Hemielliptic proximal isovelocity surface area method modified for clinical application - More accurate quantification of mitral regurgitation in Doppler echocardiography

The proximal isovelocity surface area (PISA) method is one of the various m ethods used for quantitatively estimating mitral regurgitation. The PISA sh ape is hemielliptic rather than hemispheric on a slit-like orifice, and the hemielliptic method is more accurate than the hemispheric method for in vi tro studies. Nevertheless, the hemispheric method is used clinically becaus e of its simplicity, whereas the hemielliptic method is difficult to approa ch from 3 orthogonal directions. The present study tries to establish a mod ified hemielliptic method for use in clinical applications. A closed-circui t, constant flow system was designed to simulate PISA, and various types of slit-like orifices were selected. Three orthogonal PISA radii were measure d and flow rates were calculated using the original hemielliptic formula fr om the 3 orthogonal radii. Flow rates were also calculated indirectly using a linear regression formula, and PISA radii from a bird's eye approach and lateral approaches (modified hemielliptic method) were compared. Flow rate s that were determined using the original hemielliptic method correlated si gnificantly with actual flow rates (r=0.92, p <0.0001; y=1. 1x-13; SEE=13.6 3 ml/s). Similarly, flow rates calculated using the modified hemielliptic m ethod correlated significantly with actual flow rates (r=0.90, p <0.001; y= 0.94x-0.78; SEE=14.13 ml/s). The study's results imply that the modified he mielliptic method can be used to accurately quantify mitral regurgitation a nd could be applied for clinical examinations.