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February 2, 2006

Revolution in progress:

U-M study shows a wide range of problems in body's largest artery can be treated with a minimally invasive procedure

ANN ARBOR, MI – Tens of thousands of Americans live with a ticking time bomb in their chests. Now, a new University of Michigan study demonstrates that many of them may not need surgery in order to defuse it.

Aorta imageInstead, the research shows, a minimally-invasive procedure can repair a wide range of problems in the upper part of the aorta, the giant blood vessel leading out of the heart. In this region, called the thoracic aorta, the intense force of blood pulsing out of the heart can rip the aorta’s walls apart or cause them to balloon outward, eventually leading to a rupture that brings almost certain death.

For decades, patients have had a choice between open-chest surgery and waiting for the “time bomb” to explode. Some haven’t had a choice, because their age or health makes them too high-risk for surgery. More than 15,000 Americans die each year from ruptured thoracic aortic aneurysms, dissections and other problems.

But in recent years, a few physicians at U-M and elsewhere have tried an experimental procedure called endovascular thoracic aortic repair, or ETAR, to shore up the aorta without surgery. They’ve used devices called stent-grafts that are inserted by snaking a long tube up into the aorta from a small incision in the leg or belly. Only in the last year has the U.S. Food and Drug Administration approved the first device designed for this purpose, paving the way for more hospitals to offer it.

Earlier this week, in a presentation at the Society of Thoracic Surgeons meeting, a multi-specialty U-M Cardiovascular Center team gave data from 73 patients who had ETAR at U-M over the last 12 years. Three-quarters of them were considered too high-risk to have surgery. The average survival was nearly four years, and almost half of the patients are still alive today and have not needed additional procedures, though the researchers say close monitoring is needed after a patient has ETAR.

Himanshu Patel, M.D.“The minimally invasive approach to major aortic problems promises to revolutionize the way a broad spectrum of patients are treated,” says Himanshu Patel, M.D., the lead author of the STS scientific poster. “Even in high-risk patients who would not otherwise be treatable, we see acceptable, encouraging results.” Patel, an assistant professor of cardiac surgery at the U-M Medical School, is also chief of cardiovascular surgery at the VA Ann Arbor Healthcare System.

Patel emphasizes the team-based approach used at U-M to treat patients using ETAR. Cardiac surgeons, vascular surgeons and interventional radiologists work together to evaluate patients and determine who should have the minimally invasive procedures, and who would be able have an open-chest operation.

Because ETAR is still relatively new and has not been compared directly with open surgery for aortic conditions, the U-M team uses both approaches depending on patients’ characteristics. 

But for patients over the age of 80, and those who have stiffened arteries (atherosclerosis), diabetes, lung problems, a history of heart disease or high blood pressure, ETAR may be the only option. And since aortic aneurysms and dissections tend to form later in life and are aggravated by factors such as high cholesterol, smoking and family history, patients are inherently unlikely to be able to withstand open-chest surgery.

While the long-term effects of ETAR have not yet been established, Patel and his colleagues hope their data will help increase the appropriate use of ETAR nationwide. Among their other findings: that 96 percent of their ETAR procedures were carried out successfully, despite the fact that 22 percent of the patients had already experienced a rupture of an aneurysm or dissection at the time the procedure began – making the procedure an emergency life-saver.

Also, the researchers found that 12 percent of the patients developed “endoleaks,” in which blood entered the bulging area of the aneurysm despite the presence of the stent-graft. Nine of these patients had an additional procedure to fix the problem.

This effect, Patel and his colleagues say, means that as more and more people undergo ETAR, their physicians need to take care to monitor them carefully to look for endoleaks or other problems.

The introduction of new stent-grafts designed specifically for the upper reaches of the aorta is already leading to an increase in ETAR nationwide. This development comes after a decade during which the U-M team and other leading teams around the nation performed ETAR procedures using stent-grafts as part of clinical trials of experimental devices for the thoracic aorta.

Now, the U-M team is participating in several clinical trials of stent-grafts that are still experimental, and seeking patients who have been told they have an aortic aneurysm or aortic dissection. Many patients find out they have such a condition “by accident,” when a bulge in their aorta is discovered on a chest X-ray or other exam.

About 20,000 Americans are diagnosed with aortic aneurysms each year, and while most of those aneurysms are in the longer abdominal part of the aorta, about 25 percent are in the thoracic region. Tens of thousands of others may have the conditions but not know it, because aortic problems often don’t cause symptoms until they rupture. An estimated 3 percent of adults over age 65 have some form of aortic aneurysm.

In addition to Patel, the study’s authors include David M. Williams, M.D., director of vascular and interventional radiology at U-M and a professor of radiology; Gilbert R. Upchurch, Jr., M.D., the Leland Ira Doan Research Professor of Vascular Surgery; Michael S. Shillingford, M.D., a resident in general surgery; Mary C. Proctor, M.S.; and G. Michael Deeb, M.D., the director of the Multidisciplinary Aortic Clinic and the Herbert Sloan Collegiate Professor of cardiac surgery.

The research was funded by the University of Michigan. All of the physician authors have received research grant funding from one or more manufacturers of aortic stent-graft devices, but none of those manufacturers was in any way involved with the research presented at STS.

For information on treatment for thoracic or abdominal aortic problems, or any cardiovascular condition, at the U-M, or to learn how to take part in clinical trials for cardiovascular disease and prevention, call the U-M aortic clinic at 800-792 6782 or 734-936-1900.

Written by Kara Gavin

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