The Absorb heart stent, made by Abbott Laboratories, designed to dissolve after placement to restore the artery's natural flexibility, has proven safe and effective six and nine months after being implanted in patients.
Stent Dissolves After Implantation, Helping Restore Arterial Flexibility
Researchers at Erasmus Hospital in Amsterdam report that the Absorb heart stent, made by Abbott Laboratories, designed to dissolve after placement to restore the artery's natural flexibility, has proven safe and effective six and nine months after being implanted in patients.
If angiography indicates a "blockage," then the cardiologist uses ultrasound to determine the size and thickness of the cholesterol deposit. If the blockage is not total, then the choice may be made to insert a permanent tube into the artery so blood can continue to flow.
Until recently, all heart stents were made of metal mesh. The problem with an inflexible, metal stent is that the surgeon has to make sure that the entire outside surface of the stent is in contact with the walls of the artery. Otherwise, blood can leak behind the stent and clot. To prevent clots, patients are usually given two different anti-clotting agents. Since it is easy to overdose the medications, patients have to be carefully monitored to make sure they do have problems with excessive bleeding.
Another problem with metal stents is that they are foreign objects. The artery often grows scar tissue to cover them, or they may cause an accumulation of white blood cells that attack them as if they were an infectious agent. Since the stent is a mesh, scar tissue in the stent makes it impossible to remove and replace.
The white blood cells themselves may also "clog" the artery. Many metal stents fail just a few months after implantation.
The soluble Absorb heart stent was designed to avoid all of these problems. Dissolving into the wall of the artery, it is much less likely to cause clotting. And since it disappears in the year after it is implanted, it does not trigger the growth of scar tissue or activate the immune system.
Initial results of studies in the Netherlands were so encouraging that the European Union approved the Absorb stent in January 2011, without extensive testing. About 7 per cent of patients implanted with the stent suffered adverse events, including heart attacks, but this is much better than the results of implanting metal stents. The US Food and Drug Administration, however, will require a 2,000-patient trial of the device, for possible approval in 2015, several years before any other product by any other large pharmaceutical company.
Smaller pharmaceutical companies, however, developed similar products before Abbott Labs.In 2010 Abbott Laboratories' competition, a California company called Biosensors, gave up trying to get its own soluble stent approved the US Food and Drug Administration. Already approved in Europe, Mexico, and Canada, the company's stent was not approved in the US because of sensitivity to justifiable claims that the FDA had rushed approval for "blockbuster" health products that later turned out to have dangerous side effects.