Myocardial Infarction with Nonobstructive Coronary Arteries: The Importance of Achieving Secondary Prevention Targets.

BACKGROUND: Approximately 5% to 10% of all patients with myocardial infarction have nonobstructive coronary arteries. Studies investigating the importance of follow-up and achievement of conventional secondary prevention targets in these patients are lacking.

METHODS: In this analysis from the Swedish Web-system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies (SWEDEHEART) registry, we investigated 5830 patients with myocardial infarction with nonobstructive coronary arteries (group 1) and 54,637 patients with myocardial infarction with significant coronary artery disease (≥50% stenosis; group 2). Multivariable- and propensity score-adjusted statistics were used to assess the reduction in the 1-year risk of major adverse events associated with prespecified secondary preventive measures: participation in follow-up at 6 to 10 weeks after the hospitalization and achievement of secondary prevention targets (blood pressure and low-density lipoprotein cholesterol levels in the target ranges, nonsmoking, and participation in exercise training).

RESULTS: Patients in group 1 were less often followed up compared with patients in group 2 and less often achieved any of the secondary prevention targets. Participation in the 6- to 10-week follow-up was associated with a 3% to 20% risk reduction in group 1, similar as for group 2 according to interaction analysis. The improvement in outcome in group 1 was mainly mediated by achieving target range low-density lipoprotein cholesterol levels (24%-32% risk reduction) and, to a smaller extent, by participation in exercise training (10%-23% risk reduction).

CONCLUSIONS: Selected secondary preventive measures are associated with prognostic benefit in patients with myocardial infarction with nonobstructive coronary arteries, in particular achieving target range low-density lipoprotein cholesterol levels. Our results indicate that these patients should receive similar follow-up as myocardial infarction patients with significant coronary stenoses.