Multimodality Imaging to Determine Underlying Causes of Myocardial Infarction With Nonobstructive Coronary Arteries in Women and Men

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BACKGROUND: Myocardial infarction with nonobstructive coronary arteries (MINOCA) has several underlying causes, including mimicking conditions in some cases. Imaging is recommended to identify MINOCA etiologies, but it remains unclear which patients are most likely to have abnormal findings. We characterized MINOCA mechanisms, analyzed predictors of imaging abnormalities, and explored sex differences. METHODS: We enrolled patients with clinical diagnosis of myocardial infarction in an international, prospective, diagnostic study at 28 sites in the United States, Canada and United Kingdom. After a women-only phase, we included both sexes. Individuals with ≥50% diameter stenosis or coronary dissection on angiography, or alternate causes for the clinical presentation, were excluded. Participants had multivessel coronary optical coherence tomography (OCT) during index coronary angiography and cardiac magnetic resonance imaging (CMR) within 1 week. Independent core laboratories interpreted imaging, blinded to other results. RESULTS: Among 754 patients enrolled, 389 had MINOCA, and 336 with MINOCA underwent OCT (270 women and 66 men); CMR was completed in 284 (85%). An OCT-defined culprit lesion was identified in 45% (116 of 270 women [43%] and 35 of 66 men [53%], P =0.18). CMR demonstrated an ischemic pattern in 114 of 284 (40%), similar by sex (96 of 225 women [43%] versus 18 of 59 men [31%], P =0.12). A nonischemic pattern was observed in 23% (23% of women, 25% of men, P =0.78). We identified a cause of the clinical presentation in 79% of patients with both tests completed; 59% had an ischemic cause of MINOCA, and 20% had a non-ischemic mimicking condition. OCT alone found a MINOCA etiology in 151 of 336 (45%) and CMR alone in 180 of 284 (63%). Predictors of an OCT culprit lesion included age, abnormal angiogram, and number of vessels imaged, but 27% of normal angiograms harbored a culprit lesion. Predictors of abnormal CMR were peak troponin, shorter time to CMR, and non-Asian race, but CMR was abnormal in 40% when troponin was <4-fold above the upper reference limit. CONCLUSIONS: The combination of multivessel coronary OCT and CMR in patients with a clinical diagnosis of MINOCA confirmed myocardial infarction in 59% and identified an alternate cause (MINOCA mimic) in 20%. Clinical factors had limited usefulness to predict imaging abnormalities. No sex differences in imaging results were detected. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02905357.

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