Could 37 degrees C storage temperature extend homovital valve allograft viability?

Preservation of allograft valves is the most important determinant of their durability. Unprocessed, homovital valve allografts stored at 4 degrees C in nutrient medium have provided superior mid-term results over routinely used cryopreserved or antibiotic-sterilized allografts. As storage temperature may alter viability, it was hypothesized that allograft storage at 37 degrees C may maintain greater viability over time.

Porcine aortic (n = 10) and pulmonary valve conduits (n = 10) were harvested under sterile conditions. Valve leaflets and sinus walls were separated, and each was divided into two specimens, which were stored in modified culture medium at 4 degrees C and 37 degrees C, respectively. Cell viability was tested by monitoring metabolic activity at 37 degrees C at days 1, 3, 7, 10, and 14. The proliferative ability of cells isolated from valve leaflets was assessed after 14 days by cell culture. Sterility testing of the storage medium was also carried out.

Valve leaflet cells and sinus wall cells had significantly higher metabolic activity when stored at 37 degrees C. The median number of isolated cells at 4 degrees C was 3,231.5 (range: 422-3,844), and at 37 degrees C was 8,317.50 (range: 4,329-8,650). The storage medium was sterile in all cases.

Storage at 37 degrees C significantly improved valve allograft cell metabolic activity and viability compared with storage at 4 degrees C for up to 14 days. The lower concentration of antibiotics did not affect the sterility of tissues stored at 37 degrees C.