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January 3, 1994
Hershey Studies new X-ray Technique On heart Valves

Hershey, Pa. -- Researchers at Penn State's Milton S. Hershey medical Center have received a $2.5 million-contract from Shiley Heart Valve Research Center of Irvine, Calif., to evaluate the ability of a new high-magnification X-ray technology to assess the condition of artificial heart valves.

The Penn State study will compare the new imaging system, developed by feinfocus GMBH of Garbsen, Germany, with current state-of-the-art imaging X-ray techniques in evaluating the physical condition of Bjork-Shiley Convexo-Concave (C/C) heart valves. The contract includes $1,335,000 for the system and its installation.

Between 1979 and 1986, some 86,000 Bjork-Shiley valves were implanted worldwide. A small number of these valves have developed tiny cracks, which in some cases, have led to valve failure. The Bjork-Shiley valve outlet strut has two legs which support the valve disc. When one of the two legs of the outlet strut separates from the valve flange, this is known as single-leg separation. Valve failure, or strut fracture, involves a separation of both of these legs, allowing the valve disc to float free. Identifying small cracks or early signs of wear in these metal legs may provide information for patients and physicians to make more informed decisions about undergoing valve replacement surgery before the valve breaks.

"The feinfocus system may be able to spot early signs of wear and metal fatigue in these valves that we might not have been able to see as clearly before," explains principal investigator Kenneth Hopper, M.D., associate professor of radiology and chief of radiology research at Hershey. "The feinfocus system uses less radiation and has the potential to view the valve with greater accuracy than the current technology," he says.

According to Hopper, the work will combine Hershey expertise in five fields: cardiology, cardiothoracic surgery, radiology, veterinary medicine, and biostatistics. "The interdisciplinary cooperation and the detailed planning are essential to the success of this exciting project" says Hopper.

"Hershey is one of the few institutions which can support this project because of its ongoing leadership in developing the artificial heart and its strong radiology and caardiology research experience," he says. "In addition, the animal facilities and veterinary staff are world reknowned and the biostatistics team is especially experienced in this area of research.

Hershey's research efforts, according to Hopper, are aimed at" evaluating both existing technology and this new machine in evaluating these valves." The researchers hope to find out whether" premature wear in these valves can be detected with either X-ray system at an early stage."

The initial stages of the project have already begun. The first phase, essentially a laboratory test of the feinfocus system, involves the Penn State Left Ventricular-Assist Device, which is designed to wean patients off the heart-lung machine after heart surgery. The valves are installed on specially modified assist devices immersed in water to mimic the conditions in the human body. Researchers will compare the ability of this new feinfocus X-ray technology and Hershey's recently installed Siemen's HICOR, a state-of- the-art computer-assisted heart imaging system, to image both normal valves and those with single-le separations. Specially trained image reviewers, unaware of which valves are normal and which are not, will evaluate the X-rays. The results will be compared to the known condition of the valves.

Similarly, in the second part of the study, the scientists will use the feinfocus system to examine valves in research animals.

"There's a spectrum of valve wear--from mild risk to complete failure," explains co- principal investigator Ian C. Gilchrist, M.D., assistant professor of medicine and director of cardiac critical care. One question the Hershey researchers hope the feinfocus system will help answer is how well it can detect defects in these valves before they cause patients any problem.

"We hope to determine whether a new imaging technology will be able to detect which valves have these defects, or single-leg separations," Gilchrist explains, which in turn may help patients decide if the valve needs to be replaced.

In an ongoing study, a research team at the William Beaumont Hospital in Royal Oak, Mich., is using the Siemen's HICOR to evaluate the condition of 300 implanted heart valves that, from a statistical perspective, were at a higher risk of strut fracture. However, single-leg separations are difficult to detect and may elude definitive imaging by even a very sensitive X-ray system.

If both phases of the Hershey project indicate the feasibility of sing the feinfocus system to identify the condition of the implanted valves, the researchers say. Shiley will submit an Investigational Device Exemptions application to the federal Food and Drug Administration in 1994, with the hope of beginning human clinical trials later in the year.


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