Regurgitant Volume Estimation in Patients with Mitral Regurgitation: Initial Studies Using the Color Doppler “Proximal Isovelocity Surface Area” Method

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Abstract
Doppler color flow mapping of a proximal isovelocity surface area (PISA), calculated from a blue-red aliasing radius, has been shown in vitro to be accurate for estimating volume flow rate across a narrowed orifice. Volume flow rate (in cm3/sec) can be calculated as PISA (in cm2) x aliasing velocity (in cm/sec). This method has advantages over other color Doppler approaches in that PISA-derived volume flow rate calculations appear to be independent of machine parameter settings and orifice shape. We evaluated the clinical applicability of the PISA method in 49 patients with native valve mitral regurgitation (MR). Color Doppler flow mapping was performed at color aliasing velocities of 54–72 cm/sec. Twenty-four patients were excluded because a color aliasing radius was not clearly seen: 20 of these 24 patients had mild MR. In the remaining 25 patients, the ratio of maximum regurgitant jet area-to-left atrial area, as well as the regurgitant stroke volume estimated using the time-velocity integral method, were compared to regurgitant stroke volume calculated from the PISA method. Maximum PISA was calculated using a formula derived from previous in vitro studies: PISA = 8.05 × r2, where r is the maximum color Doppler aliasing radius in the apical four-chamber view. Regurgitant stroke volume using the PISA method was calculated as 8.05 × r2× V × MRTVI/MRPFV, where V is the aliasing velocity, MRTVI is the time-velocity integral of the MR jet from continuous-wave Doppler, and MRPFV is the peak velocity of the MR jet on the continuous-wave Doppler recording. Calculated regurgitant stroke volume using the PISA method correlated well with the ratio of maximum MR jet area-to-left atrial area (r = 0.84, P < 0.01), and fairly well with the regurgitant stroke volume calculated using the time-velocity integral method (r = 0.77, P < 0.05). We conclude that in patients with moderate or severe native valve MR, the color Doppler PISA method is useful for estimating regurgitant stroke volume.

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