Stents have been used for many years to clear blockages in the arteries of the heart and neck. But the arteries in the brain present a very different challenge because they are more fragile and have many more curves, making it harder to get the stent to the site of the blockage. Physicians use a minimally invasive technique to deploy the stent inside the brain.
A coronary stent is stainless tube with slots. It is mounted on a balloon catheter in a "crimped" or collapsed state. When the balloon of is inflated, the stent expands or opens up and pushes itself against the inner wall of the coronary artery. This holds the artery open when the balloon is deflated and removed. Coronary artery stents were designed to overcome some of the short comings of angioplasty.
Angioplasty is a technique that is used to dilate an area of arterial blockage with the help of a catheter with an inflatable, small, sausage-shaped balloon at its tip. It helps to keep arteries open after balloon angioplasty. The stent then allows the normal flow of blood and oxygen to the heart.
There are two basic kinds of stents: bare-metal stents and drug-eluting stents:
* Bare-metal stents, as the name implies, are metal stents with no special coating. Bare-metal stents act as simple scaffolding to prop open blood vessels after they are widened with angioplasty.
* Drug-eluting stents are coated with medication that is slowly released (eluted) to inhibit the growth of scar tissue in the artery lining. This helps the artery remain smooth and open, assuring good blood flow through it. Drug-eluting stents reduce this risk to less than 10 percent, and less than 5 percent of people need repeat procedures.
Fighting atherosclerosis means attacking the disease on all fronts: with exercise and healthful eating; medications that stabilize plaque, hinder blood clots from forming in the heart’s arteries, and prevent harmful changes in the shape of the heart; and efforts to control blood pressure and cholesterol. Sudy shown that for people with stable coronary artery disease (clogged arteries nourishing the heart), artery-opening angioplasty was no better than medications and lifestyle changes at preventing future heart attacks or strokes, nor did it extend life.
Previously study suggested that although the use of stents to treat coronary artery disease has soared during the past decade thanks to novel equipment and new implant techniques, clinical data has recently raised concerns around the safety of drug-eluting stents (DES) and their risk of post-procedure complications.
Historically, insulin-requiring diabetic patients constitute about 30 percent to 45 percent of diabetics who undergo coronary angioplasty. The outcomes of these patients after angioplasty or stent implantation have been known to be worse than that of patients with non-insulin-requiring diabetes. According to study in Journal of the American Heart Association shown that drug-eluting stents significantly reduced the risk of recurring blockages in arteries of diabetic patients compared to bare metal stents.
Researcher found; over seven months of follow-up, the clinical and angiographic outcomes were better in patients who received a stent than in those who received standard coronary angioplasty.
Another study reported that stenting is the best alternative among excellent treatment options for women,” she said. “There is no difference in the death rates between stenting and angioplasty, but stenting offers a substantial benefit by decreasing the recurrence rate of new blockages.” Women in this study had more diabetes, hypertension and high cholesterol than men and were older than men.
A study conducted at Cedars-Sinai Medical Center's Cardiovascular Intervention Center confirms that newer generation stents that slowly release medication are far more effective than conventional stents in preventing the overgrowth of scar tissue, thereby reducing incidence of restenosis (re-narrowing), heart attack and death.There was a fourfold reduction in the incidence of restenosis with the medicated stents. They suggested that medicated stents appear to provide localized benefits, preventing restenosis at the site of the stent but not in other parts of the bypass graft, which often occurs.
The American Heart Association latest research shown that inflammatory response was substantially reduced among patients who received the drug eluting stent compared to the bare metal stent. "The advantage of the drug used on this stent is that it does not kill the cells, it just inhibits their growth," said researcher, noting that when cells die, thrombosis (blood clots) could result.
The "super aspirin" drug called abciximab keeps platelets from clumping and forming blood clots that can obstruct blood flow and trigger a heart attack. Study confirmed that this "super aspirin" that greatly reduces complications and death rates following a procedure called stenting.
One of the most surprising findings was that the re-blockage rate was cut in half in the patients who received both the stent and the drug. The stent-abciximab combination brought the re-blockage rate in the diabetic heart patients to about the same levels as heart patients without diabetes.
As measured one year study after the procedure found that coronary stenting for multivessel disease is less expensive than bypass surgery and offers the same degree of protection against death, stroke, and myocardial infarction. However, stenting is associated with a greater need for repeated revascularization. Researchers supported the study added "Elective coronary stenting was effective in the treatment of restenosis after balloon angioplasty. Stenting resulted in a lower rate of recurrent stenosis despite a higher incidence of subacute thrombosis."
Drug-coated stents offered a clear advantage over the bare-metal kind for high-risk patients with blocked coronary arteries, a large Canadian study found.
The rate of restenosis -- having the artery become blocked again after stent implant -- was "significantly lower" over the following two years for those getting drug-coated stents, 7.4 percent versus 10.7 percent. The three-year death rate was 5.5 percent in the coated-stent group, compared to 7.8 percent in the bare-metal group.
"We found the results in low-risk patients were almost identical [between the two types of stents], so we would reserve coated stents for high-risk cases," said study lead author Dr. Jack V. Tu, a senior scientist at the Institute for Clinical Evaluative Sciences in Toronto.
The study findings also provide some comfort about worries that a high rate of restenosis increases the risk of heart attacks in those getting coated stents. The two-year heart attack rate was similar in the two groups, 5.2 percent for bare-metal stents and 5.7 percent for coated stents.
"These were traditional heart attacks rather than being caused by restenosis, so it provides a lot of reassurance," Tu said.
The study defined high risk as the presence of two of three risk factors for restenosis -- diabetes, having smaller blood vessels and having very long blockages.
Use of a bare-metal stent versus a drug-coated stent thus depends on a recipient's risk profile, Tu said. "Unless I were a high-risk patient with two or three risk factors, I would be better off with a bare-metal stent," he said. I would reserve the coated stent for high-risk patients.
Dr. Steven Nissen, chairman of cardiovascular medicine at the Cleveland Clinic, said the findings should be interpreted with care, because the study was "observational," looking at what was done in medical practice without the strict effort to balance all factors done in a controlled trial.
"Observational data has significant limitations, particularly that the patients who received bare-metal stents rather than coated stents may have been different," Nissen said. "Observational studies try to account for those differences by matching patients carefully, but matching is an imperfect science."
The "big surprise" of the study was the reduction of the death rate with drug-eluting stents, Nissen said. "But the authors appropriately caution that the finding needs confirmation by randomized clinical trials," he said.
"In my view, we've learned all we can from observational trials," Nissen added. "We need a good long-term controlled trial" of stents.However, Dr. Kirk Garratt, clinical director of interventional cardiovascular research at Lenox Hill Hospital in New York City, said the Canadian trial was no ordinary observational study.
"The best thing about this paper is the technique they used for matching bare-metal stent patients with drug-coated stent patients," Garratt said. "It was easy for me to figure out quickly and easily the impact of having put a drug-coated stent into a patient. It was linked to an important improvement in how patients do over a long period of time."
One reason the coated stents performed so well is that Canada's health-care system automatically provides the clot-preventing drug Plavix, plus aspirin, for all stent recipients. Those drugs are recommended for American recipients, and the federal government recently began to pay for them, Garrate.
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