Data from the PYTHAGORAS (Prospective aneurysm trial: high angle Aorfix bifurcated stent graft) clinical trial suggest that the Aorfix (Lombard Medical) endograft remains the only on-label alternative to open abdominal aortic aneurysm repair for patients with highly angulated aortic necks, according to Mark Fillinger, Dartmouth Hitchcock Medical Center, Lebanon, USA, who presented the data at the 2015 VEITHsymposium (17–21 November, New York, USA).
“Despite predictors of worse short- and long-term outcomes for the Aorfix group”, Fillinger said, “the incidence of major adverse events is superior to open repair, and EVAR-specific outcomes are similar to trials with much less severe anatomy, even when followed to five years.”
The Aorfix device—designed to treat highly-angulated aortic necks—utilises four pairs of proximal hooks and an 8mm primary seal zone, and is most commonly placed in a trans-renal position. The US PYTHAGORAS trial is the first EVAR trial in aortic neck angles of 60–90 degrees. The EVAR arms of the trial are the “roll-in” group of 67 EVAR patients with neck angle
Fillinger said that the patients in both arms had similar aneurysm sac diameters (5.8cm in each group). However, the high angle group differed in factors that have previously been shown to adversely affect outcomes, including: age (EVAR 76 years vs open 69 years, p<0.001), gender (EVAR 29% female and 35% in high angle vs open 20%, p<0.02) and neck angle (EVAR all 71 degrees and high angle 83 degrees vs open 48 degrees, p<0.001). Sixty-nine per cent of EVAR patients had a neck angle of >60 degrees compared to 27% in the open arm. “This is the first trial with more extreme anatomy in the EVAR group,” Fillinger noted, “and females also have known worse outcomes, so we had more challenging factors in the test group than in the open group”.
The number of female patients was “two to three times higher than any other trial to date”. This was because in this trial, as neck angle became more severe, the proportion of female patients increased. Another important thing to note, Fillinger explained, is that the inclusion criterion for this study was a 15mm long neck, measured on the centre-line, and in high neck angles, this sometimes resulted in an inner curve seal zone as short as 8mm. Although, in angled necks, the centre-line length can give a poor estimate of the minimum seal zone length, the results of PYTHAGORAS showed that this measure was satisfactory for Aorfix and it is now forms part of the approved indication for the implant.
Aortic endografts were successfully implanted in 210/218 cases. Mortality was 1.8% for the entire cohort (4/218), 2% for the 60–131 degree angle group (3/153) and 2.8% for open surgery patients (9/323). Thirty-day outcomes favoured the Aorfix group for procedure duration, blood loss, transfusion and length of hospital stay (all p<0.05).
Freedom from major adverse events was “highly superior” in the Aorfix group at both 30 days and one year compared with the open group. At long-term follow up (one to three years) all-cause mortality was “significant” at three years, at 21.9% in the high angle group (60–131 degrees), though Fillinger did explain that this could be expected in what is the most vulnerable group. In the lower angle group of
Sac expansion rates for the Aorfix group were 1.2% at one year, 5.4% at two years and 7% at three years, representing “excellent sac shrinkage and a small amount of sac expansion”. Fillinger told delegates that these figures are in-line with existing data in the literature from trials with anatomy that was far less severe than that treated in this trial.
Fillinger also gave the audience a taste of what is to come with the trial’s five-year results. Freedom from all-cause mortality at 0.64 and five-year freedom from aneurysm-related mortality are both in-line with existing data from the Lifeline 2005 study (0.977 five-year freedom from aneurysm-related mortality), which treated far less severe anatomies. This is also true of five-year freedom from secondary intervention, which at 0.81 was comparable with the Lifeline study (0.78), and for five-year freedom from sac rupture (0.98 in the Aorfix trial and 0.987 in the Lifeline study). Fillinger stressed that the ability of the Aorfix endograft to achieve comparable results in far more severe anatomies means that these data represent “excellent results”.
Fillinger suggested some tips for using Aorfix. He suggested that operators start with normal anatomy to learn correct deployment and become comfortable with the device, and to avoid severely irregular necks (≥5mm diameter change over 15mm length). Furthermore, he suggested placing the device at the renal arteries where the neck is most stable and watching the renals in angulated necks, using proper C-arm gantry angles based on CT angiography.