Intravascular ultrasound-derived virtual fractional flow reserve in the superficial femoral artery

Background Fractional flow reserve (FFR) can be estimated by analysis of intravascular imaging in a coronary artery; however, there are no data for estimated FFR in an extremity artery. The aim of this concept-generating study was to determine whether it is possible to estimate the value of peripheral FFR (PFFR) by intravascular ultrasound (IVUS) analysis also in femoropopliteal artery lesions. Methods Between April 2022 and February 2023, PFFR was measured before endovascular therapy in 31 stenotic femoropopliteal artery lesions. High-definition IVUS measurement was simultaneously performed in automatic pullback mode in 6 of those 31 lesions. IVUS-derived PFFR was calculated by an algorithm based on fluid dynamics as the following equation: ΔP = FV + SV2. F is the coefficient of pressure loss because of viscous friction (Poiseuille’s equation) and S is the coefficient of local pressure loss because of flow separation (Bernoulli’s equation). The values of F and S were calculated by analysis of IVUS. V is velocity and the value of V was obtained from previously reported data in a duplex ultrasound study. The mean pressure was assumed to be 80 mmHg, and IVUS-derived PFFR was calculated by the following equation: IVUS-derived PFFR = (80 – ΔP) / 80. Results The values of IVUS-derived PFFR and actual PFFR were similar: 0.73 and 0.72, 0.87 and 0.92, 0.90 and 0.92, 0.66 and 0.73, and 0.79 and 0.72, respectively. In one case in which run-off of the below-the-knee artery was poor, PFFR (0.91) was higher than the IVUS-derived PFFR (0.73). Conclusion Virtual PFFR in the superficial femoral artery can be estimated from IVUS analysis.