New approach to pulmonary valve replacement raises hopes

© corlife, Hannover

For patients whose pulmonary valve is failing there is the option of replacing the valve; this option has been available for several decades now. However, the valve replacements often do not last for a lifetime and eventually have to be replaced, which usually necessitates reoperations. This holds true especially for young patients, due to the valve replacements’ incapacity to grow with the children.

This problem might be solved by a method from the field of tissue engineering, where new valves are engineered by stripping human donor valves (homografts) of their cells (“decellularising” them) so that the recipient’s own cells can repopulate them. A recent German-Moldovan study directed by Prof. Dr. Dr. h.c. Haverich (Hannover Medical School, Germany) indicated that these new valve replacements, called decellularised pulmonary homografts or DPH, might be superior to both bovine valve transplants (xenografts) and human donor valves preserved by liquid nitrogen freezing (conventional homografts).

The major advantage of tissue engineered valves such as those based on DPH is that the implanted valvular scaffolds can be repopulated by the recipient’s own cells and therefore should not cause immune responses. Besides, DPH do not seem to be significantly prone to degeneration or calcification, which are the major causes for reoperations in conventional pulmonary valve replacement. Most interestingly, the findings indicate that the described homografts are capable of adaptive growth. According to Haverich, “No valve has been rejected so far and no patient had to be reoperated. There is much evidence for the assumption that these heart valves have a much higher durability than previous valves that have not been decellularised – and that they even grow adaptively.” The growth characteristic is especially relevant for newborns and small children, as it could significantly reduce the need for reoperations.

The presented results are based on a retrospective comparison of a relatively small group of patients receiving either decellularised pulmonary homografts or xenografts or cryopreserved homografts during a 5-year observation period. They are to be considered preliminary. Valid data can be expected from a large prospective trial funded by the European Commission (ESPOIR project) by the above mentioned study group, including eight leading European centres for congenital cardiothoracic surgery, which started in January 2012.

A similar approach has been investigated for several years by a further German working group at the Charité Berlin directed by Dr. Pascal Dohmen. The tissue engineered valves developed by this group are also based on (preserved) decellularised scaffolds; they are patent-registered and have been in use since 2004.

At the time being there are several different approaches to tissue engineering heart valves, which differ mainly in the scaffold material used. Besides biologic-based approaches such as those described above there are studies investigating the use of synthetic scaffold materials. All of these methods aim at the recipient’s cells adhering to the valvular scaffolds which act as a matrix. However, the approaches using synthetic materials are still in an experimental stage, while pulmonary valve replacements based on decellularised pulmonary homografts are already used in clinical practice.

It should be noted, however, that, in clinical practice, there are different views on which method is the best for pulmonary valve replacement. In particular the alleged ability of the tissue engineered valves’ adaptive growth is a subject of great controversy at present. However, they do seem to be a promising option for pulmonary valve replacement and might revolutionise the treatment of patients requiring this treatment.

Valve replacement – Basic information

Basically, each valve can be replaced. There are four valves in the human heart:

If one of them fails to function appropriately due to either a narrowing (stenosis) or failure to close properly (insufficiency), valve replacement may become necessary.

There are three major types of replacement

Biological valvesMechanical valvesNew:
Tissue engineered valves
What are they?

Human or animal (porcine/bovine) tissue specially treated to be tolerated by the recipient’s body

Available with or without a mounting frame (stent)

Artificial valves made of synthetic material, metal or graphite

Consisting of artificial leaflets and a ring to support them
Scaffolds of biological (human/animal) or synthetic material populated by the recipient’s own cells
StrengthsNo need of lifelong treatment with blood thinnersMay last indefinitely

Long-term results not yet available!

Presumably: less immune response, less degeneration/calcification, adaptive growth


Not as durable as mechanical valves

prone to calcification or abrasion

Require lifelong treatment with blood thinners

Audible clicking sound that can be annoying for the patient

None known to date

Long-term results have to be awaited

The most suitable type of valve replacement in each case is identified by individual assessment by the treating physician.

Pulmonary valve replacement

Pulmonary valve replacement can become an option for all congenital heart defects involving right ventricular outflow tract malformations, i.e. a blocked or narrowed passage between the right ventricle and the pulmonary artery. This applies to malformations such as tetralogy of Fallot, pulmonary stenosis or pulmonary atresia.

According to the German nationwide PAN study, pulmonary stenosis is the third most common congenital heart defect and occurs in 6.2 % of all congenital heart defects (6.6 per 10,000 live births). Tetralogy of Fallot is further reported to be among the three most common severe congenital cardiac malformations, representing 2.5 % of all congenital heart defects (2.7 per 10,000 live births). Pulmonary atresia can occur with or without an intact ventricular septum and is a very rare severe congenital heart defect, affecting approximately 1 in 10,000 live births.


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Author(s): Eva Niggemeyer
Last updated: 2012-02-23