Allograft heart valve sterilization: a six-year in-depth analysis of a twenty-five-year experience with low-dose antibiotics

Abstract

At the Prince Charles Hospital, from a 25-year experience with allograft heart valves (1969 to 1994), a 6-year analysis from March 1988 to August 1994 of the contamination rates and efficiency of a short-duration, low-dose antibiotic sterilization protocol was made. This analysis covered 642 collections and 680 aortic and pulmonary valve implants. Tissue samples obtained at collection, valve trimming, postantibiotic incubation, and implant provided the raw data. At collection, valves retrieved in open mortuaries produced the highest contamination rate of 54%. Minimal exposure to antibiotics during transport and trimming reduced the contamination rate to 11% (p < 0.05). This was similar to the contamination rate at trimming for valves collected in the "sterile" operating room from multiorgan donors (12%). Antibiotic incubation at 37 degrees C for 6 hours reduced the contamination rate to 4% (p < 0.05). Only valves that showed no contamination at cryopreservation were implanted. However, at implant, resected tissue from valves that had been incubated in antibiotics showed a contamination rate of 3%, presumably from the theater environment, compared with 15% (p < 0.05) for tissue from valves that had not been incubated. A residual antibiotic effect appears present at the time of implant in valves that have been incubated in antibiotics and may assist in the reduction of and resistance to infection in the immediate postoperative period. This is supported by the low incidence of endocarditis in the first 3 postoperative months. The simple and effective protocol of collection within 24 hours of death combined with low-dose antibiotic sterilization is sufficient to produce pathogen-free valves in the majority of cases (> 95%).