Dissection of the heart (dissecting the large blood vessels) must take place within 40 hours after the donor’s circulation has stopped. In order to guarantee aseptic conditions, all procedures performed on the heart and valves will take place in a laminar air flow (LAF) cabinet set up in a clean room.
Heart valves prepared by ETB-BISLIFE consist of a skirt of myocardial tissue and a blood vessel (vascular tissue), with the valve situated at the transition between the two tissue types. The valve consists of three valve leaflets that normally prevent blood from flowing back into the heart after being pumped towards the lungs or the body.
To determine whether a heart valve is suitable for transplantation, its morphological and anatomical status is assessed. If the quality of the valve does not meet the criteria for implantation, it will be rejected and not be processed further. Heart valves that do meet the criteria will be decontaminated using a mix of antibiotics for a period of six hours at 37 °C.
Following decontamination, the tissue is prepared to be frozen. For that purpose, the valve is incubated in a medium containing 10% dimethyl sulfoxide (DMSO), also referred to as preservation or freezing medium, for half an hour. The valve is sealed in an impenetrable film that can withstand extreme cold. The freezing takes place in a controlled process. The tissue is then transferred to the storage vessel and stored in the vapour of liquid nitrogen. Tissues must be frozen within 48 hours after the donor’s circulation has stopped. By using this method, the tissue can be stored for up to five years.
To prevent the transmission of diseases (incl. viruses) from donor to recipient, blood samples taken during the removal of organs and tissue undergo serology testing for a number of pathogens. In addition, a clinical pathologist will subject the remaining heart tissue (after removal of the valves) to a thorough histopathological examination to rule out inflammations of the heart, such as endocarditis or myocarditis, as well as connective tissue disorders including Marfan’s disease.
The microbiological safety of the tissue is also assessed. In the event of microbiological contamination of cardiac tissue prior to decontamination, the tissue may still be approved depending on the type of bacterium identified. Any remaining contamination in the freezing medium found after decontamination will always result in rejection of the tissue.
Following assessment of the results of serology, microbiological and histopathological testing, we may decide to release the tissue via a Quality Assessment Review. After its release, the tissue is made available for transplantation.