From the Guidelines
To convert Doppler pressure half-time (PHT) in seconds to mitral valve area (MVA) in cm², use the formula MVA = 220/PHT, as this method is widely accepted and supported by guidelines from reputable sources such as the American College of Cardiology/American Heart Association 1. When applying this formula, it is essential to understand that the mitral pressure half-time is inversely related to the mitral valve area, and this relationship can be influenced by factors such as left atrial and left ventricular compliance, as noted in the 2014 AHA/ACC guideline for the management of patients with valvular heart disease 1. Key points to consider in the assessment of mitral stenosis include:
- The use of 2D scanning from the parasternal long-axis window to identify diastolic doming of the mitral valve
- Short-axis scanning to demonstrate commissural fusion and allow planimetry of the mitral orifice
- Doppler hemodynamics obtained from the apical 4–chamber or long-axis view, including peak and mean transvalvular gradient
- The importance of heart rate in affecting transvalvular gradient
- The potential impact of concomitant mitral regurgitation and other valve lesions on the assessment
- The utility of the Wilkins score in assessing mitral valve morphology and feasibility for percutaneous mitral balloon commissurotomy or surgical commissurotomy For example, if the PHT is 110 milliseconds (0.11 seconds), the calculated MVA would be 220/110 = 2.0 cm², which can be a critical value in determining the severity of mitral stenosis and guiding clinical decision-making, as emphasized in the guideline 1. It is crucial to correlate the calculated MVA with other echocardiographic measurements, such as planimetry, and clinical presentation to ensure accurate assessment and management of patients with mitral stenosis, considering the potential limitations of the formula in certain conditions, such as aortic regurgitation or impaired left ventricular compliance 1.
From the Research
Conversion of Doppler Slope to Mitral Valve Area
- The conversion of Doppler (Doppler ultrasound) slope in seconds to mitral valve area can be calculated using the equation: MVA = 220 / pressure half-time 2.
- Pressure half-time is the interval between peak transmitral velocity and velocity divided by the square root of 2, as measured from the outer border of the spectral envelope 2.
- The mitral valve area can also be estimated using the proximal isovelocity surface area (PISA) method, which is calculated as follows: 2 x Pi x (proximal aliasing color zone radius)2x aliasing velocity/peak velocity across mitral orifice 3.
- The Doppler pressure half-time method has been compared with other methods, such as the Gorlin equation and 2-dimensional planimetry, and has been found to be a useful and accurate method for estimating mitral valve area 4, 2, 5.
- However, the accuracy of the Doppler pressure half-time method can be affected by factors such as heart rate and atrial fibrillation, and should be used with caution in these cases 4, 2.
Limitations and Considerations
- The Doppler pressure half-time method may not be accurate in patients with tachycardia or atrial fibrillation 4, 2.
- The method should be used with caution and in combination with other methods, such as the Gorlin equation and 2-dimensional planimetry, to ensure accurate estimation of mitral valve area 6, 4, 2.
- The PISA method has been found to be a useful and accurate method for estimating mitral valve area, but may require more validation and should be used in combination with other methods 3.