A stent is a type of medical implant in practical terms, even though the regulatory picture is slightly more nuanced. Most stents are placed inside the body and left there permanently, which fits the common understanding of what an implant is. The distinction matters mainly when you’re filling out medical forms, preparing for imaging scans, or trying to understand what’s been placed inside your body after a procedure.
Why the Classification Gets Confusing
The FDA categorizes some stents, particularly temporary and retrievable ones, as non-implanted devices. But the vast majority of stents used in cardiology and other specialties are designed to stay in the body indefinitely. Once a coronary stent is placed inside an artery, for example, the blood vessel’s inner lining gradually grows over it. Animal studies show this process is less than 20% complete at four days, under 40% at one week, and nearly finished by about 28 days. At that point, the stent is essentially woven into the vessel wall. By any functional definition, that’s an implant.
The regulatory nuance exists because “implant” has a specific technical meaning for the FDA that affects how a device is tested, approved, and labeled. For your purposes as a patient, if a stent has been placed in your body and left there, you have an implant.
Where Stents Are Used in the Body
Most people associate stents with heart arteries, and that is their most common application. In Germany alone, over 528,000 coronary procedures were analyzed in a single year, and more than 55% of those patients received at least one stent. But stents are used across many organs and body systems.
- Coronary arteries: to hold open narrowed or blocked heart vessels
- Peripheral arteries: in the legs, kidneys, or other areas with reduced blood flow
- Bile ducts: to relieve blockages caused by tumors or gallstones
- Esophagus: to keep the swallowing passage open when a tumor narrows it
- Colon and stomach: to open strictures in the digestive tract
- Ureters: to maintain urine flow from the kidneys to the bladder
- Airways: to support a collapsed or compressed trachea
Some of these stents are permanent. Others, particularly those used in the bile ducts or ureters, are designed to be removed or replaced after weeks to months. Whether a stent counts as a “permanent implant” depends on the specific type and location.
What Stents Are Made Of
Permanent stents are typically built from metal alloys. The most common is 316L stainless steel, which contains chromium, nickel, and molybdenum. It’s strong enough to keep a vessel propped open but can release metal ions that trigger low-level inflammation over time.
Cobalt-chromium alloys are now widely used because they resist corrosion better and allow thinner stent struts, which means less material sitting inside the artery. Nitinol, a nickel-titanium alloy, naturally forms a protective oxide layer on its surface, giving it better compatibility with body tissue than stainless steel. It’s also shape-memory metal, meaning it can be compressed for delivery through a catheter and then expand to its intended shape once in place.
A newer category, bioresorbable scaffolds, represents a fundamentally different approach. These are made from materials like poly-L-lactic acid (a biodegradable polymer) or magnesium alloys that dissolve in the body over months. The idea is to prop open the artery long enough for it to heal, then disappear entirely, avoiding the long-term drawbacks of having permanent metal in a blood vessel, such as vessel stiffening, loss of natural flexibility, and late inflammation. These are still being refined, as early versions showed higher rates of re-narrowing compared to standard metal stents.
How a Stent Affects MRI Scans
One of the most common reasons people ask whether a stent is an implant is because they need an MRI. The answer depends on what kind of stent you have. Coronary artery stents, including both bare-metal and drug-coated versions, are generally safe for MRI at 3-Tesla strength or lower. Multiple stents, even overlapping ones, are also considered safe under these guidelines. Each imaging sequence should be limited to 15 minutes, though multiple sequences are allowed in the same session.
This guidance applies specifically to coronary stents. Peripheral vascular stents, aortic stent grafts, biliary stents, ureteral stents, esophageal stents, and airway stents each have their own safety profiles. If you have a non-coronary stent and need an MRI, your imaging team will need to verify compatibility for your specific device. You should always tell the MRI facility what type of stent you have and, ideally, carry your implant card with the manufacturer and model information.
Medications After Stent Placement
If you receive a coronary stent, you’ll be placed on two blood-thinning medications taken together, a regimen that typically lasts 6 to 12 months. The American Heart Association recommends at least 12 months for patients with stable heart disease who receive a drug-coated stent. European guidelines allow a slightly shorter window of 6 to 12 months. For patients who had an acute heart event like a heart attack, both guidelines recommend a minimum of 12 months, with the option to extend beyond that if your bleeding risk is low.
This medication period corresponds roughly to the time it takes for your artery’s inner lining to fully grow over the stent. Until that biological covering is complete, the exposed metal surface can attract blood clots. The medications keep your blood from clotting on the stent while your body incorporates it. Stopping these medications early, without medical guidance, is one of the most significant risks after stent placement.
Permanent vs. Temporary Stents
Most coronary stents are permanent. Once placed, they stay in the artery for the rest of your life, eventually becoming part of the vessel wall. You won’t feel the stent, and after the initial recovery and medication period, most people don’t need to think about it daily.
Temporary stents are more common outside the heart. A ureteral stent placed to relieve a kidney obstruction is typically removed after a few weeks. Esophageal stents for cancer may be repositioned or replaced as treatment evolves. Some biliary stents are designed to be swapped out periodically. In these cases, the stent functions more like a medical tool with a defined lifespan than a permanent addition to your body.
Bioresorbable coronary scaffolds sit somewhere in between. They’re placed permanently in the sense that they’re not retrieved, but they dissolve on their own, typically over one to three years. The long-term goal is a vessel that returns to near-normal function without any foreign material left behind.