July 16, 2009
A new study concluded that the most commonly used method for extracting leg veins for grafts in coronary bypass surgery was more dangerous than the traditional method, and resulted in more deaths among patients.
Companies making vein-extraction devices, and some doctors, cast doubt on the study’s conclusions, saying that it wasn’t scientifically rigorous enough. But the finding is likely to raise concerns in the cardiology field and among patients undergoing cardiac bypass, an operation done about 300,000 times a year in the U.S. Some surgeons say they have already made adjustments in the way they harvest veins.
Over the past decade, bypass surgeons have migrated from a traditional vein-extraction technique to a “minimally invasive” method that weaves a thin tube through a small incision in the leg. The minimally invasive method is now used in at least 70% of bypasses, the study authors said.
But the study, led by scientists from Duke Clinical Research Institute, suggests this method of harvesting veins puts patients at a higher risk of death and other long-term complications. In the three years after bypass, 7.4% of patients who had the minimally invasive surgery died, versus 5.8% who underwent a traditional vein extraction. Although the causes of the deaths weren’t known, the researchers speculate that the higher death rate of the first group may have been linked to the vein-extraction method.
In minimally invasive, or endoscopic, harvesting, a clinician pulls a vein through a leg incision, using instruments to bore a tunnel and see inside it. The leg vein is then used to craft a bypass around a blocked coronary artery. Driven by faster recovery times and fewer wound complications, the endoscopic technique largely displaced open-leg harvesting, in which doctors cut the leg from ankle to groin to remove the vein.
In 2005, the International Society for Minimally Invasive Cardiothoracic Surgery recommended endoscopic harvesting as a standard of care in bypass surgeries.
Authors of the new study don’t call for abandoning endoscopic harvesting, but said more rigorous research is needed into its long-term effects.
“We found that patients who underwent endoscopic harvesting had higher rates of vein-graft failure 12 to 18 months after [the bypass] and, more important, also had significantly worse clinical outcomes at three years, including higher mortality,” the researchers wrote.
“This is a potentially important public-health issue,” says Robert Harrington, a Duke cardiologist who co-authored the study. He noted that the results suggest that among a thousand patients undergoing endoscopic harvesting, there will be 16 more deaths than among a thousand patients undergoing open harvesting.
In evaluating endoscopic harvesting, the researchers drew on data from patient records gathered in an earlier study designed to measure the efficacy of an unrelated procedure. Of the 3,014 patients included, 1,753 underwent endoscopic harvesting and 1,247 went through open harvesting, beginning in 2002. The assignment to either group wasn’t random, which makes the study’s design less scientifically rigorous.
The researchers suggested that the adverse effects of endoscopic harvesting may stem from a greater damage inflicted on the vein as it’s pulled out. The pressurized surgical tunnel may cause blood to clot, damaging the vein. Endoscopic devices also generate heat, which may burn parts of the vein.
“While open harvesting is much more traumatic to the patient, it may not be as traumatic to the vein,” says John Alexander, a Duke cardiologist who co-authored the study.
Some surgeons have begun already to make adjustments in how they harvest veins. Michael Mack, a thoracic surgeon in Texas and a study co-author, says he now gives his patients the blood thinner Heparin to protect their leg veins from clotting damage.
Robert Poston, chief of cardiac surgery at the Boston Medical Center, says he uses infrared imaging to spot tears in the extracted leg veins. Dr. Poston, who wasn’t involved in the study, questions its conclusions about endoscopic harvesting and higher risk of death.
Makers of endoscopic devices are also skeptical. The industry, dominated by three competitors, generated $165 million in sales last year, according to an estimate by Millennium Research Group.
Patrick Walsh, chief operating officer of Maquet Cardiovascular, a unit of Sweden-based Getinge AB, says he was surprised by the study’s conclusions. Mr. Walsh cites other studies that describe patient benefits of endoscopic harvesting, and says, “We are always looking to improve the product.” Maquet now markets a device that generates less heat than older devices.
A spokesman for Sorin Group, a rival Milan-based medical-equipment maker, says, “We completely disagree with the study’s conclusions and with the study’s method.”
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