A method and device for reducing mitral regurgitation. An elongated body is positioned in a coronary sinus of a patient in a vicinity of a heart mitral valve posterior leaflet. The body is adapted to straighten a natural curvature of at least a portion of the coronary sinus in the vicinity of the posterior leaflet to move a posterior annulus anteriorly, which in turn moves the posterior leaflet anteriorly, thereby to improve leaflet coaptation.