A cardiac valve for life

Artificial cardiac valves for children typically come from animals and need to be replaced every few years. It would be a great improvement, if a substitute made from the child’s own body tissue were at hand which needed not to be replaced. Pediatrician Dr. Boris Schmitt has developed exactly such biological cardiac valves from the pericardium, the heart sac. Very soon, the first child patients could benefit from this unique and animal-free method.

Owing to artificial cardiac valves, children suffering from congenital heart defects now have excellent survival rates. And yet, their years of childhood are not untroubled. Frequently, they are facing multiple surgeries in their infant years and the children sometimes spend months in the hospital.

Since there are no artificial cardiac valves for newborns and infants in the right size, doctors at first need to apply bypassing techniques, which can be harmful for the heart. The right-side ventricle can become so stretched out that the cardiac valve must be replaced. Most children have reached school age when they receive their first artificial cardiac valve.

Repeated surgery every few years
Biological substitute valves mostly come from bovine veins and they trigger immune reactions of the body. The body’s defences gradually damage the valve tissue making further surgery indispensable.  Cardiac valves made from metal or synthetic materials can last considerably longer, but they are prone to blood clotting. The little patients thus need to continually take blood-thinning medications.
Both alternatives have the added disadvantage that these cardiac valves do not grow with the body. Children will need a new implant every few years. And since many artificial valves deteriorate at some point, these children will need a substitute valve every ten years even as adults.

Receiving a custom-fit cardiac valve in four hours
These aren’t particularly uplifting prospects, PD Dr. Boris Schmitt thinks, who is a pediatric cardiologist at the Charité and the German Heart Center Berlin (Deutsches Herzzentrum Berlin). It motivated him to develop a cardiac valve from endogenous tissue. In a four-hour only procedure, the new valve is fashioned from pericardium tissue taken from the patients themselves. With the aid of data won from computer and magnetic resonance tomography, a custom-fit cardiac valve is made during the surgery and then implanted. In many cases this can be done in a minimally invasive procedure with a catheter that is inserted via the femoral or jugular vein and then pushed toward the heart.

Only when the anatomy should prove unfit for this procedure, the doctors have to revert to open-heart surgery. The cardiac valve has been developed as a substitute pulmonary valve for both children and adults; that is. the cardiac valve that connects the right heart chamber with the pulmonary artery to the lungs. The dysfunctional cardiac valve is not removed in the procedure, but is “stented” with the new cardiac valve. This is time-saving and involves less risk. “The cardiac valve made from endogenous tissue does not trigger any rejection reaction, it does not deteriorate and will presumably last a lifetime,” Dr. Schmitt explains. “What is more, this method is cost-effective and no animal must die for it.”

Less suffering for humans and animals
With the research done on a cardiac valve from endogenous tissue, the pediatrician consciously set out to supply an animal-free alternative. Animals are not only involved in biological valves, but valves made from metal or synthetic materials are also tested on animals. But his globally unique method cannot do wholly “without”:´every invasive medicinal product in Germany has to be successfully tested on animals, before it can be used on human patients. This is the procedure prescribed by law.

In order to win approval, Schmitt and his colleagues have to test the new method on 18 sheep altogether – sheep being the standard animal model for cardiac valves. “I think this small number is acceptable, if it means that we can completely discard cardiac valves from animal tissue in the future,” he says. You couldn’t tell from just looking at the heathland sheep that live on the campus of the Virchow clinic, that these Heidschnucken, as they are called in Germany, have all received a new cardiac valve. They are doing exceptionally well. “This is what we want to achieve for our patients,” says Boris Schmitt, who regularly examines his 18 sheep for the mandatory long-term study to be presented to the authorities.

The heart specialist already has implanted these valves in three children in India in 2016 already as part of a curative trial treatment -- and successfully. This also makes him optimistic that his method will fulfill its promises. Curative trial treatments are not considered scientific studies by the German authorities, however, so Schmitt will have to gain approval as laid out above.

Permanent cure is very likely
About 2,000 children in Germany alone need a substitute cardiac valve every year.  For them, a Berlin cardiac valve made from their own heart sac would be a blessing.  “How much longer?” is the question that is often asked of the pediatric cardiologist by parents whose children desperately need a new cardiac valve.  It will take another two or three years, he reckons.  But parents also hope for it.  “It is our goal that one day we can supply all patients who suffer from a cardiac valve defect, be they children or adults, with our method,” Boris Schmitt says.  And he is offering a prospect that up to now has never been achieved with any substitute cardiac valve. A permanent cure.

(Text: Beatrice Hamberger)

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