Balloon-expandable Stainless Steel Stents Research Articles

Pathological analysis of local delivery of paclitaxel via a polymer-coated stent.

Paclitaxel can inhibit vascular smooth muscle proliferation in vitro, and early studies suggest that paclitaxel may be useful in preventing restenosis. Early and late intimal growth and local vascular pathological changes associated with paclitaxel delivered via stents have not been fully explored. Localized drug delivery was accomplished with balloon-expandable stainless steel stents coated with a cross-linked biodegradable polymer, chondroitin sulfate and gelatin (CSG), containing various doses of paclitaxel. CSG-coated stents with paclitaxel (42.0, 20.2, 8.6, or 1.5 microgram of paclitaxel per stent), CSG-coated stents without paclitaxel, and uncoated stents (without paclitaxel or CSG) were deployed in the iliac arteries of New Zealand White rabbits, which were killed 28 days after implant. Mean neointimal thickness at stent strut sites was reduced 49% (P<0.0003) and 36% (P<0.007) with stents containing 42.0 and 20.2 microgram of paclitaxel per stent, respectively, versus CSG-coated stents without paclitaxel. However, histological findings suggested incomplete healing in the higher-dose (42.0 and 20.2 microgram) paclitaxel-containing stents consisting of persistent intimal fibrin deposition, intraintimal hemorrhage, and increased intimal and adventitial inflammation. Stents coated with CSG alone (without paclitaxel) had similar neointimal growth as uncoated stents. In a separate group of rabbits killed at 90 days, neointimal growth was no longer suppressed by CSG-coated stents containing 42.0 or 21.0 microgram of paclitaxel CSG coating appears to be a promising medium for localized drug delivery. Paclitaxel polymer-coated stents reduce neointima formation but are associated with evidence of incomplete healing at 28 days. However, neointimal suppression was not maintained at 90 days.

The effects of uncontrolled hyperglycemia on thrombosis and formation of neointima after coronary stent placement in a novel diabetic porcine model of restenosis.

Results of recent clinical studies suggest that patients with diabetes mellitus have a higher than normal rate of restenosis after percutaneous transluminal coronary angioplasty or coronary stenting. The mechanism for this exaggerated neointimal response is not known. To determine the technical feasibility of a model of in-stent restenosis in swine with streptozotocin-induced hyperglycemia and to compare the late arterial responses to injury induced by placement of oversized coronary stents in diabetic and nondiabetic animals. Eighteen 25-40 kg castrated male or intact female Yucatan miniature swine aged 6 months were obtained from a commercial supplier. Twelve of the miniature swine were randomly selected for intravenous treatment with 125 mg/kg streptozotocin to induce a hyperglycemic state. Twelve weeks after treatment, all animals underwent placement of oversized balloon-expandable stainless steel stents in the coronary arteries. After 28 days, histomorphometric analysis of the stented coronary arteries to determine the neointimal responses for the diabetic and nondiabetic animals was completed. Sudden death due to stent thrombosis occurred for five of 11 (45%) of the diabetic animals and none of the age-matched nondiabetic control animals (P=0.05). For histology after 28 days, the neointimal response was correlated to the extent of arterial injury for the diabetic (r=0.79, P < 0.0001) and nondiabetic (r=0.86, P < 0.0001) animals. The surviving diabetic animals had areas of neointimal (1.67 +/- 0.74 mm2) and percentages of in-stent stenosis (28 +/- 14) similar to those of the nondiabetic swine (1.36 +/- 0.40 mm2, P=0.26; 22 +/- 6, P=0.17). Multiple regression analysis also demonstrated that arterial injury (P < 0.0001) alone, not hyperglycemia (P=0.237), was independently correlated to formation of neointima. Uncontrolled hyperglycemia results in greater than normal thrombosis after coronary-stent placement in swine with streptozotocin-induced diabetes. These data suggest that greater than normal early formation of thrombus rather than proliferation of smooth muscle cells contributes to restenosis after coronary stenting in patients with diabetes mellitus.

Experimental evaluation of a short transitional edge protection balloon for intracoronary stent deployment.

