Low Utility of Frequent Imaging Follow-up for Incidental Ascending Aortic Aneurysms

See also article by Hammer and Kong in this issue.

Jody Shen, MD, is a clinical assistant professor in cardiovascular imaging at Stanford University School of Medicine.

Dominik Fleischmann, MD, is a professor and chief of cardiovascular imaging at Stanford University School of Medicine, and the medical director of the Stanford 3D and Quantitative Imaging Laboratory in Stanford, California. His clinical and research interests include imaging and image analysis of aortic diseases for diagnosis, treatment planning, and patient-specific risk prediction. Dr Fleischmann is a fellow of the American Heart Association and a deputy editor of Radiology: Cardiothoracic Imaging.

Current guidelines for surveillance imaging of incidental ascending aortic dilatation (≥40 mm) are vague, and the optimal imaging interval is unknown (1–3). The 2022 American College of Radiology/American Heart Association Guideline proposes that initial follow-up at 6–12 months and continued surveillance imaging every 6–24 months thereafter may be “reasonable” (3). These recommendations are primarily based on observational studies drawing from data collected in the 1980s and 1990s, which included heritable aneurysms and chronic dissections with short-term follow-up (4,5). There are no prospective studies exposing patients to different follow-up time intervals, and we should not expect those to be conducted anytime soon. But more recent literature on the natural history of nongenetic, nonsyndromic, moderately dilated ascending aortas reports that the growth rate is relatively slow, or even negligible, with low occurrence of aortic-related events and high survival (6–9). Consequently, the utility and cost-effectiveness of frequent surveillance have been called into question.

To address this clinically relevant issue, in this issue of Radiology: Cardiothoracic Imaging, Hammer and Kong take an interesting approach to determine an optimal CT follow-up strategy by applying a simulation model based on cost-effectiveness (10). While annual surveillance of ascending aortas above 40 mm for a wide range of ages improved quality of life, it did so at a prohibitively high cost. The most cost-effective strategy restricted follow-up to a baseline ascending aortic size of 40–50 mm for a younger age range (less than 60 years) with less frequent surveillance (every 3 years). This suggests that moderately dilated ascending aortas grow so slowly that older patients are more likely to die of causes other than aneurysm-related complications. Restricting follow-up to younger patients also resulted in a substantial reduction in follow-up imaging to only 17% of the simulated cohort.

Although less frequent imaging may be met with hesitance, this proposed surveillance strategy is more concordant with the slow growth rate of 1–4 mm in 10 years for incidental ascending aortic dilatation (6–9). While no substitute for randomized controlled trials that are unlikely to happen, this simulation model study helps recalibrate expectations for incidental ascending aortic aneurysm growth rate and follow-up, with the potential to shape recommendations and decision-making based on imaging.