Regarding “Standard endovascular aneurysm repair in patients with wide infrarenal aneurysm necks is associated with increased risk of adverse events”

LETTERS TO THE EDITOR Regarding “Standard endovascular aneurysm repair in patients with wide infrarenal aneurysm necks is associated with increased risk of adverse events” We read with great interest the paper published by Oliveira et al in the Journal.1 In this study, the authors highlighted the potential role of wide abdominal aortic aneurysm neck diameter on the outcomes using the Endurant endograft, and they found that neck diameter $30 mm may be related to adverse events during the midterm follow-up. This finding apparently will have a potential influence on the decision-making for the treatment of patients with large necks. Nevertheless, the results of this study should be interpreted with caution. No matching between the two groups was performed. Whereas the control group included patients with neck diameters ranging between 22 and 28 mm, in the wide-neck group there were patients in whom at 0 cm, 5 cm, and 10 cm the neck was below 30 mm. This by inference means that not all necks classified as being $30 mm were above this level in their entire length. From a theoretical point of view, when the diameter is $30 mm, by definition it is an aneurysmal area and thus may become more prone to a negative remodeling. In addition, the methodology followed to define whether the neck diameter was $30 mm did not take into account the configuration of the neck (tapered vs reversed tapered). Another point of interest is that Endurant instructions for use (IFU) recommend treatment of aneurysms with a neck diameter up to 32 mm with a 10% to 20% proximal oversizing. In the present study, the median stent graft oversizing was significantly different between the two groups, ranging from 7.9% to 23.1%; thus, at least some patients in the wide-neck group have been treated outside the IFU. This may have biased the results, given the small number of patients included and the low event rate recorded. It is well known that endovascular aneurysm repair (EVAR) appears less effective if it is performed outside the IFU, increasing the risk for long-term failure and worse outcome.2,3 It would have been more appropriate to include only patients treated inside the Endurant’s IFU to avoid inclusion and systematic biases. In addition, although preoperative proximal neck length did not differ between the two groups, at 30 days the median proximal seal length was 19.5 mm for the $30-mm group and 28 mm for the control group. This loss of the initial proximal landing zone in the $30-mm group from the first postoperative month may imply a negative remodeling process that accounted for the increased risk of neck-related adverse events. Besides the aforementioned weakness of this study,1 it should be admitted that it adds to the existing

knowledge on the understanding concerning the remodeling process of a wide infrarenal proximal aortic neck after the implantation of the Endurant endograft. Future studies should focus on the identification and evaluation of predictive risk factors of neck-related adverse events in treating patients with wide necks. This could help to determine the group of patients who may warrant a different EVAR strategy or a closer post-EVAR surveillance.

George Kouvelos, MD, MSc, PhD Konstantinos Spanos, MD, MSc, PhD Athanasios Giannoukas, MD, PhD, FEBVS Miltiadis Matsagkas, MD, PhD, FEBVS Department of Vascular Surgery Faculty of Medicine School of Health Sciences University of Thessaly Larissa, Greece

REFERENCES 1. Oliveira NF, Bastos Gonçalves FM, Van Rijn MJ, de Ruiter Q, Hoeks S, de Vries JP, et al. Standard endovascular aneurysm repair in patients with wide infrarenal aneurysm necks is associated with increased risk of adverse events. J Vasc Surg 2017. [Epub ahead of print]. 2. Troisi N, Torsello G, Weiss K, Donas KP, Michelagnoli S, Austermann M. Midterm results of endovascular aneurysm repair using the Endurant stent-graft according to the instructions for use vs. off-label conditions. J Endovasc Ther 2014;21:841-7. 3. Oliveira-Pinto J, Oliveira N, Bastos-Gonçalves F, Hoeks S, van Rijn MJ, Ten Raa S, et al. Long term results of outside “instructions for use” EVAR. J Cardiovasc Surg (Torino) 2017;58: 252-60. http://dx.doi.org/10.1016/j.jvs.2017.03.423

Reply We are grateful for the attention our manuscript has received from Kouvelos et al and for the opportunity to clarify their inquiries. The outcomes of 427 consecutive endovascular aneurysm repair (EVAR) patients treated at three highvolume centers with the Endurant stent graft (Medtronic, Santa Rosa, Calif) were assessed.1 Patients were included in the study group if the reference neck diameter was $30 mm. Despite that other neck morphologic characteristics were not used for group selection, all relevant morphologic factors associated with increased risk of neck-related adverse events were addressed, unlike Kouvelos et al suggest, and the most relevant subanalyses were performed. We acknowledge that both groups were not formed as 679