Stenosis is the abnormal narrowing of a blood vessel structure. One of the main causes of stenotic lesions is atherosclerosis, a progressive disease in which the lumen of an artery narrows due to the build-up of fatty plaque. It is usually asymptomatic in early stages, but as the disease progresses, it can lead to serious complications such as coronary artery disease (CAD), stroke, peripheral arterial disease, or renal problems, depending on the affected vessels. However, the exact etiology is still unknown. Many risk factors were identified including high cholesterol levels, elevated blood pressure, diabetes mellitus (type 1 and 2), tobacco use, and obesity. This leads to the accumulation of plaque in the blood, composed of cholesterol, fibrin, calcium and cellular waste products. This plaque narrows blood vessels thus limiting the flow of oxygenated blood to all parts of the body. Thus, a definitive diagnosis of its severity is of great importance for physicians to decide the best treatment plan. One of the most accurate method to pinpoint the stenosis severity is Fractional Flow Reserve (FFR). The FFR clinical procedure is surgically performed before angioplasty by placing a guide-catheter up to the coronary ostia. Through this guide-catheter, a sensor-tipped guidewire can advance and situate along the stenotic lesion to measure the pressure drop across the lesion. The main advantage of the FFR is the instantaneous estimation of a stenotic lesion effect and simultaneous treatment with ballooning and stenting. Unfortunately, the FFR is an invasive procedure where incision under anesthesia is required. Furthermore, introducing the guidewires along the stenotic lesion may cause a “tight-fit” in the lumen of the affected vessel and can lead to an increase in the pressure drop, resulting in a false overestimation of the flow parameters. The guidewire and the blood vessel centerlines in this procedure should be aligned. However, the long distance from insertion location and the stenosis position eventually causes difficulties in alignment. Consequently, it leads to inaccurate diagnosis.  To estimate the errors in diagnosis procedures due to misalignment, a comprehensive three-dimensional model blood flow along with guidewire is developed. Reconstructed three-dimensional coronary artery geometry from patient-specific scan is used. Blood is considered non-Newtonian and the flow is pulsatile. The comprehensive model is numerically simulated using patient-specific boundary conditions, and the predicted results are compared with the available clinical measurements.  Based on the predicted results, the ratios between pressure drop and distal dynamic pressure (CDP) and between pressure recovery coefficient and the area blockage (��) are studied. The predicted results for each case are compared with the control case (the case without guidewire) and analyzed. The findings of the current work help improve the FFR accuracy in diagnosis of stenosis severity.


Assessment of Invasive Fractional Flow Reserve Procedures Using Computational Fluid Dynamics

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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