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across the mitral annulus is difficult. SV is therefore measured at the aortic annulus and used in the numerator of the equation; the denominator is the integral of the mitral stenosis jet.
The method is quite accurate in the absence of associated mitral
regurgitation (MR).5 b.
Mitral valve area with the pressure half-time method The pressure half time (P1/2t) method is a simple and accurate method of
determining valve area in mitral stenosis (Figure 14). Pressure half time represents the time that the maximal pressure gradient takes to decrease by one half. When expressed in terms of velocity, this time is equivalent to the time that the peak stenotic velocity takes to drop by 30%. Early studies established an inverse relation between P1/2t and mitral valve area (MVA),46 and from this relation the following empirical equation was derived: MVA = 220 / P1/2t
(8)
This formula works surprisingly well in most patients and can be reliably used in clinical decision making.47,48 Potential sources of errors must be considered, such as rapid heart rate, the presence of significant aortic regurgitation, and conditions that alter left atrial or LV compliance and/or LV relaxation.49-51 In some patients the early velocity descent is curvilinear rather than linear, resembling a ski slope. In these instances, derive a pressure half time by extrapolating the mid-diastolic linear descent backwards, as illustrated in Figure 15. Although there are similarities between mitral and tricuspid stenosis, the P1/2t method has not been as extensively validated for the calculation of tricuspid valve area. 5.
Application of Doppler in regurgitant valve lesions Doppler echocardiography is the most commonly used diagnostic technique for
detecting and evaluating valvular regurgitation. Multiple indexes have been developed to assess severity of regurgitation with PW, CW, and color Doppler. Although techniques for measuring these indexes are described in this document, recommendations concerning their clinical application will be discussed in an upcoming document dedicated to the evaluation of regurgitant valve lesions.
a.
Regurgitant volume, regurgitant fraction, and effective regurgitant orifice area
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