Aneurysmal degeneration of the thoracoabdominal aorta after medical management of type B aortic dissections

Abstract

Patients with uncomplicated type B aortic dissections who are managed medically are at risk of aortic aneurysmal degeneration over time. However, the effect of improvement in antihypertensive medications and stricter blood pressure control is unknown. The goal of this study was to determine the rate of aneurysmal degeneration in a contemporary cohort of patients with medically treated type B dissection. Included were all patients with acute uncomplicated type B aortic dissection who were initially managed medically between March 1999 and March 2011 and had follow-up axial imaging studies. Maximum aortic growth was calculated by comparing the initial imaging study to the most current scan or imaging obtained just before any aortic-related intervention. An increase of ≥5 mm was the threshold considered as aortic growth. Predictors of aortic aneurysmal degeneration were determined using Cox proportional hazards models. We identified 200 patients (61% men) with medically managed acute type B dissections receiving multiple imaging studies. Patients were an average age of 63.4 years, and 75.5% had a history of hypertension. Mean follow-up was 5.3 years (range, 0.1-14.7 years). Mean time between the initial and final imaging studies was 3.2 years (range, 0.1-12.9 years). At 5 years, only 51% were free from aortic growth. Fifty-six patients (28%) required operative intervention (50 open, 6 endovascular repair) for aneurysmal degeneration, and the actuarial 5-year freedom from intervention was 76%. After excluding five patients (2.5%) with early rapid degeneration requiring intervention within the first 2 weeks, the mean rate of aortic growth was 12.3 mm/y for the total aortic diameter, 3.8 mm/y for the true lumen diameter, and 8.6 mm/y for the false lumen diameter. Only aortic diameter at index presentation >3.5 cm was a risk factor for future growth (odds ratio, 2.54; 95% confidence interval, 1.34-4.81; P < .01). Complete thrombosis of the false lumen was protective against growth (odds ratio, 0.19; 95% confidence interval, 0.11-0.42; P < .01). Although medical management of uncomplicated acute, type B aortic dissections has been the standard of care, at 5 years, a significant number of patients will require operative intervention for aneurysmal degeneration. Further studies of early intervention (eg, thoracic endovascular aortic repair) for type B aortic dissection to prevent late aneurysm formation are needed.