Ascending Aortic Aneurysms <4.5 cm for Nonsyndromic Adults: Very Slow Growth and Low Risk.

Background:  Current practice guidelines for patients with thoracic aortic aneurysms (TAAs) recommend 6 to 12-month intervals for surveillance imaging based on growth estimates of 0.10 to 0.42 cm/y gleaned from limited studies which included patients with thoracoabdominal aneurysms, known acute or chronic aortic dissection, and other syndromic and nonsyndromic high-risk conditions (TAA-HRC) associated with high-risk for adverse aortic events and death. Our objective was to determine TAA growth and event-free survival rates for patients with aortic root or midascending diameters <5.0 cm, and without thoracoabdominal aneurysms, acute or chronic aortic dissection or higher risk syndromic or nonsyndromic conditions (TAA-NoHRC).

Methods:  A retrospective review of patient records and imaging studies were done. Aortic diameter measurements were all performed by the lead author.

Results:  For 197 TAA-NoHRC found incidentally during chest imaging, with 616 chest imaging studies over 868 patient-years, the mean aortic root and midascending aortic growth rates were 0.018 and 0.022 cm/y, respectively. The growth rate was significantly lower for aneurysms initially measured at <4.5 cm versus ≥ 4.5 cm at both the aortic root (0.011 vs. 0.068 cm/y) and midascending aorta (0.013 vs. 0.043 cm/y). Survival free from adverse aortic events (dissection, rupture, and surgery) or death at 5 years was 99.5%.

Conclusion:  Adult TAA-NoHRC patients with initial aortic root and/or ascending aortic diameters <5.0 cm, and particularly <4.5 cm, have very low aortic growth, and adverse event rates which may permit longer intervals between surveillance imaging, up to 3 to 5 years, after initial (6-12 months) stability is documented.