Long-Term Histopathologic and IVUS Evaluations of a Novel Coiled Sheet Stent in Porcine Carotid Arteries

Neointimal hyperplasia after stent placement across size-discrepant vessels in an animal study

PURPOSE

To examine differences in neointimal hyperplasia (NIH) after placing a self-expanding (SE) stent across size-discrepant vessels.

MATERIALS AND METHODS

The subjects were 6 beagles, and the target vessels were the abdominal aorta and the external iliac artery (EIA). A nitinol SE stent was placed which was normal-sized in the aorta and oversized in the EIA. Angiography and intravascular ultrasound (IVUS) were performed immediately and after 1 and 3 months; histopathologic examinations were then performed. Furthermore, the chronic outward force (COF) on the same type of stent was investigated in vitro.

RESULTS

On IVUS, thickened intima was seen on the EIA at 1 month (5.1 ± 4.2 mm(2)) and at 3 months (7.8 ± 2.5 mm(2)). For the aorta, thickening of the intima was negligible at any time. Histopathologically, the percentage of the vessel obliterated by NIH was significantly greater on the iliac side than on the aortic side (33.2 ± 10.4 vs. 13.4 ± 4.4 %). The COF exerted when stent diameter reached that of the EIA and the aorta was 0.73 and 0.17 N/mm(2), respectively.

CONCLUSIONS

When a non-tapered stent is placed in vessels with a large discrepancy in diameter, attention must be paid to increased NIH in the oversized side.

New possibilities in the endovascular treatment of supraaortic vessels

Cerebrovascular disease, including stroke, represents the third-leading cause of death in Hungary and a leading cause of disability among the elderly population. The majority of all strokes are ischemic, mostly secondary to thromboembolic disease of the supraaortic vessels. We investigated new therapeutic methods in the endovascular treatment of these diseases. Surgical revascularization of supraaortic trunk stenosis is associated with high morbidity and mortality rates. Balloon angioplasty has become an increasingly accepted treatment of stenoocclusive supraaortic arterial disease. Natural history data and treatment guidelines do not exist for innominate and proximal common carotid artery lesions. We have confirmed in a large series of innominate artery angioplasties that it is a safe and effective procedure with an excellent initial success rate, with a lower complication rate than the surgical option and with a similar long-term patency rate as for surgery.

In the largest published study on transfemoral angioplasty of ostial and proximal common carotid artery stenosis we have proved that endovascular treatment has high success rate with low stroke/death rate. Carotid stenting (CAS) is an evolving alternative to surgery in the treatment of patients with carotid stenosis. Stent selection is influenced by several factors, including the carotid anatomy and lesion characteristics. We examined the wall adaptability of a new closed-cell carotid stent (NexStent), which was designed for carotid bifurcation treatment. Data obtained from angiographic and computed tomographic images indicate that the stent provides adequate expansion and adaptation to the carotid bifurcation.

There are two types of restenosis after carotid artery interventions: the early restenosis develops mainly within the first 24 months after the revascularization procedure and its pathological background is myointimal hyperplasia; on the other hand late restenosis is rather due to progression of primary atherosclerosis and occurs more than 2 years after carotid endarterectomy (CEA). We compared the early restenosis rate in a consecutive series of CAS versus CEA patients at a single cardiovascular institution. The data suggest that the incidence of restenosis after stenting was less common than after surgery.

Our results may help vascular surgeons and interventional radiologists to consider risk versus benefit when deciding treatment options for supraaortic arterial stenosis.

Coronary stents: looking forward

Despite all the benefits of drug-eluting stents (DES), concerns have been raised over their long-term safety, with particular reference to stent thrombosis. In an effort to address these concerns, newer stents have been developed that include: DES with biodegradable polymers, DES that are polymer free, stents with novel coatings, and completely biodegradable stents. Many of these stents are currently undergoing pre-clinical and clinical trials; however, early results seem promising. This paper reviews the current status of this new technology, together with other new coronary devices such as bifurcation stents and drug-eluting balloons, as efforts continue to design the ideal coronary stent.

Intravascular ultrasound: principles and cerebrovascular applications

Intravascular sonography is a valuable tool for the morphologic assessment of coronary atherosclerosis and the effect of pharmacologic and nonpharmacologic interventions on the progression or stabilization of atherosclerosis. An analysis of the different modes, applications, and limitations is provided on the basis of review of existing data from multiple clinical case studies, trials, and mechanistic studies. Intravascular sonography has been used to assess the outcomes of different percutaneous interventions, including angioplasty and stent implantation, and to provide detailed characterization of atherosclerotic lesions, aneurysms, and dissections within the cerebrovascular circulation. Evolution of intravascular sonographic technology has led to the development of more sophisticated diagnostic tools such as color-flow, virtual histology, and integrated backscatter intravascular sonography. The technologic advancement in intravascular sonography has the potential of providing more accurate information prior, during, and after a medical or endovascular intervention. Continued assessment of this diagnostic technique in both the intracranial and extracranial circulation will lead to increased use in clinical practice with the intent to improve outcomes.

High-resolution CT and angiographic evaluation of NexStent wall adaptation

Carotid stenting is a minimally invasive treatment for extracranial carotid artery stenosis. Stent design may affect technical success and complications in a certain subgroup of patients. We examined the wall adaptability of a new closed-cell carotid stent (NexStent), which has a unique rolled sheet design. Forty-one patients had 42 carotid arteries treated with angioplasty and stenting for internal carotid artery stenosis. The mean patient age was 65 +/- 10 years. All patients underwent high-resolution computed tomographic angiography after the stent implantation. Data analysis included pre- and postprocedural stenosis, procedure complications, plaque calcification, and stent apposition. We reviewed the angiographic and computed tomographic images for plaque coverage and stent expansion. All procedures were technically successful. Mean stenosis was reduced from 84 +/- 8% before the procedure to 15.7 +/- 7% after stenting. Two patients experienced transient ischemic attack; one patient had bradycardia and hypotension. Stent induced kinking was observed in one case. Good plaque coverage and proper overlapping of the rolled sheet was achieved in all cases. There was weak correlation between the residual stenosis and the amount of calcification. The stent provides adequate expansion and adaptation to the tapering anatomy of the bifurcation.