The Great Masquerader: Vasospastic Angina Mimicking Left Main Coronary Artery Disease

A significant proportion of patients undergoing invasive coronary angiography for angina have no obstructive coronary artery disease (CAD). In such patients, coronary microvascular dysfunction (CMD) and vasospastic angina (VSA) represent key pathophysiological mechanisms. We report a case of a 58-year-old male with exertional chest pain and exercise ECG changes typical of left main or multivessel CAD. Coronary computed tomography angiography (CCTA) showed borderline stenosis of the distal left main coronary artery. Coronary angiography revealed no critical stenosis. A comprehensive functional assessment demonstrated reduced coronary flow reserve (CFR = 2.0) and an elevated index of microcirculatory resistance (IMR = 25), consistent with CMD. An intracoronary acetylcholine provocation test induced severe focal vasospasm of the mid-left anterior descending artery (LAD) with ST-segment elevation and anginal pain, promptly relieved by nitroglycerin, confirming VSA. This case highlights the diagnostic and clinical importance of invasive functional testing in patients with angina and non-obstructive coronary arteries (ANOCA/INOCA). The coexistence of CMD and VSA (two distinct but overlapping pathophysiological endotypes) is increasingly recognized as a marker of adverse prognosis. Functional coronary assessment should be considered in all patients with angina and non-obstructive coronary arteries, as identifying mixed endotypes enables precise, mechanism-guided therapy.