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UBC Theses and Dissertations

In vitro fluid dynamics of the Bjork-Shiley monostrust mitral disc valve using laser doppler anemometry Ma, Zhi-Yong


In recent decades, several different types of prosthetic devices have been introduced in clinical practice to replace the diseased natural heart valves. In Canada alone, around 10,000 operations aimed at treatment of valvular diseases are carried out every year. Although evolution of prosthetic heart valves have, in general, succeeded in increasing the patient’s lifespan, scope exists in improvement of their design as attested by failure of several commonly used heart valves. Successful design of prosthetic heart valves depends on thorough understanding of several aspects including biocompatibility, structural integrity and complex fluid dynamics. Focus of the present thesis is on the fluid dynamical performance with emphasis on fundamental information of long range value which can serve as reference: (i)ina assessing performance of prosthetic heart valves widely in use at present; (ii) in development of improved configurations of new designs (iii)for government health agencies and manufacturers in formulating performance criteria which must be met to protect the user community; (iv) for practising cardiac surgeons in selecting appropriate prostheses for implantation. This thesis first introduces the basic knowledge about the heart, heart valves and the laser Doppler anemometry (LDA) as the general background. This is followed by a description of the test methodology. One of the challenging aspects is the analysis and display of the vast amount of data obtained in a meaningful way. Computer codes developed to this end thus form an important part of the thesis. Finally, the thesis focuses on the fluid dynamic results and their analysis with respect to the Bjork-Shiley monostrut tilting disc valve, in mitral location, using a sophisticated cardiac pulse duplicator in conjunction with a 3-beam, two-component, LDA system. Time histories of the velocity profile, turbulence intensity, Reynolds stress, etc., are presented for both posterior and anterior orientations of the valve, for five different pulse rates. Results suggest relatively favourable performance in the posterior position. The stress level was found to be safe and would not present the danger of haemolysis. In general, the valve performance was found to be insensitive to the flow rate.

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