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Session: Poster session I
Session starts: Thursday 24 January, 15:00

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Jelle Schrauwen ()
Jolanda Wentzel ()
Ton van der Steen ()
Frank Gijsen ()

Abstract:
Fractional Flow Reserve (FFR) is an important indicator for the hemodynamic significance of a coronary stenosis. The FFR is defined as the ratio between the pressure distal of the stenosis and the aortic pressure under hyperemia. In clinical practice the FFR is measured with a pressure wire and intervention is warranted if it is below 0.8. With current coronary angiography it is possible to obtain the coronary geometry instantly. Therefore the goal of our research is to assess how well we can determine the FFR based on geometrical features derived from imaging data. Sixteen coronary arteries of patients with coronary artery disease were imaged with MSCT and intravascular ultrasound (IVUS). Each artery was modeled in three consecutive steps, where in each step a geometrical complexity was added. This geometrical change could be correlated to the change in pressure drop it caused. First a tapered model was made with the mean inlet and outlet radius of the artery and its length. Secondly, in the stenosed model the lumen outline from IVUS data was used to replace the wall of the tapered model. Thirdly, a curved model was created by adding the centerline obtained with MSCT, which resulted in the complete 3D reconstruction of the artery. CFD was performed to compute the pressure drop in all these models with steady flows for Reynolds numbers ranging from 5 to 300. The computed pressure drop was compared to the pressure drop determined from geometrical features alone. For flows with low Reynolds numbers the pressure drop in the tapered geometry could be predicted excellently with the tapering angle (r=0.99). The additional pressure drop in the stenosed geometry was captured best by the maximal degree of stenosis (r=0.84). The curvature had no significant contribution for low Reynolds numbers. In flows with high Reynolds numbers the pressure drop in the tapered and stenosed geometry could best be fitted with the product of the tapering angle and the maximal degree of stenosis (r=0.93). The additional pressure drop in the curved model correlated to the sum of the angular change along the centerline (r=0.51). Although the estimated pressure drop could deviate from the CFD results (majority within ±25%), we found an excellent correlation between the FFR from the CFD simulations and our FFR based on geometrical features (r=0.96). With our approach of forward geometrical modeling the effects of the geometric features on the pressure drop could be determined. With these correlations we were able to predict the pressure drop and therefore the FFR in coronary arteries based solely on its geometry. However high FFR values were found (>0.85), meaning that the arteries were relatively healthy. To assess clinical relevance of the current findings we need to include more heavily diseased coronary arteries.