Comparison of UFR With QFR in Stable Coronary Artery Disease

Invasive CAG was conducted following standard clinical procedures, encompassing multiple projections of both the left and right coronary arteries. The FFR was precisely measured using either an intracoronary pressure wire (Pressure Wire X; Abbott Vascular, Santa Clara, USA) or a rapid-exchange pressure microcatheter (Insight Lifetech, Shanghai, China) during peak hyperemia. This state of maximal hyperemia was achieved through the intravenous infusion of adenosine triphosphate (ATP) at a concentration of 150 μg/kg/min, administered via the forearm vein. Upon completion of the FFR assessment, the pressure wire or microcatheter was carefully retracted to the tip of the guiding catheter for a routine drift check. IVUS imaging was meticulously conducted using the iLab™ IVUS system, coupled with a 40-MHz OptiCross IVUS catheter (Boston Scientific, Fremont, USA), at a steady pullback speed of 0.5 mm/s.