Stents wrapped in autologous vein: an experimental study

Coronary covered stents

Covered stents offer an effective bail-out strategy in vessel perforations, are an alternative to surgery for the exclusion of coronary aneurysms, and have a potential role in the treatment of friable embolisation-prone plaques. The aim of this manuscript is to offer an overview of currently available platforms and to report results obtained in prior studies.

Fabrication of Small Caliber Stent-grafts Using Electrospinning and Balloon Expandable Bare Metal Stents

Stent-grafts are widely used for the treatment of various conditions such as aortic lesions, aneurysms, emboli due to coronary intervention procedures and perforations in vasculature. Such stent-grafts are manufactured by covering a stent with a polymer membrane. An ideal stent-graft should have a biocompatible stent covered by a porous, thromboresistant, and biocompatible polymer membrane which mimics the extracellular matrix thereby promoting injury site healing. The goal of this protocol is to manufacture a small caliber stent-graft by encapsulating a balloon expandable stent within two layers of electrospun polyurethane nanofibers. Electrospinning of polyurethane has been shown to assist in healing by mimicking native extracellular matrix, thereby promoting endothelialization. Electrospinning polyurethane nanofibers on a slowly rotating mandrel enabled us to precisely control the thickness of the nanofibrous membrane, which is essential to achieve a small caliber balloon expandable stent-graft. Mechanical validation by crimping and expansion of the stent-graft has shown that the nanofibrous polyurethane membrane is sufficiently flexible to crimp and expand while staying patent without showing any signs of tearing or delamination. Furthermore, stent-grafts fabricated using the methods described here are capable of being implanted using a coronary intervention procedure using standard size guide catheters.

Novel stents for the prevention of restenosis

Since the introduction of Interventional Cardiology in 1976, there has been rapid expansion both in its clinical application and the tools of the trade. This growth was accelerated with the introduction of the intra-coronary stent in 1987. The demonstration that stents may reduce the incidence of restenosis after percutaneous coronary revascularization has further stimulated the search for the perfect endovascular prosthesis. By creating a hybrid stent, incorporating natural coatings and local drug delivery in the design, it is hoped that the complications associated with stent thrombosis and restenosis can be eradicated. (Trends Cardiovasc Med 1997;7:245-249). © 1997, Elsevier Science Inc.

Coronary stents and the uptake of new medical devices in the German system of inpatient reimbursement

OBJECTIVES

This study aims to analyze mechanisms for facilitating the uptake of new medical devices in the German system of hospital reimbursement, focusing on the example of coronary stents, including (1) trends in their coding, (2) associated diagnosis-related group (DRG) payments, (3) their integration in the German DRG (G-DRG) system, and (4) their diffusion within the inpatient sector.

METHODS

Published and gray literature provide the basis for analyzing the system of hospital reimbursement. Data on coronary stents were obtained from various regulatory and government bodies and examined in a longitudinal fashion.

RESULTS

Although German Procedure Classification (Operationen- und Prozedurenschlüssel; OPS) codes were created for a range of stent technologies between 2004 and 2009, the regular system of G-DRG reimbursement does not distinguish between different stents by means of unique DRGs. Instead, supplementary payments or extrabudgetary payments are used to ensure that newer technologies are reimbursed adequately. The limitations of extrabudgetary payments restrict the use of some devices to a small proportion of patients. Data on the diffusion of different stents show that factors other than the reimbursement regime likely also play a role in the frequency with which certain technologies are used. Bare metal stents currently account for most stent implantation procedures in Germany, followed by drug-eluting stents.

CONCLUSION

The current system of G-DRG reimbursement and of extrabudgetary payments ensures that even the most recently developed technologies can be used in the German inpatient sector. Nevertheless, certain technologies may not be reaching the broad patient population.

