Assessment of the criteria for elective surgery in screen-detected abdominal aortic aneurysms.

OBJECTIVES

Apart from aortic diameter, two other widely used criteria for considering surgery in screen-detected abdominal aortic aneurysms (AAAs)--annual aortic expansion > or =1.0 cm and presence of symptoms attributable to the AAA--are based on accepted practice and AAA expansion rates, rather than direct evidence. The Multi-centre Aneurysm Screening Study (MASS) enables assessment of their contribution to this risk reduction.

METHODS

MASS employs three criteria for referral for considering elective open surgery: maximum aortic diameter > or =5.5 cm, rapid aortic expansion (> or =1.0 cm/year), and/or the presence of symptoms attributable to the AAA. Data from MASS are used to examine the value of these criteria in practice.

RESULTS

No patients were referred for symptoms alone. Of those referred for rapid expansion, 88% were returned to surveillance, compared with only 12% of those referred for diameter > or =5.5 cm at initial scan, and 34% of those referred for diameter > or =5.5 cm at a follow-up scan. Return to surveillance following referral for rapid expansion was strongly associated with aortic diameter (age-adjusted odds ratio for return 0.89 per mm, 95% confidence interval 0.79-1.00). Of those 5.0-5.4 cm at the time of referral for rapid expansion who were returned, 31% reached 5.5 cm during a median post-referral follow-up of 0.9 years. Among those referred for expansion, the rupture rate was only 8 per 1000 person-years of follow-up prior to reaching 5.5 cm.

CONCLUSIONS

A single criterion for considering elective surgery is recommended in screen-detected AAA, based on a maximum aortic diameter of > or =5.5 cm. This criterion detects the majority of those at risk from rupture, and is simple to assess.