Evelyn Pringle January 24, 2007
Drug eluting stents were promoted as working so much better than the old bare metal stents that 6 million people worldwide have received them in the few years since the arrived on the market.
"It was a modern record for any medical device," the Boston Globe reported on December 4, 2006. Some 2 to 3 million people in the US now carry one of these devices in an artery, according to FDA estimates, with new implants topping 900,000 per year.
Only two brands of DES are sold in the US, the Taxus, by Boston Scientific, and the Cypher, by Johnson & Johnson's Cordis Division.
The trials submitted by the DES makers to obtain FDA approval for use in limited procedures with non-complex patients with single-vessel heart disease, involved a low risk population. However, off-label DES use for procedures not approved by the FDA has become rampant and according to the agency:
"It is estimated that a majority of DES are implanted in lesions outside of their current indications for use, such as in-stent restenosis lesions, bifurcation lesions, coronary artery bypass grafts, acute myocardial infarction, chronic total occlusions, overlapping and multiple stents per vessel and in patients with multivessel disease and chronic renal insufficiency."
Surgeons have been implanting the new devices in every kind of heart patient. And for good reason. The stenting business represents maga bucks to device makers, hospitals and surgeons alike. In the US, the implant procedure itself costs $38,203, according to a report by the Associated Press on December 26, 2006.
But as has been the case with so many pharmaceutical products in recent years, after being massively promoted, and implanted in millions of patients for indications not approved, DES are proving to be no better than the bare metal stents, and in fact research has shown them to worse because they come with more adverse reactions.
In early December 2006, the FDA's Circulatory System Devices Advisory Committee held a public meeting to review data on thrombosis both when DES were used according to their label and when they are implanted off-label for unapproved uses, and to address the appropriate duration for the use of the blood-thinning drug, Plavix, with DES patients.
In the briefing provided to the Committee before the hearing, the FDA informed the panel that recent presentations at scientific meetings had indicated a small but significant increase in the rates of death or myocardial infarction, and non-cardiac mortality, in DES patients when compared to patients who received bare metal stents.
The briefing included a specific discussion of presentations made at the Transcatheter Cardiovascular Therapeutics meeting, in October 2006, where doctors, Martin Leon and Gregg Stone, presented a meta-analyses of patient data from the Cypher and Taxus clinical trails.
Based on these analyses, Dr Stuart Pocock reported that after one year, five Cypher patients, compared to no bare metal patients, had experienced late thrombosis, and with the Taxus, thrombosis occurred in nine patients after one year compared with two bare metal stent patients.
Last year, the Swiss government commissioned a study to determine whether the DES were worth their price of between $2,200 and $2,700, when compared to the $600 to $800 for bare metal stents, and also to test how long Plavix should be prescribed to patients after the implantation of a DES to prevent blood clots from developing.
The study appeared in the December 19, 2006, Journal of the American College of Cardiology, and reported that patients with DES had double the risk of cardiac problems after stopping Plavix compared to patients with bare metal stents.
The Swiss researchers, led by Dr Matthias Pfisterer, found that when patients stop taking Plavix, they had a small but serious risk of blood clots leading to death or heart attack.
The lead author noted that the majority of DES implants in the study were off-label. "About two-thirds of our patients were really treated with off-label use of drug-eluting stents," Dr Pfisterer told WebMD on December 5, 2006.
"The FDA label says these are only for stable patients with limited disease," he notes. "But, in fact," he told WebMD, "most doctors who use drug-eluting stents use them in unstable patients and in more complex disease."
In an editorial accompanying the Pfisterer study, Dr Robert Califf and Dr Robert Harrington, warned that research on DES has not kept up with clinical realities. "As is frequently seen with new cardiac devices," they wrote, "rapid increase in clinical adoption quickly outstripped what is known about the device from limited clinical trials."
Medical professionals say an important point to keep in mind when considering the risks associated with the DES is that these devices have only been on the market in the US for less than four years and that many more unknown risks could surface in years to come.
More problems may have already surfaced according to Dr Joseph Muhlestein, a professor at the University of Utah. He told ABC New's Healthday reporter on December 4, 2006, that his research group has followed patients receiving DES implants very carefully and has found "something we don't understand."
As expected, he said, the DES did reduce artery closure at the site where they were implanted, but the incidence of artery problems at other sites occurred "significantly more often than when we used bare-metal stents," he told Healthday.
So, the overall incidence of artery problems ended up being the same, regardless of which type of stent was implanted, Dr Muhlestein said.
It is possible that the problem occurred because DES were used on more high-risk patients, he noted. But it's also possible, he said, that the DES interfered with the endothelium, the delicate tissue that lines the arteries.
These doubts have caused some doctors to cut back on DES use. "We used to use them in 90 percent of cases," Dr Muhlestein told Healthday. "Now, it's about 40 percent."
Finally, experts are warning that if unexpected health problems do develop in patients already implanted with the DES, removal of the stent is not possible because once it is placed in the body, the tissue in the artery grows over the stent.