Single-wire pressure and flow velocity measurement for quantifying microvascular dysfunction in patients with coronary vasospastic angina.

Endothelial and vascular smooth muscle dysfunction of epicardial coronary arteries play a pivotal role in the pathogenesis of vasospastic angina (VSA). However, coronary microvascular (MV) function in patients with VSA is not fully understood. In the present study, subjects without coronary obstruction were divided into two groups according to the acetylcholine provocation test: VSA group (n = 29) and non-VSA group (n = 21). Hyperemic MV resistance (hMR) was measured using a dual-sensor (Doppler velocity and pressure)-equipped guidewire, and guidewire-derived hemodynamic parameters were compared. There were no between-group differences in clinical demographics, including potential factors affecting MV function (e.g., diabetes). Although coronary flow velocity reserve was similar between the two groups [2.4 ± 1.0 (VSA group) vs. 2.4 ± 0.9 (non-VSA group); P = 0.8], coronary vessel resistance and hMR were significantly elevated in the VSA group compared with the non-VSA group (2.6 ± 3.1 vs. 1.2 ± 0.8, P = 0.04; 1.9 ± 0.6 vs. 1.6 ± 0.5, P = 0.03, respectively). Coronary vasospasm, older age, E/e', and estimated glomerular filtration rate were significantly associated with MV dysfunction [defined as ≥ median value of hMR (1.6)] in univariate analysis. Coronary vasospasm most strongly predicted higher hMR in multivariate logistic regression analysis (odds ratio, 4.61; 95% confidence interval, 0.98-21.60; P = 0.053). In conclusion, coronary MV resistance is impaired in patients with VSA compared with non-VSA patients, whereas coronary flow velocity reserve is maintained at normal levels in both groups. In vivo assessment of hMR might be a promising index of coronary MV dysfunction in patients with VSA.