We sought to evaluate the microscopic characteristics of pulmonary autograft valve explants.
Cell density and thickness of the autograft valve ventricularis were determined and compared with those of normal aortic and pulmonary valves (n = 11). Cellular phenotype and extracellular matrix involvement were assessed with immunohistochemistry. Collagen 3-dimensional architecture was studied by means of confocal microscopy.
The autograft valve exhibited characteristic thickening of the ventricularis compared with the normal aortic and pulmonary valves (137 vs 77 [P = .058] vs 37 mum [P = .002], respectively). Its cell number was increased compared with those of the normal aortic and pulmonary valves (396 vs 230 [P = .02] vs 303 [P = .083], respectively). Myofibroblasts and stressed endothelial cells, both of which were present in pulmonary autografts, were absent in control valves. The exclusive presence of matrix metalloproteinase 1 was an additional sign of extracellular matrix turnover. Apoptosis, elastinolysis, cell proliferation, and senescence were not expressed. Dense fibrosis of the autograft ventricularis with relatively well-aligned collagen fibers was observed with confocal microscopy.
Fibrous hyperplasia of the ventricularis and cellular and extracellular matrix characteristics of active remodeling were a consistent finding in pulmonary autograft valve explants. The observations suggest a primary valve-related cause to be involved in pulmonary autograft valve failure.
"The cause of the detrimental changes on pulmonary autografts are not fully elucidated but Schoof et al.  performing histological analysis on explanted specimens from the Ross procedure demonstrated that the elastic tissue of the autograft had been slowly substituted with fibrous material, including both the conduit wall and the valve cusps, a "degeneration" considered as a negative "remodelling" process. The observation of fibrous hyperplasia of the ventricularis and changes in the cellular and extracellular matrix characteristics in pulmonary autograft valve explants has lead to the suggestion that a primary valve-related cause is involved in pulmonary autograft valve failure . "
[Show abstract][Hide abstract] ABSTRACT: To retrospectively analyze the clinical outcome of a totally biological composite stentless aortic valved conduit (No-React® BioConduit) implanted using the Bentall procedure over ten years in a single centre.
Between 27/10/99 and 19/01/08, the No-React® BioConduit composite graft was implanted in 67 patients. Data on these patients were collected from the in-hospital database, from patient notes and from questionnaires. A cohort of patients had 2D-echocardiogram with an average of 4.3 ± 0.45 years post-operatively to evaluate valve function, calcification, and the diameter of the conduit.
Implantation in 67 patients represented a follow-up of 371.3 patient-year. Males were 60% of the operated population, with a mean age of 67.9 ± 1.3 years (range 34.1-83.8 years), 21 of them below the age of 65. After a mean follow-up of 7.1 ± 0.3 years (range of 2.2-10.5 years), more than 50% of the survivors were in NYHA I/II and more than 60% of the survivors were angina-free (CCS 0). The overall 10-year survival following replacement of the aortic valve and root was 51%. During this period, 88% of patients were free from valved-conduit related complications leading to mortality. Post-operative echocardiography studies showed no evidence of stenosis, dilatation, calcification or thrombosis. Importantly, during the 10-year follow-up period no failures of the valved conduit were reported, suggesting that the tissue of the conduit does not structurally change (histology of one explant showed normal cusp and conduit).
The No-React® BioConduit composite stentless aortic valved conduit provides excellent long-term clinical results for aortic root replacement with few prosthesis-related complications in the first post-operative decade.
Journal of Cardiothoracic Surgery 06/2011; 6(1):86. DOI:10.1186/1749-8090-6-86 · 1.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pulmonary autograft dilatation requiring reoperation is an Achilles' heel of the Ross procedure, as exposure to systemic pressure increases autograft wall stress, which may in turn lead to tissue remodeling and aneurysmal pathology. However, the magnitude of autograft wall stress with the Ross procedure is unknown. The study aim was to develop a realistic finite element (FE) model of the autograft, and to perform simulations at systemic pressure to determine wall stress distribution immediately after the Ross operation.
The porcine pulmonary root geometry was generated from high-resolution microcomputed tomography (microCT) images to create a mesh composed of hexahedral elements. Previously defined constitutive equations were used to describe the regional material properties of the native porcine pulmonary root. The anterior and posterior pulmonary arteries, and each of the pulmonary sinuses, were best described by non-linear, anisotropic Fung strain energy functions, and input individually into the model. Autograft dilatation and wall stress distribution during pulmonary and systemic loading prior to remodeling were determined using explicit FE analysis in LS-DYNA.
The autograft was highly compliant in the low-strain region, and the majority of dilation occurred with < 30 mmHg of pressurization. During pulmonic loading, a typical inflation/deflation was observed between systole and diastole, but the autograft remained almost completely dilated throughout the cardiac cycle at systemic pressure. Although the systolic blood pressure was 380% greater in the aortic than in the pulmonary position, the peak systolic diameter was increased by only 28%. The maximum principal wall stress increased approximately 10-fold during systole and 25-fold during diastole, and was greater in the sinus than the distal artery for all simulations.
Under systemic loading conditions, the pulmonary autograft remained fully dilated and experienced large wall stresses concentrated in the sinus. The future correlation of this model with explanted autografts may lead to an improved understanding of tissue remodeling following the Ross procedure.
The Journal of heart valve disease 01/2011; 20(1):45-52. · 0.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mathematical models can provide valuable information to assess and evaluate the mechanical behavior and remodeling of native tissue. A relevant example when studying collagen remodeling is the Ross procedure because it involves placing the pulmonary autograft in the more demanding aortic valve mechanical environment. The objective of this study was therefore to assess and evaluate the mechanical differences between the aortic valve and pulmonary valve and the remodeling that may occur in the pulmonary valve when placed in the aortic position. The results from biaxial tensile tests of pairs of human aortic and pulmonary valves were compared and used to determine the parameters of a structurally based constitutive model. Finite element analyzes were then performed to simulate the mechanical response of both valves to the aortic diastolic load. Additionally, remodeling laws were applied to assess the remodeling of the pulmonary valve leaflet to the new environment. The pulmonary valve showed to be more extensible and less anisotropic than the aortic valve. When exposed to aortic pressure, the pulmonary leaflet appeared to remodel by increasing its thickness and reorganizing its collagen fibers, rotating them toward the circumferential direction.
08/2013; 29. DOI:10.1016/j.jmbbm.2013.07.009
Note: This list is based on the publications in our database and might not be exhaustive.
Rugmani Padmanabhan Iyer, Ying Ann Chiao, Elizabeth R Flynn, Kevin Hakala, Courtney A Cates, Susan T Weintraub, Lisandra E de Castro Brás
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