Hershey Is The Primary Site In The Country To Test Heart Valves

November 7, 2000

Hershey, Pa. -- Penn State Milton S. Hershey Medical Center will serve as the primary site in the United States to image selected patients with the Björk-Shiley Convexco-Concave (BSCC) artificial heart valves manufactured by Shiley Incorporated. This trial, which is now underway, is expected to enroll approximately 150 patients who have a BSCC heart valve.

"The patients enrolled in this trial are those at highest risk of valve failure," explains Ian Gilchrist, M.D., associate professor of medicine at Penn State College of Medicine and a cardiologist at the medical center. "We will use a special x-ray technique to examine the valves of each patient. In those patients who require valve replacement, we will then compare the x-ray test results with the BSCC valve that has been removed to see how well x-ray imaging techniques work."

Between 1979 and 1986, about 86,000 BSCC valves were implanted worldwide. A small percentage of these valves have developed tiny cracks, which have led to valve failure.

The BSCC valve has two legs that support the valve disc. Valve failure occurs when both legs break. Physicians hope to use x-rays to identify small cracks for early signs of wear in these metal legs in order to help patients decide if a new valve is needed.

The patients presently being contacted are those at highest risk of valve failure. Based on the serial numbers on the valves, we know when a valve was manufactured and whether it is at increased risk from fracture," explains Gilchrist. He notes that if a crack or problem is found, the patient may be at further risk for valve failure and should consider valve replacement.

"We have specialized x-ray fluoroscopy machines and computer systems that allows us to use equipment that is normally used for cardiac catheterizations. By modifying the amount of x-ray and intensifying it, we can obtain a picture of the valve. We also know we have to get the exact angle so you can see the flare of the weld; if you are a few degrees off you will not see it and miss the signs of a fracture," says Gilchrist.

Hershey researchers have done extensive work with BSCC valves for more than eight years, and Gilchrist says that this experience is why Hershey was chosen as the primary test site for patients in the United States, Canada and United Kingdom.

Historically this type of valve has been very reliable. However, modifications were made to the original disk to improve its performance and unfortunately, some models of the valve developed fractures of the struts over time, allowing the disc itself to break free from the valve structure. In the absence of the disk, blood can still flow freely from the left atrium to the left ventricle between the heart's contraction. However, without the valve to check blood flow during contractions, blood may flow from the ventricle back toward the atrium. This both interferes with normal blood flow and may "overload" the lungs as pressure there builds due to the reverse blood flow. The individual may become gravely ill very quickly and, if immediate intervention is not taken, may die.

"Detailed studies of fractured valves revealed that often the end of one leg of the broken strut had been worn down while the end of the other leg were rough. This meant that one leg had broken free of the valve structure some time before the other, and had been worn down by the action of the tilting valve. The valve continued to work until the other leg broke," says Gilchrist. "This means that often there is a period of time from the first fracture of the valve until the valve breaks altogether. If some means of detection could be found to inspect implanted valves for signs of fracture, physicians would be able to replace the damaged valve before the other leg of the strut also broke."

Patients will be coming to Hershey literally from around the world to have their BSCC valve tested. Gilchrist explains that the x-ray and then evaluation will take only about an hour, so patients will know very quickly what needs to be done. He also notes that cardiothoracic surgery and radiology have been heavily involved in this project. "Since we know these patients are at highest risk and may have to undergo additional surgery, we also want to give them the option to have that surgery here at Hershey or they can simply return to their home areas to have it done," states Gilchrist.

The research study is being funded by the Trustees of the Bowling-Pfizer Heart Valve Settlement Funds.

TO DOWNLOAD A PHOTO OF THE BSCC VALVE:

Go to http://www.hersheyheart.com/pfizer/bscc_valve.htm on which a large image may be seen.