Informational only. This page describes how this condition appears on ultrasound imaging for educational purposes. It is not medical advice, diagnosis, or treatment guidance.
Aortic stenosis is narrowing of the aortic valve, the gatekeeper between the left ventricle and the systemic circulation. It is one of the most common valve disorders in adults and is graded primarily with echocardiography — the imaging study that defines severity, drives surgical timing, and follows patients across years of disease progression.
ICD-10 Code: I35.0 | MeSH ID: D001024 | Primary Anatomy: Aortic Valve, Left Ventricle, Aorta
What it is
The aortic valve normally opens to roughly 3 to 4 cm² during systole, allowing the left ventricle to eject blood into the aorta with minimal resistance. In aortic stenosis, the valve leaflets become thickened, calcified, or fused, reducing the opening area and creating a pressure gradient between the left ventricle and the aorta.
Three pathways lead to AS in adults: degenerative calcific disease (overwhelmingly the most common, typically presenting in patients over 70), bicuspid aortic valve (a congenital variant that calcifies decades earlier), and rheumatic disease (less common in resource-rich countries but still important globally). Severe symptomatic AS carries roughly a 50 percent two-year mortality without intervention; valve replacement — surgical or transcatheter (TAVR) — is highly effective when timed appropriately.
How it appears on ultrasound
Transthoracic echocardiography (TTE) is the primary imaging modality. The protocol uses multiple acoustic windows — parasternal long and short axis, apical five and three chamber — to visualize the valve leaflets, measure their motion, and interrogate flow.
B-mode imaging shows leaflet thickening, calcification, and reduced opening excursion. Severe disease shows a heavily calcified valve with restricted leaflet tips that fail to open beyond a slit. Color Doppler shows turbulent, accelerated flow across the valve in systole. The diagnostic backbone, however, is spectral Doppler, particularly continuous-wave (CW) Doppler aligned through the stenotic jet.
Severity is graded primarily on three measurements: peak transvalvular velocity, mean pressure gradient, and aortic valve area calculated by the continuity equation. American Society of Echocardiography guidelines associate severe AS with peak velocity above 4.0 m/s, mean gradient above 40 mmHg, and valve area below 1.0 cm². Low-flow low-gradient subgroups — patients with severe AS but reduced ejection fraction or restrictive physiology — require additional measurements and sometimes dobutamine stress echocardiography for accurate grading.
The exam also documents secondary findings critical to management: left ventricular hypertrophy and ejection fraction, left atrial size, the presence of associated aortic regurgitation, and the dimensions of the ascending aorta (which dilates in many bicuspid valve patients).
Transesophageal echocardiography (TEE) is used when transthoracic windows are inadequate, before and during surgical valve replacement, and for guidance during TAVR procedures.
Which specialty images it
Adult cardiac sonography (RDCS-credentialed) is the imaging discipline. Echo sonographers perform the studies in dedicated echo labs, hospital cardiology departments, and cardiologists’ offices. The cardiac specialty page covers credential and scope. Pediatric cardiac sonography is a separate sub-specialty for congenital aortic valve disease in children.