BACKGROUND: Approximately one-half of patients undergoing diagnostic coronary angiography for angina have no significant coronary stenosis, in whom coronary functional abnormalities could be involved. OBJECTIVES: This study examined the significance of coronary functional abnormalities in a comprehensive manner for both epicardial and microvascular coronary arteries in patients with angina and nonobstructive coronary artery disease (CAD). METHODS: This study prospectively enrolled 187 consecutive patients (male/female 113/74, 63.2 ± 12.3 years), who underwent acetylcholine provocation test for coronary spasm and measurement of index of microcirculatory resistance (IMR) to evaluate coronary microvascular function, and followed them for a median of 893 days. RESULTS: Of all subjects, acetylcholine test identified 128 patients with vasospastic angina (VSA) (68%), and cardiac events occurred in 10 patients (5.3%) during the follow-up. Multivariable analysis revealed that IMR correlated with the incidence of cardiac events (hazard ratio: 1.05; 95% confidence interval: 1.02 to 1.09; p = 0.002) and receiver-operating characteristics (ROC) curve analysis identified IMR of 18.0 as the optimal cut-off value. Among the 4 groups based on the cut-off value of IMR and the presence of VSA, the Kaplan-Meier survival analysis showed a significantly worse prognosis in the group with high IMR (≥18.0) and VSA compared with other groups (log rank, p = 0.002). Importantly, intracoronary administration of fasudil, a Rho-kinase inhibitor, significantly ameliorated IMR in the VSA patients with increased IMR (p < 0.0001). CONCLUSIONS: These results indicate that in patients with angina and nonobstructive CAD, coexistence of epicardial coronary spasm and increased microvascular resistance is associated with worse prognosis, for which Rho-kinase activation may be involved.