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%).

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The Dacron sewing ring material of the St. Jude Medical mechanical heart valve (St. Jude Medical, Inc., St. Paul, Minn.) was passively impregnated with rifampicin (60 mg/ml) both in its unsealed state and after sealing by the methods of preclotting in blood, autoclaving in blood, and autoclaving in 20% albumin. Antistaphylococcal activity in the Dacron material was assessed immediately after rifampicin impregnation and at regular periods up to 5 days after implantation into the goat aorta. When the Dacron material had been sealed by autoclaving in blood and autoclaving in 20% albumin significant retention of antistaphylococcal activity was found after 5 days in vivo. Best results were obtained with the use of autoclaved blood (p < 0.05). We also compared these results with those obtained from impregnating commercially available gelatin-sealed (Gelseal) and collagen-sealed (Hemashield) Dacron material with rifampicin. Although antistaphylococcal activity was equivalent immediately after rifampicin impregnation, after 4 days in vivo the activity was negligible in Gelseal material (p < 0.05) and could not be demonstrated in Hemashield material. Rifampicin impregnation of the intact St. Jude Medical mechanical valve sewing ring may have an application in the prevention of prosthetic valve endocarditis and a clinical protocol is suggested.