Aortic Surveillance Assistant

Size cutoffs: DHMC cardiology–radiology consensus (Oct 28, 2026). The whole thoracic aorta uses one rule: normal <4.0 cm, dilated 4.0–4.4 cm, aneurysm ≥4.5 cm. The abdominal aorta has no dilated category: aneurysm over 3.0 cm, otherwise normal. Values are reported in cm to one decimal, the ACC/AHA convention. “Ectasia” and “ectatic” are not used. The root and ascending cutoffs match the 2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease (Isselbacher et al., Circulation 2022;146:e334–e482); extending them to the arch and descending aorta is a local decision. Growth and surgical thresholds below are from that guideline. Cutoffs encoded in this tool (maximal diameter, cm):

Location	Normal	Dilated	Aneurysm
Sinus of Valsalva (root)	<4.0	4.0–4.4	≥4.5
Sinotubular junction	<4.0	4.0–4.4	≥4.5
Mid ascending aorta	<4.0	4.0–4.4	≥4.5
Proximal / mid aortic arch	<4.0	4.0–4.4	≥4.5
Proximal / mid descending aorta	<4.0	4.0–4.4	≥4.5
Aorta at diaphragm	<4.0	4.0–4.4	≥4.5
Abdominal aorta (celiac, max)	≤3.0	—	>3.0
Medium branch vessels	<1.5× adjacent normal		≥1.5× adjacent normal

Measurement (DHMC). Aortic root: sinus-to-sinus, three manual lines, report the largest. All other landmarks keep their usual locations: report two orthogonal dimensions, perpendicular to the vessel axis (double-oblique), with calipers including the wall whenever it is visible. Cardiology measures on AQI.

Growth. The guideline defines rapid growth as ≥0.5 cm in 1 year, or ≥0.3 cm/year over 2 consecutive years (thoracic). For heritable aortopathy, ≥0.3 cm/year is treated as rapid. Rates are valid only when modality and technique are consistent; interval changes within ~2 mm may reflect measurement variability.

Technique. ECG-gated CTA is preferred for the thoracic aorta, especially for a baseline study, since it is the comparison for every later scan (currently CT3 and CT4). MRA is accepted as equivalent to CTA for aneurysm measurement and surveillance. For suspected large-vessel vasculitis, the MRA aortitis protocol is preferred over CTA.

Surgical-threshold flag (advisory). Root/ascending ≥5.5 cm (sporadic, BAV) or ≥5.0 cm (heritable); descending thoracic ≥5.5 cm; abdominal ≥5.5 cm (≥5.0 cm in women). Family history of dissection, rapid growth, planned pregnancy, and experienced-center factors lower these and are not captured here.

Indexing (root and ascending aorta). The raw diameter understates risk in a small patient and overstates it in a large one, so the Flags column adds two indexes with the yearly risk of rupture, dissection or death in each band. Moderate bands show amber and higher bands red.

Index	Low	Moderate	High	Severe
ASI = diameter (cm) ÷ BSA (m²)	<2.75 (~4%/yr)	2.75–4.24 (~8%/yr)	≥4.25 (~20%/yr)	—
AHI = diameter (cm) ÷ height (m)	≤2.43 (~4%/yr)	2.44–3.17 (~7%/yr)	3.21–4.06 (~12%/yr)	≥4.10 (~18%/yr)

ASI: Davies et al., Ann Thorac Surg 2006. AHI: Zafar et al., J Thorac Cardiovasc Surg 2018, who found height alone predicts as well as BSA, since weight changes BSA without changing aortic risk. ASI needs height and weight (or BSA); AHI needs height only. A value in the small gaps between Zafar's published AHI bands takes the lower band.