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Patient has severe Aortic Regurgitation, reduced LV compliance, or if assessed immediately following mitral valvuloplasty. These conditions alter the transmitral pressure gradient independent of the valve area.
The Pressure Half-Time (PHT) is the time required for the peak transmitral pressure gradient to decline to one-half of its original value. In mitral stenosis, the time it takes for the pressure in the left atrium to equilize with the left ventricle is prolonged because the stenotic valve orifice restricts flow.
Empirically, a PHT of 220 ms has been found to correspond to a Mitral Valve Area (MVA) of 1.0 cm2. Thus, MVA = 220 / PHT.
If left ventricular compliance is reduced (e.g., in elderly patients with LVH/HTN), the PHT will be shortened, falsely underestimating the severity of MS. Conversely, if LA compliance is increased, the PHT will be lengthened.
Planimetry of the mitral valve in the short-axis view remains the anatomical gold standard for MVA, but can be technically difficult and requires excellent image quality.
Noninvasive assessment of atrioventricular pressure half-time by Doppler ultrasound.
Echocardiographic assessment of valve stenosis: EAE/ASE recommendations for clinical practice.
MVA (Pressure Half-Time): Estimates Mitral Valve Area from the deceleration of mitral inflow. Standard method for grading Mitral Stenosis.