Coronary microvascular function and atherosclerotic plaque burden in ischaemia and no obstructive coronary arteries: a secondary analysis of the CorMicA trial.

Background: The relationship between atherosclerosis and endotypes of myocardial ischaemia with no obstructive coronary artery disease (INOCA) is unclear. We investigated potential associations between cumulative atherosclerotic plaque burden quantified using the Gensini score, novel invasive indices of coronary microvascular function (microvascular resistance reserve (MRR); resistive reserve ratio (RRR)) and related INOCA endotypes.

Methods: Coronary angiography and invasive coronary function tests were simultaneously acquired in the CorMicA cohort. A comprehensive physiological assessment was performed using both a thermodilution-based diagnostic guidewire and intracoronary acetylcholine provocation testing. Angiograms were examined for luminal stenosis in each segment of the SYNTAX coronary model. Cumulative plaque burden was quantified using the Gensini score, which incorporated both the number of diseased coronary segments and stenosis severity. Results were compared with indices of microvascular function and INOCA endotypes. Angiographic analyses were performed blind to coronary physiology findings.

Results: In 151 participants (median age 61 years; 73.5% female) without flow-limiting coronary artery disease, medical history included 41.7% smoking, 63.6% hypertension and 19.2% diabetes mellitus. The left anterior descending artery underwent diagnostic guidewire testing in 85.4%, and 55.0% of participants had abnormal coronary flow reserve (CFR) and/or Index of Microcirculatory Resistance (IMR). The median Gensini score was 6.0 (IQR 2.5-11.0). CFR (p=0.012), MRR (p=0.026) and RRR (p=0.026), but not IMR (p=0.445), were univariably associated with raised Gensini scores. These significant effects persisted in multivariable models controlling for potential confounders. Considering INOCA endotypes, Gensini scores differed among participants with microvascular angina (MVA) (7.0 (2.5-11.0)), vasospastic angina (VSA) (4.5 (2.0-10.0)), mixed MVA/VSA (9.0 (5.0-11.5)) and non-cardiac symptoms (3.5 (1.5-8.0)); Kruskal-Wallis p=0.030.

Conclusions: Reduced CFR, MRR and RRR, and MVA were associated with increased coronary atherosclerotic plaque burden, as evidenced by higher Gensini scores. These novel findings provide a mechanistic link between INOCA and cardiovascular events, reinforcing the importance of antiatherosclerosis therapy in patients with MVA.