A novel approach to calculation of mean mitral valve gradient by Doppler echocardiography

The Doppler-derived mean mitral valve gradient (DeltaP(M)) based on the sim plified Bernoulli equation requires computerized integration of the Doppler signal and evaluation by a technician with the use of special equipment. W e have noted empirically that the DeltaP(M) can be derived by the equation DeltaP(M) = (P-P P-T) / 3 + P-T. Peak (P-P) and trough (P-T) pressures are derived from the simplified Bernoulli equation (P = 4V2). This equation can be used by the experienced observer to calculate the mean mitral valve gra dient without specialized equipment. The purpose of this study is to valida te the above empirically derived equation in patients with mitral stenosis. We retrospectively reviewed 41 consecutive studies done at our institution from October 1, 1997, through September 30, 1998, in which mean mitral val ve gradient was assessed. Each study was reviewed and the DeltaP(M), P-P, a nd P-T were measured for 3 beats by using the software package on an HP Son os 2500. DeltaP(M) was also calculated with our formula. A linear regressio n model was used to compare the results of the measured versus the calculat ed DeltaP(M). The following sub-categories were also evaluated: transthorac ic studies (TTE), transesophageal studies (TEE), native valve gradients (NV ), prosthetic valve gradients (PV), sinus rhythm (SR), and atrial fibrillat ion (AF). The results of the regression analysis of the entire population o f mean versus calculated DeltaP(M) are n = 41, r = 0.99, P < .001, and stan dard error of the estimate (SEE) = 0.67. The regression results for the sub groups are as follows: TTE: n = 30, r = 0.99, P < .001, SEE = 0.51; TEE: n = 11, r = 0.99, P < .001, SEE = 59; NV: n = 26, r = 0.99, P < .001, SEE 0.5 9; PV: n = 15, r = 0.98, P < .001, SEE = 0.84; SR: n 23, r = 0.99, P < .001 , SEE = 0.58; and AF: n = 18, r = 0.98, P < .001, SEE = 0.82. In conclusion , the simple formula that we have derived is an accurate method for calcula tion of mean mitral valve gradient, and it is accurate over multiple subgro ups. Furthermore, die formula allows visual verification of mean mitral gra dient without specialized software.