Assessing Coronary Microvascular Dysfunction Using Angiographic Frame Count in Patients With Angina and...

Coronary microvascular dysfunction (CMD) is underdiagnosed, mainly because of the low clinical adoption of wire-based invasive coronary function testing. Angiography-based, wireless methods might facilitate widespread assessment of CMD. To our knowledge, the diagnostic utility of angiographic Thrombolysis In Myocardial Infarction (TIMI) frame count and frame count reserve (FCR) in identifying CMD in patients with angina and nonobstructive coronary arteries (ANOCA) has never been explored.

A total of 140 ANOCA patients underwent coronary angiography and invasive coronary function testing with thermodilution-derived index of microcirculatory resistance (IMR) and coronary flow reserve (CFR). CMD was defined as CFR < 2.5 or IMR ≥ 25. TIMI frame count was measured from resting (TFC_rest) and hyperemic (TFC_hyp) angiography, with FCR calculated as TFC_rest/TFC_hyp.

Among the 140 patients enrolled, the mean age was 63.3 years and 50.7% were women. TFC_hyp correlated more strongly with IMR than TFC_rest (r = 0.557 [P < 0.001] and r = 0.394 [P < 0.001], respectively) and had superior diagnostic performance for CMD with abnormal IMR (area under the curve, 0.810 vs 0.711; P = 0.015). FCR showed a good correlation with CFR (r = 0.686; P < 0.001) and high diagnostic accuracy (area under the curve, 0.871; P < 0.001) for CMD with abnormal CFR. TFC_hyp ≥ 19 independently predicted CMD with abnormal IMR (odds ratio, 13.11; 95% confidence interval, 5.39-35.59), whereas FCR < 2 independently predicted CMD with abnormal CFR (odds ratio, 24.21; 95% confidence interval, 9.93-65.97).

TFC_hyp combined with FCR offers a comprehensive, accurate, wireless alternative for CMD diagnosis, facilitating a broader assessment of CMD in ANOCA patients.