Diagnostic Yield and Testing Characteristics of an Invasive Coronary Function Testing Program

Angina, ischemia, or myocardial infarction without non-obstructive coronary arteries (ANOCA, INOCA, or MINOCA) are common conditions yet often underdiagnosed. Invasive coronary function testing (CFT), which includes coronary thermodilution and coronary reactivity testing, can provide accurate diagnoses and improve patient outcomes.

This study describes the diagnostic yield of an invasive CFT program at a single tertiary care center and presents the findings of coronary thermodilution and coronary reactivity testing in the first 104 patients from 2021 to 2025.

We conducted a retrospective cohort study of consecutive patients who underwent invasive CFT. Descriptive statistics summarized patient characteristics, diagnostic outcomes, and changes in management following invasive CFT.

One hundred and four patients (mean age 61.6 ± 10.5 years; 48.1% female) included patients tested ad hoc during an index coronary angiogram (n = 23) or during a scheduled functional assessment (n = 81). Testing indications were post-revascularization angina (39%), ANOCA (35%), INOCA (14%), MINOCA (6%), or heart transplant (5%). Invasive CFT consisted of thermodilution-based coronary flow reserve only (35%), coronary reactivity testing only (10%), or both (55%). A definitive diagnosis was achieved in 74 of 104 patients (71.2%). Of these, 28 (27%) were diagnosed with epicardial coronary spasm, 9 (9%) with microvascular spasm, 6 (6%) with endothelial dysfunction, 13 (13%) with CMD, and 18 (17%) with a mixed phenotype. Management changes occurred in 76 of 104 (73%) patients, primarily through the adjustment of antianginal therapy. Nitrates, calcium channel blockers, and β-blockers were modified in 52%, 51%, and 52% of patients, respectively. The association of CFR values derived from PET and by Thermodilution demonstrated a fair overall agreement (k = 0.39, 95% CI 0.09-0.68). Dose-response to acetylcholine (2-200 ucg) showed that diagnostic criteria were achieved with the 100 mcg dose in most participants. Invasive CFT was safe with only two safety events recorded.

An invasive CFT program was safely implemented, demonstrating high diagnostic yield and an association with frequent changes in anti-anginal therapy of patients with non-obstructive coronary artery disease.