[Experimental research with a new percutaneously insertable and expandable vascular prosthesis]

Balloon angioplasty, stenting, and role of atherectomy

Endovascular interventions for the treatment of lower-extremity atherosclerotic disease have undergone a rapid course of development during the past 30 years. Balloon angioplasty is the most widely applied of these techniques and has been shown to yield excellent results, at least in the short and intermediate terms, in appropriately selected patients. The ideal candidate is one with a focal stenotic lesion of the iliac artery; this is also the type of patient in whom placement of an endoluminal stent, whether primarily or as an adjunct to balloon angioplasty, has been shown to be most effective. The initial enthusiasm for transluminal atherectomy of lower-extremity atherosclerotic lesions has met with some disappointing long-term results. It is now used mainly in conjunction with either or both of the above modalities in a select group of patients. Clearly, more controlled studies of all these techniques are needed to better define their exact indications and limitations in treatment of lower-extremity arterial disease.

Strength, elasticity, and plasticity of expandable metal stents: in vitro studies with three types of stress

PURPOSE

Five types of expandable metal stents (Palmaz, Strecker, Gianturco, Cragg, and Wallstent) were subjected to standardized tests to obtain objective, comparable data of their mechanical characteristics.

MATERIALS AND METHODS

The stents were subjected to area loads, point loads, and circular loads; the resistance of the stents to a continually increasing deformation was measured. Elasticity and deformation characteristics of the stents were also noted. Another experiment simulated the situation of the stent in an implanted state. The stents were covered with a thin self-adhesive foil to simulate optimal wall contact by limiting the mobility of the mesh struts.

RESULTS

For all types of stress, the Palmaz stent showed the highest resistance but was completely inelastic. The Strecker stent and the Wallstent showed higher resistance when coated in foil (simulating good wall contact). The Gianturco stent showed the lowest resistances but was completely elastic. A point load on a Wallstent caused concentric constriction over a longer distance.

CONCLUSIONS

Palmaz stents are appropriate for insertion into highly resistant obstructions. Strecker stents and Wallstents require good wall contact to achieve adequate strength. Because of their unique deformation characteristics, Wallstents may not function well if implanted into eccentric stenoses of tough consistency. The Gianturco stent showed the lowest resistances.

Historical overview on the development and characteristics of stents and future outlooks

The history and development of endovascular stents is described beginning with the Maass double helix spiral prosthesis, the first stent used in human clinical trials in the early 80s. This is followed by a description of the three main groups of stent techniques: the shape memory alloy stents, the balloon-expandable stents, and the self-expanding stainless steel stents. Requirements and new trends for improving clinical results in the future complete this text.

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.

Intravascular stents. Status of development and clinical application

A variety of intravascular stents are currently under investigation and in various stages of achieving governmental approval for clinical application. The Palmaz balloon-expandable stent has recently been approved for use in the iliac arteries based on specific indications for application. Stents are generally described according to their method of deployment and are either balloon-expandable or self-expanding. Clinical application has been proved in the iliac arteries, where the use of stents has greatly enhanced the treatment of patients with total occlusions, complex dissections, and restenoses. Additionally, there is promise that stents will enhance the percutaneous treatment of renal artery ostial lesions, infrainguinal arterial lesions, and strictures in large veins. Clearly, the increasing application of intravascular stents has ushered in a new era of percutaneous intervention.