Pulmonary autograft valve explants show typical degeneration
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.
Available from: Manuel Galiñanes
- "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.
Available from: Elaine Tseng
[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.
[Show abstract] [Hide abstract]
ABSTRACT: Mechanical and bioprosthetic substitute heart valves have dramatically improved life expectancy and quality of life in patients with valvular heart disease. Complications of substitute heart valves are a relatively infrequent occurrence, often due to thrombosis, infection, or structural/mechanical failure. It is important to accurately identify and systematically evaluate prosthetic heart valves when encountered as surgical pathology specimens or in the autopsy setting.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.