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Infection of glutaraldehyde-preserved porcine valve heterografts
Abstract:
Gross, histologic and ultrastructural changes associated with bacterial infection are described in four porcine valve heterografts that had been in place in patients for 6 days to 28 months. In one patient, culture of the aortic tissue tag included in the heterograft container grew Mycobacterium chelonei; however, examination of the heterograft, recovered at necropsy 6 days after implantation, revealed small colonies of bacteria that differed morphologically from mycobacteria. A second heterograft was the site of staphylococcal infection associated with extensive destruction of collagen in the leaflets. Similar destruction was observed in a third heterograft, which was found to have organisms on ultrastructural study even though bacterial cultures of the valve were negative. The fourth heterograft, from a patient who died of coronary embolism secondary to dislodgment of vegetative material, contained structures resembling lysed bacteria. Observations in these 4 patients and review of published reports of infection involving 43 other patients with porcine valve heterografts indicates that infection in these valves: (1) develops in the fibrin layer that covers the cusps, (2) can involve the collagen in the leaflets, and (3) is uncommonly (three patients) associated with valve ring abscesses.
Insights
Bacterial infection in porcine valve heterografts can damage leaflets and fibrin layers. Early detection and understanding infection pathways are crucial for patient outcomes.
Area of Science:
- Cardiovascular Surgery
- Infectious Diseases
- Biomaterials Science
Background:
- Porcine valve heterografts are widely used in cardiac surgery.
- Bacterial infection is a serious complication of prosthetic heart valves.
- Understanding the pathogenesis of heterograft infection is critical for improving patient care.
Purpose of the Study:
- To describe the pathological changes associated with bacterial infection in explanted porcine valve heterografts.
- To identify the common sites and mechanisms of infection within these valves.
- To correlate clinical findings with microbiological and histological observations.
Main Methods:
- Histological examination of explanted porcine valve heterografts.
- Ultrastructural analysis of valve tissues.
- Bacterial culturing of valve samples and associated tissues.
- Review of clinical data and published literature on heterograft infections.
Main Results:
- Infection was observed in the fibrin layer covering the cusps and could extend into the collagen of the leaflets.
- Different bacterial morphologies were noted, including organisms resembling lysed bacteria.
- Staphylococcal infection led to extensive collagen destruction.
- Negative bacterial cultures did not rule out infection, as organisms were detected ultrastructurally in one case.
- Valve ring abscesses were an uncommon finding.
Conclusions:
- Porcine valve heterograft infections initiate in the fibrin layer and can progress to involve leaflet collagen.
- Diagnostic challenges exist, as bacterial cultures may be negative despite histological evidence of infection.
- Further research is needed to optimize the prevention and treatment of porcine valve heterograft infections.