The Cutting Edge: Computing / Technology / Innovation : At the Heart of Computer Modeling : Design: New program is expected to help create artificial cardiac valves and possibly even entire replacement hearts.

Three-dimensional computer models of cars and airplanes and other expensive machines are old hat for industrial designers, but only recently have scientists built such a computer model for the most sophisticated mechanical device of them all: the human heart.

Developed by two researchers at New York University, the new heart model is intended initially to help in the design of artificial heart valves. Eventually, doctors might be able to use it to examine your heartbeat and other cardiac functions while you’re out on the golf course--or even to build you a new heart.

“Given the right parameters, we can painlessly model any heart we like--any shape, any size,” said David McQueen, a computational scientist and mechanical engineer at NYU’s Courant Institute and one of the heart’s developers. “The model is a very versatile and valuable engineering tool which will help design any artificial device to be used in the heart, including possibly an entirely artificial heart.”

McQueen and colleague Charles Peskin acknowledge that they have a long way to go before they can design complete hearts on a computer. Many aspects of heart functioning are not yet fully understood, and a computer model can only be as good as the scientific knowledge used to create it.

But the model is expected to be quite useful for designing heart valves, enabling scientists to create a sort of computerized test chamber for mechanical designs that cannot be tested in the real world without putting someone’s life at risk.

For decades, manufacturers and designers have relied on trial and error to build artificial valves, and that has sometimes brought trouble. In the 1980s, some valves produced by Irvine-based Shiley began to fracture, resulting in deaths and numerous lawsuits against the company.

“Valves that are currently available have been designed empirically, and there has not really been an opportunity to design them in a more systematic way,” said Peskin, a physiologist and mathematician.

Applying the laws of fluid mechanics to all that is known about the anatomy of the heart and the physiology of the muscle, the researchers created a model that simulates the mechanical functions of the heart, such as contractions of the muscle, blood flow and the opening and shutting of the valves.

The model consists of a grid--a regular cubic lattice--with fluid mechanics, through which run rubber-band-like muscular fibers that ordinarily make up the heart and its pumping function. The scientists say the key to the process is a computational method they devised to determine the pattern and volume of the flow of blood inside the heart chambers, with valves posing as flexible barriers.

The idea is to quantify the interaction of a flexible object--the heart valve--with the fluid into which it is immersed--the blood. The researchers call it the Immersed Boundary Technique. Already, they have designed a cardiac valve with curved leaflets intended to alleviate clotting, a serious problem encountered when artificial devices come in contact with blood.

An existing artificial valve design, which is quite successful, uses two flat leaflets. “We studied this in the computer and found that it could become better in various ways if we curved the leaflets. We used the computer to determine how curved they should be,” Peskin said.

The NYU group has received some inquiries from companies about using the system to improve on existing valves, but McQueen declined to divulge details. There are about half a dozen manufacturers of artificial valves, with worldwide demand totaling about 200,000 units a year.