Feasibility and Yield of a Diagnostic Protocol for Myocardial Infarction With Nonobstructive Coronary Arteries.

Current guidelines recommend a structured diagnostic protocol to determine the underlying final diagnosis for myocardial infarction with nonobstructive coronary arteries (MINOCA). Yet, a comprehensive diagnostic workup is often hindered by economic and time constraints, and real-world data is scarce. This study thus aimed to examine the diagnostic strategy of a structured protocol beyond initial invasive coronary angiography (ICA) for MINOCA. This prospective multicenter cohort study enrolled MINOCA patients who underwent ICA between December 2020 and June 2024. The protocol with a stepwise approach recommended ad hoc optical coherence tomography (OCT) for culprit lesion identification. Left ventricular angiography (LVA) or echocardiography was indicated for screening takotsubo syndrome (TTS). In case no overt diagnosis was found, cardiac magnetic resonance (CMR) was performed to distinguish focal myocardial infarction from other diagnoses, including myocarditis, TTS, and other nonischemic cardiomyopathy. Coronary functional testing (CFT) was considered in the case of persistent angina. A total of 183 patients (60% female) were enrolled. The diagnostic yield per test was 19% with OCT (21/112), 29% with LVA and/or echocardiography (32/112), 62% with CMR (64/104), and 50% (1/2) with CFT. An incremental diagnostic yield in 183 patients was observed by combining modalities (11% with OCT alone vs 29% with OCT and LVA/echocardiography vs 58% with OCT, LVA/echocardiography, and CMR vs 59% by adding CFT to all the imaging, p < 0.01). In conclusion, a structured diagnostic protocol with multiple diagnostic tests increases the diagnostic yield in the workup of MINOCA, resulting in an identified final diagnosis in 59%.