P1779Quantitation of severe degenerative mitral regurgitation by echocardiography and CMR with acetate PET for external reference for left ventricular volumes

Abstract Background Quantitative echocardiographic assessment of severity of primary mitral regurgitation (MR) is challenging. CMR is recommended if MR severity cannot be clearly determined, since quantitation of regurgitation as well as of left ventricular (LV) volumes and function is crucial for the indication for surgery especially in asymptomatic patients. Purpose We aimed to compare volumetric measurements obtained from transthoracic echo (TTE) and cardiovascular magnetic resonance (CMR) using ECG-gated [(11)C]acetate PET as reference for assessment of LV volumes. Methods A total of 51 asymptomatic patients with severe primary mitral regurgitation underwent TTE, CMR and PET on the same day. Mitral regurgitant volumes (RVol) were measured by TTE using proximal convergence (PISA) method and by CMR, subtracting aortic forward flow volume from LV stroke volume. LV volumes were measured by TTE, CMR and PET. Results Despite a fair correlation between regurgitant volumes measured by TTE and CMR (r=0.53, p<0.001), PISA method heavily overestimated regurgitant volumes on TTE as compared to CMR (103±60ml vs. 78±35ml, p<0.001). TTE systematically underestimated LV volumes as compared to CMR (see table) despite a good correlation (r=0.81, 0.67 and 0.76 respective for LV EDV, ESV and SV, p<0.001 for all). There was no difference in LV EF between the methods. LV volumes obtained by CMR and PET showed a strong correlation (r=0.92, 0.79 and 0.89 respective for LV EDV, ESV and SV, p<0.001 for all) and agreement (see table). Comparison of TTE, CMR and PET TTE CMR PET PET TTEvs.CMR PET CMRvs.PET F-test LV EDV, ml 145±34 241±57 234±51 <0.001 0.004 <0.001 LV ESV, ml 47±11 76±22 81±23 <0.001 0.067 <0.001L LV SV, ml 99±26 164±38 152±34 <0.001 <0.001 <0.001 LV EF, % 68±5 69±5 65±6 0.236 <0.001 <0.001 Conclusions As compared to CMR, PISA method used by TTE substantially overestimates regurgitant volumes in patients with asymptomatic primary mitral regurgitation. Conversely, LV volumes in spite of good correlation are heavily underestimated by TTE in comparison with CMR. A strong correlation and agreement between LV volumes measured by CMR and PET confirms the accuracy of the former method which is considered as a golden standard for assessment of ventricular function and volumes. Thus, even so-called quantitative echo measures should be understoas essentially semi-quantitative indicators of severity.