Atherosclerosis can have deadly consequences, one of the deadliest results being the development of a thoracic aortic aneurysm (TAA), a bulging of part of the wall of the aorta, the body's largest artery.

Treatment depends on the location of the aneurysm, with the least invasive therapy (after medication) being stenting. However, to date, no studies have taken a long-term analysis of survival following stenting, a technique now only a few years in use.

Medtronic (Minneapolis) has now reported the initiation of THRIVE, the company's U.S. post-market clinical study of its Talent Thoracic Stent Graft for the endovascular repair of TAAs. With several hundred patients to be enrolled, this is likely to be the largest and longest-term study to examine the survival potential of patients who receive stents to treat these aneurysms.

"We are trying to get overall realistic outcomes data," Karthikeshwar Kasirajan, MD, the principal investigator of THRIVE, told Medical Device Daily. "We are hoping to have more than 400 patients followed for five years. It's probably the largest trial for this indication and the largest number of patients enrolled and followed for the longest period of time."

Kasirajan, who is also the leader of the team that performed the first study implant on April 20 at Emory University Hospital (Atlanta), predicts that full data won't be available from the study until 2018 because enrollment will be graduated.

Medtronic's Talent stent was approved less than a year ago (MDD, June 6, 2008), with this study part of an FDA post-market requirement.

The Gore TAG Endoprosthesis System from W. L. Gore & Associates (Flagstaff, Arizona) was the first endovascular grafting system approved in the U.S. to treat TAA, in early 2005 (MDD, March 25, 2005).

Left untreated, aortic aneurysms can burst and cause death from internal bleeding. And TAAs affect nearly 10 of every 100,000 seniors in the U.S., according to the National Institutes of Health.

The study's primary goal is to see if patients who receive the stent after being diagnosed with an aneurysm survive beyond five years.

"There's usually a 40% mortality rate at five years for people with thoracic aortic aneurisms who receive some kind of treatment," Kasirajan said. "If you don't treat them at all, two year mortality is 60%. You don't make people immortal, but you're trying to remove this as a cause of mortality."

Thoracic endovascular aortic repair (TEVAR) is a minimally invasive procedure in which a stent graft – a fabric tube reinforced with metal springs – is threaded through the femoral artery and expanded at the site of the aneurysm. This graft is intended to create a new path for blood flow, lowering pressure on the aneurysm and reducing the risk of rupture.

Other treatment options include medication or open surgical repair.

THRIVE will include a test group of 195 subjects from the earlier study that supported the device's FDA approval, with the addition of 256 new subjects.

Late last year, Medtronic launched the Talent Abdominal Stent Graft with a new delivery mechanism called Xcelerant, which the company says makes the minimally invasive treatment of TAAs easier to perform (MDD, Oct. 24, 2008). Xcelerant has a twist-and-release design which allows stent deployment from the top (proximal) end of the stent graft down for a more controlled deployment compared to the more traditional method of deploying the stent graft from the middle to the ends.

"They changed the way Talent's delivered since we first started the study, and the newer system allows for more precise control," Kasirajan said.

Medtronic's portfolio of aortic stent grafts includes the Talent abdominal and thoracic stent graft systems worldwide; the AneuRx AAAdvantage abdominal stent graft system in the U.S.; and the Endurant abdominal and Valiant thoracic stent graft systems outside the U.S.