C-19 | Vessel-Specific Analysis of Patients With Angina and No Obstructive Coronary Artery Disease Undergoing Coronary Function Testing

Patients with angina and no obstructive coronary artery disease (ANOCA) are increasingly referred for invasive coronary function testing (CFT) with coronary thermodilution. However, there is limited knowledge regarding the range of normal values for physiologic measurements in unobstructed arteries. We report the angiographic findings and vessel specific physiology from patients with ANOCA who underwent CFT. We included patients from January 2018 to November 2023 who underwent coronary angiography and coronary thermodilution. We obtained angiographic findings, fractional flow reserve (FFR), resting full cycle ratio (RFR), thermodilution transit times (Tmn), coronary flow reserve (CFR), and the index of microcirculatory resistance (IMR). A descriptive analysis and a comparison between the left anterior descending (LAD) and non-LAD coronary arteries was performed. We included 189 patients (192 vessels). 169 (88%) of the vessels tested were the LAD and 23 (12%) were a non-LAD vessel. Overall, 85 (44%) were angiographically normal, 102 (53%) vessels had non-obstructive CAD, and 5 (2.6%) had obstructive CAD. Among unobstructed vessels, there was no difference in the visual percent stenosis between the LAD and non-LAD vessels. The median FFR was lower in the LAD compared to non-LAD vessels (0.89 vs 0.98, p < 0.001), and the median RFR was also lower (0.92 vs 0.99, p < 0.001). There was no difference in median CFR (3.2 vs. 3.0), or IMR (22 vs 22). The median baseline Tmn was 1.04 vs 0.99, and the median hyperemic Tmn was 0.3 vs 0.24 for LAD compared to non-LAD vessels. CFT is increasingly performed in clinical practice, and interpretation of physiologic findings requires reference values across coronary vessels and diverse populations. We found that in unobstructed arteries there is a significant difference in the FFR and RFR between LAD and non-LAD vessels, likely due to friction loss rather than significant stenoses. We also found that there was no significant difference in the CFR, IMR, or thermodilution transit times. Future studies in large populations or pooled cohorts will help determine standard reference values for this emerging technology.