The protective potency of two commonly used cardioplegic solutions on cultured endothelial cells exposed to free-oxygen radicals injury.

Human umbilical vein endothelial cells were incubated with Bretschneider and St. Thomas II cardioplegic solution followed by a stimulation with cumene hydroperoxide (CHPO), which was used as an oxygen radicals generating agent. A statistically significant decrease of intracellular high energy phosphates (adenosine-5-trisphosphate: ATP; creatine phosphate: CP) compared to controls was observed in response to Bretschneider cardioplegia and CHPO. Furthermore, significant rises in prostaglandin I2 (prostacyclin; PGI2) production and lipidperoxidation were measured. The authors failed to record such alterations of endothelial cell metabolism for the St. Thomas II cardioplegic solution. They could also demonstrate that the cellular protection against oxygen radicals exerted by the St. Thomas II solution is attributable to procaine. The enhanced cytotoxicity of CHPO observed in presence of the Bretschneider solution was found to be partially caused by its constituent L-histidine, which led to significant decreases of high energy phosphates and increased lipidperoxidation when cells were subsequently treated with CHPO. However, alterations of high energy phosphate content initiated by CHPO and amplified by the Bretschneider solution could not be inhibited by adding procaine. Simultaneous pretreatment of cells with the Bretschneider solution and procaine and stimulation with CHPO resulted in decreases of ATP and CP, as observed using the Bretschneider cardioplegia alone.

In vitro and in vivo endothelialization of glutaraldehyde treated bovine pericardium.

In an experimental study, endothelial cell seeding on glutaraldehyde-fixed and detoxified bioprosthetic tissue, suitable for valve fabrication, was investigated in vitro. These findings were compared to spontaneous endothelial cell ingrowth on vascular grafts fabricated from the same materials. Special consideration was given to the quality of cell attachment with regards to improved shear stress resistance in the endothelial layer covering the bioprosthetic surface. On glutaraldehyde detoxified bovine pericardium, in vitro endothelial cell seeding resulted in uninhibited cell proliferation, but the cells were loosely bound to the underlying tissue. In vivo, endothelial cells grew spontaneously over the surface of vascular implants in direct contact with the bioprosthetic material. In contrast to standard fixed bovine pericardium, a significant decrease in thrombotic appositions could be observed. Cells exhibited intensive production of extracellular matrix, which renders the method of spontaneous in vivo cell ingrowth as the most promising approach for further research.

Failure mode of a new pericardial valve prosthesis (Sorin Pericarbon). A morphological study.

Between February 1986 and February 1992, 144 patients (mean age 69 years) received 149 bovine pericardial valve bioprostheses (Sorin Pericarbon). Out of this group 10 patients required reoperation because of valvular dysfunction. Defect bioprostheses (7 aortic valves, 3 mitral valves), removed 34 to 81 months after implantation, were studied by X-ray analysis as well as light and electron microscopy. Seven out of ten valves were explanted because of valvular stenosis, two valves had to be replaced because of valvular regurgitation and one because of paravalvular leakage. X-ray analysis revealed severe clacification of the cusps in all cases. Mineralization occurred predominantly next to commissural attachment zones. Cuspal tearing, associated with calcific degeneration of the tissue, was observed in two cases. Beside the commissures, accelerated tissue degeneration could be detected near the basal suture line: disintegration of collagen bundles by invading macrophages and mineral deposits was prominent in these regions. Scanning electron microscopy revealed the presence of circumscribed areas of endothelial-like cell lining on both surfaces of the cusps of five explants. Valvular stenosis, caused by severe calcification of commissural as well as basal regions of the leaflets, is the principal failure mode of the Sorin Pericarbon heart valve prostheses. As an additional aspect, the basal suture line must be assumed to be a critical determinant in accelerating tissue degeneration. Long-term clinical studies will be required to evaluate the clinical performance of this valve, focusing on thromboembolic complications, hemodynamic function and long-term durability.

Decreased tissue reaction to bioprosthetic heart valve material after L-glutamic acid treatment. A morphological study.

Degenerative alterations of two different glutaraldehyde (GA)-fixed bioprosthetic heart valve materials were investigated in subcutaneous rat implants: Bovine pericardium, prepared according to clinically used bioprosthetic heart valve material (BHV) was compared to alternatively preserved pericardium (APHV), which was fixed in GA and treated with L-glutamic acid. Following 63 days of subcutaneous implantation, calcification of APHV implants was significantly lower as compared to BHV implants (13 +/- 6 versus 158 +/- 18 micrograms Ca/mg dry weight tissue; p less than 0.05). In BHV implants ultrastructural investigations showed nucleation of plate-shaped hydroxyapatite crystals at the surface of collagen fibrils and in remnants of connective tissue cells; no signs of calcification could be detected in APHV implants. The time-course of the inflammatory reaction was determined by quantification of immunohistochemical stained mononuclear host-cells invading the implants. In both preparation groups inflammatory reaction reached maximum 42 days after implantation. However, infiltration rate of inflammatory cells was markedly decreased in APHVs as compared to BHVs (p less than 0.05).

Changes following in vitro endothelial cell lining of ePTFE prostheses: late morphologic evaluation of six failed grafts.

This paper describes the morphologic appearance during long term follow-up of in vitro endothelialised ePTFE grafts (IVECL) implanted in patients with crural reocclusions. Between June 1989 and December 1990, 13 femorocrural IVECL bypasses were implanted. Follow-up angiograms demonstrated stenoses in the middle of the graft in six patients. Two of these patients developed symptoms, and the grafts were biopsied approximately 1.5 years after implantation during a patchplasty procedure. The remaining four patients with asymptomatic stenoses refused elective reoperation and suffered a graft occlusion 53 to 619 days after implantation, all leading to amputation. Biopsy specimens and explanted grafts were examined with standard and electron microscopy. Both biopsies demonstrated multiple layers of degenerating myofibroblasts (MFB). The four explanted grafts also showed altered MFB in addition to necrosis of the graft surface. No endothelial cells were seen on any of the preparations. Long term follow up of IVECL protheses in the crural position has demonstrated that it is possible to lastingly bind cells on an artificial surface. Whether the MFB found are a substitute of lost endothelial cells, or are an end product of metaplastic and/or degenerative alterations, can only be clarified through further biopsy studies.