Following a fenestrated endovascular aneurysm repair (FEVAR), the infrarenal aortic neck often continues to dilate. At the 2017 VEITHsymposium, Benjamin Starnes (University of Washington, Seattle, USA) suggested that such dilation is harmful when observed in standard EVAR practised outside instructions for use (IFU) or in association with a hostile neck. However, Starnes said that aortic neck dilation is harmless when observed with FEVAR, and that “less device oversizing may be acceptable given long seal zone lengths”.
Long-term device durability after standard EVAR procedures is dependent on rates of aortic neck dilation, graft migration and subsequent endoleak development (especially type Ia endoleak). According to a 2011 study (Schanzer et al, Circulation), between 40% and 50% of all abdominal aortic aneurysm patients are treated outside of IFU.
“We have to think about the premise that type Ia endoleaks lead to rupture and are the primary failure mode of endovascular therapy to treat abdominal aortic aneurysms,” Starnes said, as such endoleaks account for 74% of post-EVAR ruptures.
Aortic neck dilation is observed in up to 86% of EVAR patients during follow-up. Type Ia endoleak has been associated with greater mean neck dilation, one 2017 study (Lee et al, Annals of Vascular Surgery) finding mean dilation of 8.8±3.3mm compared with 3.35±2.71mm for those patients who did not develop type Ia endoleak.
A 2017 systematic review (Kouvelos et al, Journal of Endovascular Therapy) analysed data from 9,721 patients followed out to nine years and concluded that “aortic neck dilation affects a considerable proportion of EVAR patients and was related to worse clinical outcomes, as indicated by increased rates of type Ia endoleak, migration and reinterventions.” Hostile necks—with significant angulation, circumferential thrombus, calcification and a reversed conical morphology—make aortic neck dilation particularly harmful, Starnes said.
Starnes and colleagues conducted a study to find out when aortic neck dilation is harmless. Seventy-seven consecutive subjects treated with FEVAR were evaluated for aortic neck dilation, the rate of which was measured and compared with baseline at six months, twelve months, and annually thereafter. The mean age of these patients was 74 years and 75% were male. The median nominal device size was 30mm, the mean device oversizing was 17%, and mean proximal seal zone length after treatment was 41mm.
Starnes reported that the infrarenal aortic neck size dilated to the nominal size of the stent graft used, but not beyond that, while sac size reduced “dramatically”.
Starnes compared these results with the contemporary ANCHOR, ENGAGE and ASCEND registries. The most notable difference was in seal zone length, 40.8mm in Starnes’ study and <10mm, 8–15mm and 15–20mm for ANCHOR, ENGAGE and ASCEND, respectively. Despite this, there were 0 type I endoleaks in Starnes study over the entire follow up period out to five years.
“In conclusion, aortic neck dilation is harmful when observed in standard EVAR procedures practised outside the IFU or with a hostile neck,” Starnes said. “After FEVAR, the infrarenal aortic neck often continues to dilate over time but never exceeds the device diameter at any point during follow-up.”