelines and uploaded the relevant Equator, ICMJE or other checklist(s) as supplementary files, if applicable. Not Applicable All data referred to in the manuscript are available. * SD : Sudden Death SCD : Sudden Cardiac Death P/LP : Pathogenic or Likely Pathogenic CoD : Cause of Death HCM : Hypertrophic Cardiomyopathy DCM : Dilated Cardiomyopathy LQTS : Long QT Syndrome ARVD : Arrhythmogenic Right Ventricular Dysplasia