Effects of heart rate on the pulsatile flow characteristics of a stenotic aortic valve model: An in vitro experimental study

In this paper, the characteristics of pulsatile flow past a silicone-based artificial stenotic aortic valve under varied heart rates have been studied using particle image velocimetry (PIV). Pulsatile flow waveforms were generated by a closed-loop cardiovascular flow simulator. Phase-locked PIV was employed to quantify the average and turbulent flow field information. Pressure gradient waveforms were recorded to evaluate the severity of the stenosis. Results suggest that as the heart rate increases, the peak pressure gradient across the stenotic aortic valve increases significantly under the same cardiac output. Under the same cardiac output, the aortic valve area (AVA) estimated using Gorlin equation decreases as the heart rate increases, while the trend is reversed using Hakki equation estimation. PIV results suggest that the peak systolic jet velocity downstream of the valve increases as the heart rate increases, implying a longer pressure recovery distance as heart rate increases. While the turbulence at peak systole is higher under the slower heart rate, the faster heart rate contributes to higher turbulence during the late systole and early diastole phases. Based on the comparison with no-valve cases, the differences in turbulence kinetic energy (TKE) was mainly related to the dynamics of leaflets under different heart rates. Overall, the results obtained in this study demonstrate that the hemodynamics of a stenotic aortic valve is complex, and the assessment of AS could be significantly affected by the pulsating rate of the flow.