Progress and problems in the development of vascular prostheses.
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Animals↗
Biomedical subjects
Y Noishiki
Publications and source records attributed to Y Noishiki.
The vicious cycle of nonhealing neointima in fabric vascular prostheses.
Delayed neointimal healing of a fabric vascular prosthesis was investigated in an animal study focusing on the relationship between red thrombus, fibrinolysis, and endothelialization on the luminal surface. Fabric vascular prostheses were implanted into the descending aortas of 72 dogs. Fifty-nine grafts were explanted from 1 h to 1,705 days after implantation. One hour after implantation, the graft wall was red in color due to fresh thrombus; however, at 1 day the luminal surface became white. Red thrombus reappeared at 1 week and remained present in the long-term. Microscopically the initial red thrombus contained numerous erythrocytes. The white thrombus at 1 day was composed of a dense fibrin network without erythrocytes. At 2 days numerous lacunae appeared in the fibrin layer, and at 3-5 days cavernae and low density fibrin areas were present secondary to fibrinolysis. These areas allowed the blood components to infiltrate into the fibrin layer, and as a result red thrombus reformed within it. The thrombi on the luminal surface in the long-term was always red in color and composed of complicated, multiple stages of thrombus formation, i.e., fresh thrombus with erythrocytes, dense fibrin without erythrocytes, low fibrin density areas, lacunae and cavernae in the fibrin layer, and blood component infiltration into these spaces. Thrombus was always newly formed and present, and involuted in parallel due to fibrinolysis, suggesting that these phenomena perpetuated in a vicious cycle. However, at the anastomoses fibrinolysis was present, but blood component infiltration was prevented by the endothelial cell lining. These results suggest that endothelialization may arrest the vicious cycle of nonhealing neointima in fabric vascular prostheses.
Anastomosis, Surgical↗
Transplantation of autologous tissue fragments into an e-PTFE graft with long fibrils.
An expanded polytetrafluoroethylene (e-PTFE) graft with long fibrils transplanted with bone marrow showed rapid and uniform neointima formation in a dog study. The e-PTFE grafts (fibril length, 90 microns; 6 mm internal diameter; length, 6-8 cm) transplanted with autologous bone marrow were implanted in the abdominal aortae of 10 dogs and retrieved at 3 weeks and 3 months after implantation. Control e-PTFE grafts without bone marrow treatment were also implanted in the same manner in 8 dogs. Macroscopically the treated graft wall appeared red in color; however, there was no thrombus deposition on the surface. Light microscopic observation revealed that the treated grafts were completely lined with endothelial cells at 3 weeks. The neointima was uniform without intimal hyperplasia at the anastomotic sites. Inside the graft wall many capillary blood vessels were observed. At 3 months moderate intimal hyperplasia throughout the graft with complete endothelialization was observed. In the control grafts, endothelialization was observed at the anastomotic sites; however, half of the other areas were covered with a fibrin layer devoid of endothelial cells even in the 3-month grafts. These results indicated that neointima formation was effectively accelerated with the autologous bone marrow transplantation, but moderate intimal hyperplasia throughout the graft was inevitable in e-PTFE grafts even after complete endothelialization.
Animals↗
Sealing of a fabric vascular prosthesis with autologous adipose tissue: a preliminary report of its clinical application.
A new method of sealing fabric vascular prostheses with autologous adipose tissue was clinically applied as an alternative to preclotting with fresh blood. Thirty-six patients with peripheral arterial occlusive disease were implanted with highly porous fabric prostheses. The prostheses were prepared by sealing the fabric pores with autologous adipose tissue that had been chopped up into small pieces and enmeshed in the fabric by forceful injection of the tissue suspension through a syringe. There was no complication related to the sealed graft such as graft bleeding after implantation. In-hospital mortality occurred in 4 patients: 1 case each of pneumonia, pulmonary infarction, sepsis, and acute myocardial infarction. During the period of 274 +/- 190 days, 3 prostheses were found to be occluded. All the other grafts were patent. The overall patency rate was 91.4%. Postoperative angiography revealed neither intimal thickening at the anastomotic sites nor irregularity of the prosthetic surface. The method proved safe and useful for implantation of smaller caliber artificial grafts.
Adipose Tissue↗
Clinical use of low porosity woven ultrafine polyester fiber grafts.
