Predictors of Mortality in Myocardial Infarction and Nonobstructed Coronary Arteries: A Systematic Review and Meta-Regression

Background: The long-term mortality of patients with myocardial infarction and nonobstructed coronary arteries (MINOCA) remains poorly defined. This study aimed to determine the long-term mortality of patients with MINOCA and to identify potential prognostic determinants of long-term outcome. Methods: We searched PubMed, EMBASE, and Cochrane databases and reviewed cited references up to December 31, 2018 to identify studies with > 6 months’ follow-up data. Results: We selected 44 studies including 36,932 patients (20,052 women and 16,880 men). During a median follow-up of 25 months (interquartile range: 23-39 months), 1409 patients had died (3.8%). Overall, annual mortality rate was 2.0% (95% confidence interval [CI]: 1.5% to 2.4%), with significant heterogeneity (I² = 80%, P <.001). Meta-analysis of the 26 studies comparing patients with MINOCA with those with myocardial infarction and obstructive coronary artery disease showed that annual rates of long-term total mortality were 2.2% (95% CI: 1.7% to 2.7%) and 5.0% (95% CI: 4.1% to 5,9%), respectively, with a significant difference between the two groups (relative risk: 0.60, 95% CI: 0.46 to 0.78, P <.001). Meta-regression analysis demonstrated that normal ejection fraction (P ≤.0001) and normal coronary arteries at angiography (P =.004) were inversely related to long-term mortality, whereas use of beta-blockers during follow-up (P =.010) and ST depression on the admission electrocardiogram (P =.016) were directly related with worse outcome. Conclusions: The long-term mortality after MINOCA is lower than that in patients with myocardial infarction and obstructive coronary artery disease, but it is not trivial. Reduced ejection fraction, nonobstructive coronary artery disease, use of beta-blockers during follow up and ST depression on the admission electrocardiogram are significant predictors of long-term prognosis.