Apparatus for applying a signal to a heart of a human subject is provided. The apparatus includes a set of one or more electrodes, adapted to be coupled to the right ventricular septum of the heart. A control unit of the apparatus is adapted to drive the electrode set to apply an Excitable-Tissue Control (ETC) signal to the septum. Preferably, the control unit is adapted to configure the signal to be capable of modifying contractility of a portion of the heart.