# An Assisted Numerical Simulation Diagnosis Method for Atherosclerosis Based on Hemodynamics
## 3 Calculation Results and Analysis  
### Effect of a Single Intravascular Atherosclerosis Lesion on Blood Flow Velocity  
Figure 4 shows the effect of point-protruding atherosclerosis lesion tissue on blood flow rate. A comparison of the velocity distribution in the axial cross-section at various moments during a cardiac cycle showed that the blood flow velocity upstream from the lesion tissue varied largely with the pulsatile blood pressure input signal, producing only a small area of low flow velocity near the proximal end of the connection to the lesion tissue. Substantial changes in flow velocity distribution were observed at the lesioned tissue and downstream from the lesioned tissue at the distal end. Cross-section I shows the proximal blood flow velocity distribution. The blood flow velocity upstream from the protruding lesion tissue was almost independent of the lesion site, with no obvious flow separation zones and no areas of greater velocity within the entire vascular cross-section. Cross-section II displays that at the protruding lesioned tissue, blood could not form a fully developed flow in the abruptly narrowed vessel, resulting in a thin boundary layer on the vessel wall, a rapid increase in the luminal radial velocity from zero velocity at the wall to the main stream velocity, and an overall flow distribution characterized by a very high flow velocity. The flow velocity at the distal end of the lesion in cross-section III showed a clear separation between the high and low flow velocity regions. The blood flow velocity at the medial wall of the arc was abruptly decreased, creating a distinct secondary flow region with high pressure and low velocity. The flow line shown in Figure 3 indicates that the protruding lesion plaque triggered blood reflux, which occurred throughout the cardiac cycle. The return flow and reflux area were small in the early part \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & \multicolumn{3}{c}{**Male (38 Cases)**} & \multicolumn{3}{c}{**Female (24 Cases)**} \\ \cline{3-8}
**Item** & **Reference** & **Detected** & **Simulation** & **Error** & **Detected** & **Simulation** & **Error** \\  & & **Value** & **Value** & **Value** & **Value** & **Value** & **Error** \\ \hline Heart rate (HR) & 60–100 B/min & 69.38 \(\pm\) 7.49 & 75 & +8.10\% & 68.63 \(\pm\) 8.06 & 75 & +9.28\% \\ Cardiac output (CO) per minute & 4–9 L/min & 5.35 \(\pm\) 0.87 & 4.93 & \(-\)7.85\% & 4.53 \(\pm\) 0.98 & 4.93 & +8.83\% \\ Pre-jection period (PEP) & 0.05–0.12 s & 0.10 \(\pm\) 0.02 & 0.11 & +10\% & 0.10 \(\pm\) 0.02 & 0.11 & +10\% \\ Left ventricular ejection time (LVET) & 0.24–0.40 s & 0.33 \(\pm\) 0.04 & 0.35 & +6.11\% & 0.36 \(\pm\) 0.04 & 0.35 & \(-\)2.78\% \\ Mean artery pressure (MAP) & <114 mmHg & 91.67 \(\pm\) 10.61 & 91.12 & \(-\)0.61\% & 90.04 \(\pm\) 11.00 & 91.12 & +1.19\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of simulated results and measured data. Figure 4: Influence of protruded plaques on the secondary flows in different cross sections. of the cardiac cycle (0-0.15 s), whereas the reflux phenomenon increased remarkably in the second half of the cardiac cycle (0.15-0.8 s). The simulation results of a single atherosclerotic vessel indicated that the medial arc at the distal end of the stenosis site of the lesioned vessel showed a high flow velocity region in the middle of the lumen and a low flow velocity region near the medial wall of the lumen. Greater stenosis resulted in a lower flow velocity in the region of secondary flow caused by the vessel and a greater the difference in flow velocity at the peak and trough of the cardiac cycle. A comparison of the simulation results of vessels with point-protruded plaques and narrow plaques showed that the low-flow region caused by narrow plaques was larger in length but smaller in volume and was located at the stenosis site and the distal end; the low-flow region caused by the point-protruded plaques was shorter in length but larger in volume and was mostly found at the distal end.