Predictors of Dissection in Aortic Aneurysms From Giant Cell Arteritis

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.