Abstract 17001: Enhancing Coronary Functional Angiography: Integrating Doppler-Based Left Circumflex Coronary Flow Reserve in Assessment

Background: Coronary microvascular dysfunction (CMD), predominantly affecting women is associated with poor outcomes and has limited diagnostic options. Coronary functional angiography (CFA) is used for diagnosing CMD in patients with refractory angina and no obstructive coronary artery disease (ANOCA). The assumption is that endothelial-independent CMD is a homogenous disease process, therefore current gold-standard for diagnosis is measure of coronary flow reserve (CFR) in the proximal left anterior descending artery (LAD). However, there is limited data on CFR in the left circumflex (LCx).

Objective: Examine the benefits of measuring CFR using Doppler-tipped guide wire in LCx in addition to proximal LAD.

Methods: Examined 191 ANOCA patients with Canadian Cardiovascular Society (CCS) class 3 or 4 angina despite optimal medical treatment who underwent CFA for assessment of CMD. CFR measurements were obtained using Doppler-tipped guidewire during the administration of 72 mcg of adenosine in both the proximal LAD and LCx and CFR of <2.5 was used to define CMD.

Results: 191 patients underwent CFA including 91% female with a median age of 59 years (IQR: 50, 67). The correlation in CFR measurements between the proximal LAD and LCx was 0.610 (p<0.001). 149 (78%) patients had concordant results including 113 (59%) with abnormal CFRs and 36 (19%) with normal CFRs in both vessels. 12 (6%) had abnormal proximal LAD CFR and normal LCx CFR; and 30 (16%) had an abnormal LCx CFR and normal proximal LAD CFR and would have gone undiagnosed without measuring LCx CFR.

Conclusion: The addition of LCx CFR measurement to the current standard CFA protocol using the Doppler guidewire improves diagnosis of CMD in patients. Further studies are needed to evaluate a comprehensive assessment of CMD including measurement of LCx CFR.