Stents are metallic hollow devices that serve to scaffold an area of obstruction within the coronary artery. The stents made today are 2.0 to 4.5 mm in diameter and vary in length from 5 mm to 40 mm. Most stents are made of stainless steel.
The first stent was successfully implanted in a human in 1993 in Europe. Shortly thereafter in 1994, the first stent was successfully implanted in the U.S. Then followed two large randomized trials: STRESS and BENESTENT. These two trials the former in the US, the latter in Europe, showed that stents placed in coronary arteries were better than conventional balloon angioplasty (PTCA) in maintaining vessel patency. The restenosis rates were 17-25% for stents while PTCA restenosis rates were 35%.
In 1995, when stents were first available for clinical use, stent implantation was fraught with two major problems:
- Large doses of blood thinners were required leading to unacceptable high rates of bleeding. If the blood thinner was not used, stents quickly clot off resulting in large disastrous heart attacks!
- Long hospitalization rates two to three times that of conventional PTCA.
Both these limitations were overcome when it was found that Ticlid was far superior that Coumadin in preventing acute stent occlusion from clot. Ticlid also had much lower rates of bleeding compared to Coumadin. Clopidogrel, a drug similar in molecular structure to Ticlid but with fewer side effects, is used instead of Ticlid. With the replacement of Ticlid or Clopidogrel instead of Coumadin, patients’ rates of excessive bleeding fell dramatically. As a direct consequence, the duration of hospital stays also fell dramatically. Now days, patients usual stay in the hospital for only one day after an uncomplicated stent deployment. With the use of Ticlid or Clopidogrel, acute stent occlusion is a now a rare phenomenon.
What about restenosis? Restenosis is the gradual process by which the stented or ballooned area gets plugged up by tissue ingrowth and plaque. The rates of restenosis for conventional angioplasty are 40% in four to six months after the PTCA. In BENESTENT and STRESS trials, the restenosis rates were 17 and 25% respectively. With the newer generation stents, restenosis rates have fallen to 10 to 15% in national registries. In order to get around this challenge of stent restenosis, newer Drug eluting stents were designed. In 2003, two drug eluting stents were introduced: Cypher which elutes the drug Sirulimus and Taxus which elutes the drug Paclitaxel. After placing these types of drug eluting stents (DES) the stent restenosis rates fell dramatically down to single figures. As of this update, in 2012, there are now three new drug eluting stents available eluting two different drugs: zotarulimus, and Evarilimus. Both these drugs are variants of the Sirulimus drug from the initial Cypher stent. Stent restenosis is reduced but not totally resolved by implantation of Drug Eluting Stents. There is also procedural differences in how the stents are implanted by the Cardiologist. Before getting your stent procedure, you should ask your cardiologist for his/her specific restenosis rates.
Stent deployment in a coronary artery has made it possible for most patients to avoid a disastrous heart attack. However neither stent deployment nor any other intervention can reverse the atherosclerosis process. Atherosclerosis is the abnormal accumulation of cholesterol and lipids in the walls of blood vessels. Atherosclerosis, if left untreated, can culminate in a heart attack.
Reversing the process requires changing your life style: increasing activity, lowering the fat intake in your diet and reducing your blood cholesterol. Read more about how you can prevent a heart attack here.