Stents are small, expandable tubes used to treat narrowed or blocked arteries or other hollow structures in the body. They are classified based on various characteristics including material, design, function, and the presence or absence of drug coatings. Here are the main types of stents:


Based on Material and Design:

  1. Bare-Metal Stents (BMS):

    • Made from stainless steel, cobalt-chromium, or other metal alloys.

    • Simple metal mesh tubes that provide structural support to keep arteries open.

    • Typically used when there is a lower risk of restenosis or when drug-eluting stents are not advisable.

  2. Drug-Eluting Stents (DES):

    • Similar to BMS but coated with drugs that are slowly released to inhibit the growth of scar tissue in the artery, reducing the risk of restenosis.

    • Common drugs include sirolimus, everolimus, zotarolimus, and paclitaxel.

  3. Bioresorbable Vascular Scaffolds (BVS) or Bioresorbable Stents:

    • Made from biodegradable materials like polylactic acid (PLA) or polyglycolic acid (PGA).

    • Designed to dissolve over time, leaving behind a healed vessel without a permanent implant, potentially reducing long-term complications like thrombosis.

    • Their use has been limited due to concerns over higher rates of adverse events compared to traditional stents.

  4. Stent-Grafts or Covered Stents:

    • Consist of a fabric or synthetic covering over a metal stent.

    • Used primarily for treating aneurysms or vascular perforations to prevent blood leakage.

    • The fabric can be polyester or PTFE (polytetrafluoroethylene).


Based on Delivery and Expansion Mechanism:

  1. Balloon-Expandable Stents:

    • Delivered via a balloon catheter; the stent expands when the balloon is inflated and remains at that size when the balloon is deflated and removed.

    • Precise control over stent diameter makes them suitable for coronary and renal arteries.

  2. Self-Expanding Stents:

    • Made from materials like nitinol (a nickel-titanium alloy) that naturally expand to a predetermined size once released from a constraining sheath.

    • Better for use in peripheral arteries where vessel movement or shape variation is common.


Specialized Stents:

  1. Dual-Therapy Stents (DTS):

    • Combine features of both DES and BVS, aiming to provide drug delivery with eventual resorption.

  2. Polymer-Free Drug-Eluting Stents:

    • Designed to deliver drugs without the use of a polymer coating to avoid potential adverse reactions to the polymer over time.

  3. Endovascular Aneurysm Repair Stents (EVAR):

    • Specifically designed for treating abdominal or thoracic aortic aneurysms. These are large stent-grafts that create a new path for blood flow, excluding the aneurysm sac.

  4. Ureteral Stents:

    • Used in the urinary system to keep the ureter open, allowing urine to flow from the kidney to the bladder. Made of silicone or other biocompatible materials.

  5. Esophageal, Biliary, and Tracheobronchial Stents:

    • Used in non-vascular applications to maintain the patency of these hollow organs, often for palliative care in cancer or to manage strictures.


Emerging and Research Stents:

  • Magnetic Resonance Imaging (MRI) Compatible Stents: Designed to be safer under MRI conditions.

  • Nanotechnology Stents: Incorporate nanoparticles for drug delivery or to enhance imaging.

  • Smart Stents: With embedded sensors for monitoring artery health or drug release.


The choice of stent type depends on the location of the lesion, the patient's medical history, the risk of restenosis, and the need for long-term antiplatelet therapy. Each type has its unique advantages and potential complications, necessitating careful selection by the medical team.