Aorta

TTE evaluates the aortic root, proximal ascending aorta, proximal arch, and portions of the descending thoracic aorta. CT or MRI is required when the thoracic aorta is incompletely visualized or an acute aortic syndrome is suspected.

Aortic Segments¶

Measure and report:

Aortic annulus
Sinuses of Valsalva
Sinotubular junction
Proximal ascending aorta

Additional views may evaluate:

Distal ascending aorta
Aortic arch
Proximal descending thoracic aorta
Abdominal aorta

Measurement Technique¶

Aortic Annulus¶

Measure during mid-systole.
Measure inner edge to inner edge.
Measure between the leaflet hinge points.
The annulus is elliptical; 2D TTE may underestimate its maximal diameter.

Root and Ascending Aorta¶

Measure at end-diastole using the leading-edge to leading-edge convention:

Perpendicular to the long axis of the aorta
At the maximal diameter
From the parasternal long-axis view
Avoid oblique measurements

Measurements by CT and MRI generally use an inner-edge convention. Serial comparisons should use the same modality, technique, and anatomic landmarks.

Aortic Dilation¶

In average-sized adults:

Aortic diameter ≥4.0 cm is considered dilated.
Ascending aortic diameter ≥4.5 cm is generally considered aneurysmal.

Interpret diameter in relation to age, sex, height, and body size, particularly in very small or very tall patients.

Common indexed measurements include:

\[ \text{Aortic size index} = \frac{\text{Aortic diameter}} {\text{BSA}} \]

\[ \text{Cross-sectional area/height} = \frac{\pi(D/2)^2} {\text{Height}} \]

A cross-sectional area-to-height ratio ≥10 cm²/m identifies increased risk in selected patients.

Bicuspid Aortic Valve¶

When a bicuspid valve is present, evaluate:

Aortic root
Sinotubular junction
Entire visualized ascending aorta
Aortic arch
Aortic coarctation

Bicuspid aortopathy may produce predominant dilation of the root, tubular ascending aorta, or both.

CT or MRI is indicated when the aorta is incompletely visualized or measurements are discrepant.

Serial Assessment¶

Compare measurements with prior studies using the same method whenever possible.

Rapid growth is defined as:

≥0.5 cm in 1 year, or
≥0.3 cm/year over 2 consecutive years for sporadic aneurysms
≥0.3 cm in 1 year with bicuspid or heritable aortopathy

Apparent changes of only 1–2 mm may reflect measurement variability rather than true growth.

Acute Aortic Syndrome¶

Acute aortic syndromes include:

Aortic dissection
Intramural hematoma
Penetrating atherosclerotic ulcer
Aortic rupture

Potential echocardiographic findings include:

Mobile intimal flap
True and false lumens
Flow within the false lumen
New aortic regurgitation
Aortic root dilation
Pericardial effusion or tamponade
Regional wall-motion abnormality from coronary involvement

TTE cannot exclude aortic dissection. Obtain urgent CT angiography or TEE when clinical suspicion remains high.

Features favoring the true lumen include systolic expansion and direct continuity with the LV outflow tract. The false lumen is often larger, may contain spontaneous echo contrast or thrombus, and may demonstrate delayed flow.

Coarctation of the Aorta¶

Coarctation usually occurs near the aortic isthmus, immediately distal to the left subclavian artery.

Evaluate from the suprasternal notch and obtain:

2D imaging of the arch and isthmus
Color Doppler through the narrowed segment
CW Doppler across the obstruction
PW Doppler in the abdominal aorta
Assessment for bicuspid aortic valve
LV wall thickness and systolic function

Findings supporting significant coarctation include:

Focal narrowing of the isthmus
Increased systolic velocity
Persistent forward flow into diastole
Diastolic runoff or a prolonged Doppler tail
Dampened abdominal aortic pulsatility
Collateral arterial flow
LV hypertrophy

\[ \text{Peak instantaneous gradient} = 4(V_{max})^2 \]

Doppler may overestimate the catheter peak-to-peak gradient. Severe collateral flow may reduce the measured gradient despite important obstruction.

A resting arm-to-leg blood pressure gradient >20 mm Hg supports hemodynamically significant coarctation.

Aortic Atheroma¶

Describe:

Location
Thickness
Mobility
Ulceration
Superimposed thrombus

Complex aortic plaque is generally defined by:

Thickness ≥4 mm
Ulceration
Mobile components

TEE better evaluates the thoracic aorta when an embolic source is suspected, although the distal ascending aorta may remain difficult to visualize.

Suggested Reporting¶

The aortic root and proximal ascending aorta are normal in caliber.

The aortic root is dilated, measuring ___ cm at the sinuses of Valsalva. The proximal ascending aorta measures ___ cm.

The proximal ascending aorta is aneurysmal, measuring ___ cm. Compared with the prior study dated ___, the diameter has [not significantly changed/increased from ___ cm].

The aortic arch is incompletely visualized. CT or MRI should be considered if complete thoracic aortic assessment is clinically indicated.

There is focal narrowing of the aortic isthmus with persistent antegrade diastolic flow, concerning for aortic coarctation.

A linear mobile echodensity is present within the ascending aorta, concerning for an intimal flap. Urgent definitive aortic imaging is recommended.

Key Points¶

Measure the annulus inner edge to inner edge in systole.
Measure the root and ascending aorta leading edge to leading edge in end-diastole.
Measurements must be perpendicular to the aortic long axis.
Use the same modality and technique for serial comparisons.
Evaluate the entire visualized aorta in patients with a bicuspid valve.
TTE cannot exclude an acute aortic syndrome.
Persistent antegrade diastolic flow is an important clue to coarctation.
Avoid calling a 1–2 mm interval difference true growth without reviewing technique.