A stent is a small, tube-shaped device inserted into a blocked or narrowed passageway in the body to keep it open and maintain the flow of fluid. While most commonly used to treat coronary artery disease by opening blood vessels that supply the heart, stents also support other ducts, such as those in the kidneys or lungs. The primary function of a stent is to provide structural support, restoring adequate flow through the previously obstructed vessel. The answer to whether a stent remains in the body indefinitely depends entirely on the material composition of the specific device implanted.
Understanding Stent Permanence
The duration a stent remains functional within the body is not uniform across all designs. Medical technology has developed two fundamentally different categories of stents based on their intended lifespan and biological interaction. These two paths—lifelong placement or temporary support—are determined by the clinical need and the material used. Understanding this distinction is fundamental to grasping the long-term implications of the stenting procedure.
Stents are broadly classified into permanent implants, which are typically metallic and intended to stay in place for the remainder of a person’s life, and temporary scaffolds. The temporary devices are designed either to dissolve completely after a period of healing or to be physically removed once their short-term structural role is complete. This difference dictates the patient’s post-procedure care and future monitoring requirements. The choice between a permanent or temporary device is carefully considered based on the location of the blockage and the anticipated healing response of the surrounding tissue.
Stents Designed to Remain Indefinitely
The majority of stents used in coronary arteries are metallic and are intended to be permanent fixtures. These devices are constructed from medical-grade metal alloys, such as cobalt-chromium or stainless steel, engineered to provide continuous, long-term radial support to the vessel wall. Their function is to mechanically counteract the forces that would otherwise cause the artery to collapse or re-narrow, a process known as restenosis.
Two primary types of permanent coronary stents exist: bare-metal stents (BMS) and drug-eluting stents (DES). Bare-metal stents are simple mesh tubes that maintain the vessel’s structure using only mechanical support. Drug-eluting stents (DES), which are the most common type used today, are metallic but feature a polymer coating that slowly releases a specific antiproliferative medication. This drug, often a limus-based compound, works at the cellular level to prevent the excessive growth of scar tissue inside the stent, which is the main cause of restenosis.
The metallic structure of both BMS and DES does not degrade, meaning the physical scaffold remains embedded in the artery wall permanently. Although the drug coating on a DES is typically depleted within the first one to six months, the metal framework continues to provide structural integrity indefinitely. Over time, a thin layer of natural arterial tissue grows over the stent struts, incorporating the device into the vessel wall. This integration is crucial for long-term function and minimizing complications.
Stents Designed for Temporary Use
Not all stents are permanent; some are engineered to provide only temporary support before disappearing or being removed. One advanced option is the bioabsorbable vascular scaffold, which provides structural support similar to a metallic stent but is made from materials like polylactide that gradually dissolve. These scaffolds are designed to break down into harmless compounds, such as lactic acid, carbon dioxide, and water, which are safely metabolized and excreted by the body.
The mechanical support from a bioabsorbable scaffold typically lasts for approximately six to twelve months, which is enough time for the vessel wall to stabilize and heal. The complete absorption of the material occurs over a longer period, often ranging from two to three years. The goal of this technology is to restore the artery’s natural ability to expand and contract, which is inhibited by a permanent metal cage. While this technology has shown promise, initial versions were associated with safety concerns, leading to their withdrawal from some markets.
Other temporary stents are used outside the coronary system and are designed for physical removal. Ureteral stents, used to keep the ureter open to drain urine from the kidney to the bladder, are made of flexible plastic or silicone. These devices are typically left in place for a few weeks to several months and must be actively retrieved by a physician once the underlying condition, such as a kidney stone or swelling, has resolved. Airway and some biliary stents are also often placed for later removal after the immediate obstruction is cleared.
Monitoring and Management of Permanent Implants
Because most coronary stents are permanent metallic implants, they require specific long-term management to ensure their continued safety and function. The primary concern with a permanent foreign object in the bloodstream is the risk of blood clots, or stent thrombosis, forming on the metal surface. To counteract this, patients are universally prescribed dual antiplatelet therapy (DAPT), a regimen that typically combines aspirin with a second antiplatelet medication, such as a P2Y12 inhibitor.
DAPT reduces the “stickiness” of platelets, preventing them from aggregating and blocking the newly opened stent. The duration of this therapy is personalized but generally involves taking both medications for a minimum period, often six to twelve months, after the procedure. For some patients with lower bleeding risk and higher clotting risk, DAPT may be extended for several years to maximize protection. Regular long-term medical follow-up with a cardiologist is also required to monitor for complications.
The two main complications that necessitate monitoring are restenosis, the re-narrowing of the vessel due to scar tissue growth, and late-stent thrombosis, a clot that forms months or years after the procedure. Physicians use non-invasive techniques, such as stress tests or computed tomography angiography (CTA), to assess the stent’s patency and detect any signs of obstruction. This ongoing management ensures the permanent implant continues to function effectively.