Prognosis and risk stratification in first-presentation myocardial infarction with nonobstructive coronary arteries using stress cardiac MRI

OBJECTIVES: To evaluate the prognostic value of stress cardiac MRI in myocardial infarction with nonobstructive coronary arteries (MINOCA), and to investigate its efficacy in risk stratification. MATERIALS AND METHODS: A total of 279 MINOCA patients undergoing stress cardiac MRI were retrospectively enrolled. Patients were classified into 4 subgroups according to the cardiac MRI phenotype: (1) presence of late gadolinium enhancement (LGE) and inducible ischemia+ (n = 95); (2) LGE+/inducible ischemia- (n = 72); (3) LGE-/inducible ischemia+ (n = 69); and (4) LGE-/inducible ischemia- (n = 43). The primary outcome was major adverse cardiovascular events (MACE). RESULTS: Over a median follow-up of 41 months, MACE occurred in 11.5% of patients. Those who developed MACE showed significantly reduced cardiac function (left ventricular ejection fraction (LVEF): 38.6 [35.2; 51.6] vs 54.5 [48.7; 61.6], p < 0.001), severe microvascular dysfunction (myocardial perfusion reserve (MPR): 1.5 [1.4; 1.7] vs 1.9 [1.8; 2.6], p < 0.001), and extensive myocardial damage (LGE: 9.6 [7.7; 25.6] vs 2.4 [0.0; 6.2], p < 0.001). Multivariate Cox regression showed that LGE (HR: 1.108, 95% CI: 1.047-1.172, p < 0.001) and MPR (HR: 0.062, 95% CI: 0.007-0.524, p = 0.011) were independently associated with MACE. Kaplan-Meier analysis indicated that patients with LGE ≥ 8.39 and MPR < 1.75 had a significantly higher MACE risk (p < 0.001). CONCLUSION: In MINOCA patients, LGE and MPR independently predict MACE risk. Particularly, MPR offers incremental prognostic value by further stratifying patients with limited LGE. CRITICAL RELEVANCE STATEMENT: MINOCA is a clinically important and heterogeneous entity, often associated with adverse long-term outcomes. Stress cardiac MRI parameters, LGE and MPR, can predict the prognosis of patients with MINOCA, facilitating risk stratification and guiding subsequent management decisions. KEY POINTS: Stratifying MINOCA patients into subgroups based on cardiac MRI tissue and functional characteristics enables refined risk stratification. In MINOCA patients with limited LGE, impaired MPR is associated with a higher incidence of MACE. Microvascular dysfunction may be recognized as one of the potential mechanisms contributing to MINOCA and is associated with adverse cardiovascular outcomes.