Additive Value of Acetylcholine Testing in ANOCA: A US-Based Multicenter FlowLab Study.

Abstract

Background: Angina with non-obstructive coronary arteries (ANOCA) is an underrecognized cause of angina with non-universal diagnostic techniques and patient management strategies. Among ANOCA testing, vasospasm provocation is not always performed mainly due to differences in institutional availability.

Aims: Using the FlowLab Study, we quantified vasospasm prevalence among patients with ANOCA at US centers and compared physician decision-making, endotype distribution, and management between sites that did and did not include vasospasm testing in their workup.

Methods: The FlowLab Study was a prospective, multicenter, US-based study of patients who were referred for coronary angiography and underwent ANOCA testing using the bolus thermodilution method. Presumed diagnosis before cardiac catheterization and final diagnosis after ANOCA testing were compared between participating sites with or without acetylcholine testing availability.

Results: A total of 253 procedures at 14 US sites were included in this study. There were 155 procedures among sites performing spasm provocation testing and 98 procedures among sites not performing spasm provocation testing. Prior to cardiac catheterization, sites with spasm provocation testing were less likely to suspect epicardial coronary artery disease as the cause of angina compared to sites without (27% vs. 59.2%, p < 0.0001). A diagnosis of CMD was made more frequently at sites performing spasm testing compared to sites not performing spasm testing (68% vs. 29.6%, p < 0.0001). Similarly, among 125 patients who underwent spasm provocation testing, diagnostic yield increased from 34.4% with bolus thermodilution alone to 84.8% after the addition of spasm provocation testing (p < 0.001). In these patients, intensification involving calcium channel blockers was more frequent with epicardial (67%) and microvascular spasm (41%) than without spasm (24%, p = 0.001).

Conclusions: In contemporary US practice, adding spasm provocation testing to bolus thermodilution more than doubled diagnostic yield and was followed by medication changes directed toward the diagnosed endotype. Differences between sites with and without spasm testing also reflected variation in procedural practice.