Page 78 - Advanced echocardiography in characterization and management of patients with secondary mitral regurgitation

Chapter four. Regurgitant Volume/Left Ventricular End-Diastolic Volume Ratio
ratio was independently associated with improved survival. For both therapies, the degree of LV remodeling has been associated with response to treatment and survival (5,6). Therefore, when evaluating patients with HF and secondary MR, assessment of the degree of LV remodeling is likely to be fundamental in estimating the potential benefit of interventional therapies. However, patients in the present analysis were not randomized to MV interventions according to RVol/EDV ratio. Thus, further investigations are warranted to assess the utility of this ratio in predicting the benefits from surgical or transcatheter interventions. Such an analysis should be possible from the recently completed COAPT (Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Patients with Functional Mitral Regurgitation) and MITRA-FR (Percutaneous Repair with the MitraClip Device for Severe Functional/ Secondary Mitral Regurgitation) randomized trials (15,16).
Grading secondary MR in HF patients
Grading secondary MR remains challenging for various reasons. RVol usually is smaller than that observed in primary MR because the total LV SV is reduced. In contrast to RVol calculated according to the PISA method, RF takes into consideration the degree of LV remodeling measured either with quantitative pulsed Doppler (because the mitral annulus dimensions are included) or volumetrically (via LVEDV and LVESV). Accordingly, it has been suggested that RF provides a metric of proportionality of the secondary MR to LV dimensions and function (17). However, measurement of RF with echocardiography is prone to error. When using the quantitative pulsed Doppler method, calculation of RF can be inaccurate because of failure in tracing the modal velocity on spectral Doppler, locating the sample volume, and assuming that the mitral or aortic valve annuli are circular (leading to a squared error in the formula) (10). When the quantitative volumetric method is used, foreshortened images of the LV may lead to underestimation of SV (10). Various studies have suggested that cardiac magnetic resonance (CMR) may be a more accurate method to quantify secondary MR, although the majority of studies did not have a reference standard to resolve discrepancies between techniques (18, 19, 20). Lopez-Mattei et al. (18) showed a modest agreement between transthoracic echocardiography and CMR in quantifying RVol and RF. The discrepancy between techniques was more prominent among patients with secondary MR.
The RVol/EDV ratio proposed in the present study shares some of the limitations mentioned but provides a metric of proportionality of secondary MR and can be used in patients with concomitant aortic regurgitation (in whom RF cannot be used).
76