ADAPT Treated Pericardium for Aortic Valve Reconstruction in Congenital Heart Disease: Histology of a Series of Human Explants

Objectives: Different types of patch materials are in use for aortic valve (AV) reconstruction in children with significant AV pathology for avoidance of early valve replacement. CardioCel (Admedus, Perth, Australia) consists of bovine pericardium treated with the ADAPT-method (Admedus’ tissue engineering process-treated). The material has been claimed to mitigate both the effects of inflammation and calcification locally related to the patch material with subsequently lower rates of re-stenosis.

Methods: We studied and compared tissue reactions in CardioCel-Patch augmented AV tissue specimen. Explants were worked up using a uniform protocol with methylmethacrylate and/or paraffin embedding after fixation in formalin. Besides standard histology staining, Kossa stain (for identification of calcifications) and immunohistochemical staining was applied with antibodies specific for muscular, inflammatory, and connective tissue component antigens. Findings regarding the aspects proliferation, calcification, and inflammation were rated using a 4-grade scale (G0 no/G1 few/G2 moderate/G3 massive).

Results: Eight aortic valve tissue specimen (augmented with CardioCel patch material) were examined (7 explanted surgically, 1 autopsy). Indication for explantation had been AV stenosis in 3, AV regurgitation in 3 and suspicion for endocarditis in 1 patient. Low-grade AV stenosis had been known in the remaining patient. Time interval between implantation and explantation (implant time) was 8 to 29 months (mean 22 months).

Superficial endothelialization was demonstrated in all patients by immunohistochemistry. Whereas 4 specimen showed no inflammatory cell infiltration (G1: 3; G2: 1), there was not a single one without tissue proliferation (G1: 3, G2: 5). 6 of 8 samples with implant times of 23 to 29 months revealed low-grade calcifications. Only the two specimens with “short” implant times of 8 and 11 months showed no calcifications. No active inflammation was demonstrated histologically in the patient with clinical suspicion of endocarditis or thrombus.

Conclusion: In contrast to advertisement statements, CardioCel patches demonstrated proliferations in every specimen and calcifications in all 6 specimen with implant times of 23 months or more. However, histology of this patch material showed less optimal results in-short and medium-term explants. Long-term follow-up in larger cohorts is required to determine the definitive patch performance for AV reconstruction.