Aortic Valve

Evaluate valve morphology, leaflet mobility and calcification, stenosis, regurgitation, and the aortic root and ascending aorta.

Valve morphology is best determined in systole from the parasternal short-axis view. A raphe may make a bicuspid valve appear trileaflet in diastole.

Aortic Stenosis¶

Acquisition¶

LVOT Diameter¶

Measure in the parasternal long-axis view during mid-systole.
Measure inner edge to inner edge at the same location as the LVOT velocity sample.
The diameter should be parallel and immediately proximal to the aortic valve.
Small measurement errors are amplified because the diameter is squared.

\[ CSA_{LVOT} = \pi \left(\frac{D_{LVOT}}{2}\right)^2 \]

LVOT Velocity¶

Record pulsed-wave Doppler from the apical long-axis or five-chamber view.

Position the sample volume in laminar flow proximal to the valve.
Move toward the valve until spectral broadening appears, then withdraw slightly.
Trace the modal LVOT velocity envelope.
Avoid including the proximal acceleration zone.

Aortic Valve Velocity¶

Use CW Doppler from multiple windows:

Apical
Right parasternal
Suprasternal
Subcostal

Report the highest reproducible velocity, regardless of window. A nonimaging Pedoff probe may identify the highest velocity.

Continuity Equation¶

\[ AVA = \frac{CSA_{LVOT} \times VTI_{LVOT}} {VTI_{AV}} \]

Dimensionless Index¶

The dimensionless index avoids error from the LVOT diameter measurement.

\[ DI = \frac{VTI_{LVOT}}{VTI_{AV}} \]

Peak velocity ratios may be used when both velocities are obtained from comparable beats.

AS Severity¶

Severity	Peak velocity	Mean gradient	AVA	Dimensionless index
Mild	2.6–2.9 m/s	<20 mm Hg	>1.5 cm²	>0.50
Moderate	3.0–3.9 m/s	20–39 mm Hg	1.0–1.5 cm²	0.25–0.50
Severe	≥4.0 m/s	≥40 mm Hg	≤1.0 cm²	<0.25

Additional severe AS criteria:

Indexed AVA ≤0.6 cm²/m²
Very severe AS: peak velocity ≥5 m/s
Low flow: stroke volume index <35 mL/m²

AVA should generally not be interpreted alone. Confirm that valve morphology, velocity, gradient, AVA, DI, stroke volume, and clinical findings are internally consistent.

Discordant Aortic Stenosis¶

Classical Low-Flow, Low-Gradient AS¶

AVA ≤1.0 cm²
Mean gradient <40 mm Hg
LVEF <50%
Stroke volume index <35 mL/m²

Low-dose dobutamine stress echocardiography helps distinguish:

True severe AS: velocity or gradient increases while AVA remains ≤1.0 cm²
Pseudo-severe AS: AVA increases to >1.0 cm² with increased flow
Absent flow reserve: <20% increase in stroke volume

Paradoxical Low-Flow, Low-Gradient AS¶

AVA ≤1.0 cm²
Mean gradient <40 mm Hg
LVEF ≥50%
Stroke volume index <35 mL/m²

Recheck LVOT measurements, Doppler alignment, blood pressure, rhythm, and indexed valve area. CT aortic valve calcium scoring may clarify severity.

Normal-Flow, Low-Gradient AS¶

An AVA ≤1.0 cm² with stroke volume index ≥35 mL/m² and mean gradient <40 mm Hg is often related to measurement error, body size, prolonged ejection time, or thresholds that do not align perfectly.

Common AS Pitfalls¶

Failure to obtain the highest velocity from multiple windows
Measuring the LVOT diameter too far below the valve
Placing the LVOT sample within the acceleration zone
Tracing noise rather than the dense modal velocity
Using unmatched beats in atrial fibrillation
Ignoring severe hypertension or abnormal flow
Mistaking dynamic LVOT obstruction for valvular AS

A late-peaking, dagger-shaped envelope favors dynamic obstruction. Valvular AS usually produces a smoother, rounded envelope.

Aortic Regurgitation¶

AR severity should integrate valve anatomy, color Doppler, CW Doppler, quantitative measurements, aortic flow reversal, and LV remodeling.

Parameter	Mild	Moderate	Severe
Vena contracta	<0.3 cm	0.3–0.6 cm	>0.6 cm
Jet width/LVOT width	<25%	25–64%	≥65%
Pressure half-time	>500 ms	200–500 ms	<200 ms
EROA	<0.10 cm²	0.10–0.29 cm²	≥0.30 cm²
Regurgitant volume	<30 mL	30–59 mL	≥60 mL
Regurgitant fraction	<30%	30–49%	≥50%

Findings supporting severe AR include:

Large vena contracta
Dense CW Doppler signal
Holodiastolic flow reversal in the descending or abdominal aorta
Descending aortic end-diastolic velocity >20 cm/s
Progressive LV dilation

Pressure half-time is affected by LV compliance, aortic pressure, vasodilator therapy, and acute versus chronic AR. It should not be used alone.

Acute severe AR may occur without LV dilation. Premature mitral valve closure, rapid pressure equalization, and a short pressure half-time support hemodynamically important acute AR.

Suggested Reporting¶

The aortic valve is trileaflet with normal leaflet thickness and excursion. No aortic stenosis or regurgitation is present.

The aortic valve is heavily calcified with severely restricted excursion. Severe aortic stenosis is present with a peak velocity of ___ m/s, mean gradient of ___ mm Hg, valve area of ___ cm², and dimensionless index of ___.

Findings are discordant for severe aortic stenosis. The calculated valve area is ___ cm² with a mean gradient of ___ mm Hg and stroke volume index of ___ mL/m².

Severe aortic regurgitation is present with a vena contracta of ___ cm, holodiastolic flow reversal in the descending aorta, and associated LV dilation.

Key Points¶

Obtain aortic valve velocity from multiple acoustic windows.
Errors in LVOT diameter are squared in the continuity equation.
DI <0.25 supports severe AS.
Low flow is defined as stroke volume index <35 mL/m².
Do not diagnose severe AS from AVA alone when other parameters are discordant.
Holodiastolic aortic flow reversal strongly supports severe AR.
Acute severe AR may have a normal-sized LV.