Eight-year clinical and angiographic follow-up after implantation of autologous arterial graft covered stent in a de novo thrombus-containing lesion

In this case report, we present the clinical and angiographic follow-up 8 years after implantation of autologous arterial graft covered stent in a thrombus-containing lesion in the proximal segment of left anterior descending artery. The patient was asymptomatic after the implantation of the covered stent until 2 months prior to the coronary angiography. In the repeat angiography, the left anterior descending artery was patent at the site of the covered stent implantation. At the proximal and distal sites of the covered stent, there was no restenosis. In this case report, there were no long-term technique-related complications after the successful autologous arterial covered stent deployment.

Endovascular Delivery of Vein Segments With Valves Versus Direct Anastomosis

PURPOSE

To demonstrate an experimental model designed to allow placement of a vein segment containing a valve into a femoral vein without the need for anastomoses or surgical incision on the target limbs.

METHODS

Segments of jugular veins containing valves were harvested bilaterally from 7 female dogs weighing 30 to 40 kg. One of the vein segments was then interposed into one femoral vein, using a standard surgical end-to-end anastomosis. Another segment was loaded into a self-expanding nitinol stent, everted, and secured outside of the stent. This vein-coated stent was then deployed from the jugular approach into the opposite common femoral vein. The endpoint of the study was thrombosis of one of the veins segments or patency at 120 days. The function of the valves was tested prior to completion of the study by instilling dye under incremental pressures and recording the pressure necessary to cause reflux. Light microscopy and electron microscopy were utilized to evaluate structure of the valves at study endpoint.

RESULTS

Both grafts in one dog occluded during the second week after surgery. Anastomotic and vein-stented sites remained patent in the remaining 6 animals for 120 days. Retrograde phlebography demonstrated valve competency bilaterally in all cases. The reflux pressures on the stented side averaged 70 mmHg while the transplanted vein segment averaged 55 mmHg. Light microscopy and electron microscopy showed intact vein valve structure in all segments at the completion of the study.

CONCLUSIONS

This experimental work demonstrates that endovascular delivery of a native canine vein containing a competent valve is feasible and effective.

New stent design for autologous venous graft-covered stent preparation: first human application for sealing of a coronary aneurysm

In this case report, we present the first clinical application of a new stent design for autologous venous graft-covered stent preparation. This stent consists of a main body, resembling the configuration of conventional stents, and two connecting arms at the edges of the stent for the stabilization of the venous graft on the external surface of the stent. This new stent design was applied in a patient with an aneurysm in a stented segment in the right coronary artery. The immediate and long-term angiographic evaluation after the covered stent implantation showed complete sealing of the aneurysm without restenosis.

Successful long-term therapy following saphenous vein-covered stent deployment for atherosclerotic coronary aneurysm

We describe a case of atherosclerotic aneurysm involving the left main coronary artery in a patient with prior coronary artery bypass surgery. A saphenous vein-covered stent was used to seal the aneurysm in conjunction with conventional stenting of an associated native vessel coronary stenosis. Focal late restenosis involving the stent graft was successfully treated with repeat angioplasty and brachytherapy. Autologous vein-covered stent deployment should be considered in the treatment of symptomatic or progressively enlarging coronary aneurysms.

Transjugular intrahepatic portosystemic shunt with an autologous vein-covered stent: results in a swine model

PURPOSE

To investigate the feasibility, safety, and efficacy of an autologous vein-covered stent (AVCS) to prevent shunt stenosis in a porcine transjugular intrahepatic portosystemic shunt (TIPS) model.

MATERIALS AND METHODS

TIPS were created with an AVCS in 12 healthy domestic swine and with a bare stent in 10 additional swine. Tissue response was compared with use of venography, histology, and computerized morphometry analysis 2 weeks after implantation. Differences between AVCS and noncovered stents (established by a t-test), as well as regional differences within a single stent (established by an f test), were considered significant at P <.05.

RESULTS

Twenty of 22 TIPS procedures were technically successful. Ten of 12 shunts with an AVCS (83%) and two of 10 with bare stents (20%) remained patent (<50% diameter narrowing) at euthanasia 2 weeks later (P <.01). Histologic evaluation of harvested bare stents showed marked intimal hyperplasia (IH), composed of smooth muscle cells, myofibroblasts, and fibroblasts. In contrast, the AVCS were remarkably free of IH and thromboses. In patent TIPS in both groups, endothelial coverage of the luminal surface was present histologically. IH accounted for 57% (26.27/45.79) of total stent cross-sectional lumen area in the control group and 21% (8.34/39.54) in the AVCS group (P <.01), with no intrashunt differences (P >.05).

