Stanford Computer Model Shows Bypass Surgery More Cost-effective Than Stents

"Stents are hugely popular but also expensive. It's not really clear that the benefit is there for all the patients who receive them," said Cynthia Yock, research associate in the Center for Primary Care and Outcomes Research and lead author of the study that appears in the October edition of the American Journal of Medicine. While it requires less hospitalization time and initially costs less than surgery to install a stent, the savings are lost over roughly five years as these patients suffer greater recurrent chest pain and undergo repeat procedures more often than surgery patients.

To compare these two common artery-clearing treatments, researchers took advantage of previous data from the Bypass Angioplasty Revascularization Investigation, or BARI, conducted from 1988 to 1991. That study compared more than 1,800 patients with two or more coronary arteries blocked who were randomly assigned bypass surgery or angioplasty, a procedure that uses tiny balloons to open blocked arteries. In patients tracked over more than a 10-year period, the study found no significant differences between the two groups other than angioplasty patients requiring repeat procedures more often than surgery patients.

Stents, which help hold blood vessels open after angioplasty, were just becoming available after patients in the BARI trial had received their initial treatments. Since then, the hardware has rapidly taken over; more than three-quarters of angioplasty procedures now include stents. "The technology advances so quickly, especially in cardiology," said Yock. "By the time they finished the follow-up to the BARI trial, one big objection was that it was already obsolete."

So Yock came up with a way to modernize the BARI trial with an elaborate computer model. Along with Mark Hlatky, MD, professor of health research and policy, they incorporated all the known information and expanded it to make estimates about what the costs and quality of life would be had a new technology, such as stents, existed then.

As the model's first test, it had to accurately replicate the results that were seen in the BARI trial. The researchers found that the model did indeed mimic the costs and quality-of-life measures seen in the trial. Once the model was shown to work, they could change parameters based on how much a new procedure costs, what complications it prevents and how it improves patient outcome. "The model allowed us to update the usefulness of the BARI trial for new technology and also to extend the data that we have for the trial, which was just 10 years long, through the lifetime of the patients."

Even the researchers were surprised by their findings. "We expected stenting to be much better than bypass surgery," said Yock. But, she explained, surgery also has had technological advancements, becoming safer and more effective, especially in older and sicker patients, without experiencing the same cost escalation as stenting.

Stents treat only the small section of the artery that has a blockage, while bypass surgery replaces a more extensive length of artery and therefore better protects against disease progression. "Stents are not the curative procedure that people think. If people choose stent procedures they should be prepared to come back," she said. "If your house has a major plumbing problem do you fix one drain, or replace the pipes?"

Surgery also provides better relief from chest pain. "People tend to think that less invasive is better and that new technology has to be better," said Yock. "There has been so much industry hype for stenting but very little industry promotion of surgery, so patients get an imbalanced perspective from the media about therapeutic options available to them. I don't think people realize they can have 15 years of symptom-free life with bypass surgery."

One of the biggest problems with stents is that the blockage often reappears, a process called restenosis, requiring a repeat procedure. A new generation of stents includes drugs to combat the re-narrowing of the blood vessel. While the current study did not address drug-coated stents directly, Yock said their model shows that even eliminating the costs and detrimental effects of restenosis does not make stenting a better choice than bypass surgery for patients with blockages in more than one artery. "My hope is that physicians will say, 'Stents aren't the only good thing for my patient. There are other options that may result in better outcomes'," said Yock.

Stanford collaborators were Derek Boothroyd, PhD, staff statistician; Douglas Owens, MD, at the VA Palo Alto Health Care System and associate professor of medicine at the Center for Primary Care and Outcomes Research; and Alan Garber MD, PhD, also with the VA and professor of medicine at the Center for Primary Care and Outcomes Research.

The study was funded by grants from the Robert Wood Johnson Foundation and the National Heart Lung and Blood Institute.

Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children's Hospital at Stanford. For more information, please visit the Web site of the medical center's Office of Communication & Public Affairs at http://mednews.stanford.edu.