Aortic Stenosis

AS Severity

Severe: Vmax ≥4.0 m/s | Mean gradient ≥40 mmHg | AVA ≤1.0 cm² | AVAi ≤0.6 cm²/m² | DI <0.25 | Low flow: SVI <35 mL/m²
Aortic Stenosis Severity Grading
Parameter Mild Moderate Severe
Peak velocity <3.0 m/s 3.0–3.9 m/s ≥4.0 m/s
Mean gradient <20 mmHg 20–39 mmHg ≥40 mmHg
AVA >1.5 cm² 1.0–1.5 cm² ≤1.0 cm²
Indexed AVA >0.85 cm²/m² 0.60–0.85 cm²/m² ≤0.60 cm²/m²
Dimensionless Index >0.50 0.25–0.50 <0.25
Stroke Volume Index Normal flow ≥35 mL/m² Low flow <35 mL/m²
TTE Suspicious for Aortic Stenosis Assess Velocity and Mean Gradient LOW-GRADIENT AS Vmax < 4 m/s • ΔPm < 40 mmHg HIGH-GRADIENT AS Vmax ≥ 4 m/s • ΔPm ≥ 40 mmHg Assess AVA High Flow Status Excluded? AVA ≤ 1.0 cm² AVA > 1.0 cm² No Yes Moderate AS Exclude Measurement Errors Severe High-Gradient AS Is High Flow Reversible? Not reversible Reversible Severe AS Reassess at Normal Flow Define Flow Status by SVi Low flow SVi ≤35 mL/m² Normal flow SVi >35 mL/m² Severe AS Unlikely Assess LVEF LVEF <50% LVEF ≥50% Dobutamine Echo Integrated Approach Flow reserve No flow reserve Pseudosevere AS or True Severe AS CT Aortic Valve Calcium Score
AS Severity Grading
Parameter Mild Moderate Severe
Mean gradient (mmHg) <20 20–39 ≥40
AVA (cm²) >1.5 1.0–1.5 ≤1.0
Dimensionless index
(LVOT VTI / AV VTI)		 >0.50 0.25–0.50 <0.25
Mild
Mean gradient
<20 mmHg
AVA
>1.5 cm²
Dimensionless index
>0.50
Moderate
Mean gradient
20–39 mmHg
AVA
1.0–1.5 cm²
Dimensionless index
0.25–0.50
Severe
Mean gradient
≥40 mmHg
AVA
≤1.0 cm²
Dimensionless index
<0.25

1. LVOT Diameter (PLAX)

  • PLAX view
  • Zoom on the aortic valve and LVOT
  • Timing: Mid-systole (valve open)
  • Measure inner-edge to inner-edge
  • LVOT Area = 0.785 × (LVOT diameter)²

2. LVOT VTI (PW Doppler)

Represents forward stroke flow before the stenotic valve.

  • Apical 5-chamber or 3-chamber
  • PW doppler
  • 0.5–1.0 cm below the aortic valve

3. Aortic Valve VTI (CW Doppler)

Measures velocity through the stenotic orifice

  • CW Doppler
  • Use multiple windows:
    • Apical 5-chamber
    • Apical 3-chamber
    • Right parasternal
    • Suprasternal notch
  • Use the window with the highest reproducible velocity
  • Trace the full systolic envelope
  • Peak velocity (Vmax)
  • Mean gradient
  • AV VTI

4. Aortic Valve Area (Continuity Equation)

AVA = (LVOT Area × LVOT VTI) ÷ AV VTI

5. Dimensionless Index (DI)

DI = LVOT VTI ÷ AV VTI

  • ≤ 0.25 = Severe
  • 0.25–0.50 = Moderate
  • 0.50 = Mild

6. Gradients

Echo uses the Bernoulli equation:

  • ΔP = 4V²
    • Peak gradient = highest instantaneous pressure difference
    • Mean gradient = average pressure difference across systole

7. Flow State

Stroke Volume = LVOT Area × LVOT VTI

  • Index to BSA → SVI
  • Low flow if:
    • SVI < 35 mL/m²
    • Low flow can cause low gradients even if valve is truly severe

References

  1. Baumgartner, H., Hung, J., Bermejo, J., Chambers, J. B., Evangelista, A., Griffin, B. P., Iung, B., Otto, C. M., Pellikka, P. A., & Quiñones, M. (2017). Recommendations on the echocardiographic assessment of aortic valve stenosis: A focused update from the European Association of Cardiovascular Imaging and the American Society of Echocardiography. Journal of the American Society of Echocardiography, 30(4), 372–392. https://doi.org/10.1016/j.echo.2017.02.009
  2. Otto, C. M., Nishimura, R. A., Bonow, R. O., Carabello, B. A., Erwin, J. P., III, Gentile, F., Jneid, H., Krieger, E. V., Mack, M., McLeod, C., O’Gara, P. T., Rigolin, V. H., Sundt, T. M., III, & Thompson, A. (2021). 2020 ACC/AHA guideline for the management of patients with valvular heart disease. Circulation, 143(5), e72–e227. https://doi.org/10.1161/CIR.0000000000000923
  3. Vahanian, A., Beyersdorf, F., Praz, F., Milojevic, M., Baldus, S., Bauersachs, J., Capodanno, D., Conradi, L., De Bonis, M., De Paulis, R., Delgado, V., Freemantle, N., Gilard, M., Haugaa, K. H., Jeppsson, A., Jüni, P., Pierard, L., Prendergast, B. D., Sádaba, J. R., ... Wojakowski, W. (2022). 2021 ESC/EACTS guidelines for the management of valvular heart disease. European Heart Journal, 43(7), 561–632. https://doi.org/10.1093/eurheartj/ehab395
  4. Nishimura, R. A., Otto, C. M., Bonow, R. O., Carabello, B. A., Erwin, J. P., III, Fleisher, L. A., Jneid, H., Mack, M. J., McLeod, C. J., O’Gara, P. T., Rigolin, V. H., Sundt, T. M., III, & Thompson, A. (2017). 2017 AHA/ACC focused update of the 2014 AHA/ACC guideline for the management of patients with valvular heart disease. Circulation, 135(25), e1159–e1195. https://doi.org/10.1161/CIR.0000000000000503
  5. Clavel, M. A., Magne, J., & Pibarot, P. (2016). Low-gradient aortic stenosis. European Heart Journal, 37(34), 2645–2657. https://doi.org/10.1093/eurheartj/ehw096
  6. Clavel, M. A., Messika-Zeitoun, D., Pibarot, P., Aggarwal, S. R., Malouf, J., Araoz, P. A., Michelena, H. I., Cueff, C., Larose, É., Capoulade, R., Vahanian, A., Enriquez-Sarano, M., & Dumesnil, J. G. (2013). The complex nature of discordant severe calcified aortic valve disease grading: New insights from combined Doppler echocardiographic and computed tomographic study. Journal of the American College of Cardiology, 62(24), 2329–2338. https://doi.org/10.1016/j.jacc.2013.08.1621