Predictive factors and clinical consequences of proximal aortic neck dilatation in 230 patients undergoing abdominal aorta aneurysm repair with self-expandable stent-grafts.

OBJECTIVE: Several studies have suggested that proximal aortic neck dilatation (AND) is a frequent event after balloon-expandable endografting. Yet few data are available on AND after repair with self-expandable stent grafts. To investigate incidence, predictive factors, and clinical consequences of AND, computed tomography (CT) scans obtained at intervals during follow-up of 230 patients who had undergone endoluminal abdominal aortic aneurysm (AAA) repair with self-expandable stents were reviewed.
SUBJECTS: Between April 1997 and March 2001, 318 patients underwent endoluminal AAA repair with a self-expandable endograft at our unit. CT scans obtained at 1 and 12 months after surgery and yearly thereafter were prospectively stored in a computer imaging data base. Two hundred thirty patients were available for minimum 1-year assessment. Two vascular surgeons with tested interobserver agreement reviewed 686 CT scans. Diameter of the proximal aortic neck was measured as the minor axis of the first CT section that contained at least half of the proximal portion of the endograft. For endografts with suprarenal attachment the first scan below the lowest renal artery was considered. Diameter change of 3 mm or more between the CT scan at 1 month and subsequent evaluations was defined as AND. Nine possible independent predictors of AND were analyzed with Cox regression analysis.
RESULTS: Median follow-up was 24 months (range, 12-54 months). In 2 patients, AAA ruptured during follow-up. CT scans for 65 patients (28%) showed AND. Thirteen patients with AND (5.6%) underwent repeat intervention, including positioning of the proximal cuff in 8 patients and late conversion to open repair in five patients. Of the nine variables examined with multivariate analysis, only 3, ie, presence of neck circumferential thrombus (hazard ratio [HR], 2.51; 95% confidence interval [CI], 1.26-5.01; P =.008), preoperative proximal neck diameter (HR, 1.21; 95% CI, 1.07-135; P =.001), and preoperative AAA diameter (HR, 1.03; 95% CI, 1.00-1.06; P =.046) were positive independent predictors of AND, whereas the other 6, ie, neck angulation more than 60 degrees, neck length, suprarenal fixation, oversizing more than 15%, endoleak at 30 days, and increased AAA diameter during follow-up, showed no significant correlation. Probability of AND at 48 months was 59 +/- 6.1 at analysis with the Kaplan-Meier method.
CONCLUSIONS: AND is a frequent sequela of endoluminal repair in the mid-term. Severe AND developed in a small percentage of our patients, compromising integrity of AAA repair. Patients with large aneurysms and aortic necks and patients with aortic neck circumferential thrombus are at high risk for aortic neck enlargement after endoluminal repair of AAA.