Abstract 298: Direct Visualization of Regurgitant Orifice by Cardiovascular Magnetic Resonance Reveals Significant Asymmetry in Functional Mitral Regurgitation
Background: Regurgitant orifice area (ROA) is evolving as quantitative and reliable parameter of mitral regurgitation (MR) severity. Recent studies employing three dimensional echocardiography have suggested that shape and ROA of the regurgitant jet may vary according to the etiology of MR. The purpose of the current study was to characterize shape and ROA of the regurgitant jet for the first time by cardiovascular magnetic resonance (CMR) for various forms of MR.
Methods: Direct assessment of ROA was performed with a 1.5 T CMR scanner using a breath-hold fast imaging with steady state free precession (TrueFISP) as recently described by our group. Subsequent slices were defined parallel to the valvular plane and additionally, especially in cases of orifices with an eccentric regurgitant jet, perpendicular to the direction of the jet. The shape of the ROA was expressed as ratio of long axis diameter and short axis diameter (asymmetry index) whereby a larger asymmetry index reflects a more elliptical shape and smaller asymmetry index reflects a more rounded shape.
Results: 74 patients were studied. MR severity was mild in 39%, moderate in 27% and moderate to sever or severe in 34%. Mitral valve pathology was degenerative in 26%, prolapse in 20%, flail in 34% and functional in 20%. Mean ROA was 0.25±0.11cm2, 0.51±0.20cm2, 0.55±0.35cm2 and 0.56±0.24cm2, respectively (p<0.05 for degenerative MR vs prolapse/flail/functional MR). ROA correlated significantly with regurgitant fraction (r=0.80, p<0.001) and the overall asymmetry index was 2.43±1.30. Of note, the asymmetry index varied significantly according to the different etiologies of MR and was 1.35±0.29 in degenerative, 2.42±0.86 in prolapse, 2.32±0.82 in flail and 3.99±1.61 in functional MR (p<0.01 vs. all).
Conclusion: Direct assessment of ROA by CMR is feasible and allows accurate quantification of severity and shape of the regurgitant jet. The asymmetry index indicates a more rounded shape in degenerative, an elliptical shape in prolapse and flail and a slit- or cleft-like shape in functional MR. The latter is consistent with anular dilatation and insufficient leaflet coaptation of the mitral valve in functional MR.