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Quantitative Assessment of Secondary Mitral Regurgitation
Study Questions:
Among patients with heart failure with reduced ejection fraction (HFrEF), can quantitative data of secondary mitral regurgitation (SMR) severity be used to define all-cause mortality risk?
Methods:
At a single European center, a cohort of 423 patients with HFrEF (EF ≤40%) treated with stable guideline-directed medical therapy underwent echocardiography/Doppler for the quantitative assessment of SMR based on effective regurgitant orifice area (EROA), regurgitant volume (RV), and regurgitant fraction (RF). The primary endpoint was all-cause mortality at 5 years, obtained from the Austrian Death Registry. Quantitative SMR data were tested for the ability to predict mortality.
Results:
Five-year mortality was consistently associated with quantitative measures of SMR severity, with a hazard ratio of 1.42 for a 1-standard deviation increase (95% confidence interval [CI], 1.25-1.63; p < 0.001) for EROA, 1.37 (95% CI, 1.20-1.56; p < 0.001) for RV, and 1.50 (95% CI, 1.30-1.73; p < 0.001) for RF. Results remained statistically significant after boot-strap or clinical confounder-based adjustment. Spline-curve analyses showed a linearly increasing risk enabling the ability to stratify patients into low-risk (EROA <20 mm2 and RV <30 ml), intermediate-risk (EROA 20-29 mm2 and RV 30-44 ml), and high-risk (EROA ≥30 mm2 and RV ≥45 ml) groups. In the intermediate-risk group, a RF ≥50% (as an indicator for hemodynamically severe SMR) was associated with poor outcome (p = 0.017). A unifying concept based on combined assessment of the EROA, the RV, and the RF showed a significantly better discrimination compared to the currently established algorithms.
Conclusions:
The authors concluded that mortality risk-based thresholds of SMR provided a unifying solution to the ongoing guideline controversy regarding SMR quantitation; and that an algorithm based on the combined assessment of the unifying cutoffs for EROA, RV, and RF improved risk prediction compared to currently established integrative grading.
Perspective:
At present, different guideline statements have different thresholds for the definition of severe SMR: the 2017 American Heart Association/American College of Cardiology guideline update uses EROA ≥40 mm2 or RV ≥60 ml (the same thresholds used for primary MR, and a change from the 2014 guidelines), and the 2017 European Society of Cardiology/European Association for Cardio-Thoracic Surgery guidelines use EROA ≥20 mm2 or RV ≥30 ml (lower thresholds than for primary MR). This interesting study used 5-year all-cause mortality among patients with HFrEF to define SMR thresholds; with risk groups defined by EROA <20 mm2 and RV <30 ml (low-risk), EROA 20-29 mm2 and RV 30-44 ml (intermediate-risk), and EROA ≥30 mm2 and RV ≥45 ml (high-risk), with further prognostic differentiation within the intermediate-risk group based on RF <50% or RF ≥50%. Because EROA is affected by LV volume and LVEF, there is rationale to support a different (lower) EROA threshold for severe SMR than for primary MR:
- EROA = RV/velocity
- RV = RF x stroke volume = RF x LV end-diastolic volume x LVEF
- Therefore, EROA is affected by LV diastolic volume and LVEF
This study supports from a prognostic standpoint the use of a lower threshold for severe SMR; it does not address the impact of intervention for SMR.
Keywords: Diagnostic Imaging, Diastole, Echocardiography, Doppler, Heart Failure, Heart Valve Diseases, Mitral Valve Insufficiency, Risk Assessment, Stroke Volume, Ventricular Dysfunction, Left
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