New technology prevents need for replacement of heart valve transplants - study

Heart valve transplants from animals tend to degenerate over the next decade because of foreign sugars they produce.

 Illustration. (photo credit: TEL AVIV UNIVERSITY)
(photo credit: TEL AVIV UNIVERSITY)

A new treatment has been discovered to prevent degeneration of heart valve implants, according to a recently published Tel Aviv University study.

Heart valve disorders are among the most common cardiovascular diseases and valve replacement surgeries are the second-most frequently-performed cardiac operation.

The study, which was published in the peer-reviewed Nature Medicine journal, was led by Dr. Vered Padler-Karavani. The technological development found in the research stems from TRANSLINK that is funded by the European Union.

The implantation of heart valves made from animal tissue known as Bioprosthetic heart valves (BHV) has increased in recent years over mechanical heart valves and one of the benefits of BHVs over the mechanical type is that they don’t require the patient to take lifelong anticoagulation drugs, but they have a limited life span because of structural valve degeneration (SVD), which occurs 10-12 years after they have been implanted.

“Since bioprosthetic heart valves are made of animal tissue, we hypothesized they contain foreign non-human sugars (Neu5Gc and alpha-Gal) that are attacked by the human immune system, which then mediate the calcification that led to structural valve deterioration,” said Padler-Karavani.

 Dr. Vered Padler-Karavani. (credit: TEL AVIV UNIVERSITY)
Dr. Vered Padler-Karavani. (credit: TEL AVIV UNIVERSITY)

“Indeed, in our research, we proved that this was the reason and even suggested an implementable solution.”

“We discovered that all bioprosthetic heart valve patients developed an immune response against the foreign sugars in the valves. We could clearly see an increase in antibody responses against these sugars in implanted patients, as early as one month after implantation, some lasting even two years later. We also found that some of the patients showed signs of calcification as early as two years post-implantation.”

The foreign sugars and antibodies they caused were found in BHVs that were removed from patients about 10 years after they were implanted.

As foreign sugars cannot be produced by the human body, people with a diet of red meat were found to have fewer negative responses to them because they were present in the meat they ate.

The researchers also found that genetically modifying the BHV to stop it from producing sugars foreign to humans significantly reduced the process that caused the BHVs to degenerate, and this could increase their durability.

“This study marks breakthrough technology in the field of bioprosthetic heart valves and provides a deep understanding of the mechanisms leading to structural valve deterioration,” said Padler-Karavani “These findings can lead to a dramatic improvement in the quality of life of many heart patients.

“Now it would be interesting to study whether vegetarians, or people who consume only small amounts of red meat and dairy have a lower probability of heart valve calcification and if this could perhaps be associated with low levels of antibodies against these foreign sugars.

“In the future, it may also be possible to devise a modified diet to reduce the risk, or to actually produce biological valves from the tissues of engineered animals that do not contain the sugars at all.”