Acute coronary syndromes in the community

Objectives: To measure the incidence of acute coronary syndrome (ACS), defined as first-ever myocardial infarction (MI) or unstable angina (UA); evaluate recent temporal trends; and determine whether survival after ACS has changed over time and differs by type.

Patients and methods: This was a population surveillance study conducted in Olmsted County, Minnesota (population: 144,248). All persons hospitalized with incident ACS between January 1, 2005, and December 31, 2010, were identified using International Classification of Diseases, Ninth Revision codes, natural language processing of the medical records, and biomarkers. Myocardial infarction was validated by epidemiologic criteria and UA by the Braunwald classification. Patients were followed through June 30, 2013, for death.

Results: Of 1244 incident ACS cases, 35% (n=438) were UA and 65% (n=806) were MI. The standardized rates (per 100,000) of ACS were 284 (95% CI, 248-319) in 2005 and 184 (95% CI, 157-210) in 2010 (2010 vs 2005: rate ratio, 0.62; 95% CI, 0.53-0.73), indicating a 38% decline (similar for MI and UA). The 30-day case fatality rates did not differ by year of diagnosis but were worse for MI (8.9%; 95% CI, 6.9%-10.9%) compared with UA (1.9%; 95% CI, 0.6%-3.1%). Among 30-day survivors, the risk of death did not differ by ACS type or diagnosis year.

Conclusion: In the community, UA constitutes 35% of ACS. The incidence of ACS has declined in recent years, and trends were similar for UA and MI, reaffirming a substantial decline in all acute manifestations of coronary disease. Survival after ACS did not change over time, but 30-day survival was worse for MI compared with UA.