Aortic Stenosis

TTE Suspicious for AS Assess velocity/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 Define whether high flow is reversible Not reversible Reversible Severe AS Re-assess at normal flow Define flow status (SVi) Low flow (SVi ≤35) Normal flow (SVi >35) Severe AS unlikely Assess LVEF LVEF <50% LVEF ≥50% Dobutamine echo Integrated approach Flow reserve present No flow reserve Pseudosevere AS or true severe AS Calcium score by CT
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

AS Calculator

Severe AVA ≤1.0 cm² or DI <0.25 | Low flow SVI <35 mL/m² | Low gradient <40 mmHg | Reduced EF <50%

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