A woven fabric graft made of ultrafine polyester fibers (UFPF) (Toray Graft, water porosity: 100 ml/min/cm2:120 mm Hg H2O) was clinically applied in 81 cases (28 thoracic aortic aneurysms, 6 thoracoabdominal aortic aneurysms, 42 abdominal aortic aneurysms, and 5 atherosclerotic obstructions of the peripheral arteries). Eight patients died after surgery due to causes unrelated to the graft. The other 73 patients were in good condition after surgery. For operations requiring extracorporeal circulation, the graft was presealed with human albumin. For the abdominal aortic aneurysms, the graft was preclotted in situ with nonheparinized autoblood after the completion of the proximal anastomosis. It took about 2 min to complete the preclotting. A nonsealed graft was used for the reconstruction of peripheral arteries for the intraaortic balloon pumping procedure. The graft was easy to handle. There was no cut edge fraying problem with the graft in any direction of cutting. Even after presealing, the graft was soft and pliable enough to enable easy adaptation and anastomosis. Just after implantation, bleeding was minimal from the graft wall, anastomotic sites, and suture pores, and it stopped spontaneously. These clinical data showed that the woven UFPF graft exhibited both easy handling despite in spite of low porosity and safe application in the reconstruction of arterial systems even under totally heparinized conditions during extracorporeal circulation.
Aortic Aneurysm↗
Growth regulation of endothelial cells by tissue fragments: analysis on mechanism of rapid endothelialization of tissue-seeded vascular prosthesis in a three-dimensional culture system.
Rapid endothelialization of the inner surface was reported in an autologous tissue-seeded vascular prosthesis. We applied a three-dimensional in vitro culture system to elucidate the precise mechanism of rapid endothelial coverage of a tissue-seeded vascular prosthesis. Human venous, omental, adipose and striated muscle tissue fragments were harvested from surgical specimens. They were embedded in collagen gel, and 2.0 x 10(5) bovine aortic endothelial cells (BAECs) were seeded on the gel. The number of BAECs was counted on Days 2 and 7. Growth rate of BAECs was facilitated on the collagen gel with omental and striated muscle tissue fragments (p < 0.05). Factor VIII-negative spindle cells migrated around tissue fragments, especially around the omental and striated muscle tissue fragments. Rapid endothelialization of a tissue-seeded vascular prosthesis may result from facilitation of EC proliferation by viable tissue fragments and migrated cells. These results confirm tissue fragments regulate EC growth, and are useful as bioengineering tools.
Animals↗
Characterization of a polyepoxy compound fixed porcine heart valve bioprosthesis.
Concerns with the currently available bioprostheses are calcification, long-term durability, and suboptimal hemodynamic performance. It is well known that these concerns are all more or less related to the cross-linking reagent, glutaraldehyde or formaldehyde, used in fixing bioprostheses. To address these concerns, we undertook the development of a porcine bioprosthesis fixed with a polyepoxy compound. In the development of this polyepoxy compound valve, it was found that the porcine leaflets fixed with polyepoxy compound were softer and more pliable than those fixed with glutaraldehyde. In this study, a special microtoming technique was developed to section the biological tissue so that the fixation uniformity in distinct layers of porcine aortic wall could be characterized. The fixation index and the denaturation temperature measurements in distinct layers of aortic walls showed that the cross-linking density was uniform throughout the entire aortic wall for the polyepoxy compound fixed porcine valve. It was also noted that the fixation index of the polyepoxy compound fixed aortic wall (91.5 +/- 0.5, n = 3) was not significantly different from that of its valvular leaflet (90.6 +/- 0.8, n = 3). Similarly, the denaturation temperature of the polyepoxy compound fixed aortic wall (80.4 +/- 0.9 degrees C, n = 5) was statistically comparable to that of its valvular leaflet (79.0 +/- 0.5 degrees C, n = 5). The results of this study indicated that polyepoxy compound can adequately fix the entire porcine aortic wall as well as its valvular leaflets.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Fixation of bioprosthetic tissues with monofunctional and multifunctional polyepoxy compounds.
Collagen from a native tissue is fixed with a polyepoxy compound (PC) for use as a new biologic prosthetic material. Prior studies have shown that this biomaterial has comparable properties with collagen fixed with glutaraldehyde (GA), and thus has great promise for biomedical applications. A prior kinetic study indicated that the reaction between the functional groups of collagen and the multifunctional epoxy EX-313 is a 2.5th-order reaction. The purpose of this study was to understand the mechanism of the amino acid-PC reactions in a fixation process. Bovine arteries were fixed with a monofunctional PC (EX-131) and a multifunctional PC (EX-313) as a function of fixation time. A sequential fixation with a second fixative was used to identify the available remaining reactive sites from a prior fixation. The denaturation temperature (Td) was measured on each sample. Because the denaturation temperature is a direct indication of crosslinking of individual amino acids with the fixative, the increase in Td of a subsequent fixation may be indicative of the available remaining amino acids. The fixation index was measured on each sample to reflect the increase of fixation completion in a sequential fixation process. The fixation index and crosslink data also revealed that the reactive amino acids for EX-131 and EX-313 may not be exactly the same. The data in this study suggest that a monofunctional fixative can pre-react with the amino acids of collagen to effectively block further fixation of collagen with a second fixative. This amino acid masking may be associated with collagen branching. Collagen branching and its effect on denaturation temperature are described.
