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Collateral
Circulation in the Coronary Arteries May Be Inhibited by Drug-Eluting Stents |
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December 29, 2006 -- Adding fuel to the firestorm that many thought had subsided, the January 2 issue of the Journal of the American College of Cardiology contains an article from the team at University Hospital in Bern, Switzerland that highlights yet another potential problem with drug-eluting stents.
But the Swiss researchers found that drug-eluting stents seem to inhibit the growth of these collaterals. A cohort of 120 patients was chosen and divided into two groups: those patients who had received bare metal stents (BMS) and those who had received the newer drug-eluting stents (DES). Six months after implantation, all participants were studied, specifically with respect to their collateral circulation. The results were significant. The study states:
In other words, drug-eluting stents, which have been implicated in "slightly higher rates of late stent thrombosis", may also be responsible for that thrombosis (blood clot) resulting in a worse outcome because the development of collateral circulation has been inhibited: stent thrombosis is not only slightly more frequent, but 30-40% more likely to result in a heart attack.. The study does not explore the mechanisms that might be responsible and, in fact, only shows "an association" between the lack of collaterals and drug-eluting stents -- no causative factors were identified. And, of course, this study was relatively small, only 120 patients, and needs to be validated by replication. However, the clinical implications of having impaired collateral circulation may be significant for patients, no matter which type of stent is placed. Using a simple and inexpensive technique, called "washout collaterometry", it is possible to measure collateral circulation before stents are placed. As reported by Shelley Wood in theheart.org, Dr. Bernhard Meier explains the technique. Just before stent placement, a balloon is inflated to open up the artery. Watching the injection of contrast dye for about 45 seconds reveals the existence (or absence) of collaterals. Dr. Meier continues:
Dr. Meier added these comments when queried by Angioplasty.Org:
When referring to "conditional stenting", Dr. Meier recalls the time when "Plain Old Balloon Angioplasty" (POBA) was the dominant technique, and stents were only placed in situations where it seemed beneficial. Today stents are used in virtually all angioplasty procedures, a situation characterized by Dr. Meier as "unfortunate". Adding to the importance of collateral circulation is recent research and trials in the area of angiogenesis. For example, recent studies by Cardium Therapeutics have shown that the promotion of collateral blood vessel growth, using genetic material, can provide significant benefit for patients suffering from heart failure. Bottom line: the lack of collaterals should definitely give pause to the interventional cardiologist when deciding to implant a stent, especially a drug-eluting stent. In recent months, some American cardiologists have minimized the findings of their European colleagues, especially regarding drug-eluting stent problems. Angioplasty.Org would like to note that 30 years ago, it was Dr. Bernhard Meier's patient who underwent the very first coronary angioplasty -- his recounting of the first case can be seen in our video of "The First PTCA". We believe that there is no one with a longer experience in interventional cardiology than Dr. Meier, and that his observations should be taken very seriously.
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