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

Objective: 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. Methods: 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. Results: 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 cm², 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 cm² (≥moderate-severe MR), 45% (15 of 33) were underestimated as having mild to moderate MR by 2D EROA. Conclusions: 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.