Human Valves Used in Other Humans

Not long after the first heart valves were implanted, physicians began searching for better heart valves — including biological valves. Biological valves are valves from animals or human cadavers or valves made from other animal tissue. An aortic homograft valve was first used in 1962 to replace a mitral valve in one pa tient and an aortic valve in another. Survival was short.

That same year, Dr. Donald Ross in England reported the first successful aortic valve homograft implant. He placed the valve in the normal position. A month later, Sir Brian Barratt-Boyes performed the same implantation in New Zealand.

Shortly after his success, Dr. Ross went on to develop another technique. In 1967, he used the patient's own pulmonary valve to replace a malfunctioning aortic valve. An aortic or pulmonary valve homograft was then used to replace the patient's pulmonary valve. This procedure, known as the Ross Procedure, is currently recommended for some younger patients who require aortic valve replacement.

» Donald Ross: The Valve Pioneer

DR. DONALD ROSS QUALIFIED for his medical degree on the same day as Dr. Christiaan Barnard, a fellow South African. Although the two would take divergent paths — Ross went to England to train and Barnard went to the United States — they remained friends, and both worked to develop heart transplantation. Ross recalled in an interview a conversation he had with Barnard before the first transplantation.

"Barnard came through one day and said, 'I've just been watching Shumway do the trans

Donald Ross plant of the heart in an animal and I'm going to do that,'" Ross remembered. Later that same year, a reporter asked Ross when he thought the first heart transplantation would be performed. He predicted sometime within the next five years. Less than a month later, Barnard announced he had performed the first human-to-human transplant. Shortly afterward, Ross himself performed the first heart transplant in the United Kingdom.

Although his work in heart transplantation was cutting edge, Ross became most famous for

Other tissues that have been used for valve implants Include the pericardium, fascia lata, or tissue from tendons, and dura mater, which is the tissue that surrounds the brain and spinal cord.

In the 1960s, physicians also began to experiment with valves from other animals, or xenografts. This was first done In 1964 by Drs. Carlos Duran and Alfred Gunning in England, who replaced an aortic valve in a human by using a valve from a pig. The early results were good, but these valves often failed after a few years. In France, for instance, Dr. Alain Carpentier and his associates reported on twelve patients with pig valve replacements that all failed by five years. As a result, Carpentier developed a technique to fix the pig valves with a chemical called glutaraldehyde instead of using the accepted formaldehyde. In addition, Carpentier mounted his valves on a stent, which allowed the valves to be used to replace the mitral and tricuspid valves.

Carpentier later wrote:

"It became obvious that the future of tissue valves would depend on the development of methods of preparation capable of preventing inflammatory cell reaction and penetration intto the tissue. My background in chemistry was obviously insufficient. I decided to abandon surgery for two days a week to follow the teaching program in chemistry at the Faculty of Sciences and prepare a PhD. (at the University of Paris). It was certainly not easy to become a student in chemistry

Xenograft:

Graft tissue taken from an animal of one species and used in another species. Pig heart valves, which are commonly used to replace heart valves in humans, are one form of xenograft.

his pioneering work with heart valves. This was an area of interest from the beginning of his career. In July 1962, Ross implanted the world's first successful homograft valve (a tissue valve from a human cadaver) only two years after Starr and Harken implanted their heart valves. Ross recounted this historical implantation:

"Lord Brock was my mentor and chief and put me onto repeating earlier pioneering work in homo-graft implantation [in the animal laboratory]. It was a very exciting time. We took human valves and human aortas and stored them by a process of freeze drying so they could keep for months.

"One day during surgery while I was scratching away at a calcified valve, the whole thing disintegrated and went down the sucker. We didn't have a valve and there were no valves in England There were only Starr valves in America. So we took one of those stored human valves, which was freeze dried, reconstituted it and sewed it in."

Originally, the valve was supposed to be temporary until the surgical team could import a mechanical valve. The patient did well, however, and Ross switched to implanting homograft valves instead of artificial valves.

Over the next several years, he found that an aortic valve homograft worked well in the pulmonary valve position. That discovery led to an important milestone in valve surgery, the Ross Procedure. In this operation, the native pulmonary valve is relocated to the aortic position, and a homograft valve replaces the pulmonary valve.

It is a technically difficult operation that took almost two decades to gain widespread acceptance but it is performed today with excellent results. It has the powerful advantage that the new aortic valve will grow, an especially important quality for small children.

Alain Carpentier

Dr. Alain Carpentier (above) was a major figure in the development of pig valves for human hearts. His valves (below) were mounted on cloth rings to help physicians sew them in place.

Cardiomyoplasty:

A surgical procedure using a muscle, usually the latissimus dorsi muscle in the back, to wrap around a failing heart. The muscle is then electrically stimulated so it will contract in synchrony with the failing heart.

» Alain Carpentier

DR. ALAIN CARPENTIER DECIDED I to go Into medicine after an operation and a month-long stay in a hospital for appendicitis when he was only ten years old. At the time, antibiotics were not widely available, and his recovery was very long and painful, inspiring in the young boy a desire to help the course of healing. Today, he is best known for three major contributions to heart surgery. He developed surgical techniques to repair the mitral valve; he developed a practical method of using heart valves from pigs in humans; and he pioneered a surgical procedure called cardiomyoplasty, which is used in patients with failing heart muscle.

Carpentier began his research into heart valve replacement at a time when mechanical heart valves, such as the Starr-Edwards valve, had just recently become commercially avail-

able. Physicians were also successfully using heart valve implants from human cadavers, a technique pioneered by Ross and Barratt-Boyes. Inspired by their work, Carpentier began to research biological valve replacements but ran into a snag in French law.

"My surgical master, Dr. Charles DuBost, told me if I was interested, I would have to collect homograft valves, just like Barratt-Boyes and Ross did," he remembered in a 1999 interview. "I began to try to collect homograft valves in Paris; however, French law did not permit one to take pieces from cadavers during the forty-eight hours following death to allow the family to make an opposition. Of course, after forty-eight hours, most of the homograft valves I could collect were infected."

After a few months of this, Carpentier began researching the use of valves when you are thirty-five years old and an associate professor of surgery.

"I began to investigate numerous cross-linking-inducing factors and found that glutaraldehyde was able to almost eliminate inflammatory reaction My wife, Sophie, was a tremendous help all these years."

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