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An Alternate Treatment for End Stage Coronary Artery Disease: Transmyocardial Laser Revascularization (TMR)

Author
Danny, Catropa; Dines, Megan; Kimmel, Jeremy; Rubin, Juli; Nocerino, Christina
Abstract
Coronary artery disease involves the buildup of plaque (from cholesterol) on the
inside of the arteries, which limits the flow of blood through the vessel.
Occlusion of these vessels leads to angina and ultimately to heart attacks.
Several common treatments exist to reopen the arteries including angioplasty
(with or without a stent), atherectomy, and laser ablation. However, surgical
procedures are sometimes necessary and the available options are bypass
surgery and transmyocardial laser revascularization, TMR.
TMR is a procedure in which ten to forty 1mm channels are created in ischemic
heart tissues, where the number of channels made varies from patient to patient
based on their individual casesi. This procedure allows for oxygenated blood to
flow into the heart and will also result in revascularization the deoxygenated
heart tissuesi. This procedure was modeled using Gambit to create the mesh and
FIDAP to model the diffusivity of oxygenated blood into deoxygenated heart
tissue. The governing equations used to model the flow of oxygenated blood
through the channel and diffusion of the oxygen into the deoxygenated tissue
layer were the species and momentum equations. No reaction term was used in
the species equation because it was assumed there was no elimination of oxygen
by the tissue. A fully developed parabolic velocity profile was assumed in
conjunction with the momentum equation. The initial conditions included an
oxygen concentration of 0.2 ml 02/ml blood at the intake and 0.1 ml 02/ml blood
in the deoxygenated muscle. The boundary conditions consisted of a constant
zero flux at the top, left wall, right wall, and axis. The exit of the channel is free
as is the blood/muscle interface because FIDAP will solve for the 02
concentration based on the other parameters that were specified.
Based on this model, it is evident that oxygenated blood in the newly created
channels does diffuse into the deoxygenated heart tissue. Although there is
diffusion throughout the entire sample, the diffusion nearest the inlet is greatest
and decreases along the length of the channel and radially outward from the
channel as expected. In addition, the desired oxygen concentration, 80%
saturationvii, was achieved at the channel-tissue boundary but not within the
tissue layer. These results could be attributed to some of the assumptions that we
were forced to make in modeling the procedure due to the limitations of the
software in handling a two-phase model. However, with the optimal diameter
found, 1.4 mm, and a closer channel spacing, a more optimal diffusion profile
may be achieved.
Date Issued
2003-06-17Type
report