Aortic Stenosis Severity Grading

Primary Severity Parameters

The European Society of Cardiology recommends that aortic stenosis severity is graded by integrating three primary echocardiographic parameters: peak aortic jet velocity, mean transvalvular gradient, and aortic valve area calculated by the continuity equation, with severe AS defined as velocity ≥4 m/s, mean gradient ≥40 mmHg, and valve area ≤1.0 cm² 1, 2
Severe AS is characterized by peak aortic jet velocity ≥4.0 m/s, mean pressure gradient ≥40 mmHg, aortic valve area (AVA) ≤1.0 cm², and indexed AVA ≤0.6 cm²/m², as defined by the European Heart Journal 3, 4
Moderate AS is defined by peak velocity 3.0-3.9 m/s, mean gradient 20-39 mmHg, and AVA 1.0-1.5 cm², according to the European Heart Journal 3
Mild AS is characterized by peak velocity 2.5-2.9 m/s, mean gradient <20 mmHg, and AVA >1.5 cm², as stated in the European Heart Journal 3

The American Heart Association emphasizes that LVOT diameter measurement is the single largest source of error because it is squared in the continuity equation, magnifying small measurement errors, and recommends measuring the LVOT at the base of the aortic valve cusps or 1-5 mm below 4, 5, 6
The American College of Cardiology recommends that peak velocity must be obtained from multiple acoustic windows (apical, right parasternal, suprasternal, subcostal) to capture the highest velocity signal and avoid underestimation from beam misalignment 1, 4

High gradient AS (mean gradient ≥40 mmHg) generally confirms severe AS regardless of flow state, according to the European Heart Journal 3
Low gradient AS (mean gradient <40 mmHg) requires extensive evaluation, including calculation of AVA, determination of flow status, and flow-based classification, as recommended by the European Heart Journal 3
In cases of low flow, low gradient with reduced EF (<50%), dobutamine stress echocardiography (≤20 μg/kg/min) should be performed to distinguish true from pseudosevere AS, as suggested by the American Heart Association 7, 8
In cases of low flow, low gradient with preserved EF (≥50%), CT calcium scoring is highly valuable, with >1200 Agatston units (women) or >2000 units (men) confirming severe AS, according to the American College of Cardiology 9

The European Society of Cardiology warns that LVOT area underestimation can lead to underestimation of stroke volume and AVA, and recommends using 3D transesophageal echo or CT for direct LVOT planimetry 4, 8
Elevated blood pressure can alter velocity and gradient measurements, and the American Heart Association recommends recording blood pressure during examination and optimizing antihypertensive therapy if necessary 4, 5, 6

The American College of Cardiology recommends assessing valve morphology, LV function and geometry, hemodynamic consequences, and symptom status, in addition to the primary grading parameters, to guide clinical decision-making 1, 2, 6, 7, 8
Clinically significant progression is defined as mean gradient increase >10 mmHg or AVA decrease >25% from baseline, according to the European Heart Journal 4