Background: Factors associated with dissection from inflammatory aortic aneurysms may be different from those in the general population.

Objective: The aim of this study was to evaluate the risk factors for aortic dissection/rupture in patients with giant cell arteritis (GCA) and aortic aneurysms.

Methods: A population-based incident cohort of patients with a diagnosis of GCA from 1950 to 2004 was used. All patients with aortic aneurysms diagnosed 1 year prior to GCA diagnosis or any time thereafter were included. Cox proportional hazard models were used to evaluate risk factors for aortic dissection/rupture.

Results: The study included 33 patients (91% women) with GCA and aortic aneurysms. Mean age at diagnosis of aortic aneurysm was 83.6 years. There were 27 thoracic aneurysms and 19 abdominal aneurysms. Eight patients developed aortic dissection/rupture (both thoracic and abdominal aorta in 5 cases, thoracic aorta only in 2 cases, and isolated abdominal aorta in 1 case).Older age (hazard ratio [HR], 0.27 per 10 years; 95% confidence interval [CI], 0.09-0.86) and later calendar year at diagnosis of aortic aneurysm (HR, 0.29 per 10 years; 95% CI, 0.13-0.69) were associated with decreased risk of dissection/rupture. Size of the thoracic aneurysm (HR, 1.17; 95% CI, 0.69-1.99) was not associated with dissection/rupture. Histopathology showed active aortitis in 4 of 7 patients with aortic dissection/rupture compared with 0 of 7 patients with aortic aneurysm without dissection/rupture.

Conclusions: Aneurysm size was not a predictor of aortic dissection/rupture in this cohort of patients with GCA. The higher frequency of active aortitis in patients with dissection suggests that active inflammation may play a role.