Animals↗
Effectiveness of fragmented autologous adipose tissue as a sealer of porous textile grafts: effect on endothelial development.
PURPOSE: This study is designed to develop a sealing method for fabric vascular prosthesis with chopped tissue fragments. METHODS: A highly porous fabric vascular prosthesis was invaginated, and a suspension of chopped autologous adipose connective tissue fragments was injected repeatedly until the pores were enmeshed with the fragments. Small tissue fragments oozed out from and firmly anchored within the interstices of the fabric, which made the outer surface smooth. The graft was then invaginated to bring the smooth surface into the luminal side. RESULTS: No blood leakage was observed in an extracorporeal in vivo shunt load test with heparin (total 1400 IU/kg, actinomycin > 1500), whereas a continuous bleeding was seen in a preclotted control graft (400 IU/kg, actinomycin 657 +/- 341). The sealed in a preclotted control graft (400 IU/kg, actinomycin 657 +/- 341). The sealed grafts were implanted in the descending thoracic aorta of 40 dogs, and an equal number of control grafts was used. The grafts were removed at selected time intervals up to 738 days. No bleeding was observed with the sealed grafts, and a thin layer of neointima was observed at 30 postoperative days. Eight (20%) of the control dogs bled to death within 24 hours of implantation. The neointima in the control animals extended from the anastomotic sites slowly with complete healing observed at 217 postoperative days. CONCLUSIONS: The autologous adipose tissue fragments could reliably seal the highly porous fabric prosthesis while allowing rapid and complete neointima healing in dogs.
Adipose Tissue↗
Biologic vascular grafts in the venous position.
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Animals↗
Antiadhesive membranes for cardiac reoperations.
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Animals↗
Dialdehyde starch-tanned bovine grafts in the coronary position.
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Animals↗
Percutaneous insertion of a jacketed stent to close the entry of dissecting aortic aneurysms of DeBakey types I and II.
As a treatment for dissecting aortic aneurysms of DeBakey Types I and II, a percutaneous insertion method using a new jacketed stent was developed. The efficacy of the method was evaluated in an animal study. We developed a special stent prepared by modifying the original Gianturco self-expandable metallic stent and a fabric patch. A model of a dissecting aortic aneurysm of DeBakey Type I was created in dogs. The device was inserted into the ascending aorta from the left carotid artery through a sheath-introducer system. The aortogram showed the bloodstream through the false lumen before the insertion, but no bloodstream after the stent insertion. The autopsy showed that the entry, the reentry, and the false lumen were completely filled with fresh thrombus. By using this stent, we successfully achieved an interventional treatment for dissecting aortic aneurysms of DeBakey Types I and II.
Aortic Dissection↗
Unusual inflammatory responses around a collagen-impregnated vascular prosthesis.
A collagen-impregnated graft, called Hemashield, has been used clinically; however, some complications such as pyrexia, fluid accumulation, and unusual scar formation around the graft have been reported. To understand the cause of these problems, the graft was examined both in vivo and in vitro. Endotoxin and (1-3)beta-D-glucan were detected in the extract from Hemashield by special quantitative methods called Toxicolor and Endospecy. In an animal study, the grafts were implanted in the thoracic descending aorta of 9 dogs and were designed to explant at 2 weeks. Macroscopic evaluation of the explants showed that the graft had no infection, but fluid accumulation was found in the pleural cavity and around the graft-like seroma. Microscopical observations revealed that neither fibroblasts nor capillary blood vessels had infiltrated in the adventitial side of the graft, but numerous plasma cells, lymphocytes, and macrophages were noticed. The impregnated collagen was partially absorbed. These results indicate that the graft had some contaminants which contained a certain amount of endotoxin and (1-3)beta-D-glucan, resulting in noninfective inflammatory responses around the graft.
Animals↗
[Unusual non-infective inflammatory responses around a collagen impregnated vascular prosthesis].
Causes of some complications such as pyrexia, fluid accumulation and unusual scar formation around the graft in "Hemashield" implantation were examined both in vivo and in vitro. In an animal study, the grafts were implanted in the thoracic descending aorta of 9 dogs, and were explanted at 2 weeks after implantation. Macroscopic evaluation of the explants revealed that the graft had no infection, but fluid accumulation and a thick scar layer formation were noticed in the pleural cavity and around the graft. Microscopical observations demonstrated that the impregnated collagen was almost absorbed and numerous plasma cells, lymphocytes and macrophages had infiltrated in the interstices of the Dacron fibers, but neither fibroblasts nor capillary blood vessels. Numerous erythrocyte were also noticed in the graft wall. In vivo experiment of the extract from Hemashield, endotoxin and/or (1-3) beta-D-glucan were detected by the special quantitative methods; Toxicolor and Endospecy. These results indicated that the graft had some contaminants which contained a certain amount of endotoxin, (1-3) beta-D-glucan, resulting in non-infective inflammatory responses around the graft.
