VALIDATION OF THE PROXIMAL ISOVELOCITY SURFACE-AREA METHOD FOR ASSESSING MITRAL REGURGITATION IN CHILDREN

The proximal isovelocity surface area (PISA) method for calculating vo lume flow through the regurgitant orifice has attracted significant at tention. A number of in vitro studies and clinical studies in adults s uggest that the method is accurate. However, when applying the method to children it must be noted that the absolute regurgitation volume is small, and the range of body sizes is wide. This study investigated t he accuracy of the PISA method for quantitative assessment of the seve rity of mitral regurgitation in children. Twenty children aged 7 month s to 12 years (average 4.7 years) with mitral regurgitation but withou t interventricular shunt or aortic stenosis were selected for this stu dy. Underlying cardiac diseases included atrioventricular septal defec ts in nine, isolated mitral regurgitation in five, and association wit h other heart defects in six. The PISA radius (r) and the duration of regurgitation (T) were measured on color M-mode recordings, with the M line passing through the center of the PISA. Assuming that the PISA i s a hemisphere, maximal regurgitant flow rate (MFR: ml/s) was calculat ed as MFR = 2 pi x r(2) x V (r = maximal radius, V = aliasing velocity ), and regurgitant stroke volume (RSVpisa) as RSVpisa = 2 pi x MSR x V x T (MSR = mean square of the PISA radius during regurgitation). As a validating standard, total stroke volume (TSV) using two-dimensional echocardiography determined by the area-length volumetry method and fo rward stroke volume (FSV) by the pulsed Doppler method were measured, and regurgitant stroke volume (RSV,: RSV, TSV - FSV) and regurgitant f raction (RF: RF = RSV(D)/TSV) were calculated. A linear correlation wa s found between MFR, RSVpisa, and RSV(D) (X) (MFR = 4.2X + 54.0, r = 0 .84. RSVpisa = 1.0X + 9.8, r = 0.90), and both RSVpisa and MFR divided by body surface area (BSA: m(2)) revealed a significant correlation w ith regurgitant fraction (X) by nonlinear regression analysis (RSVpisa /BSA = 26.2 x X/(1 - X) + 16.8, r = 0.85. MFR/BSA = 121.8 x X/(1 - X) + 92.2, 1 = 0.79). It is concluded that maximal regurgitant flow rate, regurgitant stroke volume, and regurgitant fraction can be accurately predicted in children using the PISA method by Doppler echocardiograp hy.