Conceptually, a stent’s design and architecture are based on the underlying rationale of providing adequate endoluminal scaffolding support of recanalized vascular conduit for a desired period of time, with minimally possible obstruction of normal circulatory flow and propensity to reocclusions associated with healing processes or other plausible causes. Stenting device designs also tend to reflect etiological and anatomical specifics of the targeted occlusive conditions and indications, characteristics of preferred device materials, and technical capabilities of existing manufacturing tools and technologies.
Common Peripheral Vascular Metal Stent Designs. The vast majority of peripheral vascular stents on the market (which are usually made of metal structural materials) typically feature one of three basic designs: slotted tube, wire mesh, or flattened coil/spiral. The same basic designs are used in non-vascular metallic stents, which in many instances constitute a line extension of corresponding vascular systems.
The most popular slotted tube stents – which are cut from tubular metal structures with computer-guided laser and electropolished – are available in several design sub-types including closed-cell flexsegment, open-cell multilink and micromesh versions. Generally, all slotted tube stenting devices combine good radial strength, relatively even distribution of scaffolding support, and minimal foreshortening, and compatibility with low profile delivery systems. The closed-cell flexsegment architecture (usually featuring circumferentially distributed hexagonal, heart, or diamond-shaped cells with one or more common sides) offers enhanced scaffolding and relative lesion coverage at the expense of longitudinal flexibility and kink resistance. open-cell multilink design (with sinusoidal ring-segments and evenly spaced co-axial links/ connectors) provides significantly better longitudinal flexibility (particularly with the use of corrugated links) and more even endoluminal support which come at a price of reduced stent to lesion surface ratio and reduced radiopacity. The micromesh configuration (representing a high-density hybrid version of the close-cell flexsegment and open-cell multilink architectures, with larger number of smaller zigzag cells per ring and closely linked ring segments) approximates the advantageous features of the both designs by offering significant improvement in flexibility over the former one better stent-to-vessel/lesion ratio compared to the latter one.
The wire mesh – featuring unrestricted diamond-shaped cells formed by one or several diagonally interwoven (braided) wire filaments – is arguably the oldest type of metal stent design. High stent-to-vessel/lesion surface ratio, good conformability and even scaffolding, along with technological simplicity and relatively low manufacturing cost constitute the primary benefits of braided wire mesh stenting devices. Unfortunately, such devices are also characterized by a mediocre radial strength, very significant (up to 15%) foreshortening, and poor kink resistance, which radically undercut their utility in critical indications.
Coil or spiral stents (which could be configured as a single or double helix with a flat or flattened wire struts) theoretically offer the best combination of radial strength and longitudinal flexibility. However, spiral devices are also characterized by significant foreshortening, propensity to recoil, and uneven scaffolding support in bended or bending circulatory conduits.
Comparative Advantages and Drawbacks of Most Common Stenting Device Designs
See “Global Market Opportunities in Peripheral Arterial and Venous Stents, Forecast to 2020”, Report #V201. Details.