Computed tomography assessment of abdominal aortic aneurysm morphology after endograft exclusion

Objectives: Assessment of the long-term function of endografts to exclude a bdominal aortic aneurysm (AAA) includes determination of aneurysm dimension s and morphologic changes that occur after implantation. This study reports the dimensional analysis of patients treated with AneuRx bifurcated endopr ostheses with postintervention, 1-year (n = 51), 2-year (n = 28), and a-yea r (n = 10) postimplantation contrast computed tomography data. Methods: Maximal diameter (D) and cross-sectional area (CSA) of the AAA wer e measured from axial computed tomography images. Total volume, AAA thrombu s volume (AAA volume minus the volume of the device and luminal blood flow) , diameter of the aorta at the level of the renal arteries and within the d evice, distance from the renal arteries to the device, length of the device limbs, and the angle of the proximal neck were also determined at the same follow-up intervals after deployment with computed tomography angiograms r econstructed in an interactive environment. Results: Fifty-one of 98 consecutively treated patients with the AneuRx bif urcated prosthesis (29 "stiff" and 22 "flexible" body devices) had complete data from the postprocedure and follow-up computed tomography studies avai lable for analysis. Max D, CSA, total volume of the AAA, and AAA thrombus v olume decreased sequentially from year to year compared with the postimplan tation values. D and CSA decreased or were unchanged in all except four pat ients, two who had unrestricted enlargement of the aneurysm with eventual r upture and one who had surgical conversion for continued expansion despite four diagnostic angiograms and attempted embolizations. Total volume of the AAA increased in 11 of 51 patients at 1 year, eight of whom had endoleaks at some interval during the follow-up. Thrombus volume increased more than 5% in four of these patients, including the two with eventual rupture and t he one conversion. Patients with endoleaks who had spontaneous thrombosis o r were successfully treated either remained at the same volume or had decre ased volume on subsequent examinations. D at the renal arteries increased a n average of 0.9 mm during the first year, with a concomitant increase of 2 .8 mm within the proximal end of the device related to the self-expanding n ature of the Nitinol suprastructure. Subsequent enlargement of the proximal neck continued at a slow rate in some cases but never exceeded the diamete r of the endoluminal device. The distance front the renal arteries to the d evice increased by an average of 3 mm over the first year, with the greates t increases occurring in patients with a "stiff' body device and those with rapid regression (>10% total volume) in 1 year. As regression of the AAA o ccurred, the angle of the proximal neck varied from -5 degrees to +25 degre es fi om the original alignment. Limb length varied from -8 mm to +10 mm, w ith no consistent pattern for the change, that is, ipsilateral or contralat eral limb. Conclusion: Significant variation in the quantitation of aneurysm size occu rs depending on the technique of computed tomography assessment used. In mo st patients diameter assessment is adequate, although volumetric analysis a ppears to be very helpful in certain patients who do not show aneurysm regr ession, or in whom the diameter increases or where endoleaks persist. Three -dimensional reconstruction and volumetric analysis are also useful to asse ss the mechanism by which the endovascular device accommodates to morpholog y changes and to determine criteria for reintervention.