The purpose of this study was to determine if balloon injury to the adjacent arterial wall during intracoronary stent deployment influences late in-stent neointimal formation. Stent design and deployment techniques are considered important factors in determining acute and long-term success with intracoronary stenting. Experimental and clinical studies support that the extent of neointimal formation and the probability for restenosis are influenced by the magnitude of arterial trauma induced with stenting. Nineteen 18-mm-long balloon-expandable stainless steel stents (MULTI-LINK Duet) were implanted at a 1:1 stent-to-artery ratio in the coronary arteries of swine with a conventional noncompliant balloon (n = 10) or a novel noncompliant balloon with short tapered shoulders to prevent edge dissection (n = 9). Quantitative coronary angiography and histology were used to evaluate balloon and artery interactions and the chronic vascular responses to the stents. Nineteen stents were implanted in the coronary arteries of seven swines at an inflation pressure of 14 atm using a standard noncompliant (n = 10) or a unique short transitional edge protection (n = 9) balloon. Histologic analysis at 28 days demonstrated balloon-associated barotrauma in 13 of 20 (65%) of adjacent nonstented arterial segments with the conventional balloon and only 3 of 18 (17%) of the adjacent nonstented arterial segments with the short transition edge protection balloon (P = 0.022). In-stent neointimal area and % stenosis correlated with the severity of peristent arterial injury (r = 0.43, P = 0.01). In-stent vessel injury scores were similar for stents with peristent injury (1.0+/-0.3) versus stents without peristent injury (1.0+/-0.03, P = 0.73). In-stent neointimal area and % stenosis were greater for stents with peristent injury (2.36+/-0.74 mm(2), 32%+/-9%) as compared to stents without peristent injury (1.39+/-0.70 mm(2), 20%+/-10%, P = 0.01). Arterial wall injury adjacent to a stent after high-pressure deployment contributes to late in-stent neointimal hyperplasia in this model. These experimental data suggest that further study is warranted to refine stent implantation techniques and that modifications of balloon shape or material may be useful to optimize stent deployment and reduce arterial trauma.

Resultados iniciales con el stent coronario Multi-Link

The Multi-Link intracoronary stent is a balloon-expandable stainless steel stent with an interconnected ring structure designed to provide a high degree of compressive resistance while preserving longitudinal flexibility. We present the results of our initial experience with the implantation of this stent. From May 1996 to April 1997, 124 Multi-link stents were implanted in 97 patients. Mean age 62.2 +/- 11 years. All patients included had a coronary artery diameter > 2.7 mm. Clinical presentation includes stable angina in 20, unstable angina in 72, and myocardial infarction in 5 patients. According to the ACC/AHA classification 6 lesions were type A, 72 type B and 19 type C. The implantation of the stent was for "de novo" lesions in 85 patients and for restenosis in 12. Patients were treated after the procedure with a combination of aspirin and ticlopidine, except six of them who received aspirin and acenocumarol. 16 patients were treated additionally with Abciximab. The degree of stenosis was determined by quantitative angiography. The delivery of the stent was successful in all patients. The degree of stenosis before the procedure was 79.6 +/- 13.1%, and after the stent deployment was 17.7 +/- 11.4%. Three patients presented a non-Q-wave myocardial infarction, two patients had a subacute stent thrombosis, one of them died due to heart failure. During a follow-up of 4.7 +/- 2.6 months five patients were readmitted with recurrent angina (4 due to restenosis and one for vessel occlusion) and one patient with heart failure after myocardial infarction died suddenly three weeks after the dilatation. The Multi-Link stent was implanted successfully in all patients with a low incidence of complications, showing at the follow-up a reduced rate of clinical restenosis.

Right ventricular outflow stent implantation: an alternative to palliative surgical relief of infundibular pulmonary stenosis.

OBJECTIVE: Preliminary assessment of the use of stents for palliative relief of right ventricular infundibular stenosis as an alternative to palliative surgical ventricular outflow enlargement. DESIGN: Descriptive clinical study. PATIENTS:...

Coronary stenting with a novel stainless steel balloon-expandable stent: Determinants of neointimal formation and changes in arterial geometry after placement in an atherosclerotic model

