title: Hypertrophic Cardiomyopathy as a Cause of Sudden Cardiac Death in the Young: A Meta-Analysis.
abstract: BACKGROUND
  Sudden cardiac death is often linked with hypertrophic cardiomyopathy in young athletes, but with a divergence of study results. We performed a meta-analysis to compare the prevalence of sudden cardiac deaths associated with hypertrophic cardiomyopathy vs sudden cardiac deaths associated with structurally normal hearts.
  
  
  METHODS
  A structured search of MEDLINE was conducted for studies published from 1990 through 2014. Retrospective cohort studies, patient registries, and autopsy series examining sudden cardiac death etiology in young individuals (age ≤35 years) were included. A random-effects model was applied to generate pooled summary estimates of the percentage of sudden cardiac deaths with structurally normal hearts at postmortem vs those caused by hypertrophic cardiomyopathy. Heterogeneity was assessed using I(2). Subgroup analyses were conducted based on study location, patient age groups, and population types.
  
  
  RESULTS
  Thirty-four studies were included, representing a combined sample of 4605 subjects. The overall pooled percentage of sudden cardiac deaths caused by hypertrophic cardiomyopathy was 10.3% (95% confidence interval [CI], 8.0%-12.6%; I(2) = 87.2%), while sudden cardiac deaths with structurally normal hearts at death were more common (P <.001) at 26.7% (95% CI, 21.0%-32.3%; I(2) = 95.3%). In nonathlete subjects, the pooled percentage of sudden cardiac deaths associated with structurally normal hearts (30.7%; 95% CI, 23.0%-38.4%; I(2) = 96.3%) were significantly more common (P <.001) than sudden cardiac death caused by hypertrophic cardiomyopathy (7.8%; 95% CI, 5.8%-9.9%; I(2) = 80.1%). Among athletes, there was no significant difference between summary estimates of hypertrophic cardiomyopathy and structurally normal hearts (P = .57), except in Europe where structurally normal hearts were more common (P = .01).
  
  
  CONCLUSIONS
  Hypertrophic cardiomyopathy is not a more common finding at death than structurally normal hearts in young subjects with sudden cardiac death. Increased attention should be directed toward identifying causes of death associated with a structurally normal heart in subjects with sudden cardiac death.
authors.affiliation: Stanford University School of Medicine, Calif. Electronic address: aullal@stanford.edu.
authors.forename: Aditya J
authors.initials: AJ
authors.lastname: Ullal
authors.affiliation: Stanford University School of Medicine, Calif.
authors.forename: Ramy S
authors.initials: RS
authors.lastname: Abdelfattah
authors.affiliation: Stanford University School of Medicine, Calif.
authors.forename: Euan A
authors.initials: EA
authors.lastname: Ashley
authors.affiliation: Stanford University School of Medicine, Calif.
authors.forename: Victor F
authors.initials: VF
authors.lastname: Froelicher
mesh_terms: D000328:Adult; D002312:Cardiomyopathy, Hypertrophic; D016757:Death, Sudden, Cardiac / Q000209:etiology*; D006801:Humans
keywords: Athletes; Etiology; Hypertrophic cardiomyopathy; Meta-analysis; Structurally normal heart; Sudden cardiac death; Systematic review