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Unsteady Blood Flow in a Coronary Artery

Coronary heart disease is a major cause of death. This disease is characterized by atherogenesis in the coronary artery, a condition where the arterial wall thickens as a result of the accumulation of plaques. Eventually, the plaques may rupture causing blood clots, which slow or stop blood flow.

Research on coronary heart disease has found that the arterial wall shear stress plays a central role in the rupture of the atheromatous plaques. Many studies have been performed to investigate the correlation between this shear stress and the geometry of the arteries.

In this News, we present a study by a team of researchers (see reference) showing that arterial wall compliance substantially affects the shear stress, because blood flow causes the artery to deform during the cardiac cycle, and the deformation affects the blood flow. ADINA FSI was used in this study.

Figure 1 shows the left coronary artery geometry reconstructed from CT scans. Figure 2 shows the fluid and solid meshes used in the ADINA model.




Figure 1  Left coronary artery reconstructed from CT scans of a 60-year old healthy patient






Figure 2  The fluid and solid meshes used in the ADINA model



The fluid mesh contains about 400,000 elements and the solid mesh contains about 30,000 elements. Two simulations were performed, one with a compliant wall (using FSI) and the other with a rigid wall (using only CFD). The same physiological blood velocity and pressure waveforms were applied as boundary conditions in both the FSI and CFD simulations.

The movie above shows the smoothed wall shear stress during a cardiac cycle obtained from the FSI analysis (plotted on the deformed geometry). Of course, the coronary artery deformations are quite small, but they still affect the shear stress.  Figure 3 shows a comparison of the time variation of the maximum wall shear stress for the FSI and CFD conditions, while Figure 4 compares the wall shear stress at different time instants during a cardiac cycle.





Figure 3  Temporal variations of the maximum wall shear stress for the FSI and CFD simulations






Figure 4  Wall shear stress (in Pa) for the FSI and the CFD simulations at two time instants



The comparison in Figure 3 shows, as expected, differences in the results when using the FSI and CFD approaches; in particular the peak shear stress is reduced by about 10% when modeling FSI conditions.  Also, Figure 4 shows the shear stress distribution is quite different in the FSI model. Such differences confirm that arterial deformations play an important role in the computation of the arterial wall shear stress.

This study is an example of how the use of ADINA can help scientists and engineers obtain valuable insights into complex physiological phenomena in biomedical research and in the design of medical devices.

For more applications of ADINA FSI, see here.

Reference

  • M. Malvè, A. García,  J. Ohayon and M.A. Martínez, "Unsteady blood flow and mass transfer of a human left coronary artery bifurcation: FSI vs. CFD", International Communications in Heat and Mass Transfer 39 (2012) 745–751.


Keywords:
Unsteady blood flow, coronary artery, FSI, CFD, artery wall shear stress, hemodynamics, CT scan of patient, physiological pressure waveforms


Courtesy of M. Malvè, A. García, and M.A. Martínez (Universidad de Zaragoza, Spain) and J. Ohayon (Laboratory TIMC/DyCTiM, Grenoble, France and University of Savoie, France)

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