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Background: The established diagnosis of coronary endothelial dysfunction (CED) is through the response to low-dose acetylcholine during invasive coronary function testing (CFT). Current diagnostic criteria encompass deficient epicardial vasodilation and/or insufficient increase in coronary blood flow (CBF) calculated from additional Doppler flow velocity measurements. The aim is to evaluate the diagnostic yield of using angiographic epicardial vasomotion and CBF as single criteria for diagnosing CED during CFT., Methods: A total of 110 patients with angina and non-obstructive coronary arteries who underwent clinically indicated CFT were included. CED was defined as any reduction in epicardial diameter through quantitative coronary angiography and/or < 50 % increase in CBF compared to baseline after low-dose acetylcholine., Results: Based on current diagnostic criteria, 78 % of patients (N = 86/110) was diagnosed with CED. When only considering epicardial diameter, 24 % CED (N = 21/86) and 50 % severe CED diagnoses (N = 19/38) were missed. When only considering CBF, 27 % CED (N = 23/86) and 18 % severe CED diagnoses (N = 7/38) were missed. A similar diagnostic yield for CED detection was found for both parameters (OR: 0.913, 95 %CI 0.481-1.726, p = 0.763). The incidence of CFT diagnoses was comparable among all groups., Conclusions: As single parameters, both epicardial diameter and CBF were ineffective in accurately diagnosing CED compared to the current diagnostic criteria. Combining both parameters is necessary to diagnose the complete spectrum of CED, as missed diagnoses of deficient CBF responses (e.g., microvascular CED) and epicardial vasomotion (e.g., epicardial CED) might occur when relying on these parameters as single diagnostic criteria for CED., Competing Interests: Declaration of competing interest CB has received consultancy fees from Philips. JP has received support as consultant for Philips/Volcano, and has received institutional research grants from Philips. TvdH has received speaker fees and institutional research grants from Abbott and Philips. The other authors report no relationship with industry related to this work., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Invasive assessments of microvascular function are rapidly becoming an integral part of physiological assessment in chronic coronary syndromes., Objective: We aimed to establish a reference range for Doppler flow velocity-derived hyperaemic microvascular resistance index (HMR) in a cohort of angina with no significant epicardial coronary obstruction (ANOCA) patients with no structural pathophysiological alterations in the coronary circulation., Methods: The reference population consisted of ANOCA patients undergoing invasive coronary vasomotor function assessment who had a coronary flow reserve (CFR) >2.5, and had either (1) tested negatively for spasm provocation (n = 12) or (2) tested positively with only angina at rest (n = 29). A reference range for HMR was established using a non-parametric method and correlations with clinical characteristics were determined using a spearman rank correlation analysis., Results: In 41 patients median HMR amounted to 1.6 mmHg/cm/s [Q1, Q3: 1.3, 2.2 mmHg/cm/s]. The reference range for HMR that is applicable to 95% of the population was 0.8 mmHg/cm/s (90% CI: 0.8-1.0 mmHg/cm/s) to 2.7 mmHg/cm/s (90% CI: 2.6-2.7 mmHg/cm/s). No significant correlations were found between HMR and clinical characteristics., Conclusion: In this reference population undergoing invasive coronary vasomotor function testing, the 90% confidence interval of the HMR upper limit of normal ranges from 2.6 to 2.7 mmHg/cm/s. A > 2.5 mmHg/cm/s HMR threshold can be used to identify abnormal microvascular resistance in daily clinical practice., Competing Interests: Declaration of Competing Interest None., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)