Stent

For people named Stent, see Stent (surname).

Stent
3D rendering of a stent in a coronary artery
Specialty	{{#statements:P1995}}
MeSH	D015607
MedlinePlus	002303

In medicine, a stent is a metal or plastic tube inserted into the lumen of an anatomic vessel or duct to keep the passageway open, and stenting is the placement of a stent. There is a wide variety of stents used for different purposes, from expandable coronary, vascular and biliary stents, to simple plastic stents used to allow the flow of urine between kidney and bladder. Stent is also used as a verb to describe the placement of such a device, particularly when a disease such as atherosclerosis has pathologically narrowed a structure such as an artery.

A stent should be differentiated from a "shunt". A shunt is a tube that connects two previously unconnected parts of the body to allow fluid to flow between them. Stents and shunts can be made of similar materials, but perform two different tasks.

Stent types

Type and description	Illustration
Coronary stents are placed during a percutaneous coronary intervention, also known as angioplasty. The most common use for coronary stents is in the coronary arteries, into which a bare-metal stent, a drug-eluting stent, a bioabsorbable stent, a dual-therapy stent (combination of both drug and bioengineered stent), or occasionally a covered stent is inserted.	A coronary stent
Vascular stents are commonly placed as part of peripheral artery angioplasty. Common sites treated with peripheral artery stents include the carotid, iliac, and femoral arteries. Because of the external compression and mechanical forces subjected to these locations, flexible stent materials such as nitinol are used in a majority of peripheral stent placements.	Compressed and expanded peripheral artery stents
A stent graft or covered stent is type of vascular stent with a fabric coating that creates a contained tube but is expandable like a bare metal stent. Covered stents are used in endovascular surgical procedures such as endovascular aneurysm repair. Stent grafts are also used to treat stenoses in vascular grafts and fistulas used for hemodialysis.	Example of a stent used in an endovascular aneurysm repair
Ureteral stents are used to ensure the patency of a ureter, which may be compromised, for example, by a kidney stone. This method is sometimes used as a temporary measure to prevent damage to a blocked kidney until a procedure to remove the stone can be performed.	Example of a uretal stent used to alleviate hydronephrosis of the kidney
Prostatic stents are places from the bladder through the prostatic and penile urethra to allow drainage of the bladder through the penis. This is sometimes required in benign prostatic hypertrophy.	File:Spanner insitu.jpg Example of a stent / catheter used in the prostate to treat an enlarged prostate and provide relief in cases of obstructed urination
Esophageal stents are a palliative treatment for advanced esophageal cancer.	Endoscopic image of a self-expanding metallic stent in an esophagus, used to palliatively treat esophageal cancer
Biliary stents provide bile drainage from the gallbladder, pancreas and bile ducts to the duodenum in conditions such as ascending cholangitis due to obstructing gallstones.	Endoscopic image of a biliary stent seen protruding from the ampulla of Vater at the time of duodenoscopy
Glaucoma drainage stents are recent developments and are awaiting approval in some countries. They are used to reduce intraocular pressure by providing a drainage channel.
Other types are duodenal stents, colonic stents, and pancreatic stents, the designations referring to the location of their placement.

Overuse in Stable Coronary Artery Disease

In 2007 the New England Journal of Medicine published the results of a trial called COURAGE. The study compared stenting (also known as PCI), to medical therapy alone in symptomatic stable coronary artery disease. This showed there was no mortality advantage to stenting in stable CAD, though there was earlier relief of symptoms which equalized by five years. After this trial there were widely publicized reports of individual doctors performing PCI in patients who did not meet any traditional criteria. A more recent meta-analysis showed there may be improved mortality with second generation drug-eluting stents, which were not available during the COURAGE trial. Medical societies have since issued guidelines as to when it is appropriate to perform percutaneous coronary intervention. In response the rate of inappropriate stenting has declined as of December 2014.

Etymology

The origin of the word "stent" remains unsettled. The verb form "stenting" was used for centuries to describe the process of stiffening garments (a usage long obsolete, per the Oxford English Dictionary) and some believe this to be the origin. According to the Merriam Webster Third New International Dictionary, the noun evolved from the Middle English verb stenten, shortened from extenten, meaning to stretch, which in turn came from Latin extentus, past participle of extendere, to stretch out. Others attribute the noun "stent" to Jan F. Esser, a Dutch plastic surgeon who in 1916 used the word to describe a dental impression compound invented in 1856 by the English dentist Charles Stent (1807–1885), whom Esser employed to craft a form for facial reconstruction. The full account is described in the Journal of the History of Dentistry. According to the author, from the use of Stent's compound as a support for facial tissues evolved the use of a stent to hold open various bodily structures. The first (self expanding) "stents" used in medical practice in 1986 by Ulrich Sigwart in Lausanne were initially called "Wallstents". Julio Palmaz et al. created a balloon expandable stent that is currently used.

History

The first use of a coronary stent is typically attributed to Jacques Puel and Ulrich Sigwart when they implanted a stent into a patient in Toulouse, France in 1986. It was used as a scaffold to prevent the vessel from closing and to avoid restenosis in coronary surgery—a condition where scar tissue grows within the stent and interferes with vascular flow. Shortly thereafter in 1987, Julio Palmaz (known for patenting a balloon-expandable stent) and Richard Schatz implanted their similar stent into a patient in Germany. The use of these bare-metal stents helped reduce the incidence of restenosis from 30–40% in coronary surgery to 20–30%.

Though many doctors have created the stent, the first FDA approved stent was invented by Cesar Gianturco and Gary S. Roubin.

To further reduce the incidence of restenosis, drug-eluting stents (DES) were introduced which consisted of stents coated in anti proliferative agents. Animal studies and later clinical trials showed a reduction in restenosis to approximately 5%.

See also

• Angioplasty
• Bronchoscopy
• Colonoscopy
• Esophagogastroduodenoscopy
• Grommet
• Interventional radiology
• Restenosis
• Bioresorbable stents

External links

• Coronary Stent
• Drug-Eluting Stents — Angioplasty.Org
• Cardiovascular and Interventional Radiological Society of Europe
• The Cardiovascular Forum
• Stent for Life Initiative