This study is a prospective, randomized, parallel-control, open-label, multicenter clinical trial. Eligible subjects will be randomized in a 1:1 ratio to the Device group (Interventional group) or to no Device group (Control Group). The objective is to identify the safety and effectiveness of the TEER for the treatment of moderate-to-severe (3+) or severe (4+) atrial functional mitral regurgitation (aFMR) in patients who are symptomatic despite maximally tolerated guideline directed medical therapy.