Coronary microvascular dysfunction in patients with stable coronary artery disease: The CE-MARC 2 coronary physiology sub-study

Background: In patients with angina undergoing invasive management, no obstructive coronary artery disease (NOCAD) is a common finding, and angina may persist following percutaneous coronary intervention (PCI). Coronary microvascular dysfunction may be relevant. We aimed to assess the proportion of patients presenting with suspected CAD who had coronary microvascular dysfunction. Methods: Clinical Evaluation of Magnetic Resonance Imaging in Coronary Heart Disease 2 (CE-MARC 2) was a prospective multicenter randomised controlled trial of functional imaging versus guideline-based management in patients with suspected CAD. Invasive coronary angiography was protocol-directed. Fractional flow reserve (FFR) and parameters of microvascular function (coronary flow reserve (CFR), index of microcirculatory resistance (IMR), resistance reserve ratio (RRR)) were measured in major epicardial coronary arteries with ≥40–≤90% diameter stenosis. An FFR value ≤0.80 indicated the presence of obstructive CAD. Results: 267/1202 (22.2%) patients underwent angiography and 81 (30%) patients had FFR measured. 63 (78%) of these patients had microvascular function assessed in 85 arteries (mean age 58.5 ± 8.2 years; 47 (75%) male). 25/63 (40%) patients had NOCAD, and of these, 17 (68%) had an abnormality ≥1 parameter of microvascular function (abnormal IMR (≥25), abnormal CFR (