Benefits of transvenous mitral annuloplasty in heart failure with lower degrees of functional mitral regurgitation. Letter regarding the article ‘Treating symptoms and reversing remodelling: clinical and echocardiographic 1‐year outcomes with percutaneous mitral annuloplasty for mild to moderate secondary mitral regurgitation’

We read with great interest the article by Witte et al.1 This study is particularly important because there is no doubt about the detrimental impact of secondary mitral regurgitation (MR) on the progression of heart failure (HF) regardless of its primary aetiology, and that even the reduction of a mild to moderate MR and/or prevention of its further aggravation would be beneficial to left ventricular (LV) function and patient outcome. Echocardiography is a major tool for assessment of LV remodelling and dysfunction in patients with HF but its limitations make the interpretation of measurements more challenging in the presence of MR. This relates particularly to ejection fraction (EF) which reflects both contractile function and remodelling and is the most commonly used parameter for measuring LV systolic function. It is known that MR adversely affects the reliability of LVEF as an index of systolic function because the difference between end-diastolic and end-systolic volume (EDV − ESV) will be not be any more solely the forward (effective) stroke volume (SVf), but will become the sum of SVf and regurgitant volume (RegV).2, 3 Thus, with aggravation of MR, the regurgitant fraction increases to the detriment of SVf which explains the possible reduction of LVEF after mitral valve repair or replacement despite an increase in SVf.2-4 In the study by Witte et al.,1 the LVEF improved only slightly (not significantly) during the first year after mitral annuloplasty. However, considering the significant reduction of the RegV, this suggests a possibly significant increase in the SVf, which in turn explains the significantly improved clinical status after annuloplasty. The additional measurement of the SVf (LV outflow tract area × pulsed-wave Doppler-derived velocity-time integral in the LV outflow tract) might have helped to clarify this important problem. Unfortunately, because the direct measurement of the SVf is not routinely performed in all cardiologic centres, this measurement is often not included into multicentre study protocols. However, if direct stroke volume measurements are available, it would be worth a separate additional investigation to verify if indeed the significantly reduction of the RegV was associated with a significant increase in the SVf. In patients with MR, LVEF calculated by the Simpson's method [i.e. (EDV – ESV)/EDV] can overestimate LV systolic function because EDV − ESV will become the sum of SVf + RegV instead of SVf alone.3-5 Overestimation of LV systolic function can be avoided by calculation of the effective (forward) EF using the formula EF(%) = (SVf /EDV) × 100 which can improve clinical decision-making and also increase the predictive value of EF for patient outcome with LV systolic dysfunction associated with MR.2-4 In the study by Witte et al.,1 the comparison of LVEF before and after annuloplasty revealed no significant differences, but taking into account that the RegV was significantly higher before annuloplasty, the effective LVEF at baseline was overestimated. It seems therefore very likely that the comparison of the effective LVEF before and after annuloplasty could also reveal significant differences, which would in turn encourage the earlier use of percutaneous mitral annuloplasty.