Background: Decellularized equine pericardium has found its use as an alternative to autologous
pericardium for repair of congenital heart defects in children and young adults. Histological
appearance of human explants is widely unknown. We aimed to report a series of microscopical
findings in correlation with anatomical implantation sites and implant time.
Method: Tissue explants were retrieved during a reoperation either due to patch dysfunction,
or due to repeated surgery at the same implantation site. The specimens were processed
using uniform protocol with methylmethacrylate and/or paraffin embedding after fixation
in formalin. Besides standard histology staining, Kossa stain (indicating calcification)
and a panel of immunohistochemical stainings to reveal inflammation/proliferation
were applied.
Results: Twelve patch specimens from 12 patients were examined. The numbers and locations
of patch implantation were 6 for pulmonary artery plasty, five for valvular repair
and one for aortic repair. Median age at patch implantation was 18.5 months (IQR:
5.3–26.3). The indication for explantation was stenosis/dysfunction at patch implantation
site in 9, non-patch related reoperation in two and aneurysmal formation in one patient.
Median time interval between implantation and explantation (implant time) was 17 months
(IQR: 3.8–21.3). All specimens showed superficial tissue proliferation (pseudointima),
with grade 1 (minimal) in four, grade 2 (moderate) in four and grade 3 (significant)
in four, respectively. Eight specimens showed no signs of calcifications (66%). Minimal
to moderate calcifications were seen in four specimens (grade 1 = 3, grade 2 = 1).
Three of the four patches with calcification had been used for valvular repair.
Conclusion: Decellularized equine pericardium can be used in a variety of anatomical implantation
sites in congenital heart surgery. After an implant time of up to 25 months, the majority
of the specimen demonstrated no signs of significant calcifications, however pseudointimal
formation was a common finding.
