Study confirms that stents releasing medication help keep heart bypass vein grafts open
LOS ANGELES – Over time, veins removed from the legs (saphenous veins) and attached to the heart to replace clogged coronary arteries tend to resemble old, sluggish drain pipes. In fact, within five to 10 years of coronary artery bypass surgery, half of all vein grafts become diseased to the point of requiring re-intervention – either repeat open-heart surgery or balloon angioplasty with the insertion of a stent.
Stents can be inserted into a grafted vein or into a native coronary artery during a balloon angioplasty procedure. The balloon is used to open a plaque-clogged area, and the stent – a tiny mesh tube – is designed to function as a scaffold to keep the vessel open. But conventional bare-metal stents have been prone to the formation of scar tissue and subsequent re-narrowing.
Now 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," said Raj Makkar, M.D., co-director of the Center, co-director of Interventional Cardiology Research at Cedars-Sinai, and senior author of an article describing the study in the November 2005 issue of Catheterization and Cardiovascular Interventions: Journal of the Society for Cardiovascular Angiography and Interventions.
Although earlier research found that drug-eluting stents reduced scar tissue formation and re-narrowing in native coronary arteries, the new study is one of very few to focus on drug-eluting stents used in saphenous vein grafts, which pose unique challenges for cardiologists specializing in interventional procedures.
Michael S. Lee, M.D., the article's first author and an interventional cardiologist at Cedars-Sinai, said old vein grafts have a "mucky" appearance. "They are more likely to build up atherosclerotic plaque over long sections and to be filled with cholesterol debris and blood clots. The lesions are less stable, so little particles of plaque can dislodge during the procedure."
In fact, the authors noted that percutaneous coronary intervention (angioplasty) of degenerated saphenous vein grafts is associated with worse outcomes and a high incidence of in-stent restenosis compared with percutaneous intervention of native coronary arteries.
Makkar said the 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.
This study analyzed data from 223 consecutive patients who underwent angioplasty to treat diseased saphenous vein grafts that had been in place just under eight years on average. Drug-eluting stents were placed in 139 patients and conventional stents were placed in 84 patients.
During nine months of follow-up, four percent of patients treated with a drug-eluting stent experienced a heart attack, compared to 20 percent of those receiving a bare-metal stent. Also, 10 percent of patients treated with a drug-eluting stent needed a repeat procedure to reopen the vein graft, compared to 37 percent of those treated with a conventional stent. The researchers will continue to follow up to determine if similar results are seen in the long term.
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