Evaluation of Sex Differences in Relative Dilatation of Thoracic Aortic Aneurysms

Objectives: Treatment recommendations based on thoracic aortic aneurysm (TAA) diameter (D) ignore differences in proportional dilatation between patients of different body habitus and sex. This study's goal is to compare TAA diameters between sexes as a function of relative aortic size as determined by aortic size index (ASI). Methods: This is a retrospective review of all TAA's treated between 2003 and 2008. ASI was calculated for each patient, which considers aneurysm diameter, patient's height and weight. Values for males and females were plotted separately (TAA diameter vs ASI) and the resulting linear regression equations permitted comparison of proportional dilatation between sexes. Results: In 40 patients (25 males, 15 females) mean TAA diameter did not differ between sexes (6.56 ± 0.99 vs 7.03 ± 1.14, P = 0.18), while ASI was larger in females than males (4.21 ± 0.85 vs 3.24 ± 0.63, P = 0.0003). Values for ruptured and intact aneurysms did not differ. Linear regression analysis permitted comparison of TAA diameter with ASI between sexes resulting in the following equation: D_Female = 0.91D_Male - 0.49. This correlates a 6 cm TAA in a male with a 4.97 cm TAA in a female. Conclusions: TAA of equal diameter represent a larger proportional dilatation in females compared to males. This could influence repair thresholds that are historically diameter based.