Differences in patterns of progression of secondary mitral regurgitation

Aims Little data exist about the natural history and disease progression of secondary mitral regurgitation (SMR). We sought to study the temporal progression of left-sided volumes and functions in patients who progress to develop severe SMR. Methods and results We screened patients with chronic severe SMR who had at least one previous transthoracic echocardiography showing non-severe MR. Unsupervised phenotypic clustering based on baseline and rate of change in left ventricular (LV) and left atrial (LA) volumes, ejection fraction (EF), and MR severity progression identified two different phenotypes. We then compared them in terms of clinical characteristics, mechanistic and anatomical features, management, and outcomes. A total of 257 patients were included. Cluster 1 started with lower EF and LA strain and higher LV and LA volumes compared with Cluster 2, with a slower progression into severe SMR. At the onset of severe MR, Cluster 2 still had higher EF, lower LV volumes, but similar LA volumes and strain, and less proportionate SMR, compared with Cluster 1. They also had higher tenting height and more compensatory leaflet growth. On follow-up, Cluster 1 had more ventricular-directed therapies, whereas Cluster 2 received more mitral valve interventions. While the heart failure burden was higher in Cluster 1, there was no difference in mortality rates. Conclusion Based on disease progression, two distinct progression patterns of SMR exist, having different anatomical and mechanistic features with variation in management and outcomes.