Decreased Abdominal Aortic Aneurysm Size Following EVAR in Patients With CT Evidence of Subclinical Thoracic Aortic Dissection

Abstract

Aneurysm sac regression following endovascular repair (EVAR) of an abdominal aortic aneurysm (AAA) is an established indicator of surgical success. However, even with a completely excluded aneurysm, the degree of aortic sac regression may vary. This study evaluates the relationship between aneurysm sac regression after EVAR and the presence of morphological features in the thoracic aorta that can be associated with a subclinical aortic dissection, termed dissection morphology in this study. Patients who underwent EVAR to repair an infrarenal aortic aneurysm at Mount Sinai Hospital between 1996 and 2017 with a postoperative CT scan and a 3-year follow-up scan available for analysis were included in the study. Patients with a type I or type III endoleak were not included. The thoracic aorta was evaluated for dissection morphology on CT scan, which included the presence of aortic dissection, penetrating aortic ulcers, and intramural hematomas. AAA sac regression after EVAR was compared between patients with dissection morphology (n=157) and patients without those characteristics (n=141). An independent investigator performed the CT analysis and was blinded to the degree of sac regression. Demographics and comorbid clinical conditions were compared between patients with and without dissection morphology. There were no significant differences in age, gender, smoking habits, or cardiovascular conditions. The median AAA diameter after EVAR, over the course of the study, in patients with dissection morphology decreased by 11.30mm (-17.20, -3.60) compared to a median change of 0.30mm (-8.60, 8.60) in patients without dissection morphology features (p<0.001). Patients with dissection morphology also had fewer type II endoleaks in postoperative follow-up scans (22.9% vs. 53.9%, p<0.001). Additionally, patients with dissection morphology had longer EVAR operative times (192.00min [167.25, 230.00] vs.174.00min [150.00, 215.00], p=0.004). AAA-related mortality after 3 years was not significantly different between the 2 groups (p=1.0). The presence of imaging features consistent with dissection morphology in the thoracic aorta correlated with greater AAA sac regression and fewer type II endoleaks after EVAR. Assessing these imaging features in patients undergoing EVAR may be useful in understanding aneurysm behavior in terms of aneurysm growth, risk of rupture, and outcomes following endovascular surgery. Identifying differential rates of aneurysm sac regression may have implications regarding the role of subclinical dissections in the etiology of AAA development.