MONDAY, April 25, 2005 (HealthDay News) -- The more heart valve replacement operations performed at a hospital, the more likely the surgeons there will insert the type of aortic valve deemed safest for most older patients, new research finds.
So, where a patient receives the valve replacement is of utmost importance, said Dr. Erik B. Schelbert, a fellow in the division of cardiovascular diseases at the University of Iowa and lead author of the study, which appears in the April 26 online issue of Circulation.
For older patients in need of aortic valve replacement, the message is clear, he said: "Go to an experienced center. Those centers in our study performed most in accordance with the guidelines."
Those guidelines were issued in 1998 by the American Heart Association and the American College of Cardiology. They recommend that most patients aged 65 or older would be best served by bioprosthetic valves made from human or animal tissue rather than mechanical valves, which are made of metal.
While mechanical valves are more durable, they leave patients facing an elevated risk of blood clots; these patients must take powerful blood-thinning drugs such as warfarin (Coumadin) for life. Those drugs also increase the risk of dangerous bleeding.
The aortic valve is on the left side of the heart, and is the outflow valve. It opens to let blood leave the main pumping chamber of the heart, called the left ventricle, and closes to keep blood from leaking backwards into the ventricle. When the valve is very diseased by age or is abnormal, as in a birth defect, it may need to be replaced.
About 118,000 aortic valve replacement surgeries are expected to be performed in the United States in the next year, said Rich Fischer, a spokesman for Medtronic, which manufactures such devices.
In the study, Schelbert's team evaluated over 1,000 hospitals' records, focusing on more than 80,000 patients aged 65 and older who had aortic valve replacement from 1999-2001. The volume of replacements done at each hospital varied, from 20 to 573 a year.
While there is no "right" or "safe" number, Schelbert said the percentage of older patients getting the safer valve increased in a parallel fashion with the volume of repairs done at the hospital.
When Schelbert's team divided the volume of repairs done into 10 categories, they found the hospitals performing the least numbers of aortic valve replacements only inserted tissue valves in 28 percent of older patients, compared with 68 percent of similar patients at hospitals in the highest-volume category.
The use of tissue valves increased each year, from 44 percent in 1999 to 52 percent in 2001. Also, the older the patient, the more likely they were to receive a tissue valve. In the study, only 36 percent of patients aged 65 to 69 got tissue valves, versus 60 percent of those aged 90 and over.
Schelbert was surprised that the volume of surgeries was the biggest predictor, even stronger than age, of whether a patient would get a tissue or a mechanical valve.
In an accompanying editorial, Dr. Lawrence H. Cohn, the Hubbard Professor of Cardiac Surgery at Harvard Medical School and Brigham and Women's Hospital in Boston, points out the need for further publicity about the 1998 recommendations.
"These [tissue] valves are better for older people," Cohn said. The study found that, overall, only 52 percent of those aged 65 and older got the tissue valves. At Brigham and Women's Hospital, he added, 81 percent of 2,447 patients aged 65 and older got tissue valves from 1992 to 2004.
In some instances, Cohn said, mechanical valves may be acceptable in older patients, such as those already on blood thinners for other conditions.
As to why guidelines aren't followed in other cases, Cohn noted, "a lot of times it is ease of implantation," referring to the fact that mechanical models are easier for a surgeon to place.
For consumers facing valve replacement surgery, Cohn said, the message is clear. Besides finding out the volume of repairs done at your hospital, "ask what kind of a valve," he suggested. If you are 65 or older, and the answer is mechanical, ask why you are not getting a tissue valve.
To learn more about aortic valve replacement, visit the Society of Thoracic Surgeons.