A covered stent is a specialized medical device used in vascular procedures to treat conditions affecting blood vessels. Unlike other types of stents, it features a metallic mesh framework enveloped by a fabric-like covering. This design provides structural support to a weakened or damaged blood vessel while also creating a sealed barrier. It is typically deployed minimally invasively through a catheter.
Anatomy and Function
A covered stent consists of a metal scaffold, often stainless steel or cobalt-chromium, which provides the radial strength necessary to keep a vessel open. This metallic structure is covered with a thin, impermeable material like expanded polytetrafluoroethylene (ePTFE), polyester, polyurethane, or silicone. ePTFE is common due to its thin profile, flexibility, and biocompatibility, while polyester is noted for its strength and tissue integration.
The covering creates a physical barrier between blood flow and the vessel wall or surrounding tissue. This barrier prevents tissue growth into the stent (neointimal hyperplasia), which can lead to re-narrowing of the vessel. The cover also seals off leaks or tears in the vessel wall. This sealing capability is important in urgent situations, such as vessel perforations, where immediate containment of blood is necessary.
Primary Applications
Covered stents are specifically employed in medical situations where sealing or exclusion of a vascular segment is important. One significant application is the treatment of arterial aneurysms, which are bulges in a blood vessel wall that can rupture. The covered stent is positioned to exclude the aneurysm from the main blood flow, reducing pressure within the weakened sac and preventing rupture. This mechanism effectively diverts blood through the stent, bypassing the aneurysm.
They are also used to manage arterial dissections, where a tear in the inner lining of an artery allows blood to flow between the layers of the vessel wall. A covered stent can seal this tear, restoring normal blood flow and preventing the dissection from worsening. Additionally, covered stents serve as a rapid solution for vascular perforations, which are accidental punctures or tears in blood vessels that can occur during medical procedures. The stent’s covering seals the leak, stopping blood loss and stabilizing the vessel.
Key Considerations
Covered stents involve specific considerations, particularly regarding patient management post-procedure. Patients typically require antiplatelet medication, often dual antiplatelet therapy (DAPT) combining aspirin with another antiplatelet drug, to prevent blood clots from forming on the stent surface. While bare-metal stents may require antiplatelet therapy for a shorter period, covered stents often necessitate longer-term use due to their non-endothelialized surface. Duration varies, but continued therapy is often suggested unless contraindications exist.
Despite their benefits, covered stents can have device-related complications. These include in-stent restenosis (re-narrowing within the stent) and stent thrombosis (blood clots inside the stent). Stent fracture (metallic framework breaks) and stent migration (device moves from intended position) are also potential issues. Another concern, particularly in aneurysm repair, is an endoleak, signifying continued blood flow into the aneurysm sac despite stent placement. Long-term follow-up with imaging is important to monitor for these complications and ensure continued effectiveness.