We describe a case in which a left ventricular-coronary sinus communication through a dissecting ventricular septal aneurysm developed after a redo mitral valve replacement. The outlet orifice of the communication was located in the side wall of the ostium of the coronary sinus. Both the communication and the aneurysm were successfully dealt with by performing a right atriotomy and by opening the aneurysm from its outlet orifice.