Laser Ablation for Cardiac Tissue Oxygenation
Dokko, Jacqueline; Eun, Chae Young; Kiembock, Conor; Wang, Qikun
The leading cause of myocardial infarctions, commonly known as heart attacks, is the reduced blood flow to the heart muscle due to plaque buildup in the coronary artery. Transmyocardial laser revascularization (TMLR) is one of the more recently used procedures to treat blocked arteries when traditional treatments such as vascular stents and bypass grafting surgery are not suited for the patient. TMLR involves a CO2 laser heating process to ablate heart tissue and create channels through the entire myocardium wall. The new channels throughout the heart then facilitate transport of oxygenated blood from the ventricle to the oxygen-deprived heart tissue shortly after the procedure. After a long time, the heart can revascularize the affected area, healing the channels while simultaneously creating new blood vessels through a process called angiogenesis. Eventually the new blood vessels replenish oxygen in the heart tissue. Our project goal was to model the tissue ablation and oxygenation process of TMLR and optimize the channel-making procedure. Our quantities of interest were healthy tissue damage and short-term oxygen transfer, which we wanted to minimize and maximize respectively. We used COMSOLr to model the laser heating via the heat transfer module and simplified the procedure domain to a two-dimensional, axisymmetric geometry. Our model simulates the channel formation process through the use of the "Deformed Geometry" feature in COMSOL. Next, we analyzed the oxygen transfer process from the inflowing blood to the surrounding tissue on another two-dimensional, axisymmetric model with a mass transfer equation. Additionally, we coupled fluid flow equations to the mass transfer governing equation to observe the effects of blood flow on the oxygen transfer to the tissue. In optimizing this procedure, we looked at various combinations of laser power and spot size radii, the two factors that can be varied to deliver different laser heat fluxes to the tissue. Using the two simulation models, we concluded that the optimal laser power is in the range of 538 W to 600 W and optimal spot size radius is 0.55 mm. These laser configurations take into account the negative effects of overheating and the positive effects of oxygen transfer. The results of this report are significant for the patients who suffer from heart attacks and for the surgeons who are in search of better solutions. The laser heating procedure discussed in this report can serve as an alternative treatment for patients who have already received traditional methods of treating blocked arteries but did not experience significant changes in their symptoms. From the results of our models, we provide promising evidence that revascularization through TMLR successfully oxygenates the myocardial tissue in the short term.
modeling, oxygen transfer, laser ablation, myocardium, TMLR