Effect of nonobstructive coronary stenosis on coronary microvascular dysfunction and long‐term outcomes in patients with INOCA

BACKGROUND: Ischemic pain with no‐obstructive coronary artery (INOCA) is clinically significant and defined by nonobstructive coronary stenosis <50%. Coronary microvascular dysfunction (CMD) is a relevant cause associated with adverse outcomes. OBJECTIVES: Investigated the effect of no‐stenosis (0% stenosis) and non‐obstructive (0% < stenosis < 50%) on the prognostic impact of CMD in INOCA. METHOD: A retrospective study assessed the coronary microvascular function in 151 INOCA patients who underwent invasive angiography by the coronary angiography‐derived index of microcirculation‐resistance (caIMR). CZT‐SPECT was performed to evaluate myocardial perfusion imaging (MPI) abnormalities. Chi‐square test/Fisher exact test, Student t‐test, Kaplan–Meier curve, and Uni‐multivariable Cox proportional models were used for analysis. Clinical outcomes were major adverse cardiovascular events (MACE) during a median follow‐up of 35 months. RESULT: No‐stenosis was present in 71 (47%) INOCA patients, and 80 (53%) were with nonobstructive. CMD (caIMR ≥ 25) was more prevalent in patients with no‐stenosis than nonobstructive (76.1% vs. 48.8%, p = .001), along with abnormal MPI (39.4% vs. 22.5%, p = .024). The MACE rates were not different between no‐stenosis and nonobstructive stenosis. CMD showed an increased risk of MACE for all INOCA. No‐stenosis with CMD had the worst prognosis. Cox regression analysis identified CMD and abnormal MPI as predictors of MACE in all INOCA and patients with no‐stenosis. However, no‐stenosis and nonobstructive stenosis were not predictors of MACE in INOCA. CONCLUSION: CMD was more frequently present in INOCA with no‐stenosis. However, there was no difference in long‐term clinical outcomes between no‐stenosis and nonobstructive stenosis. CMD could independently predict poor outcomes in INOCA, particularly in patients with no‐stenosis.