Hemodynamic Aspects of Mitral Regurgitation Assessed by Generalized Phase-Contrast Magnetic Resonance Imaging

Purpose: To investigate the utility of MRI measurement of left atrial (LA) flow patterns and turbulent kinetic energy (TKE) in patients with clinically significant mitral regurgitation. Materials and Methods: Three-dimensional cine phase-contrast MRI (PC-MRI) data were acquired in five patients with posterior mitral leaflet prolapse and two normal volunteers. LA flow patterns were assessed using particle trace visualization. Specifically, vortices were recognized by closed streamlines. LA flow distortion was assessed by estimation of TKE. In addition, the regurgitant volume was measured. Results: Four of the mitral regurgitation patients had eccentric regurgitant jets directed towards the septum; one patient had a central jet. The dominant systolic vortex was located in proximity to the regurgitant jet. The LA flow was highly disturbed with elevated values of TKE; peak LA TKE ranged from 13 to 37 millijoule and occurred consistently at late systole. The average LA TKE per cardiac cycle was significantly related to the regurgitant volume (TKE = 0.573 + 0.179·RegVol, R 2 = 0.983). Conclusion: MRI permits investigations of atrial flow patterns and TKE in significant mitral regurgitation. The degree of LA flow distortion, as measured by the average LA TKE over one cardiac cycle, appears to reflect the severity of regurgitation.