Patterns of progression of secondary mitral regurgitation: new findings and old challenges

We read with great interest the study by Layoun et al.1 exploring the natural history and progression pattern of secondary mitral regurgitation (MR) until the onset of severe MR. The authors performed phenotypic clustering of 257 patients based on the baseline echocardiographic characteristics and the rate of change in left-sided cardiac chambers’ volumes, ejection fraction, and MR severity progression. Two different phenotypes were identified regarding the pace of the disease progression and management. The study contributes some interesting findings that could have been clinically relevant in deciding on the optimal therapeutic approach in secondary MR. However, certain methodological issues warrant attention. At the time of severe MR, the echocardiographic characteristics show significant inconsistencies that call into question the credibility of the echocardiographic assessment of MR severity. The authors report a mean effective regurgitant orifice area (EROA) obtained by the PISA method of 38.6 ± 13.3 mm2 in Cluster 1 and 41.1 ± 22.1 mm2 in Cluster 2, while a mean regurgitant volume obtained by the PISA method was 186.7 ± 58.4 mL and 201.6 ± 102.9 mL, respectively. These findings are incompatible, as EROA of 40 mm2 normally corresponds to a regurgitant volume of around 60 mL.2 Moreover, the mean value of regurgitant volume in Cluster 2 even exceeds the mean value of LVEDV (149.6 ± 46.5 mL), which is not in line with the physical laws of conservation of mass and would be incompatible with life.