Studies have shown that efforts to prevent acute myocardial infarction (MI), through improved management of patients' risk factors, have been somewhat successful. However, many of the studies have focussed on particular patient subgroups and have not distinguished between ST-segment-elevation and non-ST-segment-elevation MI (STEMI and NSTEMI, respectively)—conditions that are managed very differently. Dr. Alan Go and colleagues have now used data from a large California health-care system to examine trends in the incidence of MI, the severity of MI (assessed via biomarker measurement), and short-term mortality in a diverse, community-based cohort between 1999 and 2008.

The study incorporated data for more than 46,000 patients aged 30 years or older, who were hospitalized with a diagnosis of incident MI during the study period. In total, more than 18 million person-years of follow-up were included.

After adjustments for age and sex, the incidence of STEMI decreased each year, to result in a relative decrease of 62% between 1999 and 2008. In line with the investigators' hypothesis that the use of troponin I testing would increase the apparent incidence of NSTEMI, the incidence of NSTEMI increased by 30% between 1999 and 2004, the period in which troponin I testing was increased and CK-MB testing was decreased at the facilities involved. The incidence of NSTEMI then decreased after 2004, when troponin I testing was systematically and consistently used in the evaluation of possible MIs. During the study period, age-and-sex-adjusted 30-day mortality after MI decreased from 10.0% to 7.6% in patients with NSTEMI, but no change was observed in those diagnosed with STEMI.

Dr. Go believes that this study supports the “ongoing and innovative, systematic methods [used] to increase adherence by patients, providers, and health systems to the detection and control of known major risk factors”.