Ascending aorta
AAo, tubular segment · PLAX 1–2 cm above the STJ, end-diastole, LE-LE; add a high left parasternal and right parasternal window
Normal range & thresholds
Men 30 ± 4 mm · Women 27 ± 4 mm at the proximal tubular segment.[1] Working upper limits ≈38–40 mm; indexed <2.1 cm/m². In tall or small patients use height-indexed measures: aortic size index >2.75 cm/m² and cross-sectional area (cm²) / height (m) >10 both identify high risk at ‘subthreshold’ absolute diameters.[9]
Pathophysiology
Same medial degeneration as the sinuses, with two additions. First, the tubular aorta bears the brunt of hypertensive pulse pressure and stiffening, so it is the segment that grows with age. Second, in bicuspid valves the fused-cusp orientation produces an eccentric, helical systolic jet that scours the right-anterior convexity — abnormal wall shear stress that localises the aneurysm to precisely that wall. Post-stenotic dilatation in aortic stenosis is the same jet mechanism.[9,10,18]
Raised by
- Hypertension and age — by far the commonest cause in an unselected clinic
- Bicuspid aortic valve, ascending phenotype (the majority of BAV aortopathy)
- Post-stenotic dilatation distal to significant aortic stenosis
- Chronic severe AR (combined volume load and jet effect)
- Syndromic and familial HTAD (as for the sinuses); Turner syndrome
- Aortitis, prior dissection with false-lumen dilatation, coarctation-associated aortopathy
- Anabolic steroid and stimulant use; heavy resistance training
Lowered by
- No pathological cause. Apparent reduction on a follow-up study is a plane, convention or modality change until proven otherwise.
Technique & pitfalls
- Measure at least 1–2 cm above the STJ, end-diastole, perpendicular to the vessel axis, LE-LE.[18]
- Move the probe up one intercostal space and angle medially — the maximum diameter of an ascending aneurysm sits above the standard PLAX plane and is missed on the routine cut in a substantial minority.
- Add the right parasternal window with the patient in the right lateral decubitus; it images the mid-ascending aorta far better and is under-used.
- Report the maximum diameter and the level at which it was taken.
- TTE cannot exclude an arch or descending aneurysm — a normal ascending aorta on echo is not a normal aorta.
Pseudo-change & artefact
- Oblique planes overestimate; foreshortening underestimates.
- LE-LE (echo) vs IE-IE (CT/CMR) differences of 2–4 mm masquerade as growth or shrinkage.[9]
- Ungated CT: motion blur and a false ‘flap’ from aortic pulsation.
- Systole vs diastole: 2–3 mm.
- Different observers, different machines, different scan planes: treat <3 mm change as noise.
Treatment thresholds
- Thresholds are those in card 02 and apply to the maximum diameter of root or ascending aorta: ≥5.5 cm class I; ≥5.0 cm class IIa in an experienced multidisciplinary aortic team; syndromic and high-risk genotypes lower.[9]
- ≥4.5 cm when the patient is already undergoing AVR or other cardiac surgery (class IIa).[9]
- 2024 EACTS/STS: class I at ≥55 mm; class IIa at ≥52 mm in low-risk patients — the clearest recent lowering of the operative threshold.[10]
- Growth ≥0.5 cm/year (or ≥0.3 cm/year over two consecutive years) is an independent trigger.[9]
- Pregnancy counselling: >4.5 cm in Marfan and >5.0 cm in BAV carry materially elevated dissection risk.
Next step
- Next: gated CTA or MRA of the entire aorta — confirm the diameter, define the arch and descending aorta, and establish the baseline for growth.[9]
- Then: characterise the valve (tricuspid vs bicuspid, stenosis, regurgitation) and control blood pressure.
- Then: genetics and family screening where indicated; document the surveillance interval explicitly in the report, because interval failure is what kills these patients.
Drugs
- Beta-blockers and ARBs — reduce dP/dt and wall stress; standard in syndromic aortopathy, reasonable in BAV/sporadic aneurysm.[9]
- Antihypertensives to <130/80 mmHg (class I) — the single most evidence-supported intervention.[9,26]
- Statins are given for atherosclerotic risk, not for aneurysm growth.
- Avoid fluoroquinolones.
Reversibility
0%. No aneurysm regresses. What can be modified is the growth rate, typically 0.1–0.2 cm/year untreated in degenerative aneurysm and faster in syndromic disease; strict BP control and beta-blockade meaningfully slow it. After AVR for aortic stenosis, post-stenotic dilatation stops progressing but does not shrink — which is why the 4.5 cm concomitant-surgery threshold exists.[9,10]