Classification and Diagnosis of Severe Aortic Stenosis

Primary Hemodynamic Criteria for Severe AS

The European Society of Cardiology recommends that severe aortic stenosis be classified by any one of three primary hemodynamic criteria: aortic valve area (AVA) <1.0 cm², peak aortic jet velocity ≥4.0 m/s, or mean pressure gradient ≥40 mmHg, with further subclassification based on flow status and left ventricular ejection fraction 1, 2, 3
The diagnosis of severe AS requires meeting any one of the following thresholds: peak aortic jet velocity ≥4.0 m/s, mean transvalvular pressure gradient ≥40 mmHg, or aortic valve area <1.0 cm², according to the European Heart Journal 2, 3
Indexed AVA <0.6 cm²/m² is particularly important in small adults, children, and adolescents, as recommended by the European Heart Journal 3
Velocity ratio <0.25 is also a criterion for severe AS, as stated in the European Heart Journal 3

High-gradient severe AS is characterized by velocity ≥4 m/s and mean gradient ≥40 mmHg, which clearly indicates severe AS, according to the European Heart Journal 2, 4
Further categorization by flow status includes normal-flow, high-gradient AS (stroke volume index ≥35 mL/m²) and low-flow, high-gradient AS (stroke volume index <35 mL/m²), as defined by the European Heart Journal 4
Low-flow, low-gradient AS with reduced LVEF is defined by AVA <1.0 cm², mean gradient <40 mmHg, LVEF <50%, and stroke volume index <35 mL/m², according to the European Heart Journal 3
Dobutamine stress echocardiography is required to distinguish true-severe from pseudo-severe AS by assessing contractile reserve (≥20% increase in stroke volume), as recommended by the European Heart Journal 3, 5

The American College of Cardiology (ACC) and American Heart Association (AHA) provide a comprehensive staging system, which includes Stage C: Asymptomatic Severe AS, with subcategories C1 and C2, and Stage D: Symptomatic Severe AS, with subcategories D1, D2, and D3, as outlined in Circulation 1, 6

Underestimation of LVOT area is the most common source of error, leading to underestimation of flow and overestimation of stenosis severity, as warned by the European Heart Journal 2, 5
Inadequate Doppler alignment can underestimate velocity and falsely lower severity assessment, according to the European Heart Journal 2
Hypertension can alter peak velocity and mean gradient; blood pressure should be recorded at every examination, as recommended by the European Heart Journal 3