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Measures of AS severity obtained by Doppler-echocardiography: (1) appropriate in all patients with AS (yellow); (2) reasonable when additional information is needed in selected patients (green). VR, velocity ratio; TVI, time–velocity integral; LVOT, LV outflow tract; AS, AS jet; TTE and TEE, transthoracic and transesophageal echocardiography; AVA, continuity-equation-derived aortic valve area; v, velocity of AS jet, ΔP, mean transvalvular systolic pressure gradient, N, number of instantaneous measurements.