Prognostic Role of CMR and Conventional Risk Factors in Myocardial Infarction With Nonobstructed Coronary Arteries

Objectives: This study sought to assess the prognostic impact of cardiac magnetic resonance (CMR) and conventional risk factors in patients with myocardial infarction with nonobstructed coronaries (MINOCA). 

Background: Myocardial infarction with nonobstructed coronary arteries (MINOCA) represents a diagnostic dilemma, and the prognostic markers have not been clarified. 

Methods: A total of 388 consecutive patients with MINOCA undergoing CMR assessment were identified retrospectively from a registry database and prospectively followed for a primary clinical endpoint of all-cause mortality. A 1.5-T CMR was performed using a comprehensive protocol (cines, T2-weighted, and late gadolinium enhancement sequences). Patients were grouped into 4 categories based on their CMR findings: myocardial infarction (MI) (embolic/spontaneous recanalization), myocarditis, cardiomyopathy, and normal CMR. 

Results: CMR (performed at a median of 37 days from presentation) was able to identify the cause for the troponin rise in 74% of the patients (25% myocarditis, 25% MI, and 25% cardiomyopathy), whereas a normal CMR was identified in 26%. Over a median follow-up of 1,262 days (3.5 years), 5.7% patients died. The cardiomyopathy group had the worst prognosis (mortality 15%; log-rank test: 19.9; p < 0.001), MI had 4% mortality, and 2% in both myocarditis and normal CMR. In a multivariable Cox regression model (including clinical and CMR parameters), CMR diagnosis of cardiomyopathy and ST-segment elevation on presentation electrocardiogram (ECG) remained the only 2 significant predictors of mortality. Using presentation with ECG ST-segment elevation and CMR diagnosis of cardiomyopathy as risk markers, the mortality risk rates were 2%, 11%, and 21% for presence of 0, 1, and 2 factors, respectively (p < 0.0001). 

Conclusions: In a large cohort of patients with MINOCA, CMR (median 37 days from presentation) identified a final diagnosis in 74% of patients. Cardiomyopathy had the highest mortality, followed by MI. The strongest predictors of mortality were a CMR diagnosis of cardiomyopathy and ST-segment elevation on presentation ECG.