MONDAY, April 9, 2007 (HealthDay News) -- A new study suggests that the advent of expensive drug-coated stents did not improve the success rate of procedures used to open blocked heart arteries.
Success rates in keeping these large arteries open did rise dramatically after bare-metal stents were first introduced in the mid-1990s. But those gains have since leveled off -- even after drug-coated stents entered the scene, researchers say.
However, a closer look also shows how tough it is for surgeons to deal with these blockages and suggests that, overall, stents -- flexible tubes implanted to keep arteries open -- have made a positive difference in these cases.
The blockages described in the report are much more difficult to handle than those in smaller arteries, where most stents end up. Studies reported at the meeting of the American College of Cardiology last month found that drug treatment was as effective as stent implants -- in smaller vessels, at least.
Blocked heart arteries may be a different story.
"Stents, once a heart artery has been open, are very good," said study senior researcher Dr. David R. Holmes Jr., professor of medicine at the Mayo Clinic in Rochester, Minn. "The problem is that you can't get a wire to the blockage, and you can't get a balloon through it. The problem is simply to get through the occlusion in the first place."
And, once the heart artery is open, Holmes added, "randomized trials show that drug-eluting stents do better than bare-metal stents."
His team is expected to publish its findings in the April 17 issue of the Journal of the American College of Cardiology.
The researchers pored over the Mayo Clinic's 25-year history of 1,262 open heart procedures to fix arteries that were completely, or almost completely, blocked. The surgeries covered four periods: 1979-1989, before stents were available; 1990-1996, the use of the first stents; 1997-2003, when stent use became routine; and 2003-2005, the advent of drug-coated stents.
They found that the arrival of stents boosted success rates substantially. In fact, the success rate of these artery-opening procedures rose from 51 percent in the pre-stent period to 72 percent during the first stent era in the early 1990s.
But there has been a leveling off since, with success rates of 73 percent and 70 percent, respectively, in the latter two periods. Those stagnant numbers "highlight the need for continued development of new techniques and devices" for opening blocked heart arteries, the report said.
It's an important problem, because blocked heart arteries account for about 10 percent of all such interventions, Holmes said. "Despite that, the success rate remains pretty low," he said. "There have been some improvements but significantly less than for other arteries."
The issue was further clouded by three studies, released in March in the British Medical Journal, that found that coronary bypass surgery had fewer complications and was more cost-effective than angioplasty and stents for patients with blocked heart arteries.
Surgery can be better in some cases, agreed Dr. Deepak Bhatt, associate director of the Cleveland Clinic's cardiovascular coordinating center. But he added that the choice of treatment depends on the condition of the individual being treated. Surgery is riskier than angioplasty, which, in turn, is riskier than treatment with medications, he said. The goal in all cases would be to relieve symptoms such as the chest pain called angina.
"Medical therapy might be enough for someone with a completely blocked artery," Bhatt said. "If just one artery is blocked, it might be reasonable to try angioplasty. If there are a lot of problems with circulation, enough disease in other arteries, the decision could be to go ahead and do a bypass. If there are lots of other blockages, then surgery might make sense."
And there's some heartening news in the Mayo Clinic report, Bhatt added.
"The positive side of the study is that the rate of complications has gone down dramatically," he said. "That is true even though the patients being treated are sicker."
The report found that the percentage of patients with complicating problems such as diabetes, obesity and high blood pressure has risen steadily over the years. Still, the combined rate of death, heart attack or closing of the treated artery "was significantly lower in the two most recent cohorts compared with those patients treated before," the researchers said.
The real challenge lies in the development of new techniques to open the heart arteries, Bhatt said. "That is the new frontier," he said.
The same issue of the Journal of the American College of Cardiology also carried the final report on the BARI trial, which compared balloon angioplasty with bypass surgery for treatment of "multivessel" coronary artery disease.
The trial, a collaborative study funded by the U.S. National Heart, Lung and Blood Institute, found no significant difference in the incidence of death or heart attack between the two procedures, except for people with diabetes. They benefited more from bypass surgery.
There's much more on stents at the American Heart Association.