Mechanism of dynamic regurgitant orifice are variation in functional mitral regurgitation : Physiologic insights from the proximal flow convergence technique

Objectives We used the Doppler proximal flow convergence technique as physiologic tool to explore the effects of the time courses of mitral annular are and transmitral pressure on dynamic changes in regurgitant orifice area. Background In functional mitral regurgitation (MR), regurgitant flow rate and orifice are display unique pattern, with peaks in early and late systole and midsystolic decrease. Phasic changes in both mitral annular are and the transmitral pressure acting to close the leaflets, which equals left ventricular-left atrial pressure, have been proposed to explain this dynamic pattern. Methods In 30 patients with functional MR, regurgitant orifice are was obtained as flow (from M-mode proximal flow convergence traces) divided by orifice velocity (v) from the continuous wave Doppler trace of MR, transmitral pressure as 4v2, and mitral annular are from two apical diameters. Results All patients had midsystolic decreases in regurgitant orifice are that mirrored increases in transmitral pressure, while mitral annular are changed more gradually. By stepwise multiple regression analysis, both mitral annular are and transmitral pressure significantly affected regurgitant orifice area; however, transmitral pressure made stronger contribution (r2 = 0.441) than mitral annular are (added r2 = 0.008). Similarly, the rate of change of regurgitant orifice are more strongly related to that of transmitral pressure (r2 = 0.638) than to that of mitral annular are (added r2 = 0.003). similar regurgitant orifice are time course was observed in four patients with fixed mitral annuli due to Carpentier ring insertion. Conclusions In summary, the time course and rate of change of regurgitant orifice are in patients with functional MR are predominantly determined by dynamic changes in the transmitral pressure acting to close the valve. Thus, although mitral annular are helps determine the potential for MR, transmitral pressure appears important in driving the leaflets toward closure, and would be of value to consider in interventions aimed at reducing the severity of MR.