IMPLEMENTATION OF AN EFFECTIVE VALVE MOTION STRATEGY FOR CFD SIMULATIONS OF THE REALHEART TAH

Nathaniel Kelly, Nils Brynedal Ignell, Libera Fresiello, Andrew Cookson, Azad Najar, Pieper Ina Laura, Katharine Fraser

Research output: Contribution to journalMeeting abstractpeer-review

Abstract

Objectives: The Realheart is a total artificial heart (TAH) consisting of twin, two chamber pumps. It mimics the natural beating heart with periodic displacement of the atrioventricular plane. The mitral valve (MV) displaces with the plane and flow exits through the aortic valve (AV). The opening and closing of a valve is determined by the pressure difference across the valve, which controls the flow through the valve, and hence the torque on the leaflets. This work aimed to find a modelling strategy for motion of both valves.

Methods: The left side of the Realheart was simulated at 80 bpm. Autodesk CFD was used to solve Navier-Stokes equations with an immersed solid approach for motion. Four motion strategies were assessed: (1) assumed motion of the device, with MV closing instantly at the top and opening at the bottom and AV the opposite; (2) flow driven motion of the MV and AV; (3) MV motion from experiment and AV flow driven; (4) MV and AV motions from experiment. Experiments were video recorded, and videos analysed using MATLAB.

Results: (1) Assumed motion of the valves gave sharp increases in pressure when both valves were moving. (2, 3) The flow driven motion became numerically unstable, resulting in unrealistic pressure fluctuations. (4) Video motion of MV and AV gave the most realistic results. Cycle averaged ventricular pressures were compared between (1) and (4) and differences were 4.2% for the atrium and 8.6% for the ventricle. Compared to experimental data, the difference was 15%. Motion (4) produced effective washout of the chambers, not found with other motions.

Discussion: The two valves in series make simulations unstable but results are sensitive to timing so prescription is difficult. We developed a method for prescribing motion based on videos. Simulations were validated and initial results indicate good washing of the ventricular chamber. Simulations are currently underway to investigate different heart rates.

Acknowledgements: Funded by Realheart
Original languageEnglish
JournalThe International Journal of Artificial Organs
Volume43
Issue number8
DOIs
Publication statusPublished - 18 Aug 2020

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