Functional mitral regurgitation and left atrial myopathy in heart failure with preserved ejection fraction

Aims Mild to moderate functional mitral regurgitation (MR) is common in patients with heart failure and preserved ejection fraction (HFpEF) where it is usually considered as an innocent bystander. We hypothesized that MR in HFpEF reflects greater left atrial (LA) myopathy, leading to more adverse haemodynamics and poorer exercise reserve. Methods and results Patients with HFpEF (n = 280) with and without MR underwent echocardiography, invasive haemodynamic exercise testing, and expired gas analysis. As compared to non-MR-HFpEF (n = 163), patients with MR-HFpEF (n = 117; 78 mild and 39 moderate, central jet in 90%) were older, more likely female, with lower body mass and higher prevalence of atrial fibrillation (AF). HFpEF patients with MR displayed greater LA volume, reduced LA strain and compliance, and greater mitral annular dilatation, which was strongly correlated with LA dilatation (r = 0.63, P < 0.0001) but was only weakly related to left ventricular remodelling (r = 0.37). Patients with MR-HFpEF displayed worse biventricular function, more adverse pulmonary haemodynamics, impaired pulmonary vasodilatation, blunted right ventricular reserve, and reduced cardiac output with exercise as compared to non-MR-HFpEF. Importantly, these findings were maintained after excluding patients with HFpEF and AF, suggesting a role for LA myopathy in contributing to MR in HFpEF, independent of rhythm. Conclusions Functional MR in patients with HFpEF reflects LA myopathy, even in the absence of AF, and is associated with greater haemodynamic severity of disease and poorer functional capacity. Further study is required to better define causal mechanisms and potential treatments for MR and LA dysfunction in patients with HFpEF.