This study evaluated the delivery characteristics and vascular response to placement of a novel balloon-expandable stent in swine with experimentally induced atherosclerosis. The Multi-Link stent is a balloon-expandable stainless steel stent with an interconnected ring structure designed to provide a high degree of compressive resistance while preserving longitudinal flexibility. The placement characteristics and vascular response to this stent in atherosclerotic coronary arteries have not been characterized. We tested the delivery characteristics and vascular response to the Multi-Link stent in 19 miniature swine with experimentally induced coronary atherosclerosis created in 37 coronary artery segments by overstretch balloon injury and high cholesterol diet. Quantitative coronary angiography was used to define stent performance characteristics, such as lesion dilation and compressive resistance. Pathologic assessment of the stented arteries was used to evaluate the immediate and long-term vascular response to stent placement. Nineteen (95%) of 20 stents were successfully implanted in the left anterior descending (n = 11), left circumflex (n = 7) or right (n = 1) coronary artery. The baseline angiographic minimal lumen diameter of the stented coronary segment was 2.48 +/- 0.09 mm (reference diameter 2.87 +/- 0.06 mm, mean +/- SE) and increased to 2.82 +/- 0.05 mm (p < 0.001) after stent placement. The balloon-inflated stent diameter was 2.98 +/- 0.06 mm with minimal recoil to a final minimal lumen diameter of 2.82 +/- 0.06 mm at 15 min after implantation (p = 0.001). Angiographic and histologic follow-up at 72 h (n = 7), 14 days (n = 4) and 56 days (n = 8) demonstrated that all stents were patent, without evidence of migration, intraluminal filling defects or side branch occlusion. At 56 days, mean neointimal thickness was significantly greater at the stent wire sites in the region of the plaque where the media was absent than the stent wire sites, where the internal elastic lamina was intact with underlying normal media (0.48 +/- 0.01 vs. 0.27 +/- 0.02 mm, p < 0.0001). Compared with the nonstented atherosclerotic lesions, after 56 days the stented vessels had a mildly reduced lumen area when normalized to the proximal reference vessel (2.81 +/- 0.27 vs. 2.68 +/- 0.30 mm2, p = 0.07). The mean change in the area within the external elastic lamina relative to a normal proximal reference segment was significantly greater in stented vessels (1.45 +/- 0.34 mm2) than nonstented atherosclerotic vessels (0.44 +/- 0.28 mm2, p = 0.033). Morphologic data confirm that the principal beneficial effect of stent placement is vessel expansion and attenuation of constrictive remodeling. In vessels with eccentric atherosclerotic fibrocellular plaques, the presence of normal media underlying the stent determines the degree of neointimal formation. These data may be useful in understanding the mechanism of stent restenosis in patients with prior percutaneous transluminal coronary angioplasty.

Transluminally placed endovascular stented graft repair for arterial trauma

Purpose: Intravascular stents have become important tools for the management of vascular lesions; however, stents in combination with vascular grafts have only recently reached clinical application. This report describes an experience with stented grafts for the treatment of penetrating arterial trauma.Methods: Seven transluminally placed stented grafts were used to treat one arteriovenous fistula and six pseudoaneurysms. These grafts were successfully inserted percutaneously or through open arteriotomies that were remote from the site of vascular trauma. The devices were composed of balloon-expandable stainless steel stents covered with polytetrafluoroethylene grafts.Results: Patency up to 14 months was achieved (mean follow-up 6.5 months) with these stented grafts. The use of stented grafts appears to be associated with decreased blood loss, a less invasive insertion procedure, reduced requirements for anesthesia, and a limited need for an extensive dissection in the traumatized field. These advantages are particularly important in patients with central arteriovenous fistulas or false aneurysms who are critically ill from other coexisting injuries or medical comorbidities.Conclusions: The use of stented grafts already appears justified to treat traumatic arterial lesions in critically ill patients. Although the early results with the seven cases in this report are encouraging, documentation of long-term effectiveness must be obtained before these devices can be recommended for widespread or generalized use in the treatment of major arterial injuries.

Stenting of proximal venous obstructions to maintain hemodialysis access

The purpose of the study was to evaluate the efficacy of stenting central venous obstructions in patients dependent on hemodialysis to preserve or restore central venous patency and allow for continued hemodialysis from the affected side. Twenty-five self-expanding (17) and balloon-expandable (8) stainless steel stents were deployed in 19 patients with end-stage renal disease and central venous stenosis or occlusion. Nineteen lesions were treated: 11 subclavian and eight innominate. Twenty-two stents were initially implanted. Stent deployment was successful in all cases and immediately remedied the underlying cause of venous hypertension. Follow-up at up to 17 months revealed three deaths from unrelated causes, one occlusion at 3.25 months, and three restenoses at 16 days, 2.5 and 5 months, respectively, with successful implantation of three additional stents for a primary central patency rate of 68% (+/- 14%) and secondary central patency rate of 93% (+/- 7%). Stenting of subclavian and innominate venous stenoses and occlusions effectively corrected the underlying lesions responsible for disturbed hemodynamics and, in most cases, prolonged available hemodialysis access from the affected side. Stents seem to be valuable adjuncts in the management of failing hemodialysis access due to central venous stenosis or occlusion.

Self‐expandable stents for tracheal stenosis: Experience in two patients

Two patients with cervical tracheal stenosis, following prolonged ventilatory support, underwent balloon dilatation and expandable stainless steel stent placement across the stenoses. Following the successful release of the stent, there was gradual widening of the stenosed trachea in one patient, while in the other re-stenosis occurred due to columns of tracheal tissue projecting between the limbs of the stent. In the chronically ill and debilitated, use of expandable stents provides a good alternative to complex reconstructive surgery.

