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Effects of Cardiac Motion on the Flow Rate of the Left Coronary Artery Considering Different Blood Viscosities

Coronary arteries are one of the most vulnerable sites of diseases in the cardiovascular system. It is a known fact that the curvatures of coronary arteries change during every cardiac cycle due to cardiac motions, which can significantly affect their hemodynamics. In this study, effects of human left coronary artery motions on its blood flow rate were investigated using an experimental model. Also, the different blood viscosities were experimented as the working fluid in order to find out the effect of cardiac motion on the flow rate of the artery for more viscous blood. The artery was simplified into a straight flexible tube that experienced an in-plane sinusoidal motion utilizing a coronary artery motion simulator device, while the artery's cross-section did not change. A steady state pressure gradient was applied at the tube inlet, making a laminar flow close to the physiological values in the quasi-static state, while the outlet was at atmospheric pressure. Meanwhile, variations in flow rate were accurately measured by a nozzle flowmeter that was designed, optimized, and fabricated for these experiments. Several experiments were performed on fluids with different viscosities to find out the effects of both motion and viscosity on the flow rate. In all experiments, two sets of results were obtained: (i) the flow rate of the static tube with a mean curvature radius (quasi-static state) (ii) the flow rate of the moving tube at the frequency of 1 Hz. According to the results, artery motions can increase the mean flow rate up to 12% compared with the quasi-static state, when the working fluid has characteristics similar to normal blood. In addition, it was found that the effect of cardiac motion in increasing the flow rate can be amplified if the blood is more viscous than normal. Taken together, the results suggest that the cardiac motion may play an important role in changes of left coronary artery flow rate, and emphasize the need for future investigations.