title: Relative importance of aneurysm diameter and body size for predicting abdominal aortic aneurysm rupture in men and women.
abstract: OBJECTIVE
  Women have been shown to have up to a fourfold higher risk of abdominal aortic aneurysm (AAA) rupture at any given aneurysm diameter compared with men, leading to recommendations to offer repair to women at lower diameter thresholds. Although this higher risk of rupture may simply reflect greater relative aortic dilatation in women who have smaller aortas to begin with, this has never been quantified. Our objective was therefore to quantify the relationship between rupture and aneurysm diameter relative to body size and determine whether a differential association between aneurysm diameter, body size, and rupture risk exists for men and women.
  
  
  METHODS
  We performed a retrospective review of all patients in the Vascular Study Group of New England (VSGNE) database who underwent endovascular or open AAA repair. Height and weight were used to calculate each patient's body mass index and body surface area (BSA). Next, indices of each measure of body size (height, weight, body mass index, BSA) relative to aneurysm diameter were calculated for each patient. To generate these indices, we divided aneurysm diameter (in cm) by the measure of body size; for example, aortic size index (ASI) = aneurysm diameter (cm)/BSA (m(2)). Along with other relevant clinical variables, we used these indices to construct different age-adjusted and multivariable-adjusted logistic regression models to determine predictors of ruptured repair vs elective repair. Models for men and women were developed separately, and different models were compared using the area under the curve.
  
  
  RESULTS
  We identified 4045 patients (78% male) who underwent AAA repair (53% endovascular aortic aneurysm repairs). Women had significantly smaller diameter aneurysms, lower BSA, and higher BSA indices than men. For men, the variable that increased the odds of rupture the most was aneurysm diameter (area under the curve = 0.82). Men exhibited an increased rupture risk with increasing aneurysm diameter (<5.5 cm: odds ratio [OR], 1.0; 5.5-6.4 cm: OR, 0.9; 95% confidence interval [CI], 0.5-1.7; P = .771; 6.5-7.4 cm: OR, 3.9; 95% CI, 1.9-1.0; P < .001; ≥ 7.5 cm: OR, 11.3; 95% CI, 4.9-25.8; P < .001). In contrast, the variable most predictive of rupture in women was ASI (area under the curve = 0.81), with higher odds of rupture at a higher ASI (ASI >3.5-3.9: OR, 6.4; 95% CI, 1.7-24.1; P = .006; ASI ≥ 4.0: OR, 9.5; 95% CI, 2.3-39.4; P = .002). For women, aneurysm diameter was not a significant predictor of rupture after adjusting for ASI.
  
  
  CONCLUSIONS
  Aneurysm diameter indexed to body size is the most important determinant of rupture for women, whereas aneurysm diameter alone is most predictive of rupture for men. Women with the largest diameter aneurysms and the smallest body sizes are at the greatest risk of rupture.
authors.affiliation: Division of Vascular and Endovascular Surgery, Beth Israel Deaconess Medical Center, Boston, Mass.
authors.forename: Ruby C
authors.initials: RC
authors.lastname: Lo
authors.affiliation: Department of Rheumatology, Immunology, and Allergy, Brigham & Women's Hospital, Boston, Mass.
authors.forename: Bing
authors.initials: B
authors.lastname: Lu
authors.affiliation: Division of Vascular and Endovascular Surgery, Beth Israel Deaconess Medical Center, Boston, Mass.
authors.forename: Margriet T M
authors.initials: MT
authors.lastname: Fokkema
authors.affiliation: Division of Vascular and Endovascular Surgery, Massachusetts General Hospital, Boston, Mass.
authors.forename: Mark
authors.initials: M
authors.lastname: Conrad
authors.affiliation: Division of Vascular and Endovascular Surgery, Massachusetts General Hospital, Boston, Mass.
authors.forename: Virendra I
authors.initials: VI
authors.lastname: Patel
authors.affiliation: Section of Vascular Surgery, Dartmouth-Hitchcock Medical Center, Lebanon, NH.
authors.forename: Mark
authors.initials: M
authors.lastname: Fillinger
authors.affiliation: Division of Vascular and Endovascular Surgery, Beth Israel Deaconess Medical Center, Boston, Mass.
authors.forename: Robina
authors.initials: R
authors.lastname: Matyal
authors.affiliation: Division of Vascular and Endovascular Surgery, Beth Israel Deaconess Medical Center, Boston, Mass. Electronic address: mscherme@bidmc.harvard.edu.
authors.forename: Marc L
authors.initials: ML
authors.lastname: Schermerhorn
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017544:Aortic Aneurysm, Abdominal / Q000150:complications* / Q000175:diagnosis / Q000601:surgery; D001019:Aortic Rupture / Q000175:diagnosis / Q000209:etiology*; D019540:Area Under Curve; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects; D001827:Body Height; D015992:Body Mass Index; D049628:Body Size; D001830:Body Surface Area; D001835:Body Weight; D016009:Chi-Square Distribution; D004108:Dilatation, Pathologic; D057510:Endovascular Procedures / Q000009:adverse effects; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors