Computational fluid dynamics with application of different theoretical flow models for the evaluation of coronary artery stenosis on CT angiography: comparison with invasive fractional flow reserve

The purpose of this study is to use the coronary computed tomography angiography (CCTA) to simulate the coronary blood flow with different theoretical flow models by using not only the computation fluid dynamics (CFD) method, but also additional patient boundary conditions obtained with echocardiography, and evaluate the feasibility of simulated fractional flow reserve (FFRCTS), compared with the invasive CTA-based FFR. The laminar and three turbulence models (k-epsilon(k-epsilon), k-omega(k-omega), SST (Menter's shear stress transport)) were implemented to predict coronary blood flow. The study investigates an ideal stenosis model and six patients, with invasive FFR measurements. Three-dimensional reconstructions of coronary arteries of six subjects were performed from CCTA images of 320-detector scanner. The measured velocity profile of the left ventricular outflow tract from the echocardiography was employed for the inlet velocity in simulation. The pressure waveform of the patient aortic blood flow was used as the pressure profile at the outlet. With simulations, we found that the maximum velocity in the stenotic coronary artery reached about 395 cm s(-1), which was about 2.4 times faster than the inlet velocity of 165 cm s(-1) for the patient with coronary stenosis diagnosed 50%-75% on CTA. The pressure drop across the stenosis was about 28 mmHg. Meanwhile, the value of FFRCTS using the laminar flow pattern was 0.788 closely to its invasive FFR of 0.79. In conclusion, this study demonstrated that the CFD method has moderate more blood flow information to assess the hemodynamic significance of the coronary blood flow and calculate the non-invasive FFRCTS values, which were very close to those measured with invasive FFR.