Abstract 3461: A Simplified Method of Quantitation of Mitral Regurgitation by Cardiac MRI
Introduction Mitral regurgitation (MR) based on echocardiographic (echo) studies has been shown to be associated with increased morbidity and mortality even in asymptomatic patients. Yet, estimation of MR by Echo has been primarily limited to quantification of effective regurgitant orifice area (ERO) derived via many geometric assumptions from proximal isovelocity surface area (PISA) which is markedly operator dependant.
Hypothesis Using cardiac MRI, adding one PVM plane at the level of the aortic root when combined with standard 3D LV volumetrics will accurately, rapidly and easily quantitate MR without reliance on the geometric assumptions of echo, and is verifiable in a phantom model.
A phantom flow pump (Shelley, Toronto) was used with PVM to correlate quantitated flow (ml/s) against calibrated flow.
Subjects (53) incorporating 14 normals (average age 43±20), and 39 pts with varying degrees of MR (trace – 4+) (mean age 60±22yrs) underwent 3D LV volumetric CMR (GE CV/i 1.5T) with an aortic thru-plane PVM acquisition to quantitate LV stroke volume (SV).
Exclusion criteria include aortic regurgitation or intracardiac shunt. Subtraction of the PVM derived SV (SVPVM) from the volumetic derived SV (SV3D) yields, in the absence of AR or shunt, the mitral regurgitant volume. Regurgitant fraction was defined as (SV3D- SVPVM/ SV3D).
Results The correlation of flow between the phantom model and PVM was 0.98 (p=<0.001). The correlation in the controls between SV3D and SVPVM ( 75±9 vs 70±10ml) was r=0.88, p<0.001. The resultant 3D EF ranged from 10 to 76%. The range of Regvol and Regfract was 15ml to 56ml and 15 to 46%, respectively. Quantitative MR was highly correlated with clinical qualitative findings from FIESTA imaging (r=0.9). No geometric assumptions were required to derive either Regvol or Regfract. The additional scanning time is 120±15 seconds only.
Conclusion CMR derived quantitation of mitral regurgitant volume and fraction using aortic PVM in conjunction with 3D LV stroke volume permit accurate, rapid and easily obtained, non-assumption based clinical metrics without requirements for assessing the mitral orifice. This simple method can be easily incorporated into CMR studies giving additional prognostic information.