Calculation of mitral regurgitant orifice area with use of a simplified proximal convergence method: Initial clinical application

To validate a previously proposed simplified proximal flow convergence method for calculating mitral regurgitant orifice area (ROA), a prospective study was conducted in ambulatory patients and in patients undergoing open heart surgery. Assuming a pressure difference between the left ventricle and left atrium of approximately 100 mm Hg (jet velocity [v_p] 500 cm/s) and setting the color aliasing velocity (v_a) to 40 cm/s, we simplified the conventional proximal convergence method formula (ROA = 2πr²v_a/v_p) to r²/2, where r is the radius of the proximal convergence isovelocity hemisphere. For 57 ambulatory patients with a wide range of mitral regurgitant severity (1 to 4+), ROA was calculated by the conventional (x) and simplified (y) methods, demonstrating excellent accuracy (r = 0.92; P < .001; ΔROA [y - x] = 0.004 ± 0.08 cm²). For 24 intraoperative patients, ROA calculated by the simplified formula (y) correlated well with the pulsed Doppler-thermodilution method (x) (r = 0.84; P <] .01; ΔROA [y - x] = -0.002 ± 0.08cm²). This simplified proximal convergence formula yields an accurate assessment of ROA for a wide range of regurgitant severity, while the time required for this measurement is shortened by half (1.5 ± 0.5 minutes versus 3.2 ± 0.7 minutes). This may increase the frequency of calculating ROA in the clinical laboratory.