The following are key points to remember from this state-of-the-art review on the pathophysiology, echocardiographic diagnosis, and treatment of atrial functional mitral regurgitation (FMR):

1. Functional mitral regurgitation (FMR) historically has been attributed to changes in the left ventricle (LV) leading to papillary muscle displacement and restriction of the mitral leaflets. In contrast, atrial FMR occurs due to left atrial (LA) and/or mitral annular enlargement.
2. Atrial FMR can occur in the setting of atrial fibrillation (AF; with an incidence substantially higher among patients with long-standing AF compared to recent-onset AF) or heart failure with preserved ejection fraction (HFpEF).
3. The histopathological alterations responsible for atrial FMR are not well understood. The authors describe the pathophysiology of atrial FMR in terms of ‘atriogenic mitral leaflet tethering,’ abnormalities of mitral annular structure and dynamics, and variable adaptive leaflet growth.
4. The authors describe variable echocardiographic features of atrial FMR, including normal LV size and systolic function or LV enlargement and/or systolic dysfunction caused by the volume overload of atrial FMR, variable leaflet restriction, variable anterior leaflet pseudo-prolapse, and variable central or eccentric MR jets.
5. The authors propose an echocardiographic definition of atrial FMR: MR with structurally normal mitral leaflets and no mitral annular calcification, LA enlargement (LA volume index >34 mL/m²), LV end-diastolic volume index normal for age and sex, and LVEF ≥60%.
6. Imaging modalities other than echocardiography can be useful among patients with atrial FMR, including computed tomography for anatomic detail and mitral annular measurements in the context of transcatheter procedures, cardiac magnetic resonance imaging for assessment of LA fibrosis, and strain imaging for LA (reservoir) strain.
7. There is no consensus on the medical management of patients with atrial FMR, although standard heart failure therapy including a diuretic can be used. Some studies show an effect of rhythm management on MR reduction among patients with AF and atrial FMR, but outcomes data are lacking.
8. There is no consensus on the role for surgical intervention to treat atrial FMR. If pursued, surgery typically involves reduction annuloplasty, although patch augmentation of the posterior mitral leaflet or surgical mitral valve replacement also could be considered.
9. Transcatheter options to treat atrial FMR include edge-to-edge repair and direct or indirect annuloplasty, albeit with limited available outcomes data. Transcatheter heart valve replacement has not been studied among patients with atrial FMR.
10. With a paucity of data and absent broad consensus, the authors describe a proposed algorithm for the treatment of atrial FMR that considers the severity of MR, symptoms, LV function, and surgical candidacy toward pursuing rhythm control, medical therapy, cardiac surgery, or transcatheter intervention.
11. Atrial FMR due to AF commonly is accompanied by atrial functional tricuspid regurgitation. With limited data, diuretic therapy can be considered; although surgery might be associated with improved symptoms, outcomes data are lacking.

Clinical Topics: Arrhythmias and Clinical EP, Cardiac Surgery, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Valvular Heart Disease, Atrial Fibrillation/Supraventricular Arrhythmias, Cardiac Surgery and Arrhythmias, Cardiac Surgery and Heart Failure, Cardiac Surgery and VHD, Acute Heart Failure, Interventions and Imaging, Interventions and Structural Heart Disease, Echocardiography/Ultrasound, Magnetic Resonance Imaging, Mitral Regurgitation

Keywords: Atrial Fibrillation, Cardiac Surgical Procedures, Diagnostic Imaging, Diuretics, Echocardiography, Fibrosis, Heart Failure, Heart Valve Diseases, Magnetic Resonance Imaging, Mitral Valve Insufficiency, Prolapse, Stroke Volume, Tomography, Tricuspid Valve Insufficiency

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