Aortic valve on echocardiography

EchoCG evaluation of aortic stenosis (AS)

A comprehensive approach is required to determine the severity of aortic stenosis (aortic stenosis). Transvalvular pressure gradients directly depend on blood flow. Therefore, isolated measurement of a single parameter is insufficient: it is necessary to simultaneously take into account blood flow velocity, pressure gradient, the patient's functional status, and ventricular contractile function.

The theoretically ideal criterion for the degree of narrowing is the aortic valve area.

• Severe stenosis is diagnosed when the valve area is less than 1.0 cm².
• If the patient has an atypically large or small body surface area, an indexed parameter is used: a value of less than 0.6 cm²/m² corresponds to severe valvular disease.

There are several forms of aortic stenosis that can be identified on imaging:

1. Valvular AS: the most frequent group of pathologies, varying from critical stenosis in infants (imp_airing systemic perfusion) to mild forms often caused by a bicuspid aortic valve.
2. Subvalvular AS: a rare form that may occur in isolation or accompany hypertrophic cardiomyopathy.
3. Supravalvular AS: a specific anomaly associated with Williams-Beuren syndrome (a genetic defect in elastin synthesis leading to decreased distensibility of the aortic wall).

EchoCG evaluation of aortic regurgitation (AR)

The main task of EchoCG in aortic regurgitation (aortic regurgitation) is monitoring left ventricular (LV) function. Progressive increase in the regurgitation volume against the background of deteriorating LV function is the main indication for valve replacement.

Depending on the rate of development of the lesion (acute or chronic form), the imaging picture differs. In chronic regurgitation, the LV adapts through marked eccentric hypertrophy (dilatation) and increased compliance. Acute AR (e.g., due to trauma or infective endocarditis) proceeds without LV dilatation, leading to a sharp spike in intraventricular pressure and the risk of pulmonary edema.

Doppler modes are used for semiquantitative assessment of severity:

• Color Doppler: visualizes the regurgitant jet. Important nuance: the maximum jet length does not correlate with the severity of the pathology. One should rely on the cross-sectional area and the width of the jet neck (vena contracta). A value of ≥ 6 mm indicates severe regurgitation (sensitivity 95%), and < 3 mm indicates mild regurgitation.
• Continuous-wave Doppler (continuous-wave Doppler): allows measurement of the pressure gradient decay rate (pressure half-time). The faster the gradient drops, the more severe the lesion: < 200 ms — severe AR, > 400 ms — mild AR. Holodiastolic retrograde flow in the descending aorta is also evaluated.
• Pulse-wave Doppler: used to measure regurgitation volumes by comparing stroke volume at the aortic level with effective stroke volume at the mitral valve level (however, the method has measurement errors).

Imaging of prosthetic valves and endocarditis

After aortic valve replacement, a baseline transthoracic 2D and Doppler EchoCG examination must be performed immediately. The data obtained will serve as a reference for comparison during subsequent examinations if device dysfunction is suspected.

One of the rare (0.9–4.4%) but severe complications of replacement is infective endocarditis, which most frequently develops in the first 6 months after surgery. The infection localizes in the area of the aortic valve fibrous ring and the ascending aorta.

Two-dimensional EchoCG (especially transoesophageal — transoesophageal) details the shape, size, and location of thrombi or vegetations (pannus). High-velocity regurgitant jets can damage parts of the valve attachment, causing the formation of local abscesses, pseudoaneurysms, and paravalvular leakage due to the destruction of surgical sutures.

Class and exam questions

What else to study on this topic

• Cardiovascular magnetic resonance (CMR) for accurate quantitative assessment of regurgitation volume
• The role of computed tomography (CT) in planning transcatheter aortic valve implantation (TAVI)
• Pathogenesis of degeneration and structural destruction of bioprostheses
• Etiological factors of aortic regurgitation: leaflet involvement versus aortic wall pathology
• Hemodynamic features and left ventricular compensation in acute and chronic aortic regurgitation

Other topics in the «Chest Radiology» section

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