Influence of stent edge angle on endothelialization in an in vitro model

PURPOSE: To investigate the influence of topographic features in the path of migrating endothelial cells, specifically the effect of edge angle of intravascular metallic material on endothelialization. MATERIALS AND METHODS: Flat 1-cm x 1-cm 316-L pieces of stainless steel were placed on confluent monolayers of human aortic endothelial cells. The thickness of each metal piece was ground to achieve an edge angle of 35 degrees, 70 degrees, 90 degrees, or 140 degrees (n = 6 each) in relation to the endothelial surface. Migration distance and density of endothelial cell coverage on the metal pieces were measured in groups of six each under static conditions at 4, 7, and 11 days and flow conditions (16 dynes/cm(2)) at 4 days. RESULTS: Endothelial cell migration distance along the surface of the pieces with edge angles of 35 degrees was significantly greater than that with those with larger angles (P < .05) under static and flow conditions. The migration distances on the 35 degrees piece were 87.5%, 47.3%, 57.1%, and 66.1% greater than those on the 90 degrees piece at the upstream, downstream, right, and left edges, respectively. There were no significant differences in cell density among different angle groups under flow or static conditions. CONCLUSION: The edge angle of intravascular metallic material has an influence on the rate of endothelialization. A smaller edge angle facilitates endothelialization over metallic material when compared to a larger angle. These results demonstrate the importance of metallic stent profile on endothelialization rate.     

Fibrinogen: structure, function, and surface interactions

Fibrinogen plays a central role in the mechanism of coagulation and thrombosis and is partially involved in the development of postintervention restenosis. Because of therapeutic implications, it is convenient for the vascular interventionalist to revisit its structure, function, and relationships within the vascular environment. This review focuses on the molecular structure, mechanisms of polymerization and lysis, and fibrinogen interaction with the platelet alpha(IIb)beta(3) [corrected] integrin. It also addresses the less understood interaction of fibrinogen with artificial surfaces. Glycoprotein IIb-IIIa blockers, targeted to interfere with fibrinogen-platelet interactions, widely used in clinical practice, are discussed, and trials of new drugs are also summarized.     

Expandable intraluminal vascular graft: a feasibility study

An expandable intraluminal graft mounted coaxially over an angioplasty balloon catheter was used in dog arteries. The graft, a wire mesh tube that has the ability to retain its expanded shape, opposes elastic recoil of the arterial wall after maximum balloon inflation. Eighteen grafts were placed in the abdominal aorta and iliac femoral, renal, superior mesenteric, and carotid arteries of eight dogs through femoral or carotid arteriotomies. Two grafts were placed in areas of artificially induced stenosis, completely restoring the lumen. Overall patency rate at 35 weeks was 77%. Histopathologic examination of patent grafts showed complete endothelialization at 3 weeks. The smaller caliber grafts and those that had outflow obstruction showed significant degrees of intimal hyperplasia.     

Normal and stenotic renal arteries: experimental balloon-expandable intraluminal stenting

Elastic recoil of the vessel wall is a common cause of failure of percutaneous transluminal angioplasty in renal arteries. To oppose such recoil, balloon-expandable metal stents were implanted in artificially stenotic renal arteries in pigs and normal renal arteries in dogs and pigs. The stents were then examined angiographically and histologically at regular intervals. All stents were completely covered with endothelialized neointima in 3 weeks. There was no difference in intimal thickness between the stenotic and nonstenotic renal arteries. A large stent diameter and a large open or nonmetal surface may cause less intimal hyperplasia, but nonturbulent, fast arterial flow is probably the most important factor in ensuring long-term patency of the vessel.     

Expandable intrahepatic portacaval shunt stents in dogs with chronic portal hypertension

A canine experimental model was used to investigate the feasibility of using balloon-expandable portacaval shunts in humans with chronic portal hypertension. Intrahepatic portacaval shunts were created in nine dogs with stable portal hypertension previously induced by intraportal injections of polyvinyl alcohol (Ivalon). Embolic material was injected periodically through a subcutaneous port that allowed repeated access to the portal system. Shunts were placed 14 weeks after the last embolization. A shunt patency rate of 100% was observed up to 48 weeks. Low portacaval pressure gradient and high shunt flow accounted for the good results.     

Intravascular stenting: from basic research to clinical application

Although the use of intravascular stents is approaching widespread clinical use, several questions remain regarding their safety and efficacy. Several factors have direct bearing on the immediate and long-term results of intravascular stenting. The technical results of stenting are dependent on the mechanical characteristics of the device and long-term patency is closely related to thrombogenicity and endothelialization. Although stents are used most frequently for the treatment of atherosclerotic disease there is no clear understanding of how they influence the atheromatous lesion.     

In vivo technetium-99m S12 antibody imaging of platelet alpha-granules in rabbit endothelial neointimal proliferation after angioplasty.

To examine the specificity of technetium-99m monoclonal antibody (S12) imaging for identifying activated platelets at interventional injury sites in atherosclerotic rabbit arteries, subgroups of unheparinized rabbits (n = 39) underwent serial percutaneous transluminal aortic angioplasty (PTA) procedures (with or without intravascular stent placement) followed by in vivo and then ex vivo gamma camera imaging, scanning, and immunoelectron microscopy to determine the intravascular loci of S12 Fab' antibody binding. Despite angiographic vessel patency, image-derived ratios of in vivo S12 binding in injured versus uninjured vascular segments were significantly increased (p less than 0.05) after one PTA (1.3 +/- 0.17, n = 7), PTA twice at 6-week intervals (1.4 +/- 0.22, n = 7), and PTA plus stent placement (1.6 +/- 0.28, n = 7) compared with control experiments (1.1 +/- 0.13, n = 7). Ex vivo imaging of blood-free excised aortas confirmed S12 localization at PTA (2 +/- 0.4, n = 3) and PTA plus stent placement (5 +/- 3.8, n = 7) sites (both p less than 0.05 versus controls). S12 antibody uptake decreased significantly (p less than 0.05) at 1 week after PTA plus stent placement in vivo (1.1 +/- 0.10, n = 4) and ex vivo (1.6 +/- 0.7, n = 3). Electron microscopic studies confirmed dense platelet, fibrin, and red blood cell deposition in regions of acute injury, with endothelial neointimal proliferation at 1 week after PTA. Immunoelectron microscopic studies confirmed specific in vivo S12 binding (22:1 versus nonrelevant IgG) at sites of alpha-granule GMP-140 expression in activated platelets. Therefore, S12 studies may be useful to localize sites of platelet-derived mitogen release at arterial PTA injury sites.     

Percutaneous Aortic Stent Placement for Life Threatening Aortic Rupture Due to Metastatic Germ Cell Tumor

Patients with testicular carcinoma frequently present with advanced disease and symptoms resulting from metastatic lesions. We report an unusual case of successful emergency management of a massive rupturing aortic pseudoaneurysm midway through systemic chemotherapy for stage III germ cell tumor by percutaneous trans-luminal placement of an aortic bypass stentgraft. Unstable hemorrhage was controlled, allowing our patient to complete chemotherapy and undergo elective retropertineal lymph node dissection with resection of the pseudoaneurysm and residual disease after normalization of tumor markers. Final pathological evaluation revealed only fibrosis in the resected tissue. Followup angiography demonstrated a patent stentgraft and the patient was without evidence of disease 1 year after retroperitoneal lymph node dissection.