March 2004 NUI Galway Researchers devise new technique for replacement heart valve research

The implantation of prosthetic or artificial heart valves in patients suffering acute cardiovascular problems has taken place for many years. Each year around 275,000 patients worldwide receive replacement heart valves, of which 55% are mechanical prostheses. An innovative technique to aid design of these implants has been developed by a research team at NUI Galway.

"One of the many engineering challenges prosthetic valves present is the difficulty of avoiding clot formation," says Dr. Nathan Quinlan, of NUI Galway's Department of Mechanical and Biomedical Engineering and the National Centre for Biomedical Engineering Science, which is also based on the Galway campus. "The valves can give rise to unnaturally severe fluid dynamics in the blood that flows through them. This in turn aggravates blood cells and can trigger the coagulation process."

Many artificial valve recipients require lifelong drug therapy to prevent clot formation. Understanding of dynamics of blood flow in all kinds of heart valves is therefore crucial to development of better valves.

The NUI Galway team studied heart valve flows with an experimental fluid dynamics technique that had not previously been widely used for this purpose. "The technique allows us to visualise and measure the flow of an artificial blood substitute without disturbing the flow, and at a level of detail that was more difficult to attain by existing methods," says Dr. Quinlan. "Specifically, we have demonstrated the technique in a realistic model heart system to study the flow from two types of mechanical prosthetic valve into the ventricle."

The research team found surprising complexity in the flow in the ventricle itself, which may have some clinical significance. "Our visualisation of the flow in the model ventricle raises some interesting questions" says Dr. Quinlan. "What we have developed is an improved tool for developers and designers of artificial heart valves. This should aid understanding of complex fluid dynamics in the next generation of replacement heart valves."

The research team of Dr. Quinlan, Dr. John Eaton and postgraduate student, Donal Taylor, were awarded the Bronze Medal for the best paper at the annual conference of the Bioengineering Section of the Royal Academy of Medicine in Ireland, in January. Their paper was entitled "Measurements of three-dimensional unsteady flow in a model left ventricle with prosthetic valves."

The work draws on the expertise and facilities of the Aerospace Research Centre, which since 1990 has been a centre of excellence for fluid dynamics research in the University. Other projects underway in the Biofluid Dynamics Laboratory in the NCBES include investigations of air flow in the lung and of microscopic blood flow around individual cells. The heart valve research was funded by the HEA Programme for Research in Third Level Institutions (PRTLI).

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