CONCLUSION

Based on short-term follow-up, AVCS significantly improved TIPS patency by prevention of both IH and in-stent thrombosis. TIPS created with an AVCS was feasible and safe in our porcine model.

Successful closure of coronary artery perforation using makeshift stent sandwich

An elderly woman underwent stenting of mid left anterior descending coronary artery (LAD) 2 days after myocardial infarction. During high-pressure stent dilatation, vessel perforation was noted. We assembled a "stent sandwich" in the cardiac catheterization laboratory and used it successfully to seal the perforation with good angiographic result. Although the long-term patency remains an issue, this case demonstrates the feasibility of using makeshift covered-stent as a bailout for arterial perforation in selected cases where emergency thoracotomy is undesirable.

The polytetrafluoroethylene-covered stent: a device with multiple potential advantages

The polytetrafluoroethylene (PTFE)-covered stent has emerged in the past year as a device with multiple potential advantages. Its structure (a sandwich composed of a layer of PTFE membrane between two stents) makes this the ideal tool for treating coronary ruptures, and for excluding coronary aneurysms. Furthermore, this device may be useful in the treatment of aortocoronary vein graft stenosis. In the present review, the authors summarize experiences with covered stents, and focus attention on available data on the implantation of PTFE-covered stents in human beings to treat coronary ruptures, aneurysms and aortocoronary vein graft stenosis.

Coronary perforation during percutaneous coronary intervention in the era of abciximab platelet glycoprotein IIb/IIIa blockade: an algorithm for percutaneous management

Coronary perforation is an uncommon but potentially life-threatening complication of percutaneous coronary intervention. The use of both atheroablative technologies for coronary intervention and adjunctive platelet glycoprotein blockade pharmacology may increase the incidence of or risk for life-threatening bleeding complications following the occurrence of coronary artery perforation. The interventional database for 6,214 percutaneous coronary interventions performed between January 1995 and June 1999 was analyzed. Hospital charts and cine angiograms for all patients identified in the database as having had coronary perforation were reviewed. Coronary perforation complicated 0.58% of all procedures and was more commonly observed in patients with a history of congestive heart failure and following use of atheroablative interventional technologies (2.8%). There was no association of abciximab therapy with either the incidence of or classification for coronary perforation. Adverse clinical outcomes (death, emergency surgical exploration) were related to the angiographic classification of perforation and were more frequently observed in patients who experienced a class 3 coronary perforation. These data suggest that specific clinical and procedural demographic factors are associated with the occurrence and severity of angiographic coronary perforation. An angiographic perforation class-specific algorithm for treatment of coronary perforation is proposed.

Stents covered by autologous venous grafts: feasibility and immediate and long-term results

BACKGROUND

Previous experimental studies with a new covered stent, the autologous venous graft-covered stent (AVGCS), have shown favorable results. The aim of this study was to evaluate the feasibility and safety of this new technique in human coronary arteries and to compare the long-term outcome with uncovered stents.

METHODS AND RESULTS

A venous graft was removed from an upper limb. A conventional stent then was covered by the venous graft. Fifty-eight AVGCS were implanted in 56 patients, including 16 patients with acute coronary syndromes (ACS). Additionally, in 114 patients, 138 uncovered stents were implanted, serving as a control group, including 38 patients with ACS. The procedure was successful in all patients. Stent thrombosis was observed in 3 patients in the control group and in 1 patient with an AVGCS. There was a trend for the minimal luminal diameter to be greater in the AVGCS group at follow-up (P =.07), and statistical significance was observed in patients with ACS (P <.01). The target vessel revascularization and the restenosis rates were similar between the 2 groups. In patients with ACS, the restenosis rate was less (P <.04) and there was a trend for target vessel revascularization to be less in covered stents (P =.09). The event-free survival rate at 4 years was 85% in the AVGCS group versus 81% in the control group (P = not significant); in ACS it was 94% versus 78%, respectively (P = not significant). Stents covered by thicker venous grafts were associated with improved clinical outcome.