Animals↗
Development and evaluation of a pliable biological valved conduit. Part I: Preparation, biochemical properties, and histological findings.
Different types of external valved conduits have been used for the repair of complex congenital cardiac anomalies that may have otherwise been inoperable. However, an ideal conduit has yet to be found due to complications such as stenosis, thrombosis, calcification of the valve and graft wall, and "peeling" of the neointima. To address those problems, a new extracardiac valved conduit made of bovine jugular vein was developed and evaluated in a preliminary animal study. Harvested bovine vein containing a naturally existing valve was initially incorporated with protamine on the inner surface and then was cross-linked in diglycidyl ether (DE). Fixation with DE allowed the vein and its leaflets to retain a tissue-like elasticity. To provide antithrombogenicity to the graft, heparin was introduced into the lumen to bind ionically to the pre-entrapped protamine. The biological valved conduit of approximately 14 mm diameter was implanted from the right ventricle to pulmonary artery as bypass graft in three dogs. After implantation, the native main pulmonary artery was ligated between the anastomotic sites of the bypass conduit. No anticoagulant or antiplatelet drugs were administered after surgery. One DE-fixed valved conduit was retrieved at 3 months, and the others were removed at 5 months. Only small thrombus areas were found on the white luminal surfaces. The valves and the conduits maintained softness and pliability, similar to before implantation. Additionally, the collagen content, shrink temperature, and tanning index of this newly developed biological valved conduit before and after fixation were measured in the study.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Development and evaluation of a pliable biological valved conduit. Part II: Functional and hemodynamic evaluation.
Many congenital cardiac malformations may require a valved conduit for the reconstruction of the right ventricular outflow tract. In spite of many endeavors made in the last 25 years, the clinical results of right ventricular outflow tract reconstruction with currently available valved conduits are still not satisfactory. Specific problems encountered clinically include suboptimal hemodynamic performance, conduit kinking or compression, and fibrous peeling from the luminal surface. To address these deficiencies, we undertook the development of a biological valved conduit: a bovine external jugular vein graft with a retained native valve cross-linked with a diglycidyl ether (DE). This study, using a canine model, was to evaluate the functional and hemodynamic performance of this newly developed valved conduit. Three 14 mm conduits, implanted as bypass grafts, right ventricle to pulmonary artery, were evaluated. The evaluation was conducted with a noninvasive color Doppler flow mapping system at pre-implantation, immediately post implantation, one- and three-months post implantation, and prior to retrieval (five-months post implantation). The two-dimensional tomographic inspection of the leaflet motion at various periods post implantation showed that the valvular leaflets in the DE treated conduit was quite pliable. No cardiac failure or valvular dysfunction was observed in any of the studied cases. The color Doppler flow mapping study demonstrated that the valve in the DE treated conduit was competent, with no conduit kinking or compression observed in any of the three cases. The spectral Doppler velocity study evidenced that the transvalvular pressure gradients of the DE treated conduit were minimal as compared to those of the currently available conduits. In conclusion, from the functional and hemodynamic performance points of view, this newly developed valved conduit is superior to those currently available.
Animals↗
[Disadvantages of "Gelseal graft" as a vascular prosthesis].
In clinical use, the Gelseal Triaxial graft have been shown to have several problems, such as pyrexia, pleural effusion and seroma formation around the graft. To investigate the cause of these complications, we examined mechanical and biological properties of the graft. The water permeability was found to be 0 ml at 120 mmHg in an in vitro study. Scanning electron microscopical observation revealed that gelatin in the graft wall was not uniform and easily detached from the luminal surface. The amount of impregnated gelatin in the graft was found to be 6.73 mg/cm2. In addition, this graft contained 297 and 73 pg endotoxin in extract/g of graft wt at 25 degrees C 72 hrs as assessed by Toxicolor and Endospecy pyrogen tests, respectively. The grafts were implanted in the descending aorta of 8 dogs for 2 weeks in an animal study. Three out of 8 animals died of graft occlusion. Both macroscopic and microscopic evaluations of the explants from 5 dogs showed that neither fibroblasts nor capillary blood vessels had infiltrated in some area of the graft wall. Serous fluid was found to be retained between the graft and the surrounding host tissue in three cases. These results indicated that the Gelseal graft was easy to implant due to zero porosity, but the coated gelatin was not clean and gelatin was easily detachable. Hence, the graft would be prone to some complications such as pyrexia, immune response, thromboembolism, seroma, and pleural effusion. One must be aware of the potential disadvantages of the Gelseal grafts before using it in patients.
Animals↗