Stenting of a renal artery stenosis achieves better relief of the obstructive lesion than balloon angioplasty

A balloon-expandable (Palmaz-Schatz) stainless steel stent was utilized following balloon angioplasty (PTRA) to determine if the obstructive lesion, using quantitative methods (automated measuring the diameter stenosis, and transstenotic peak systolic and mean pressure gradients), was significantly further reduced or abolished. Hemodynamic transstenotic gradient and stenoses measurements were made during 21 renal artery stenting procedures; prior and following PTRA, and subsequent to stent deployment. The stent sizes placed in the renal arteries were 5 mm (19%), 6 mm (67%), and 7 mm (14%). The results were as follows: [table: see text] The balloon-expandable (Palmaz-Schatz) stent significantly further reduced, and in fact effectively abolished, the obstructive renal artery lesion in comparison to balloon angioplasty (PTRA). The stent's effectiveness with regard lesion recurrence, maintenance, and preservation of renal function; cure or improved management of hypertension; and survival will be determined by careful clinic follow-up.

Balloon-expandable stent treatment of experimental coarctation of the aorta: early hemodynamic and pathological evaluation.

The present study was intended to evaluate the acute and short-term hemodynamic, angiographic, and pathological response to balloon-expandable stent treatment of experimental coarctation of the aorta. A discrete thoracic coarctation was surgically created in six mongrel dogs (two adults, four puppies). Two months postoperatively all six dogs (8.9-30 kg) underwent left heart catheterization and coarctation stenting performed through a femoral artery cutdown. A Palmaz PS-30 stent was advanced to the coarctation through a 10 French sheath, and expanded with an angioplasty balloon chosen to equal the diameter of the proximal aorta (9-12 mm). Stent implantation was successful in each dog. The systolic pressure gradient decreased from 26.3 +/- 9.1 mmHg (mean +/- SE) to 0.5 +/- 0.5 mmHg (P = 0.04), and the coarctation diameter improved from 50 +/- 6% to 82 +/- 6% of the diameter of the proximal descending aorta (P less than 0.01). Follow-up catheterization 4-7 weeks after stenting documented no stent migration, early restenosis, thrombosis, obstruction of arterial side branches, or aneurysm formation. Pathological evaluation of the explanted segments of stented aorta documented that by 6-7 weeks the stents are covered by a neointima composed of intimal proliferation and fibrosis with an endothelial cell surface. These data suggest that balloon-expandable stainless steel stents provide excellent acute and short-term relief of coarctation in this experimental model. Larger and longer-term studies are needed to better assess the incidence of restenosis or aneurysm formation following stenting of coarctation of the aorta.

Direct deployment of the iliofemoral balloon expandable (Palmaz) stent utilizing a small (7.5 French) arterial puncture.

A new, smaller (7.5F) stent delivery sheath system is described for deployment of the iliofemoral large balloon expandable (Palmaz) stainless steel stent which allows a brachial or ipsilateral retrograde femoral or popliteal approach. The procedure described does not require predilatation of the lesion prior to stent deployment.

Use of Balloon-expandable stents to treat experimental peripheral pulmonary artery and superior vena caval stenosis: Preliminary experience

Current therapy of congenital or acquired stenoses of the peripheral pulmonary arteries and superior vena cava are frequently ineffective. This report describes our initial experience with the use of a balloon-expandable stainless steel stent to treat experimentally created branch pulmonary artery and superior vena cava stenosis. Fifteen adult mongrel dogs had surgically created stenoses of either a branch pulmonary artery and/or superior vena cava. A balloon-expandable stainless steel (0.076 mm), 3 cm long, intravascular stent was used in all animals. Stents were successfully placed in 13 of 15 dogs (nine with branch pulmonary stenosis and four with superior vena caval stenosis) with hemodynamic and angiographic relief of the stenoses in all. In three animals, successful stent placement was not accomplished because the distal right pulmonary artery was found to be totally obstructed in two and in one dog with combined vena cava and pulmonary stenosis the distal right pulmonary artery was so severely stenotic that the stenosis could not be crossed. Repeat catheterization performed 6 months following stent placement documented persistent gradient relief and angiographic evidence of unobstructed flow through the stent without thrombus formation and with patent side branch vessels. Our preliminary results suggests that balloon-expandable stents are a potential therapy for the treatment of branch pulmonary artery and superior vena cava stenoses.

Redilation of balloon expandable stainless steel stents placed in the branch pulmonary arteries of dogs

Redilation of balloon expandable stainless steel stents placed in the branch pulmonary arteries of dogs