Clinical alert on drug-eluting stents and late thrombosis
(12 January 2007: VIDYYA MEDICAL NEWS SERVICE) -- The Society for Cardiovascular Angiography and Interventions (SCAI) today released a clinical alert advising physicians on practical steps for reducing the risk of a rare but serious complication associated with the use of drug-eluting stents. The document follows hearings held by the Food and Drug Administration's Circulatory Systems Device Panel regarding the use of these devices. The panel supported the continued use of these devices but also suggested more research to determine whether the devices contribute to an increased likelihood of heart attack and death in complex heart disease patients who receive these stents (see http://www.fda.gov/cdrh/news/010407.html).
SCAI's clinical alert, published online in SCAI's official journal, Catheterization and Cardiovascular Interventions, focuses on the importance of careful patient selection, meticulous stent implantation, and consistent use of medications to prevent the delayed formation of blood clots that can block blood flow to the heart, a condition known as late stent thrombosis.
"Practicing physicians and their patients are naturally concerned by the recent finding of a very small, but important risk of very late stent thrombosis. Since SCAI's membership includes the vast majority of practicing interventional cardiologists, we felt it was critical to give some practical advice and guidance in an attempt to ensure optimal outcomes for our patients with coronary artery disease. Coronary artery disease is still the number one cause of death in the Western world, and anything we can do to maximize therapy while minimizing risk is welcome." said John McB. Hodgson, M.D., FSCAI, the lead author of the clinical alert, a Past President of SCAI, and Chief of Academic Cardiology at St. Joseph's Hospital and Medical Center in Phoenix, AZ.
Drug-eluting stents are mesh tubes that prop open narrowed arteries in the heart while slowly releasing a medication that prevents the build-up of scar tissue inside the stent. These tiny devices have been very successful in preventing renarrowing, or restenosis, of the coronary arteries, reducing the rate of this complication by 40–60 percent compared to their bare metal counterparts. However, several recent analyses that tracked patient outcomes for four to five years after stent placement showed that blood clots were slightly more likely to form inside a drug-eluting stent than inside a bare metal stent. It is not yet clear how large the difference in risk is, but available data suggest that in the types of lesions treated in the original controlled trials it is about 0.2% excess (compared to bare metal stents) per year after year one. When this occurs, the patient may suffer a heart attack or even die.
"Given this new information, treatment decisions hinge on assessing the balance between the risk of restenosis and risk of late stent thrombosis," Dr. Hodgson said. "It is important for the clinician to consider the risk–benefit ratio for each individual patient. Interventionalists are encouraged to involve patients, whenever possible, in these discussions."
This clinical alert has been designed to provide interventional cardiologists with practical advice on how to evaluate and minimize the risk of late stent thrombosis. Its recommendations include the following:
Prior to any stent implantation, patients should meet accepted criteria for coronary intervention as described in guidelines jointly published by the ACC, AHA, and SCAI.
The decision to treat a patient with a drug-eluting stent--rather than a bare metal stent or bypass surgery--must be made on an individual patient basis, considering the relative risks and benefits of each therapy. This determination will vary according to each patient's medical history, coexisting illnesses, and lesion characteristics.
Patients must be carefully evaluated for their ability to adhere to long-term therapy with dual anti-clotting medications.
Careful attention must be paid to stent implantation technique, including the use of intravascular ultrasound, screening for arterial calcification, and pretreatment of complex lesions in some cases.
Patients should take dual anti-clotting medication for at least three to six months, preferably for 12 months unless there is a high risk for bleeding. In patients with a higher-than-average risk for late stent thrombosis--for example, those with diabetes--physicians should consider not only continuing dual anti-clotting medication for longer than 12 months, but also testing responsiveness to these medications and adjusting dosages as needed.
Discontinuation of dual anti-clotting medication requires careful consideration and must be individualized for each patient.
Several large multicenter trials to better define the risk of late stent thrombosis and assess strategies to prevent this complication are in progress or will soon begin enrolling patients. In the meantime, drug-eluting stents remain an important treatment option for many patients.
"Patients should be reassured that the implantation of a drug-eluting stent, after careful consideration with their physician, remains a very effective method for the treatment for symptoms associated with the disabling problem of coronary artery disease," Dr. Hodgson said.
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