Microvascular dysfunction in patients with angina and non-obstructive coronary artery disease– preliminary data from a single center registry

Introduction: About 50% of patients referred for coronary angiography because of angina and/or myocardial ischemia are found to have non-obstructive coronary artery disease (CAD). The role of microvascular dysfunction as the cause of angina or ischemia is becoming increasingly recognized. Our aim was to describe coronary physiology and microvascular function in patients with angina and ischemia and non-obstructive CAD (ANOCA/INOCA).

Methods: Patients with angina, referred for coronary angiography and found to have non-obstructive CAD enter a prospective registry and undergo invasive coronary physiology evaluation. Fractional flow reserve (FFR), coronary flow reserve (CFR), index of myocardial resistance (IMR) and resistive reserve ratio (RRR) are recorded. Patients with obstructive CAD (≥50% diameter stenosis and/or FFR≤0.8), acute coronary syndrome and/or hemodynamic instability are excluded. Microvascular dysfunction is considered significant if either CFR<2.5, IMR≥25 and/or RRR≤3.5.

Results and discussion: 58 patients with ANOCA or INOCA were studied. Mean age was 64.8±10.4 and 65.5% were females. Hyperlipidemia, hypertension, and obesity were the most frequent cardiovascular risk factors (65.5%, 55.1% and 39%, respectively), and approximately 25% had known ischemic heart disease with a previous percutaneous coronary intervention. Microvascular dysfunction was found in 29 (52.7%) of the patients. 10 (18.2%) had CFR<2.5, 20 (34.5%), had IMR≥25, and 27 (50%) had RRR≤3.5. Among patients with IMR≥25, mean CFR and RRR were 2.1±0.5 and 2.4±6.8, respectively.

Conclusion: microvascular dysfunction is present in approximately half of the patients with angina and/or ischemia referred for coronary angiography and found to have non-obstructive CAD.