Jury Still Out on Safety of Drug Eluting Stents

Washington, DCWhen the US Food and Drug Administration (FDA) approved 'Endeavor,' the drug-coated Medtronic stent earlier this year, it did so amidst a storm of controversy as to whether or not the stents promote potentially dire blood clots in heart attack patients. Drug eluting stents are still under FDA scrutiny, but as 2008 dawned there was little conclusive evidence to prove the suspicion as fact.

However, proven or not there has been no shortage of concern swirling about this latest innovation in stent technology.

A stent is a small, wire-mesh tube that is inserted into a previously troubled artery after it has been cleared of plaque. The stent holds the walls of the weakened artery open to promote life-giving blood flow, although the mesh stents had a tendency to foster the growth of scar tissue—a serious concern in and of itself.

First introduced in 2003, drug eluting stents were thought to ward off the effects of scar tissue formation. However, tethered with the positive appeared newfound concern that the drug eluting stent promoted the formation of blood clots. Late in the summer of 2007 it was reported that various studies showed the drug eluting stents raising the risk for a killer clot years later. This was especially true in heart attack patients, an issue that was hotly debated in early September last year at an international event in Vienna.

In a report of a study dated September 1, 2007, the risk of early death for drug eluting stent heart attack patients 6 months out was 8.6 percent, or 7 percent higher than patients with so-called 'bare metal stents.'

Given that medical stents represent a multi-billion dollar industry, various stent manufacturers have been eager to disprove those concerns.

Earlier this month, Boston Scientific Corp became the first to release data from a study that appeared to show its drug coated stent was no more dangerous than traditional, bare-metal stents for heart attack patients. According to reports, a study that involved 3,000 patients revealed comparable rates of death, stroke and other safety-related concerns with drug eluting stents as compared with their bare-metal counterparts. The study was also reported to show that patients treated with drug coated stents were 41 percent less likely to require a second angioplasty than those treated with bare-metal stents.

That news, released in mid-October of this year, appeared to allay some people's fears about drug-eluting stents, but not for long.

A separate study, this time involving the Medtronic Endeavor, indicated that of the 2,000 patients enrolled in a study that compared the Medtronic product with that of rival Johnson & Johnson, an increased number of heart patients experienced more heart attacks and blood clots, and also required repeat procedures more often, it was reported, than heart patients treated with the Johnson & Johnson product known as 'Cypher.'

The study, dubbed 'Sort Out III,' is praised by Johnson & Johnson, while a spokesperson for Medtronic pointed out after the results were made public that the data were also short term.

Addressing a separate issue, two additional studies appear to suggest that cardiac patients overall may fare better by receiving fewer stents. A study released at the recent Transcatheter Cardiovascular Therapeutics conference in Washington, and another published separately, appear to suggest that stent treatment tends to be fairly arbitrary. The studies focused on ischemia, which is the medical term used to describe what happens when an artery clogs and a patient develops chest pains when the flow of blood to the heart muscle is blocked.

So, some conflicting information on drug eluting stents. What to do?

In an unprecedented move, eight medical device manufacturers have agreed to collaborate in a $100 million study in an effort to better understand stent technology, and how they relate to blood clots. That's the good news. The bad news is that the study is expected to take 4 years and involve 20,000 patients. There was no date given as to when the study is expected to begin, nor is it known how long it would take to analyze data from 20,000 patients over a 4-year period. However it is reasonable to conclude that it will be several years before sufficient data is mined and studied and before any reasonable conclusion can be achieved.

The primary focus of the proposed study, it has been reported, is whether heart stent patients can be safely removed from aggressive blood-thinning treatment after one year, vs. remaining on medication for two and one-half years following implantation of the drug eluting stent. Current guidelines suggest that patients remain on blood-thinning therapy for a minimum of one year after the implantation of a drug eluting stent. However, with the increasing concern for the development of blood clots further along, the idea is to extend that window.

Time will tell. Over that period of time, however, hundreds of thousands of patients will be treated with stents. Given the aging baby boom, the middle-to-upper demographic will be going through the system at an age where a heart condition will be increasingly likely. Such a study, some may argue, comes too late.

Thus, the jury on drug eluting stents, may well be out for a while yet.