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 methods used for quantitatively estimating mitral regurgitation. The PISA shape is hemielliptic rather than hemispheric on a slit-like orifice, and the hemielliptic method is more accurate than the hemispheric method for in vitro studies. Nevertheless, the hemispheric method is used clinically because of its simplicity, whereas the hemielliptic method is difficult to approach from 3 orthogonal directions. The present study tries to establish a modified hemielliptic method for use in clinical applications. A closed-circuit, constant flow system was designed to simulate PISA, and various types of slit-like orifices were selected. Three orthogonal PISA radii were measured and flow rates were calculated using the original hemielliptic formula from 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 rates that were determined using the original hemielliptic method correlated significantly with actual flow rates (r = 0.92, p < 0.0001; y = 1.1x - 13; SEE = 13.63 ml/s). Similarly, flow rates calculated using the modified hemielliptic method 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 hemielliptic method can be used to accurately quantify mitral regurgitation and could be applied for clinical examinations.