CONCLUSIONS

Stents covered by autologous venous grafts may be safely prepared without complications. This technique may prove to be a useful means, especially in patients with ACS.

Early clinical experience with the implantation of a novel synthetic coronary stent graft

Coating stents with autologous venous grafts has been suggested to prevent problems associated with conventional stenting, but the need for surgical vessel harvest hampered broad application. A novel synthetic coronary stent graft (CSG) overcomes this limitation by a synthetic membrane, fixed between two thin metallic stents. We successfully implanted 21 CSGs in 18 patients for treatment of acute coronary rupture, thrombus-containing lesions, and lesions with plaque rupture or adjacent pseudoaneurysm. Substantial residual angiographic diameter stenoses were seen in seven CSGs (25% +/- 10% vs. 8% +/- 6%; P < 0.01), which were implanted with relatively small balloon catheters (balloon-to-artery ratio 1.00 +/- 0.09 vs. 1.24 +/- 0.18; P = 0.01) and required postdilatation. Overall, the largest balloon catheter applied measured 4.0 +/- 0.7 mm (balloon-to-artery ratio 1.21 +/- 0.20) and the inflation pressure was 16 +/- 3 atm. Final intravascular ultrasound imaging demonstrated adequate and symmetrical expansion of the CSG (> or = 85% +/- 15% of the reference lumen). Elective implantation was associated with two small non-Q-wave myocardial infarctions, resulting from unavoidable occlusions of side branches. Thus, implantation of CSG is feasible and safe. Adequate expansion can be achieved by the use of relatively large low-compliant balloon catheters inflated with high pressure.

Immediate results and dilatation effect of the vein-covered Palmaz-Schatz stent assessed by intravascular ultrasound

To evaluate the clinical results of stenting using the vein-covered Palmaz-Schatz (PS) stent by intravascular ultrasound (IVUS). Twenty-eight patients with angina pectoris or confirmed ischemia were entered into this study. Thirteen were allocated to the vein-covered PS stent group and 15 to the normal Palmaz-Schatz stent group. The immediate clinical results in these groups and changes in lumen dimension as assessed by IVUS, were investigated. Acute success was 100% in both groups. There were no immediate complications. Subacute thrombosis occurred in one patient in the vein-covered PS group. In the vein-covered PS group, percent diameter stenosis of the involved coronary artery changed from 70.2% before stenting to 8.8% immediately after and 42.2% at 5 months follow-up. The respective values were 84.5%, 13.4%, and 36.5% in the normal Palmaz-Schatz group. Restenosis in the vein-covered group was 23.1% and in the Palmaz-Schatz group was 20%, showing no significant differences between the two groups. The luminal area in the vein-covered group as assessed by IVUS increased from 3.2 mm2 to 7.4 mm2 (pre to post) and from 3.2 mm2 to 8.2 mm2 in the normal Palmaz-Schatz group. The plaque area decreased from 13.6 mm2 to 10 mm2 (pre to post) in the vein-covered group and from 13.0 mm2 to 9.2 mm2 in the Palmaz-Schatz group. In this study, conducted in a limited number of cases, it is possible to use vein-covered stent like as usual Palmaz-Schatz stent. The vein-covered stent had less dilative effect compared with the Palmaz-Schatz stent. This was probably because of its increased profile but there was no difference in the occurrence of subacute thrombosis or in restenosis rate.

Fibrin-film stenting in a porcine coronary injury model: efficacy and safety compared with uncoated stents

OBJECTIVES

This study was designed to test the efficacy and safety of a fibrin-film-covered stent compared with that of a bare metal stent in the porcine coronary injury model.

BACKGROUND

Biodegradable stents are a potential method of achieving total lesion coverage and delivering local, lesion-specific drug therapy.

