CARD21: In Vitro Investigation Of The Timing Of The LVAD Pulsatility Event On Intraventricular Hemodynamics

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Background: To reduce in-pump thrombosis and potentially improve left ventricular (LV) washout, pulsatility events (i.e., periodic LVAD speed modulation) have been introduced in 3rd generation LVADs. However, this pseudo-pulsatility of the centrifugal continuous flow pumps is not synchronized with native LV residual contractility. This study investigates the effect of timing of pulsatility events, with respect to LV pressure variations along the cardiac cycle, on intraventricular hemodynamics. Methods: Time-resolved stereo particle image velocimetry measurements were performed in a patient-derived quasirigid LV silicon model implanted with an LVAD. The residual LV contractility was modelled as a periodic variation in intraventricular pressure (IVP). Velocity fields in two orthogonal planes were measured for 7.5 cardiac cycles (including 3 occurrences of the pulsatility events, which happen every two seconds), for 3 LVAD speeds and 4 different synchronicities of pulsatility: at maximum/ minimum IVP and during increasing/decreasing IVP. Instantaneous measurements of the flowrate through the LVAD, with a time-resolution of 1 ms, were collected during the entire experiment. Ventricle stagnation index (VSI) was computed for each measurement plane and all experimental conditions studied. Results: Despite maintaining a constant average flowrate, the synchronicity of the LVAD pulsatility with the oscillatory IVP strongly influenced the flow rate waveforms, especially the peak and minimum instantaneous flow rates. A strong effect of the timing of pulsatility was also observed on intraventricular hemodynamics: pulsatility events taking place during decreasing IVP (diastole) resulted in higher VSI than other timing of pulsatility. Overall, these high resolution, instantaneous measurements of LVAD flow rate and pressure also highlighted the complex interrelations between LVAD speed, peripheral resistance, IVP and flow rate. Conclusion: This in vitro study elucidates the effect of LVAD pulsatility event synchronicity with the cardiac cycle on flowrate and LV flow patterns.