Structural and functional remodeling in organic mitral regurgitation: value of indexed volumes and left atrial reservoir strain

Abstract Background In organic mitral regurgitation, preserved ejection fraction may mask early dysfunction; a comprehensive evaluation including indexed chamber volumes, global longitudinal strain, and left atrial reservoir strain can enhance early detection of adverse remodeling. Aim To compare echocardiographic markers of structural and functional remodeling in patients with moderate versus severe organic MR, and to explore association between atrial volume, atrial strain, and pulmonary pressures. Methods This retrospective, single-center registry included patients with echocardiographically confirmed moderate or severe organic MR assessed between July 2020 and January 2025. Patients with ischemic heart disease, atrial fibrillation, other significant valve disease, or inadequate image quality were excluded. Key echocardiographic parameters assessed included LV end-diastolic and end-systolic volume indices (EDVi, ESVi), EF, global longitudinal strain (GLS), left atrial volume indexed (LAVi), systolic pulmonary artery pressure (SPAP), and LARs. Comparative and correlational analyses were performed using non-parametric statistics. Results A total of 71 patients were included, 44 with severe MR and 27 with moderate MR. The severe MR group was slightly older (median age 71 vs 67 years) and included a greater proportion of males (59.1% vs 40.7%), though the sex distribution did not differ significantly. Despite preserved EF and GLS across both groups (median EF: 59 vs 60%; GLS: –18.4% vs –18.7% in moderate vs severe MR), left ventricular volumes were notably higher in patients with severe MR. EDVi and ESVi trended upward (85.2 vs 75.1 mL/m² and 35.8 vs 31.4 mL/m², respectively), suggesting progressive ventricular dilation, though these differences did not reach statistical significance. LAVi was elevated in both moderate and severe MR, and SPAP showed a trend toward higher values in severe cases (42 mmHg vs 39 mmHg). Notably, LAVi correlated significantly with EDVi (ρ = 0.397, p = 0.001), ESVi (ρ = 0.414, p = 0.001), and SPAP (ρ = 0.282, p = 0.017), reinforcing its role as a marker of structural and hemodynamic burden. Most importantly, LARs demonstrated a significant inverse correlation with SPAP (ρ = –0.358, p 0.05), suggesting impaired atrial compliance is closely linked to elevated pulmonary pressures, even in the context of preserved LV systolic function. Conclusion In patients with moderate and severe organic MR and preserved EF, standard measurements like EF and GLS fail to capture the full extent of structural remodeling. Indexed LV volumes and LAVi reflect early volumetric changes, while LARs offers functional insight into atrial dynamics and pulmonary hemodynamics. The significant correlation between reduced LARs and elevated SPAP highlights its potential as an early, sensitive marker of diastolic burden in MR. These findings support incorporating LA strain into routine MR evaluation for a better disease stratification.