Early AAA Stent Grafts Graded C-minus

EINDHOVEN, The Netherlands, Jan. 18 -- First-generation stent grafts for endovascular repair of abdominal aortic aneurysms (AAA), used only in Europe, have had a high rate of rupture and other early and late complications, reported European physicians.

Among more than 1,100 patients who received one of two early devices for AAA repair, 7.1% needed to undergo conversion to open surgery, 2.4% had a rupture of the aneursysm, 20% died of any cause, and 3% succumbed to an aneurysm-related cause, reported Lina J. Leurs, M.Sc., and colleagues on behalf of investigators in the EUROSTAR registry.

"One interpretation of these results is that endovascular repair with these early predicate devices is fraught with early and late problems," wrote Jon S. Matsumura, M.D., a surgeon at Northwestern in Chicago, in a critique accompanying the registry report in the January issue of Archives of Surgery.

The FDA deserves credit for preventing commercial dissemination of these devices in the U.S., Dr. Matsumura continued. "Unfortunately, another interpretation of these data is that subsequent devices may, in longer follow-up, have similar problems."

The authors conducted a retrospective study to illuminate the long-term results of endovascular AAA repair techniques that premiered in the mid-1990s, using data from 62 centers in the EUROSTAR (EUROpean collaborators on Stent-graft Techniques for abdominal aortic Aneurysm Repair) registry.

The study included data on 1,190 patients who underwent surgery with one of two first-generation endovascular stent graft devices from 1994 to 1999.

"These first-generation commercially available stent grafts (Stentor; MinTec [Minimally Invasive Technologies SARL], La Ciotat, France and Vanguard; Boston Scientific, Natick, Mass.) were modular devices constructed from an externally placed thin-walled polyester (Dacron) graft covering, a flexible self-expanding nitinol stent," the authors noted.

"The proximal end of the stent graft was uncovered. This bare stent segment was much shorter than in modern stent grafts, in which this part routinely provides suprarenal fixation. Fixation and sealing of the stent graft was accomplished by several mechanisms, including compression fit (i.e., radial forces, exerted by the self-expanding stent, hooks, and barbs)."

The designs of the early stent grafts made them prone to endovascular leakage and tears along the seam lines and through the thin polyester material, and the metal components were subject to corrosion. Manufacturers corrected those errors in subsequent devices, the authors noted.

In their review of outcomes, the authors found that 35 patients (2.9%) died within a month of surgery; eight of these patients had small aneurysms, and 27 had large defects (P=0.002). Patients with large aneurysms were also significantly more likely to require a conversion to open repair.

Patients with large aneurysms (> 55 mm) also had significantly more intraoperative device-related complications, such as inability to deploy the device and device migration, which occurred in 11.2% of patients with large aneurysms, compared with 7.4% of those with smaller defects (P=0.03).

"From operation to hospital discharge, systemic complications (cardiac, cerebral, pulmonary, renal, hepatobiliary, bowel, and sepsis) were observed in 12.9% of the patients," the authors noted. "Patients with large aneurysms more frequently experienced these complications (15.9% versus 9.8%)."

The investigators noted that the while patients with large aneurysms were particularly at risk for early and late complications, the 4.4% early mortality rate among these patients with the stent-graft procedure was lower than that associated with reported rates of 5-6% for open repair surgery for all good- and poor-risk patients combined.

"Patients treated with the first generation of stent grafts will need lifelong surveillance, because of the risk of complications," the authors wrote. "This risk is particularly high in patients with large aneurysms at operation. The long-term effectiveness of endografts currently used has not been demonstrated. Vigilant surveillance is indicated in all patients after endovascular repair of AAAs."

When they looked at outcomes over the long haul, the EUROSTAR investigators found that up to eight years after surgery, 19.9% of patients had died from all causes, and that 3% had died from aneurysm-related causes. In addition, 7.1% required conversion to open repair, and 2.4% had rupture of the aneurysm.

The annual incidence rate for all-cause death was 7.1 per 100 patient-years (95% confidence interval, 5.7-8.5), for aneurysm-related death was 1.9 per 100 (95% CI, 1.4-2.6), for conversion to open repair was1.6 per 100 (95% CI, 0.9-2.3),and for rupture was 0.8 per 100 (95% CI, 0.3-1.2).

The complications with the highest incidence rate per 100 patient-years were endoleak (13.0 cases), stenosis/thrombosis (4.6 cases), migration (4.3 cases), and suture breakage (4.0 cases). Secondary interventions were required, with an annual incidence of 11.6 cases per 100 patient-years," the authors wrote.

Patients with larger aneurysms had significantly higher incidence rates for all-cause and aneurysms related deaths, conversion, and rupture than patients with small aneurysms.

In a Cox proportional hazards model, risk factors independently associated with increased rates of death or rupture were the age at operation and aneurysmal diameter. The diameter of the aneurysm was also an independent risk factor for conversion to open repair,

"The cumulative percentage of the combined outcome event of conversion- and rupture-free survival after eight years of follow-up was 48.0% (56.1% in patients with small aneurysms and 39.6% in patients with large aneurysms; P