Aims: The study reports the relative and absolute risk of sudden cardiac death (SCD) in patients <36 years with prior myocardial infarction (MI).
Methods and results: Through review of death certificates, we identified all SCDs in Danes aged 18-35 years between 1 January 2000 until 31st December 2006. We then used the unique Danish civil registration number, which enabled us to follow all Danes in national registries, in the same period. Through the National Patient Registry we identified those with a prior myocardial infarction [implantable cardioverter defibrillator (ICD)-8: 410, ICD-10: I21 and I22] and incidence rates for SCD were estimated for survivors of MI and for individuals who had not yet suffered an MI, respectively. We estimated the relative risk of SCD and all-cause mortality by using extended Cox regression models. The 1,862,431 Danes aged between 18 and 35 years were followed in 9,388,453 person-years between 2000 and 2006. There were 7434 deaths of which 387 (5.2%) were SCDs. Myocardial infarction was diagnosed in 1234 patients, of those 10 died of SCD. Prior MI increased the incidence rate of SCD from 4.1 to 305.0 per 100,000 person-years [95% confidence interval (CI): 164.1-567.0]. Myocardial infarction was correlated with SCD and all-cause mortality, with a hazard ratio (HR) of 55.5 (95% CI: 29.5-104.4), P< 0.0001 and HR 8.3 (95% CI: 6.0-11.3), P< 0.0001, respectively.
Conclusion: We report that prior MI at a young age significantly increases SCD incidence from 4.1 to 305.0 per 100,000 person-years. Myocardial infarction is furthermore correlated with SCD and all-cause mortality with HR of 55.5 and 8.3, respectively.