Date of Award

7-2022

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biomedical and Chemical Engineering and Sciences

First Advisor

Venkat Keshav Chivukula

Second Advisor

Mehmet Kaya

Third Advisor

James R. Brenner

Fourth Advisor

Andrew D. Knight

Abstract

The best treatment for patients with end stage heart failure is a heart transplant but given the scarcity of donor hearts, a promising alternative treatment has become left ventricular assist devices (LVAD). However, complications such as right heart failure, stroke, and adverse hemodynamic outcomes continue to occur. This thesis will cover investigations into continuous flow LVAD treatment optimization techniques to improve patient outcomes. Optimization techniques explored include an in-house developed optimization algorithm that is completed in three phases on a computational lumped parameter model that is representative of the cardiovascular system using an electrical circuit analogy. This three-phase optimization technique is tested on two patient cohorts by (1) specifying the model to the patient, (2) performing virtual blood pressure management, and (3) LVAD speed optimization. Another optimization technique investigated is the use of speed modulation waveforms. Changes to characteristics of the waveform are explored to assess the effects on the cardiovascular system via the computational model. These waveform characteristics include baseline speed, duration of speed modulation, and the drop in speed. Speed modulation waveforms allow pressure to build up in the left ventricle, allowing for the aortic valve to open. In the treatment of continuous flow LVADs the aortic valve is an area of stagnation, where platelet activation can occur, thereby leading to thrombi formation. Results from these investigations reveal that understanding the pump-patient interaction is essential to improving patient hemodynamics. Furthermore, changes must be made to both blood pressure and LVAD speed to meet hemodynamic targets. In addition, both sets of patient data revealed that patients operating at higher LVAD speeds and with higher flows may benefit most from speed optimization. The exploration of the square speed modulation waveform reveals that lower baseline speeds, longer duration of speed modulation, and bigger drops in speed lead to increased chances for the aortic valve to open, thus improving thrombogenicity. The information obtained from this work provides clinicians with insights into improvement techniques for LVAD therapy that may lead to better patient outcomes.

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