METHODS

Two coronary arteries in each pig were randomly assigned to deployment of either a fibrin-film or a bare tantalum wire-coil stent. An oversized balloon injury, 1.15 to 1.30 times the reference vessel diameter, was induced in each coronary segment before stenting to simulate angioplasty injury. Thirty pigs were studied: group 1 for 28 days (15 pigs); group 2 for 90 days (5 pigs); group 3 for 6 months (5 pigs); group 4 for 1 year (5 pigs).

RESULTS

Two pigs died of occlusion of the bare stent and one of occlusion of the fibrin stent (p > 0.99). There were no significant differences between the fibrin-stented and bare-stented coronary segments with regard to arterial injury. In group 1 (28 days, 14 pigs), the mean neointimal thicknesses in the fibrin-stented and bare-stented groups were 0.57+/-0.31 and 0.57+/-0.27 mm, respectively (p=0.89). In groups 2 to 4 (90 days, four pigs; 6 months, four pigs; 1 year, five pigs), the mean neointimal thicknesses for fibrin- and bare-stented coronary segments at the times studied were 0.48+/-0.26 versus 0.50+/-0.22 mm at 90 days; 035+/-0.04 versus 0.35+/-0.16 mm at 6 months; and 0.33+/-0.14 versus 0.30+/-0.14 mm at 1 year (p=0.98).

CONCLUSIONS

Fibrin-film stents appear to be an excellent candidate for local drug delivery because they can completely and safely cover the stented coronary segment while degrading slowly over 1 to 3 months. This result is important when compared with the poor results of previous studies of synthetic polymer stents.

Percutaneous closure of a coronary aneurysm with a vein-coated stent

Coronary artery aneurysm is a rare but recognized complication following percutaneous intervention. We report the formation of such an aneurysm after recanalization with Excimer laser wire of a chronic totally occluded left anterior descending coronary artery and stent implantation and its subsequent treatment using an autologous vein graft-coated stent.

Total reconstruction of a diseased saphenous vein graft by means of conventional and autologous tissue-coated stents

This is the first report of a total reconstruction of a diseased saphenous vein graft, with thrombus-containing lesion and multiple stenoses, by the implantation of arterial graft- and venous graft-coated stents, and of conventional stents. The procedure was successful without any complications, and follow-up angiography after 6 months revealed patency of the vessel.

Saphenous vein covered stenting for right coronary artery lesion containing thrombus

Vein covered stenting to close coronary pseudoaneurysm and perforation and in the setting of acute myocardial infarction have been described. This case report describes saphenous vein covered stenting to exclude a large thrombus in a right coronary artery lesion. Vein covered stenting may be considered as an option when dealing with a thrombus containing lesion.

Arterial autologous graft-stent for treatment of coronary artery disease: a new technique

The radial artery has been used as a free bypass graft with excellent results. An autologous vein graft-coated stent, a novel type of stent developed at our institution, has been applied successfully under both experimental and clinical conditions. To extend the spectrum of biological linings for coated stents, we used an arterial graft. We describe the first application of the radial artery as an autologous coating for a conventional stent to be used in treatment of coronary artery disease.

Autologous vein graft-coated stents for the treatment of thrombus-containing coronary artery lesions

Recent studies have shown that stents may have a potential role in the treatment of thrombus-containing lesions. We report on the application of an autologous vein graft-coated stent (AVGCS) as the primary therapeutic modality for acute myocardial infarction in 10 patients. AVGCS delivery and deployment were successful and uneventful. Mean minimal lumen diameter and TIMI trial flow grade increased significantly (from 0.04 +/- 0.09 mm pre-AVGCS to 3.02 +/- 0.32 mm post-AVGCS, and from 10 patients with flow grade 0-1 pre-AVGCS to 10 patients with flow grade 3 post-AVGCS, respectively). Ten-day angiogram revealed maintenance of the immediate results. Nine patients had a negative exercise stress test 2 mo post-AVGCS, and at a mean follow-up of 30 +/- 7 weeks, all 9 were symptom-free. One patient, 3 wk after implantation and while being hospitalized for hypovolemic shock, developed recurrent infarction. These favorable preliminary outcomes suggest that AVGCS may play a useful role in the treatment of thrombus-containing lesions.