Can preoperative spiral CT scans alone determine the feasibility of endovascular AAA repair? A comparison to angiographic measurements

Purpose: To determine whether computed tomography (CT) alone can be used for excluding patients from endovascular repair for abdominal aortic aneurysms (AAA). Methods: Among 71 patients evaluated for endovascular AAA repair using spiral CT imaging and angiography, 31 were selected who had both studies performed within 6 months of each other using a graduated measuring catheter or guidewire. Measurements of aneurysm neck diameter, neck length, and infrarenal aortic length were made from the CT and angiographic images using handheld calipers with calibration markers as guides. Infrarenal aortic length and neck length were determined from CT images by multiplying the width of the cuts by the number of slices between the lowest renal artery and the aortic bifurcation or the top of the aneurysm, respectively. Results: CT neck diameter measurements differed significantly from the angiographic dimensions (6.3 ± 5.1-mm mean difference, p < 0.001). In the majority of patients (25, 81%), CT neck diameters were larger (mean 7.3 ± 3.8 mm). The mean difference in neck length measurements was 0.5 ± 15.9 mm (p = NS). Twenty-two (71%) patients had aortic length measurements that were longer on the angiogram (mean 15.4 ± 17.2 mm, p = NS). Five patients who would have been excluded as candidates based on overestimated CT neck diameter measurements subsequently underwent successful endovascular aneurysm repair. Conclusions: Considerable discrepancies exist between preoperative neck diameter and infrarenal aortic length measurements obtained from CT scans and angiograms used to evaluate candidates for endovascular aortic aneurysm repair. CT alone may not be adequate for predicting the feasibility of endovascular AAA repair.