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In medicine, a drug-eluting stent is a stent (a metal scaffold) placed into diseased coronary arteries that slowly releases a drug blocking cell proliferation; this helps to delay or prevent the artery from being re-occluded by smooth muscle and clot (thrombus). The stent consists of a expandable metal framework, a drug to prevent restenosis, and a carrier to slowly release the drug. It is placed over a balloon on a catheter and guide wire and introduced through a peripheral artery, usually one of the femoral arteries. It is threaded back towards the heart; from the aorta, the appropriate coronary artery is entered. The balloon is inflated, cracking and compressing the plaque and expanding the stent. The balloon and catheter are then withdrawn, leaving the stent in place. The stent releases its drug over the next several months. Patients must take antiplatelet therapy afterwards, usually clopidogrel for six months and aspirin indefinitely. Drug-eluting stents have been shown to be superior for many of the conditions that traditional stents (“bare-metal stents”) have been used, and have become quite popular since their FDA approval in 2003.

Current devices

Currently, two models of drug-eluting stents are used. The first successful type released sirolimus (rapamycin), a powerful immunosuppressive and antiproliferative drug. Sirolimus, produced by the bacterium Streptomyces hygroscopicus, binds to the immunophilin FKBP-12. The resulting complex inhibits the mammalian target of rapamycin (mTOR), which has several effects, including preventing the cell from duplicating its genetic material; it blocks the cell cycle at the G₁→S transition. A sirolimus-eluting stent is produced by Cordis Corporation (Johnson & Johnson), and marketed under the name Cypher. A successful trial in 2002 led to approval in Europe, followed by FDA approval in the U.S. in 2003.

History

Heart attacks, or myocardial infarctions, are major causes of death and disability; they result when a portion of heart muscle dies from inadequate blood flow. This typically occurs at sites where coronary arteries are already narrowed and damaged. If blood flow can be restored early enough, permanent damage can be prevented, and preemptive restoration can prevent heart attacks from occurring in the first place. The first procedural method to perform a type of open-heart surgery called coronary artery bypass graft (CABG) surgery, which uses a section of vein or artery from elsewhere in the body to bypass the diseased vessel. In 1977, Andreas Grüntzig introduced percutaneous transluminal coronary angioplasty (PTCA), in which a catheter was introduced through a peripheral artery and a balloon expanded to compress and crack the obstructive plaque. As equipment and techniques improved, the use of PTCA rapidly increased, and by the mid-1980s, PTCA and CABG were being performed at equivalent rates.. PTCA could only be used on limited scenarios, and the vessels had a high rate (30–40% in six months) of restenosis; additionally, 3% required emergency bypass surgery.. Dotter and Judkins had suggested using intraluminal prosthetic devices to maintain blood flow (in arteries of the leg) in 1964, and in 1986, Puel and Sigwart implanted the first stent in humans. Several trials in the 1990s showed the superiority of stent placement to simple balloon angioplasty, and stent placement became increasingly prevalent, reaching 84% of percutaneous interventions by 1999.

References

1. Michel, Thomas (2006) . "Treatment of Myocardial Ischemia". In Laurence L. Brunton, John S. Lazo, & Keith L. Parker (ed.). Goodman & Gilman's The Pharmacological Basis of Therapeutics (11th ed. ed.). New York: McGraw-Hill. p. 842. {{cite book}}: |edition= has extra text (help)CS1 maint: multiple names: editors list (link)
2. ^ Serruys, Patrick W. (2006-02-02). "Coronary-Artery Stents". New England Journal of Medicine. 354 (5): 483–495. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help) (extract)
3. "New Device Approval — Cypher Sirolimus-eluting Coronary Stent". Food and Drug Administration. Retrieved 2006-07-22.
4. Krensky, Alan M. (2006) . "Immunosuppressants, Tolerogens, and Immunostimulants". In Laurence L. Brunton, John S. Lazo, & Keith L. Parker (ed.). Goodman & Gilman's The Pharmacological Basis of Therapeutics (11th ed. ed.). New York: McGraw-Hill. p. 1413. {{cite book}}: |edition= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: multiple names: editors list (link)
5. Grüntzig, AR (1979-07-12). "Nonoperative dilatation of coronary-artery stenosis: percutaneous transluminal coronary angioplasty". New England Journal of Medicine. 301 (2): 61–68. Retrieved 2006-07-22. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help) (abstract)
6. ^ Baim, Donald S. (2005) . "Percutaneous Coronary Revascularization". In Dennis L. Kasper, Anthony S. Fauci, Dan L. Longo, Eugene Braunwald, Stephen L. Hauser, & J. Larry Jameson (ed.). Harrison's Principles of Internal Medicine (16th ed. ed.). New York: McGraw-Hill. pp. 1459–1462. {{cite book}}: |edition= has extra text (help)CS1 maint: multiple names: editors list (link)
7. Dotter, Charles T. (1964). "Transluminal Treatment of Arteriosclerotic Obstruction". Circulation. 30: 654–670. Retrieved 2006-07-22. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help) (abstract)

See also

• Fischetti, Mark (2006). "Vascular Stents: Expanding Use". Scientific American: 94. {{cite journal}}: Unknown parameter |month= ignored (help) (subscription required)