Compared to open surgery, endovascular repair of abdominal aortic aneurysm (AAA) is associated with lower short-term rates of death and complications (1.2% vs. 4.8%), a study published last week in the New England Journal of Medicine concluded. But there are trade-offs between the two approaches, and the survival advantage of endovascular repair gradually wanes over three years.

The study, based on a review of 45,660 Medicare discharges, also found that by four years rupture was more likely in patients treated with endovascular repair than in open repair (1.8% vs. 0.5%), as was reintervention related to AAA (9% vs. 1.7%). In contrast, surgery for laparotomy-related complications was more likely among patients who had undergone open repair (9.7%, vs. 4.1%), as was hospitalization without surgery for bowel obstruction or abdominal-wall hernia (14.2% vs. 8.1%).

The study, “Endovascular vs. Open Repair of Abdominal Aortic Aneurysms in the Medicare Population” — authored by Marc Schermerhorn, MD; A. James O’Malley, PhD; Ami Jhaveri, MD; Philip Cotterill, PhD; Frank Pomposelli, MD, and Bruce Landon, MD — tracked 22,830 matched-pair Medicare patients between 2001 and 2004 with follow-up in 2005.

“We applaud these researchers for undertaking a comparative study that points to important advantages of minimally invasive AAA repair over open surgery beyond the generally accepted benefits of reductions in perioperative mortality and morbidity,” said Paul McCormick, president/CEO of Endologix (Irvine, California). “These differences confer significant clinical and economic benefits for the endovascular option and support our conviction that endovascular repair is on the way to becoming the standard of care for AAA repair.”

Endologix developed the Powerlink system endoluminal stent graft for the treatment of AAA.

While short-term results of the NEJM study favored the endovascular approach, long-term advantages were less clear. The endovascular approach avoids the laparotomy-related complications of open surgical repair, but the study suggests that the less invasive approach is associated with a higher risk for problems related to the aneurysm repair.

Still, McCormick told Medical Device Daily that the risks associated with open surgical repair of AAA – in particular, laparotomy-related complications and risk of bowel obstruction or abdominal wall hernia – are greater than the long-term risks of endovascular repair.

“The real measure of a technology would be the rate of aneurysm-related death — that’s what you’re treating,” McCormick told MDD. Because patients with AAA are usually older and sicker with more serious co-morbidities, “total mortality is probably not a good measure of anything,” he added.

AAA is a weakening of the wall of the aorta, the largest artery in the body, resulting in a balloon-like enlargement. Once AAA develops, it continues to enlarge and, if left untreated, becomes increasingly susceptible to rupture.

According to an article in Journal Watch Cardiology citing the NEJM study, endovascular approaches for AAA surgery were introduced in 1991 and now account for more than 40% of elective repairs.

During an endovascular repair procedure, the physician makes two small incisions in the groin and threads two catheters through the patient’s arteries. Once in place in the weakened section of the aorta, the catheters release a tubular device comprised of large z-shaped metal stents sewn to surgical graft material that expands to channel blood through the aorta and reduce the pressure on the aneurysmal sac, lessening the risk of rupture.

Cook Medical (Bloomington, Indiana) reported similar results in a recent two-year clinical study evaluating its Zenith AAA endovascular graft, an endovascular aneurysm repair device used to treat AAAs, in 430 patients at 15 health centers throughout the U.S. Cook’s study indicated a 98.9% rate of survival at 30 days for standard and high medical risk AAA patients following endovascular repair and 97.5% for standard risk patients who underwent open surgery. Freedom from AAA-related mortality was high for endovascular repair patients through two years, with 98.9% AAA-related survival of standard-risk patients and 93.8% for high-risk patients, Cook said.

“Both the data generated from the New England Journal of Medicine study and the results from our clinical study further reinforce that [endovascular aneurysm repair] is the favorable choice for patients in need of AAA repair,” said Barry Thomas, VP of Cook’s Aortic Intervention business.

In November, Cook launched its 36mm diameter Cook Zenith Renu AAA ancillary graft (Medical Device Daily, Nov. 15, 2007). The graft is designed for secondary endovascular intervention in patients who received prior endovascular repair of infrarenal AAA. The graft is specifically intended to treat AAA patients whose implanted stent-grafts may have shifted, Cook noted. The company reported FDA approval for the graft in 2006 (MDD, Oct. 31, 2006).

Another competitor in this space is Medtronic (Minneapolis). Earlier this year Medtronic reported the U.S. market launch of its AneuRx AAAdvantage stent graft on its new Xcelerant hydro delivery system, which features a hydrophilic coating designed to aid navigation of the device through tight and tortuous arteries by reducing friction with the artery wall (MDD, Jan. 14, 2008).

Medtronic received FDA approval of its AneuRx AAAdvantage stent graft with Xcelerant delivery system in 2006 (MDD, March 29, 2006).

The AAA market is expected to soar, according to the Millennium Research Group (MRG; Waltham, Massachusetts). Its analysis last year of the peripheral vascular device market found that the second largest segment of the market, AAA repair via stent grafts, was valued at $300 million in 2006 and would grow at a compound rate of about 13% annually over the next five years, resulting in a total market value of about $550 million by 2011 (MDD, March 9, 2007).

MRG said that a program initiated by Medicare called Screening Abdominal Aortic Aneurysms Very Efficiently (SAAAVE) Act would have a significant impact on the growth of AAA procedures over the next five years.

Last year Medicare began offering free, one-time ultrasound screening benefits to check for AAA in qualified seniors. The initiative covers men ages 65-75 with a history of smoking, and men and women in the same age bracket with a family history of AAA (MDD, Jan. 12, 2007).