Influence of Abdominal Aortic Aneurysm Size on the Feasibility of Endovascular Repair

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Abstract
Purpose: To assess the effect of abdominal aortic aneurysm (AAA) size on overall aneurysm morphology with special attention to possible relationships among various anatomic variables that determine the feasibility of endovascular repair. Methods: One hundred sixty-eight patients were assessed with spiral computed tomographic angiography to measure the length and diameter of the AAA, the proximal neck, and the common iliac arteries. Anatomic variables were correlated with aneurysm size using Spearman's rank order correlation coefficients (rs); comparisons among small, intermediate, and large aneurysms were made using the Chi-square test. Results: Correlations between aneurysm size and the anatomic variables above were weak. The strongest association was between aneurysm size and aortic length (rs = 0.41, p < 0.001). Subgroup analysis showed no difference in proximal neck length, neck diameter, or overall suitability for endovascular repair between aneurysms greater or smaller than 5.5-cm diameter. However, significantly more short (< 1.5 cm), wide (> 3 cm), and, hence, unsuitable proximal necks were found in patients with aneurysms > 7 cm in diameter (χ2 = 7.8, p < 0.01). Conclusions: Shortening and widening of the proximal neck seems to increase with aneurysm size but only after the aneurysm expands beyond 7 cm in diameter. Aneurysms with diameters in the 4.5- to 5.5-cm range are no more suitable for endovascular repair than those between 5.5 and 7 cm. The lack of any significant correlation between anatomic variables emphasizes the need for accurate preoperative assessment of the anatomy of each individual patient before endovascular repair.