PYTHAGORAS United States Trial Evaluates Lombard's Aorfix Endograft

August 28, 2015—Findings from the PYTHAGORAS United States clinical trial of the Aorfix endograft (Lombard Medical) were published by Mahmoud B. Malas, MD, et al online ahead of print in the Journal of Vascular Surgery (JVS).

The investigators compared the performance of the Aorfix in standard (< 60°), highly angled (60° to 90°), and severely angled (> 90°) aortic necks in the prospective nonrandomized PYTHAGORAS clinical study, and evaluated changes in neck morphology over time. The investigators concluded that the Aorfix endograft has performed well in excluding aneurysms with standard and highly angled aortic neck anatomy.

As summarized in JVS, the investigators divided the endovascular aneurysm repair (EVAR) cohort into groups by standard, high, and severe neck angle. The primary control group was composed of patients concurrently undergoing open repair. 

The EVAR groups were compared to the control for mortality at 30 days, 1 year, and 2 years. EVAR groups and the control group were compared for 30-day freedom from Society for Vascular Surgery major adverse events. Additionally, aneurysm-sac change, type 1 and 3 endoleaks, graft migration, and the reintervention rate at 1 and 2 years was compared between the standard, highly, and severely angled populations. The relative risk of graft complications with a neck diameter increase > 10% was also calculated. 

At predetermined anatomic points, the effect of oversizing on aortic diameter was evaluated by calculating oversize percentage ([1 − outer aortic diameter measured at a given time/stent graft diameter] × 100%) preoperatively and at 3 years. In addition, the average oversizing percentage at 30 days, and annually at 1 to 5 years, was compared with the preoperative oversizing percentage. Finally, complication rates with planned oversizing ≥ 30% versus < 30% were compared.

The investigators reported that the adverse event rate was lower for every EVAR group than the open control. In addition, the mortality rates at 30 days, 1 year, and 2 years were similar between the EVAR groups (standard-angle [1.5%, 3%, 4.5%], high-angle [0.9%, 7.3%, 13.8%], and severe-angle [4.8%, 9.5%, 14.3%]) and the open control groups (1.3%, 6.6%, 10.5%). 

At 1 and 2 years, there was no difference in graft complications among the EVAR groups. However, with neck dilatation of >10% at 5 mm above the proximal renal, and 1 mm below the distal renal, there was an increased risk of graft migration (relative risk, 4.38 and 4.33, respectively). For all predetermined anatomic points, the oversizing percentage decreased over time. The rate of oversize percentage decrease was faster at more distal aortic locations, reaching < 10% at 30 days for 15 mm below the renal, at 2 years for 7 mm below the renal, and at 5 years for 1 mm below the renal. 

The PYTHAGORAS investigators reported that half the oversize percentage achieved at the index procedure remained at 3 years (Pearson correlation coefficient = 0.5). However, there was no difference in complications between the ≥ 30% and < 30% planned oversize groups.