Assessing emerging causes of mitral regurgitation: atrial functional mitral regurgitation

Functional or secondary mitral regurgitation is linked to increased cardiovascular morbidity and mortality. From a mechanical perspective, secondary mitral regurgitation occurs due to an imbalance between the forces that tether the mitral leaflets and those that close them. This results in incomplete coaptation. Most commonly, functional mitral regurgitation, which occurs in both ischaemic and non-ischaemic disease states, is usually caused by dysfunction and changes in the left ventricle. Atrial functional mitral regurgitation (AFMR) is a disease state that has been more recently recognized. It occurs when mitral annular enlargement is associated with left atrial dilatation, preserving left ventricular geometry and function. AFMR is typically seen in patients with chronic atrial fibrillation or heart failure who have a conserved ejection fraction. Published reports and ongoing investigations vary in how they define AFMR. This publication examines the pathophysiology of AFMR and highlights the importance of having a common working standard for the definition of AFMR to ensure consistency in the data reported and to drive forward the much needed research into the outcomes and treatment strategies in this area. Several studies have reported that restrictive annuloplasty and transcatheter edge-to-edge repair can reduce mitral regurgitation and improve symptoms. This narrative review will explore the pathophysiology, echocardiographic diagnosis and treatment of AFMR.