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.