Computed tomography assessment of abdominal aortic aneurysm morphology after endograft exclusion.

OBJECTIVES

Assessment of the long-term function of endografts to exclude abdominal aortic aneurysm (AAA) includes determination of aneurysm dimensions and morphologic changes that occur after implantation. This study reports the dimensional analysis of patients treated with AneuRx bifurcated endoprostheses with postintervention, 1-year (n = 51), 2-year (n = 28), and 3-year (n = 10) postimplantation contrast computed tomography data.

METHODS

Maximal diameter (D) and cross-sectional area (CSA) of the AAA were measured from axial computed tomography images. Total volume, AAA thrombus 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 device, 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 reconstructed in an interactive environment.

RESULTS

Fifty-one of 98 consecutively treated patients with the AneuRx bifurcated prosthesis (29 "stiff" and 22 "flexible" body devices) had complete data from the postprocedure and follow-up computed tomography studies available for analysis. Max D, CSA, total volume of the AAA, and AAA thrombus volume decreased sequentially from year to year compared with the postimplantation values. D and CSA decreased or were unchanged in all except four patients, two who had unrestricted enlargement of the aneurysm with eventual rupture 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 the one conversion. Patients with endoleaks who had spontaneous thrombosis or were successfully treated either remained at the same volume or had decreased volume on subsequent examinations. D at the renal arteries increased an 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 nature of the Nitinol suprastructure. Subsequent enlargement of the proximal neck continued at a slow rate in some cases but never exceeded the diameter of the endoluminal device. The distance from the renal arteries to the device increased by an average of 3 mm over the first year, with the greatest 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 occurred, the angle of the proximal neck varied from -5 degrees to +25 degrees from the original alignment. Limb length varied from -8 mm to +10 mm, with no consistent pattern for the change, that is, ipsilateral or contralateral limb.

CONCLUSION

Significant variation in the quantitation of aneurysm size occurs depending on the technique of computed tomography assessment used. In most patients diameter assessment is adequate, although volumetric analysis appears to be very helpful in certain patients who do not show aneurysm regression, or in whom the diameter increases or where endoleaks persist. Three-dimensional reconstruction and volumetric analysis are also useful to assess the mechanism by which the endovascular device accommodates to morphology changes and to determine criteria for reintervention.