Type 2 diabetes mellitus is a well-established risk factor for atherosclerosis, but its contribution to sudden cardiac death (SCD) risk after myocardial infarction (MI) is not well defined.

The purpose of this study was to compare the incidence and time-dependent risk of SCD in diabetic patients versus nondiabetic patients during 5-year follow-up after acute MI.

A total of 3,276 patients were enrolled at the time of acute MI between 1996 and 2005. Mean age at entry was 60 ± 11 years, and the cohort was followed until 2009. At entry into the study, diabetes was present in 629 (19.2%) patients. The primary endpoint was SCD, and the secondary endpoints were non-SCD and all-cause mortality.

Among diabetic patients, the incidence of SCD was higher (5.9%) than in nondiabetic patients (1.7%), with a hazard ratio (HR) of 3.8 (95% confidence interval [CI] 2.4–5.8; P <.001) and adjusted HR of 2.3 (95% CI 1.4–3.8; P <.01). In diabetic patients with left ventricular ejection fraction >35%, the incidence of SCD was nearly identical to that of nondiabetic patients with ventricular ejection fraction ≤35% (4.1% vs 4.9%; P = .48). An excess in the incidence of non-SCD began to appear among diabetic patients within the first 6 months of follow-up (P <.001) but not in the incidence of SCD (P = .09). The excess in SCD among diabetic patients began to appear more than 6 months after the index event.

Patients with type 2 diabetes are at higher risk for SCD after MI than are nondiabetic patients. The incidence of SCD in post-MI type 2 diabetic patients with left ventricular ejection fraction >35% is equal to that of nondiabetic patients with left ventricular ejection fraction <35%.