From the Guidelines
To assess mitral stenosis with transthoracic echocardiography (TTE), first obtain standard views including parasternal long-axis, short-axis, apical four-chamber, and apical two-chamber views, as recommended by the 2014 AHA/ACC guideline for the management of patients with valvular heart disease 1. The assessment of mitral stenosis with TTE involves several key steps:
- Evaluate the mitral valve morphology for leaflet thickening, calcification, commissural fusion, and mobility restriction using 2D imaging.
- Measure the mitral valve area using planimetry in the parasternal short-axis view at the tips of the leaflets, which is considered the reference standard.
- Calculate the mitral valve area using the pressure half-time method by measuring the deceleration time of the mitral inflow on continuous-wave Doppler.
- Assess the mean and peak transmitral gradients using continuous-wave Doppler aligned parallel to mitral inflow.
- Estimate pulmonary artery systolic pressure by measuring the tricuspid regurgitation velocity and adding estimated right atrial pressure.
- Evaluate for left atrial enlargement, which typically occurs with chronic mitral stenosis.
- Assess for associated lesions such as mitral regurgitation or other valvular abnormalities.
- Finally, assess left and right ventricular size and function to determine the hemodynamic consequences of the stenosis. The severity of mitral stenosis is classified as mild (valve area >1.5 cm²), moderate (1.0-1.5 cm²), or severe (<1.0 cm²), with corresponding mean gradients typically <5 mmHg, 5-10 mmHg, and >10 mmHg, respectively. It's worth noting that the use of 3D echocardiography may provide greater accuracy in assessing mitral valve area, but it is not yet routinely used, as stated in the 2014 AHA/ACC guideline 1. Additionally, the ACR Appropriateness Criteria for dyspnea-suspected cardiac origin also supports the use of TTE as the primary modality for diagnosis, assessment, and follow-up of native and prosthetic valvular heart disease 1.
From the Research
Assessment of Mitral Stenosis with TTE
To assess mitral stenosis using Transthoracic Echocardiography (TTE), several steps can be followed:
- 2D Echocardiography: This method is used to visualize the mitral valve and assess its morphology 2.
- Planimetry of the Mitral Valve Area: This technique allows for a reliable assessment of the degree of stenosis in 75% of all patients 3.
- Doppler Echocardiography: This method measures the transmitral pressure gradient and determines pressure half-time, from which the mitral valve area can be calculated 3, 4.
- Assessment of Associated Regurgitations and Pulmonary Hypertension: Doppler echocardiography can detect accompanying disorders such as mitral and aortic regurgitation or aortic stenosis, as well as subsequent disorders like pulmonary hypertension or relative tricuspid incompetence 3, 4.
- 3D Echocardiography: This technique can provide a more accurate assessment of the mitral valve area, especially in patients with poor echocardiographic windows or for teams less accustomed to evaluating mitral stenosis patients 5, 6.
Key Parameters to Assess
Some key parameters to assess when evaluating mitral stenosis with TTE include:
- Mitral valve area (MVA)
- Transmitral pressure gradient
- Pressure half-time
- Presence of associated regurgitations or pulmonary hypertension
- Left atrial volume
Limitations and Considerations
It is essential to note that the transmitral pressure gradient can undergo considerable day-to-day variations, limiting its value for quantification 3. Additionally, echocardiography may underestimate left atrial volume compared to cardiac magnetic resonance (CMR) imaging 5.