Atrial functional and ventricular functional mitral regurgitation: definitions, epidemiology, and prognostic implications

Abstract Background Severe functional mitral regurgitation (fMR) can be divided into two subgroups: fMR of atrial (AfMR) and fMR of ventricular origin (VfMR). Studies on AfMR are scarce and inconsistent, lacking a uniform definition of AfMR. Hence, little is known about its epidemiology, morphological features, associated risk profiles, and prognostic implications. Purpose The objective of this study was to develop and test a uniform definition of fMR based on the morphological correlate and to describe demographic characteristics, detail entity-specific morphological features and to investigate the associated prognostic impact. Methods 13052 patients with severe fMR and those at risk of severe fMR (comprising mild and moderate fMR)were included. Based on the ratio of left atrial volume (LA) to left ventricular end-diastolic volume (LVEDV), those with severe fMR (n=1163) were divided into AfMR and VfMR. The median of this ratio was used for allocation. Therefore, a LA/LVEDV ratio ≤ 0.56 indicated predominantly ventricular eccentric remodelling, whereas a ratio > 0.56 indicated predominantly atrial remodelling. Results AfMR was more frequently observed in female patients and peak age was a decade later, compared to VfMR. AfMR was the predominant fMR subtype in patients with heart failure with preserved (76%) and mildly reduced ejection fraction (61%), but a significant proportion could be observed even in patients with heart failure with reduced ejection fraction (32%). Severe fMR was associated with excess mortality for both entities: VfMR HR 1.31 [95% CI: 1.14-1.50], p<0.001, with a more pronounced impact in patients with AfMR HR 1.68 [95% CI: 1.47-1.91], p<0.001; AfMR vs. VfMR: HR 1.27 [95% CI: 1.06-1.54], p=0.011. The association between fMR and excess mortality persisted even after multivariate adjustment. In both entities, ischaemic heart disease was common and resulted in a significant increase of mortality (VfMR: HR 1.67 [95% CI: 1.40-1.98], p for interaction<0.001; AfMR: HR 2.10 [95% CI: 1.75-2.52], p for interaction=0.006). Conclusion Based on the entity-specific morphological correlate, severe fMR can be classified into AfMR and VfMR. AfMR occurs across the entire HF spectrum, is more frequently observed in elderly and female patients, and exhibits a worse prognosis than VfMR. The presence of ischaemic heart disease is associated with a near doubling of mortality in both subgroups of severe fMR.Prevalence of fMRKaplan-Meier analysis