The Effect of the Sensor Position of the Pressure Wire Distal to a Coronary Stenosis on the Calculated Fractional Flow Reserve

The determination of the fractional flow reserve can be influenced by the position of the sensor of the pressure wire distal to a coronary lesion. We aimed to calculate the pressure gradients restricted to the stenosis and with the inclusion of the distal reference segment up to the position of the pressure wire. The coronary artery volumetric flow was calculated based on the velocity of the contrast material in the 3D reconstructed coronary segment. Pressure gradients were determined by fluid dynamic equations using the morphological data derived from 3D coronary angiography and contrast material velocities. The Bland-Altman analysis showed smaller differences between the calculated and the measured FFR when the distal laminar resistances were also incorporated in the model, compared to the calculations restricted to the lesions (mean difference: -0.05 vs. -0.09, limits: -0.11-0.02 vs. -0.16-0.01; range: 0.112 vs. 0.159). The FFR reflects not only the pressure gradient of the stenosis, but also the laminar resistance of the poststenotic segment. Knowing the components of the detected gradients could be important for the clinical considerations of the cases near the cut-off value of the FFR.