The prevalence and prognosis of severe atrial functional mitral regurgitation varies with its definition

Abstract Background Severe atrial functional mitral regurgitation (AfMR) is a complex and heterogenous disease, lacking a uniform definition. The definition of AfMR, however, varies considerably across studies, particularly concerning the echocardiographic parameters and comorbidities used for inclusion. This heterogeneity across definitions poses a significant challenge to the consolidation of research findings, the proper treatment and the establishment of consistent clinical guidelines. Purpose The objective of this study was to consolidate existing definitions of AfMR and to evaluate the distribution across severe functional mitral regurgitation (fMR), as well as their prognostic significance. Methods All currently used AfMR definitions were applied to our comprehensive clinical database spanning from 2010-2020. This database includes 13,052 patients with fMR, of which 1,163 patients had severe fMR. Survival analysis was performed for each definition, with moderate fMR as the comparator group. Patients with heart failure with reduced ejection fraction were excluded. The primary endpoint was all-cause mortality. Results Overall, 49 different definitions of AfMR were identified. The definitions varied in the number of included patients, with group sizes ranging between 12 and 359 patients. Baseline clinical and echocardiographic characteristics differed markedly between the AfMR cohorts. When compared to moderate fMR, in the univariate analysis 39 definitions had significantly different outcomes, with hazard ratios (HR) ranging from 1.42 (95% CI: 1.11-1.82, p=0.006) to 2.51 (95% CI: 1.49-4.25, p