Assessment Of Computational Fluid Dynamics To Calculate Individual Coronary Wall Shear Stress In-Vivo

Beyond classic risk parameters non physiologic or oscillating wall shear stress (WSS) has been proven to act as a local factor for initiation and progression of atherosclerosis as well as for plaque rupture. Direct measurement of WSS in-vivo is difficult and restricted to animal models. Computational fluid dynamics (CFD) is a validated tool to compute flow parameters and WSS. For this purpose an exact model of the underlying patient specific geometry of the coronary tree is a prerequisite. Using 3D-IVUS or modern multislice computed tomographic coronary angiography (CTA) with submilimeter resolution these data can be provided. The aim of this study was to 1.) demonstrate feasibility of in-vivo CFD calculation of human coronaries based on CTA and 2.) to correlate the findings with radio frequency tissue information derived by intravascular ultrasound. We prospectively included 10 patients with suspected coronary artery disease who received CTA (Dual source 64 slice CT) and invasive conventional coronary angiography. Intravascular ultrasound and ECG-triggered radio frequency analysis (VH) was attempted in all three epicardial vessels. In the CTA-dataset the coronaries were segmented and a mesh model for CFD was generated. CFD calculations were performed using a commercial available software package with laminar flow and blood as a Newtonian fluid as boundary conditions. Coronary models were stationary with rigid vessel walls, while the pulsatile inflow characteristics was derived from invasive Doppler velocity measurement. Flow pattern calculations, vessel wall shear stress and IVUS analysis were successfully performed in 24/30 and 17/30 coronary arteries. The presence of high shear stress and non turbulent flow was inversely correlated with the presence of plaque as determined by intravascular ultrasound. No correlation of any CFD parameter with the radio frequency tissue information could yet be observed. The findings of the present study demonstrate the feasibility of assessing fluid tissue interactions in human coronary arteries using CTA and its correlation to invasive findings. The possible impact of CFD parameters on risk- and treatment stratification has to be determined in a large scale prospective trial.