Decellularisation of valves introduced to paediatric heart surgery

The New Children’s Hospital of the Hospital District of Helsinki and Uusimaa is pioneering the use of a new technique imported from Germany by a cardiac surgeon working at the hospital.

A problem with the outflow of the right ventricle of the heart is the cause of a significant share of cardiac surgeries performed on children. The repairs are carried out with the help of spare parts, or pulmonary valves gained from brain non-living organ donors.

In 2000, a group of German physicians began utilising in surgeries valves subjected to a process known as decellularisation. In the process, cells are extracted from the donor's valve, leaving nothing but a tissue matrix.

So far, the technique is not widespread, but the results are promising. The new valve causes no silent tissue rejection, otherwise a problem in terms of durability. Normally, a donated pulmonary valve only lasts 15 years. Extending the life span of valves means that fewer repeat operations are needed over a patient's lifetime.

“Decellularisation is aimed at gaining spare parts that last throughout the patient’s life. As these surgeries are performed on children and adolescents, that’s asking a lot,” says paediatric cardiac surgeon Tommi Pätilä, a docent at the University of Helsinki.

Some years ago, Pätilä contemplated purchasing decellularisation services from Germany for the children’s hospital. However, the price was considered high by the hospital management, in addition to which sending the valves by post seemed difficult. Pätilä realised that, instead of purchasing the service, the hospital could integrate similar practices into the biobank operating under the auspices of the children's hospital.

Among the challenges involved in launching the operations were equipment procurement and funding. Pätilä succeeded in acquiring the required equipment with the help of the Association of Friends of the University Children's Hospitals. The technique was deployed in 2016. At the moment, the operations are managed by one full-time employee, nurse Hanna Lauttamus.

“The technique has now been validated at the hospital, and we occasionally provide advice to international parties. For example, the director of the European Homograft Bank visited us to learn about the method,” Pätilä states.

Arduous process, good results

The decellularisation technique comprises several stages. Simply put, the process proceeds as follows: the surgeon removes the pulmonary valve of a donated heart. During a cleaning process, the cells are extracted from the valve with the help of a range of rinses and solutions. Finally, the valve is stored in a refrigerator to wait for surgery.

Contrary to established practice, the valve is not frozen in liquid nitrogen, as freezing and defrosting may cause damage to the tissue structure, which is associated with a range of problems.

“The process is more laborious than freezing, but according to all published research the results are better. Another labour-intensive stage is documentation and storage,” says Pätilä.

According to Pätilä, the New Children's Hospital is the only Western institution that has pulmonary valves available as on-shelf product. However, due to the rarity of children's heart surgeries, the quantities are low.

Up to now, the new technique has been utilised in roughly 15 surgeries, which constitute most of the operations conducted in recent years. The goal is to soon employ the technique in all valve operations at the New Children’s Hospital.

“For the time being, decellularisation is not in use anywhere else in the Nordic countries. We are a few years ahead here,” Pätilä notes.