Open Collections

Okanagan valve : the next generation of mechanical heart valves

University of British Columbia

Valvular heart disease is a cardiovascular condition characterized by damage to any number of the four valves within the human heart. This damage can be defined as stenosis or incompetence based on a valve’s inability to completely open or close, respectively. Stenosis and incompetence are caused by calcification and the thickening of valvular tissue, and often manifest as angina, ultimately leading to congestive heart failure if left untreated. Mechanical heart valves (MHV) can be surgically implanted to replace a failing valve but require the prescription of life-long anticoagulant medication such as Warfarin to mitigate blood clotting issues. The thrombogenicity of MHVs is related to their poor hemodynamics, believed to be caused by the high shear stresses they induce. Some identified regions of high shear stress are the hinges, the trailing edges of the leaflet tips, and velocity jets. These problems have plagued the most common form of MHVs, bileaflet mechanical heart valves (BMHVs), for decades as their designs have stagnated. This research was conducted to design and validate a BMHV that would have similar hemodynamic properties to native heart valves, enabling implantation without reliance on post-operative anti-coagulants. To accomplish this, we identified the major design limitations of BMHVs, such as the gold standard St. Jude Medical Regent BMHV, as well as the believed contributing factors to their thrombogenicity. We developed a novel design architecture for BMHVs that addressed these limitations, and from it, the Okanagan Valve (OKV). A numerical analysis was performed on modifications of interest incorporated in the OKV to determine their effect on heart valve hemodynamics. In-vitro methods were utilized to experimentally observe the performance of the OKV. Our experimental assessment of the OKV found the maximum regional backflow velocity and closing volume to be 46 m/s and ~5 cc, respectively, values closer to those of a bioprosthetic valve rather than a BMHV. The results of our in-vitro assessment confirmed the results of the numerical analysis, showing the potential of the OKV to accomplish the design goal. Ultimately, this research is intended to be a proof of concept for the OKV, which may one day become a BMHV that can be implanted indefinitely without the need for anticoagulants.

Text

2020-04-15

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/74029

Mechanical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/