From the Guidelines
The primary method to assess for aortic stenosis is through echocardiography, which is the key tool for diagnosis and evaluation of the condition 1.
Assessment Parameters
The following are the primary haemodynamic parameters recommended for clinical evaluation of aortic stenosis severity:
- AS peak jet velocity: a peak gradient > 4 m/s is consistent with severe aortic stenosis, and should be obtained in multiple views 1
- Mean aortic transvalvular pressure gradient: a mean gradient of > 40 mmHg is consistent with severe aortic stenosis, and requires averaging of instantaneous mean gradients 1
- Valve area by continuity equation: an AVA of < 1.0 is consistent with severe aortic stenosis, and has been well validated in both clinical and experimental studies 1
Assessment Approach
A step-by-step approach can help to deal with the challenge of defining severe aortic stenosis, particularly in the setting of low gradient AS in clinical practice 1. This approach should include:
- Transvalvular velocity/gradient
- Valve area
- Valve morphology
- Flow rate
- LV morphology and function
- Blood pressure
- Symptoms It is essential to use multiple acoustic windows for the CW Doppler assessment of AS to avoid common sources of error such as misalignment of the beam 1.
Additional Considerations
- LVOT diameter should be measured in a parasternal long-axis view from the inner edge to inner edge of the septal endocardium, and the anterior mitral leaflet in mid-systole 1
- LVOT velocity should be recorded with pulsed Doppler from an apical approach, in either the anteriorly angulated four-chamber view or in the apical long-axis view 1
- Direct planimetry of the LVOT (3D TEE or MSCT) can avoid the source of error caused by the assumption of a circular outflow tract shape 1
From the Research
Methods to Assess Aortic Stenosis
The following methods are used to assess aortic stenosis:
- Cardiac catheterization and Doppler echocardiography to measure transvalvular gradients and valve area 2
- Echocardiography, including transthoracic and transesophageal echocardiography, to assess the severity of aortic stenosis 3, 4
- Magnetic resonance and cardiac computed tomography as additional tools for assessment 3
- Stress testing to evaluate the severity of aortic stenosis 3
- Physical examination, including the presence of a systolic ejection murmur (SEM), to initially detect aortic stenosis 5
- Focused cardiac ultrasound (FoCUS) to determine whether patients with a SEM should be referred for standard echocardiography 5
- Right parasternal view (RPV) in addition to the apical view to evaluate the severity of aortic stenosis 6
Key Parameters for Assessment
The following key parameters are used to assess the severity of aortic stenosis: