Table 1.

Proposed Standardized Diagnostic Criteria: Coronary Vascular Dysfunction

Diagnostic Group	Outcome Definitions: Disorders of Coronary Artery Function
Microvascular angina	•Abnormal microvascular resistance •Impaired coronary vasorelaxation •Microvascular spasm	IMR ≥25 HMR >2.4 CFR by thermodilution <2.0
		Angina during intracoronary infusion of acetylcholine with typical ischemic ST-segment changes without epicardial coronary constriction (<90% reduction) in coronary artery diameter∗
Vasospastic angina	Epicardial spasm	Reduction in coronary diameter >90% following intracoronary acetylcholine from baseline in any epicardial coronary artery segment together with symptoms and ST-segment deviation on ECG†
Obstructive epicardial coronary disease		FFR ≤0.80 Contrast FFR ≤0.83 Resting indices (i.e., iFR, NHPR) ≤0.89
Endothelial dysfunction		Impaired vasodilatation and/or impaired increase in coronary flow velocity in response to intracoronary infusion of low doses (1–30 μg) of acetylcholine

CFR = coronary flow reserve; ECG = electrocardiography; FFR = fractional flow reserve; HMR = hyperemic microvascular resistance; iFR = instantaneous wave-free ratio; IMR = index of microcirculatory resistance; NHPR = nonhyperemic pressure ratio.

^∗Microvascular spasm may occur earlier than diffuse, distal spasm of a conduit artery.

^†Prinzmetal vasospasm is typically focal.