Classification and Outcomes of Coronary Microvascular Disease in Myocardial Infarction and Angina With Nonobstructive Coronary Arteries

BACKGROUND: Myocardial infarction with nonobstructive coronary arteries (MINOCAs) and angina with nonobstructive coronary arteries (ANOCAs) present diagnostic and therapeutic challenges. We assessed the frequency of coronary microvascular disease (CMD) and its subtypes in MINOCA compared with ANOCA and evaluated long-term cardiovascular outcomes. METHODS: Patients with nonobstructive coronary arteries undergoing invasive coronary function testing from 2012 to 2022 were prospectively enrolled and retrospectively classified as MINOCA or ANOCA (reference group). Myocardial infarction due to atherothrombosis, myocarditis, and Takotsubo syndrome were excluded. Invasive provocation testing was performed. CMD was classified as endothelium-independent (coronary flow reserve <2.5 with adenosine) and endothelium-dependent (<50% increase in coronary blood flow with acetylcholine). Major adverse cardiovascular events (cardiac death, nonfatal myocardial infarction, heart failure hospitalization, urgent revascularization, stroke) were recorded over 8 years. RESULTS: Of 622 patients, 73 (12%) had MINOCA (69% female, median age 56 years) and 549 (88%) ANOCA (72% female, median age 53 years). CMD was common in both groups (71% versus 64%; P =0.271), while endothelium-independent CMD was more frequent in MINOCA (41% versus 21%; P <0.001). Over a median follow-up of 4.5 years, major adverse cardiovascular events occurred more often in MINOCA (40% versus 11%; adjusted hazard ratio, 2.4; P =0.001). CMD predicted higher major adverse cardiovascular events in both MINOCA (hazard ratio, 3.6 [95% CI, 1.1–12.0]; P =0.038) and ANOCA (hazard ratio, 7.9 [95% CI, 2.9–21.8]; P <0.001). CONCLUSIONS: CMD is common in both MINOCA and ANOCA. The higher prevalence of endothelium-independent CMD in MINOCA suggests a potential mechanistic role in infarction. Patients with MINOCA have a worse prognosis than ANOCA, particularly when CMD is present.