Does serial A-IMR assessment during acetylcholine spasm provocation testing identify sustained microvascular constriction in ANOCA patients with microvascular spasm?
Serial A-IMR assessment during spasm provocation testing demonstrates sustained nitrate-resistant microvascular constriction in patients with microvascular spasm, highlighting potential confounders in standard physiological assessments.
Background: Microvascular spasm (MVS), a phenotype of microvascular dysfunction in patients with angina with non-obstructive coronary arteries (ANOCA), involves transient microvascular constriction. The angiography-derived index of microcirculatory resistance (A-IMR) is a less invasive method for assessing microcirculatory resistance. We aimed to evaluate MVS characteristics using A-IMR. Methods and Results: We retrospectively studied ANOCA patients who underwent acetylcholine spasm provocation tests (SPT). Patients were classified into no-spasm, epicardial spasm (ECS), or MVS groups. A-IMR was measured before and after SPT. Of 109 patients, 21 (19.3%) had MVS. The MVS group had more women (76.2% vs. 42.0%; P=0.01) than the other 2 groups combined. While pre-SPT A-IMR values were similar, post-SPT A-IMR after nitroglycerin was significantly higher in the MVS group than the no-spasm group, especially in the left anterior descending (LAD) artery (44.60 vs. 33.54; P=0.007). ∆A-IMR (post- minus pre-SPT) was significantly greater in the MVS group for both the LAD (9.89 vs. -9.26; P=0.001) and right coronary artery (RCA; 3.22 vs. -6.83; P=0.001). Multivariable analysis showed ∆A-IMR in the LAD and RCA were independently associated with MVS. Conclusions: Serial A-IMR assessment during SPT reveals sustained nitrate-resistant microvascular constriction in patients with MVS, which may confound standard post-SPT physiological assessments such as coronary flow reserve or IMR. These findings underscore the need for careful interpretation of physiological data in the presence of MVS.
Shimosato et al. (Mon,) studied this question.