The invention relates to an implantable quadripolar electrode for sequential neurostimulation of the phrenic nerve.A matrix is provided with two branches each consisting of a hook designed to come in contact with the phrenic nerve without totally encircling it and an extension (112, 122), or strip, designed to cross the corresponding incision arranged in the pleura and fix the same on the pericardium, each hook having an orifice allowing the phrenic nerve to pass;The hooks are connected with a bridge designed to keep them at a fixed distance from each other on the longitudinal plane of said phrenic nerve and to allow the rotation of the branches in relation to one another to position the hooks around the phrenic nerve via their respective openings.