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 fo r excluding patients from endovascular repair for abdominal aortic aneurysm s (AAA). Methods: Among 71 patients evaluated for endovascular AAA repair using spir al CT imaging and angiography, 31 were selected who had both studies perfor med within 6 months of each other using a graduated measuring catheter or g uidewire. Measurements of aneurysm neck diameter, neck length, and infraren al aortic length were made from the CT and angiographic images using handhe ld calipers with calibration markers as guides. Infrarenal aortic length an d neck length were determined from CT images by multiplying the width of th e cuts by the number of slices between the lowest renal artery and the aort ic bifurcation or the top of the aneurysm, respectively. Results: CT neck diameter measurements differed significantly from the angi ographic dimensions (6.3 +/- 5.1-mm mean difference, p < 0.001). In the maj ority 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 wer e longer on the angiogram (mean 15.4 +/- 77.2 mm, p = NS). Five patients wh o would have been excluded as candidates based on overestimated CT neck dia meter measurements subsequently underwent successful endovascular aneurysm repair. Conclusions: Considerable discrepancies exist between preoperative neck dia meter and infrarenal aortic length measurements obtained from CT scans and angiograms used to evaluate candidates for endovascular aortic aneurysm rep air. CT alone may not be adequate for predicting the feasibility of endovas cular AAA repair.