Thoracic Aortic Dilation / Aneurysm
Walk the decision tree step by step, see it as a flowchart, or view the whole algorithm at once.
ACC/AHA 2022·reviewed 2026-09-22
- •Measure perpendicular to the axis of blood flow at a reproducible landmark — on CT/MRI use double-oblique reformats, inner-edge to inner-edge for the root and ascending aorta (outer-edge to outer-edge where there is mural thrombus, atherosclerosis, or wall thickening). Record the root as the maximum sinus-to-sinus diameter, and report both the longest diameter and its perpendicular when the contour is oval.
- •State the acquisition and measurement method in the report (gated vs non-gated, axial vs double-oblique, inner- vs outer-edge). Non-gated axial measurements run larger, and a modality or technique change between studies can masquerade as growth.
- •Rapid growth is itself a surgical indication: ≥0.5 cm in 1 year, or ≥0.3 cm/year across 2 consecutive years, for sporadic root/ascending aneurysms; ≥0.3 cm in 1 year in heritable thoracic aortic disease or bicuspid aortic valve. Growth rates are only meaningful when compared like-for-like.
- •Indexing helps in patients at the extremes of body size: a cross-sectional aortic area (cm²) to height (m) ratio ≥10 supports repair below the diameter threshold, and in Turner syndrome the aortic size index (diameter ÷ BSA) drives both surveillance (annual if >2.3 cm/m²) and risk (≥2.5 cm/m² marks substantially elevated dissection risk).
- •Symptoms attributable to the aneurysm, a saccular contour, or an infectious (mycotic) aneurysm move the patient out of surveillance and into urgent surgical discussion at any diameter.
- •This tree covers the intact, nontraumatic aorta. Acute aortic syndrome and blunt traumatic aortic injury are separate, urgent pathways.
Which thoracic aortic segment is dilated?
Thresholds differ by segment: the root and ascending aorta are judged on absolute diameter, the arch and descending aorta on the conventional aneurysm definition (≥1.5× expected caliber).
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Sources
- Isselbacher EM, et al. 2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease. Circulation. 2022;146(24):e334-e482.
Educational reference for clinicians — not medical advice. Verify against the primary source before acting on it; guidelines change. Final decisions rest with the interpreting physician and your institution's protocols.