Proximal Flow Convergence Region as Assessed by Real-time 3-Dimensional Echocardiography: Challenging the Hemispheric Assumption

Abstract

Traditionally, a hemispheric assumption for the proximal flow convergence region (PFCR) is used when calculating mitral regurgitant (MR) effective orifice area (EROA). However, 2-dimensional (2D) echocardiography limits evaluation of the complete PFCR contour. Real-time 3-dimensional (3D) echocardiography (RT3D) allows direct assessment of the true PFCR contour. We hypothesized that the PFCR contour is not necessarily hemispheric, but rather hemielliptic, and aimed to apply a hemielliptic calculation, based on the 3D contour of the PFCR for more accurate MR quantification. In all, 50 patients with MR underwent RT3D to characterize PFCR contour as hemispheric or hemielliptic. MR EROA by RT3D-derived PFCR was calculated using a hemielliptic formula using 3D data. The 2D EROA was computed using standard hemispheric assumption. EROAs calculated from 2D and RT3D data were compared with quantitative Doppler EROA (mitral inflow--aortic outflow/MR time-velocity integral), used as an independent comparison. Only 1 of 50 patients (2%) had a hemispheric PFCR contour by RT3D. The remaining had hemielliptic PFCR contours. Compared with Doppler method, 2D echocardiography significantly underestimated EROA (0.34 +/- 0.14 vs 0.48 +/- 0.25 cm(2), P < .001). RT3D EROA was not significantly different from Doppler EROA (0.52 +/- 0.17 vs 0.48 +/- 0.25, P = not significant). Of 33 patients with Doppler EROA greater than 0.3 cm(2) (> or =moderate-severe MR), 45% (15 of 33) were underestimated as having mild to moderate MR by 2D EROA. The true PFCR contour as shown by RT3D is generally not hemispheric but hemielliptic, tracking the orifice contour. Based on this 3D shape, a hemielliptic approach can be used for practical clinical application with improved MR quantification.