Definition of Mitral Stenosis Severity
Mitral Valve Area (PHT)
Pressure half-time (PHT) is defined as the time interval in milliseconds between the maximum mitral gradient in early diastole and the time point where the gradient is half the maximum initial value. The decline of the velocity of diastolic transmitral blood flow is inversely proportional to valve area (cm2), and mitral valve area (MVA) is derived using an empirical formula.
PHT is obtained by tracing the deceleration slope of the E-wave on Doppler spectral display of transmitral flow. The deceleration slope is sometimes bimodal, the decline of mitral flow velocity being more rapid in early diastole than during the following part of the E-wave. In these cases, it is recommended that the deceleration slope in mid-diastole rather than the early deceleration slope be traced.
Overestimation of the MVA occurs when PHT is shortened by concomitant significant aortic insufficiency, decreased ventricular compliance, immediately after mitral balloon valvuloplasty, and atrial septal defect.
||Pressure Half-Time (ms)
||Mitral Valve Area (cm2)
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