Investigators from the University of Toronto, Ontario, Canada, conducted a retrospective study to determine the incidence of sudden cardiac death (SCD) in young people with hypertrophic cardiomyopathy (HCM) and evaluate the role of exercise in HCM-SCD. For the study, they identified cases of HCM-SCD in Ontario, Canada, occurring between 2005 and 2011 among individuals 10–45 years old, as confirmed by means of autopsy at the Office of the Chief Coroner for Ontario (OCCO). OCCO maintains a centralized database and includes information about all sudden deaths attended by the coroner in the province. A diagnosis of HCM as the cause of SCD was considered definite when the autopsy findings included marked cardiomyocyte hypertrophy with pleomorphic to bizarre nuclei and myofiber disarray. Cases with other findings consistent with HCM, but no myofiber disarray, were classified as possible HCM-SCD. Sudden deaths in individuals with known HCM, but in whom no autopsy was performed, were categorized as probable HCM-SCD. The incidence of HCM-SCD among the at-risk population was estimated by using Ontario census data and assuming a prevalence of HCM of 1:500.1 To assess the role of exercise in HCM-SCD, the authors reviewed the death investigation review conducted by the coroner in each autopsied case and categorized the activity level at the time of death as being during sleep, at rest, during light activity, or during moderate or vigorous exercise.
During the study period, 44 definite, 3 probable, and 6 possible cases of HCM-SCD were identified. Based on an estimate of the population at risk, the incidence of definite HCM-SCD was calculated as 0.31 per 1,000 HCM person years (95% CI, 0.24–0.44). Including probable and possible cases increased the estimated incidence to 0.38 per 1,000 HCM person years (95% CI, 0.28–0.49). The median age of individuals with HCM-SCD confirmed by means of autopsy was 35.5 years (interquartile range, 26–42 years), and 83% were male; 70% of cases occurred in individuals without prior diagnosed HCM. Overall, 34% of cases occurred at rest, 30% during sleep, 17% during light activity, and 17% during or immediately after moderate or vigorous activity. However, among those ≤20 years, 77.4% of cases of HCM-SCD were associated with moderate or vigorous activity versus 4.8% in older victims.
The authors conclude that HCM-SCD is uncommon in the population at risk and infrequently related to exercise, at least in older individuals.
Dr Chung has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.
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