What is a covered stent?

A covered stent is a type of stent that has a covering or membrane over the metal mesh. The covering can be made of different materials such as polyethylene, polytetrafluoroethylene (PTFE), or silicone. 

Some key points about covered stents:

- They are used to treat arterial aneurysms, prevent restenosis or re-narrowing of vessels after angioplasty, and cover holes or tears in vessel walls. The covering helps prevent tissue or plaque from protruding through the stent struts.

- The covering provides a barrier between the inner wall of the vessel and the blood flow, which reduces the risk of blood clots forming within the stent. This makes them useful for treating aneurysms.

- Compared to bare metal stents, covered stents have lower porosity and higher radial force. This can help prevent vessel recoil but may also increase the risk of in-stent restenosis.

- Insertion and deployment of covered stents is more complex and they have lower flexibility compared to bare metal stents.

- Potential risks include infection, covering erosion, endoleaks, and reduced side branch access. Therefore, patient selection and procedure skills are important when using covered stents.

- Common materials for the covering include PTFE or Dacron, which have high biocompatibility and promote endothelialization to better integrate the stent into the vessel wall.