SCOTTSDALE, ARIZ. – Endovascular abdominal aortic aneurysm repair using a flexible endovascular stent graft in patients with infrarenal aortic neck angles of sixty degrees or greater had more favorable survival and major adverse event rates when compared with open repair, although the difference was not statistically significant, according to clinical, 2-year, postmarketing data.

At this year’s annual Southern Association for Vascular Surgery meeting, Dr. Mahmoud B. Malas presented 2-year safety and efficacy follow-up data from the PYTHAGORAS trial to evaluate the Aorfix (Lombard Medical, U.K.). The device, approved in 2013 by the Food and Drug Administration, is an endovascular stent graft for use in patients whose aortic neck angulation of between 60 and 90 degrees typically has disqualified them from having endovascular aneurysm repair (EVAR) for AAA.

The device is placed within the aneurysm, where it conforms to the individual patient’s anatomy, creating an internal bypass of the aneurysm to reduce the risk of rupture.

“The freedom from major adverse events, despite this hostile neck anatomy, was excellent,” Dr. Malas said of the data.

The PYTHAGORAS study enrolled and treated 151 patients with aortic neck angles of 60 degrees or greater, and 67 patients with necks less than 60 degrees using EVAR. The primary control group consisted of 67 patients undergoing actual open surgical repair (OSR). A secondary control group was a meta-analysis of 323 patients taken from other U.S. EVAR studies (SVS Lifeline).

There were no statistically significant differences between major adverse event rates, nor 30-day and 1-year mortality rates between low- or high-angle EVAR groups when compared with controls. There also was no difference between low- and high-angle EVAR patients sac shrinkage, type I/III endoleaks, and endograft migration, according to Dr. Malas.

The median neck angle in the EVAR group was 71 degrees (standard deviation of ±23 degrees; P < .05), compared with 48 degrees (SD, ± 23 degrees; P < .05) in the OSR control group. There were twice as many women in the EVAR group (35% vs.17%; P < .0001). Patient demographics and comorbidities were similar between the entire EVAR cohort and control group, with the exception of age (76 years vs. 70 years, respectively; P < .05) and heart failure (13% vs. 7%, P = .015). Operative data favored EVAR for procedure duration, blood loss, and hospital length of stay (P < .05 for all).

Dr. Malas said that in the combined EVAR cohort, there was a tendency for the infrarenal area to dilate more rapidly than the suprarenal aorta. “If the neck dilated more than 10%, there was a significant increase in risk of migration and sac expansion, especially close to the renal, but it was not true as you went beyond 7 mm distal to the renal.”

He also noted that the suprarenal aorta does change in association with migration and that there is a “clear association between the degree of oversizing and neck dilation.”

The presentation’s discussant, Dr. Jean M. Panneton, a vascular surgeon at Sentara Heart Hospital in Norfolk, Va., challenged the findings.

“Unfortunately, this trial did suffer from a slow accrual. As a result, only a small proportion of patients have reached the 5-year follow-up, and any subanalysis of such a small study population divided into three groups reduces the n value to the point that a type II error can easily be introduced into your analysis.”

Among the issues he raised was that the mortality data at 30 days, 1 year, and 2 years for the patients with the highest neck angulations could be misleading. “The patients in this group had a threefold increase [in mortality] compared with the standard group. Could this difference have been significant with a larger number?”

To overcome the lack of follow-up time, Dr. Malas said he and his colleagues used statistical modeling that gave them 500 data points on which they based their analysis.

Dr. Panneton also wondered if in the realm of EVAR AAA outside of the study, patients whose aortic neck lengths he said would average between 10 and 15 mm, would enjoy the same success rates as those EVAR patients in the study whose median aortic neck size was 20 mm-25 mm. “Do you think that this long seal zone accounted partially for the performance of the Aorfix? And will this performance hold up in real life?”

Dr. Malas responded that the investigators mandated at least a 15-mm neck for patients in the EVAR arms “because the way the seal zone is in a severely angulated neck means the effective seal zone will be on the inner curve of the neck, which might end up being only 4 or 5 mm, even if you have a 15-mm neck. So, it is very important to get the message out that if you’re going to use the Aorfix in a standard neck – less than 60 degrees – that you have zero migration. If you’re going to place this at a 90-degree angle, it’s very important you do not put it in a patient who doesn’t have a 15-mm neck.”

Dr. Mahmoud was one of the lead site investigators for the PYTHAGORAS trial, sponsored by Lombard Medical.

wmcknight@frontlinemedcom.com

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Clinical follow-up data promising for EVAR in AAA with angulated aortic neck