Page 79 - Advanced echocardiography in characterization and management of patients with secondary mitral regurgitation
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RVol/EDV ratio and outcome in secondary MR
The cutoff values of EROA ≥20 mm2 and RVol ≥30 ml/beat to define severe secondary MR included in European guidelines (8,21) are based on outcomes studies showing that patients with secondary MR and EROA or RVol values above those cutoffs have a worse prognosis (4,22, 23, 24). However, the U.S. guidelines suggest higher thresholds to define severe secondary MR (25,26). In this regard, even mild secondary MR has been associated with poor outcomes (24,27). However, MV repair in patients with moderate ischemic (secondary) MR (mean EROA ∼0.20 mm2) undergoing coronary revascularization did not show improved outcomes in a randomized trial (28). Whether the association between EROA and poor outcomes relies on the severity of MR itself, the underlying LV dysfunction/remodeling, or both remains unclear (10). By adjusting RVol for LV volume in the RVol/LVEDV ratio, the extent of LV remodeling is taken into consideration, and we demonstrated that when considering surgical and transcatheter options for correction of MR, patients with a higher RVol/EDV ratio (≥20%) had improved long-term outcomes, suggesting that the long-term prognosis is determined by the lesser severity of LV dysfunction after MR reduction. Bartko et al. (29) showed in 423 HF patients with various grades of secondary MR that the measurement of RF had incremental discriminative power over RVol and EROA in identifying patients with poor prognosis. RF partially takes into consideration the severity of LV remodeling and has been proposed as a parameter that reflects the proportionality of MR. Similarly, RVol/ EDV may reflect the proportionality of secondary MR and impact of available therapies. We hypothesize that for patients with a low RVol/EDV, resolving the volume overload caused by the MR, either by surgery or transcatheter techniques, may not have a major impact on outcome because the severity of MR may be less prognostically relevant than the extent of LV remodeling. In contrast, in patients with a high RVol/EDV, the volume overload caused by MR may have a major influence on LV hemodynamics and symptoms, and thus appropriate repair or replacement may improve outcomes. This hypothesis requires validation in prospective studies.
Study limitations
The present study has several limitations related to the retrospective nature of data analysis. However, to the best of our knowledge, this is the largest series evaluating the prognostic value of RVol/EDV ratio in patients with secondary MR. External validation of the present results is warranted. Symptomatic status could only be assessed based on NYHA functional class, and other quantitative measures such as 6-min walked distance or quality-of-life scores were not systematically available. In addition, patients with mild MR were excluded, and the value of RVol/EDV ratio was not assessed in this population. Assessment of EROA and RVol in secondary MR using echocardiography
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