Aortic neck dilation after endovascular abdominal aortic aneurysm repair: should oversizing be blamed?

Long-term durability after endovascular abdominal aortic aneurysm repair (EVAR) is dependent upon the maintenance of an effective seal between the endograft and the proximal landing zone. Continuous neck dilation might lead to the loss of such a seal. This study aims at evaluating the incidence, risk factors, and clinical consequences of post-EVAR aneurysm neck dilation in patients treated with two types of endografts: AneuRx and Ancure. We reviewed data concerning all consecutive patients submitted to primary EVAR using the AneuRx and Ancure devices. Preoperative neck anatomic characteristics (diameter, calcification, and thrombus load) were evaluated, and device oversize percentage was calculated. Postoperative same-level neck diameter was measured on all postoperative computed tomographic (CT) scans. Probabilities of neck dilation (> or = 10% and > or = 15%) relative to preoperative diameter and first postoperative diameter were estimated with the Kaplan-Meier method and compared between patients using both types of endograft. The impact of anatomic characteristics on neck dilation incidence was evaluated using Cox proportional hazards models. Mean neck dilation was compared between patients with and without device migration and proximal type I endoleak. Both groups had similar probabilities of dilating > 10% relative to preoperative diameter and to first postoperative diameter. Proximal necks in AneuRx-treated patients had higher probabilities of dilating > or = 15% relative to preoperative diameter than Ancure-treated patients (45.5% vs. 18.7% at 1.5 years, p = 0.025), but the probability of such dilation relative to the first postoperative diameter was not different between the two groups (12.4% vs. 9.1% at 1.5 years, p = 0.832). None of the preoperative neck characteristics was associated with neck dilation risk. Device oversize percentage was correlated with the percentage of neck dilation at first postoperative CT scan relative to preoperative diameter in both the AneuRx (correlation coefficient = 0.469, p < 0.0001) and the Ancure (correlation coefficient = 0.464, p < 0.011) groups, but it was not correlated with the percentage of neck dilation at 1 or 1.5 years relative to first postoperative CT scan in either group. Patients with and without caudad device migration (> or = 5 mm) had similar percentages of neck dilation at 1.5 years relative to preoperative diameter, but migrators had higher mean percentages of dilation at 1.5 years relative to first postoperative neck diameter (11.4% vs. 5.6, p = 0.012). Two phenomena may be differentiated: an immediate postimplant dilation, strongly correlated with the percentage of oversize and more likely to reach values > or = 15% with an AneuRx device than with an Ancure graft, and a subsequent dilation, relative to the first postoperatively measured diameter, equally probable with either type of device, not correlated with the percentage of oversizing but associated with caudad device migration. Our study does not support any adverse role for the degree of oversize.