NEW ORLEANS -- A new analysis by Duke University Medical Center researchers indicates that 1 in 12 implants of tiny tubes called stents to hold open newly unclogged arteries in patients with symptomatic coronary artery disease may be unnecessary.
The arteries were unclogged by an angioplasty procedure in which a tiny balloon is inflated at the site of arterial blockage, pushing the blocking plaque aside and restoring blood flow to the heart. Stents are mesh tubes used to hold arteries open after angioplasty.
The Duke study pooled the results of seven different angioplasty trials and looked at more than 5,000 angioplasty patients. The researchers found that approximately 8 percent to 18 percent of stent implants did not appear to be necessary, especially for men whose vessels had shorter atherosclerotic lesions not involving the top of the artery that feeds the left side of the heart. According to the analysis, a simple angioplasty to clear the blockage appears to work as well as implanting a stent.
"In 1998, more than 500,000 people received stents, and our data suggest that one in 12 may not have required them," said Duke cardiologist Dr. Warren Cantor. "Based on an estimated cost of $1,500 for each stent, the U.S. health care system could potentially save more than $60 million."
Cantor prepared the results of his analysis for presentation Tuesday at the annual scientific sessions of the American College of Cardiology.
The cardiologists looked at those patients who obtained 'stent-like results' from the angioplasty without having had a stent implanted. For the researchers, this meant that the degree of narrowing that persisted after balloon inflation was less than 30 percent without any residual tear in the vessel.
As a part of the study, the researchers also surveyed 133 interventional cardiologists from around the world about how they would define stent-like results, based on visual and radiographic data. As expected, there was a wide variety of opinions, with 45 percent of cardiologists saying that for them, a 10 percent residual narrowing represented stent-like results.
"Only 1 percent of the patients in our study achieved the 10 percent level, which indicates to us that 10 percent is not a practical definition," Cantor said. "On the other hand, we found that a 30 percent or less residual narrowing was associated with a favorable clinical outcome."
Before the advent of stents, up to one-third of all patients who received an angioplasty needed another angioplasty or a bypass operation after six months because the artery would become blocked again, a process known as restenosis. Since the introduction of stents in the United States less than 10 years ago, the restenosis rate has been nearly cut in half.
According to Cantor, about 80 percent of all angioplasty procedures in many institutions now include the placement of a stent.
While stents have markedly reduced the rate of restenosis, Cantor said stents have their own drawbacks. When restenosis does occur, it is more widely diffused along the artery, making it harder to treat. Also, there is a slight (1 percent) risk of clot formation, which could lead to a heart attack
In a typical procedure, the stent is implanted in the artery after the balloon has opened it up. However, it is becoming increasing common for cardiologists to automatically implant the stent before seeing if the balloon achieved the desired effect, according to Duke cardiologist Dr. Magnus Ohman, the study's senior researcher.
"This a very controversial topic, without much scientific data on either side," Ohman said. "This evidence suggests that we can achieve reasonable results with the balloon alone in a certain group of patients. We can always reserve the excellent stent technology for those patients who really need it, and there are many of them, and reduce health care expenditures at the same time."
Ohman added that since this is a retrospective database analysis, the next step is to validate the results in a prospective trial.
The researchers analyzed data from 5,143 patients who received balloon angioplasty and looked at what happened six months later. Of those patients, 18 percent achieved a stent-like result.
Of all the factors that led to stent-like results that were studied, only three were statistically significant: gender, location of the blockage, and the size of the blockage. While the last two factors didn't surprise the researchers, the first did.
"For the men with stent-like results, 17 percent needed repeat revascularization procedures at six months," Cantor said. "For the women, however, 28 percent required repeat revascularization. While we don't know the reason for this difference, it could have do with the fact that, on average, women's vessels are smaller."
At the opposite end of the spectrum would be women who had medium to long blockages.
"For this group, 46 percent needed revascularization at six months," Cantor said. "So, even if someone in this group had a stent-like result after balloon angioplasty, we should still put in a stent."
Looking at the group of patients as a whole, of the 18 percent who achieved stent-like results, 45 percent had all three of the favorable characteristics: gender, size and location of blockage. This represents about 42,000 patients, or 8 to 9 percent of all angioplasty procedures performed, Cantor said.
"The beauty of this study is that it shows we can achieve the best of both worlds -- providing the highest quality of care in a cost-effective manner," Ohman said.
The study was supported by the Duke Clinical Research Institute, as well as the Royal College of Physicians and Surgeons of Canada. Joining Cantor and Ohman in the analysis were Nancy Wilderman, Dr. Michael Sketch, Dr. Eric Peterson, Dr. James Zidar, Dr. James Tcheng and Dr. Robert Califf.
Note to editors: A graphic showing angioplasty and stent in a clogged artery is available on the web at http://ed-media.mc.duke.edu/aved/avart/angio.htm.