Relation of hyperemic response during fractional flow reserve measurement to coronary flow reserve

Coronary flow reserve (CFR) represents entire coronary compensatory capacity, while fractional flow reserve (FFR) is a standard to evaluate functional severity of epicardial coronary artery disease (CAD). ΔFFR, a decrease in a ratio of mean distal coronary pressure to aortic pressure (Pd/Pa) at rest to FFR, is conceptually associated with coronary microvascular function. This study aimed to evaluate the relation of ΔFFR to CFR in patients with stable CAD. We performed resting Pd/Pa and FFR measurements in a total of 309 vessels with intermediate coronary artery stenosis in 242 patients. ΔFFR was defined as (resting Pd/Pa – FFR), and pressure bounded-CFR was calculated to estimate low CFR. Vessels were divided as the low CFR and non-low CFR groups. Of 309 vessels, low CFR was observed in 101 (32.7 %). While FFR values were similar (0.78 ± 0.11 vs. 0.78 ± 0.09, p = 0.84), resting Pd/Pa (0.85 ± 0.08 vs. 0.93 ± 0.04, p