Occlusion of the left atrial appendage using catheter-delivered hydrogels for prevention of thromboembolic phenomena




Zimbroff, Andrew David

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The Left Atrial Appendage, once thought to be "a relatively insignificant portion of cardiac anatomy," has currently been realized to possess "important pathological associations [1a]" particularly in its role in promoting serious, frequent thromboembolic events common in individuals suffering from Atrial Fibrillation. Prior approaches to mitigating these events have either required invasive procedures, proved less than fully effective, or presented with problematic sequelae of their own. This work will present a new procedure that addresses both the prevention of the thromboembolic events and the correction of the shortcomings of the major prior methods utilized. A compliant hydrogel that can conform to the geometry of the appendage is proposed as a more effective method of occluding the chamber. This material would be transported to the LAA in liquid form via a multi-lumen catheter, and then solidify within the chamber to form a solid plug. Previous research has identified a candidate hydrogel, comprised of PEG-tetra-thiol and Dextran vinyl sulfone as a candidate hydrogel for this application. Experimental work has investigated fluid properties of the material, as well as degradation and swelling properties of the material. Results from this experimentation were used for fluid transport analysis, and for evaluation of anchoring force of the hydrogel within the chamber. Finally, subfunctions of the occlusion procedure were modeled and tested. During the actual procedure, a catheter balloon will isolate the appendage from the rest of the heart. A model was developed to study interactions between the appendage and this balloon. Additionally, due to fast solidification time, hydrogel components in the surgical procedure will be mixed in a mixing chamber at the tip of the catheter. Potential mixing chamber designs were modeled, and a ternary diffusion model was developed to better understand hydrogel mixing. Prototypes for both these subfunctions were built and tested as well. Additional analysis looked at the overall occlusion procedure, and how various subfunctions interacted with each other.



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