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Narrowed coronary arteries: Endeavor, a Zotarolimus-eluting stent

The FDA ( Food and Drug Administration ) has approved the Endeavor Zotarolimus-eluting coronary stent for use in treating patients with narrowed coronary arteries, the blood vessels supplying the heart.

Manufactured by Medtronic, the device is a tiny metal mesh tube coated with a small amount of a new drug, Zotarolimus, developed only for use on a stent. It is crimped around a balloon and delivered to the narrowed section of the coronary artery via a long thin catheter during a procedure known as an angioplasty. Once the stent is positioned, the balloon is inflated, expanding into the vessel wall where it will remain in place, acting as a mechanical scaffold to keep the artery open.

Slow release of Zotarolimus over time prevents the artery from re-narrowing when new tissue begins to form. This process, known as restenosis, can eventually require a repeat angioplasty.

Medtronic provided data from seven clinical trials in its marketing application. Studies showed that the Endeavor significantly reduced the number of major coronary events ( myocardial infarction, cardiac death and repeat procedures to re-open the artery ) compared to a bare-metal stent.
It also cut the restenosis rate by about half.

Imaging studies on a subset of patients indicated that the Endeavor’s restenosis rate was higher than what is seen in currently marketed drug-eluting stents. However, the Endeavor had a similar number of coronary events when compared to one of these stents.

The number of adverse events experienced by patients implanted with the Endeavor stent was similar to those that occurred in patients implanted with bare-metal stents and existing drug-eluting stents.

Based on recent concerns over the rare but serious side effect of blood clots or stent thrombosis, FDA asked Medtronic to combine data from all Endeavor trials to determine how often this happened at various points in time following stent implantation. The stent thrombosis rate was 0.4 percent at one year and 0.5 percent at two years, a rate similar to that for bare-metal stents. To reduce such clotting risk, patients receiving the Endeavor will need to take blood-thinning medication for at least six months after implantation and should consider continuing this regimen for 12 months if they are not at an increased risk for bleeding complications.

The safety and effectiveness of the Endeavor stent in smaller diameter arteries or for longer blockages requiring more than two stents has not been studied and there has been no evaluation of the stent’s safety and effectiveness in patients who are having an acute heart attack, patients who had previous intravascular radiation treatment, or patients who have their blockage in a bypass graft, in the left main coronary artery, or in more than one vessel.

Patients who are allergic to Zotarolimus or to cobalt, nickel, chromium, or molybdenum should not receive an Endeavor stent. Caution is also recommended for people who have had recent cardiac surgery and for women who are nursing or who may be pregnant.

Medtronic will continue to follow patients enrolled in six of the Endeavor trials for five years. Additionally, the company will conduct a 2,000-patient U.S. post-approval study, which will be combined with 3,300 patients from a study conducted outside the United States, to assess the long-term safety and effectiveness of the Endeavor stent and to look for rare adverse events such as stent thrombosis. Medtronic will also collect clinical data to identify the optimal duration of antiaggregant medication.

Before drug-eluting stents were available, about 15 percent to 30 percent of patients experienced restenosis within a year, requiring a repeat angioplasty. This number has dropped to 10 percent of patients since drug-eluting stents entered the U.S. market in 2003.

Source: FDA, 2008