M.Sc Thesis | |
M.Sc Student | Cohen Shay |
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Subject | Simulation and Optimization of Heart Restyling |
Department | Department of Biomedical Engineering | Supervisor | ASSOCIATE PROF. Amir Landesberg |
Background: Partial resection
of left ventricle (LV) wall, denoted as partial left ventriculectomy (PLV), was
suggested as a novel alternative for heart transplantation in cases of severe
heart failure. Reasonable reduction of LV radii reduces the wall stresses
according to Laplace law and increases the cardiac output. However, reducing LV radii decreases the LV mass. Currently, no defined guidelines are used to determine the
resected wedge size.
Aims: To define the criteria
for optimizing the excised wall size.
Methods: The effects of PLV
on ventricular performance are determined by the effects of loading conditions
on sarcomere functions. The failing heart function is simulated by describing
the sarcomere control of contraction and coupling calcium kinetics with
cross-bridge (motor unit) dynamics. The effects of PLV are evaluated at the
sarcomere (micro) and global LV (macro) levels, for various postoperative
radii. The LV performance before and immediately after the operation are
evaluated assuming no changes in tissue characteristics.
Results: Although reducing
the LV size increases the ejection fraction, there are bi-modal effects, with
clear optima in the stroke volume, systolic pressure, stroke work and sarcomere
external work. These optima are achieved at different postoperative LV radii. The optima are determined by geometrical parameters and by the sarcomere control
of the force-velocity relation and regulation of cross-bridge recruitment.
Reducing LV radii decreases the sarcomere energy consumption and improves
sarcomere efficiency, mainly due to the decrease in the (pseudo) potential
energy.
Conclusions: The optimal resected
wedge size is determined by the sarcomere control of contraction.