A pacing lead (20) having a lead body (22) with a central lumen and provided with structure for retaining the lead body to a wall of the coronary network, and a hollow tubular extension (26), bearing an active region of the lead and also traversed by a central lumen (28) communicating with the inner lumen of the lead body, so as to allow implantation by an over the wire technique. The hollow tubular extension has an outside diameter of between 2 and 3 French (0.66 and 1 mm) to allow implantation deep in the coronary sinus network, and it comprises on its outer surface an electrically insulated peripheral conductor, except for denuded areas intended to come into contact with the wall of a target vein and form a network of stimulation electrodes (32, 34) electrically connected together.