OBJECTIVES This study investigated the prognostic implication of coronary flow reserve (CFR) in patients who underwent fractional flow reserve (FFR) measurement.

BACKGROUND Limited data are available regarding the long-term prognosis associated with thermodilution CFR in patients with coronary artery disease.

METHODS A total of 519 patients (737 vessels) who did not undergo revascularization were classified according to FFR and CFR values. Low FFR and low CFR were defined with upper thresholds of 0.8 and 2.0, respectively. FFR and CFR were measured by a pressure-temperature sensor-tipped wire. Clinical outcomes were assessed by the vessel-oriented composite outcome (VOCO) (a composite of cardiac death, vessel-specific myocardial infarction, and vessel-specific revascularization) during 5 years of follow-up.

RESULTS The categorical agreement (kappa = 0.080; p = 0.024) between FFR and CFR were modest, and 30.6% of the population showed discordant results between FFR and CFR. During 5 years of follow-up, patients with low CFR had a significantly higher risk of VOCO than did those with high CFR (hazard ratio [HR]: 3.171; 95% CI: 1.664 to 6.042; p < 0.001). Among patients with high FFR, there were no differences in clinical risk factor profiles, FFR, or stenosis severity between the high-CFR and low-CFR groups, and low CFR was an independent predictor for VOCO (HR: 4.999; 95% CI: 2.104 to 11.879; p < 0.001). In a 4-group classification according to both FFR and CFR, patients with low FFR and low CFR had the highest risk of VOCO (17.9%; overall p < 0.001).

CONCLUSIONS Patients with low CFR had a significantly higher risk of clinical events during 5 years of follow-up. Low CFR was an independent predictor for patient-oriented composite outcome among patients with high FFR. These results support the value of CFR in patients who undergo FFR measurement. (Clinical, Physical and Prognostic Implication of Microvascular Status; NCT02186093).