New stents from Abbott Labs and others appear to reduce the risk of blood clots
John Lamb, a retired auto mechanic in New Zealand, was the first patient to get an Abbott Laboratories (ABT) experimental heart stent, to treat worsening chest pains. He now has nothing to show for it—just as doctors intended.
In March 2006 surgeons inserted Abbott's device into Lamb's coronary artery to push back fatty plaque and allow blood to flow freely to his heart. Made of a compound called polylactic acid, over the next two years the device dissolved into lactic acid (a naturally occurring chemical in the body), leaving behind what appears to be a healthy artery. "It made an immediate difference," says Lamb, now 69. "It appealed to me that it dissolved and I wouldn't have a piece of hardware in my body."
Abbott believes the device could capture a big share of the $4 billion-a-year stent market, cutting into sales of Abbott's Xience models and rivals from Johnson & Johnson (JNJ), Boston Scientific (BSX), and Medtronic (MDT). "If the results for the next 100 patients or 1,000 patients continue to demonstrate what we are seeing in these first patients, it will truly become the next revolution in interventional cardiology," says John M. Capek, Abbott's executive vice-president of medical devices. The dissolving stent is designed to have all the benefits of today's devices without leaving behind the metal mesh used in current stents, Capek says. It may be sold in Europe within 18 months, putting it at least three years ahead of similar products that competitors are developing, he adds.
Abbott, based in Abbott Park, Ill., has a way to go before the new device gains wide acceptance. The company had to redesign the stent last year after engineers found it didn't keep the artery open as well as expected during studies on humans conducted in Europe. It will be difficult for Abbott to create a device that's strong enough to prop open an artery using materials that are less robust than the metal typically found in stents today, says Laura Mauri, a cardiologist at Harvard Medical School. "They've really just passed the first hurdle," Mauri says. "Before it's used in the U.S., we'll need to see long-term results."
The disappearing devices might solve a problem that has hampered sales of the current generation of stents: the formation of potentially fatal blood clots months or years after implantation. Many of today's stents are coated with drugs to keep scar tissue from attaching to the metal tubes. The scarring often causes the arteries to narrow again, requiring further treatment. Arteries, though, never fully heal with a drug-coated device inside, which can lead to blood clots and heart attacks.
While there haven't been any cases of clots in the 150 or so people who have received Abbott's new stent, it's still not clear whether dissolving stents offer a lower risk of clots and if they will keep arteries clear for as long as existing devices do. "The concept that a stent could go away and your artery can reheal to a normal state is a little bit fanciful," says Spencer B. King, president of the Heart and Vascular Institute of St. Joseph's Hospital in Atlanta. "But it seems to happen."
At least two smaller companies are working on similar devices. San Diego-based Reva Medical has developed a stent that starts to dissolve after 90 days. The company redesigned its prototype after some patients who received it in a 2007 study ended up needing new stents. Next year the company aims to start trials and studies that could be used to gain approval for its stents in Europe. Another device, made by Berlin-based Biotronik, has been implanted in a patient in Germany, Biotronik says. Medical centers in the Netherlands, Belgium, and Switzerland are participating in Biotronik's research and will enroll additional patients, the company says.
Larger rivals are also working on dissolvable stents, though most such efforts are aimed outside the heart. Since the dissolving stents tend to be bulkier than metal ones (to provide the strength needed to prop open blood vessels), some researchers believe they're more suitable for the larger arteries in the legs, where stress and pressure on the vessel can cause metal stents to fracture. Since removing the devices is difficult, an absorbable stent may be ideal, according to Johnson & Johnson and Medtronic. "The legs, where the arteries run close to the surface of the skin, present anatomical dynamics that may warrant this kind of biomaterials innovation," says Sean Salmon, general manager of Medtronic's coronary and peripheral division. "The clinical need to reduce pain and amputations remains largely unmet."
The bottom line: Abbott's dissolvable stent appears to reduce the risk of blood clots, though questions about the technology remain.