Abstract: A device for canceling unwanted excitation waves in an excitable tissue, particularly those causing cardiac tachyarrhythmias, which comprises circuitry for generating a unidirectional Device-Generated Excitation Wave (DGEW) in the tissue. The device comprises first and second stimulation electrodes, each fed by a power supply, which generate current impulses having magnitudes respectively lower and higher than the threshold level of the excitable tissue. The positions and activation timing of the electrodes are set so that the two impulses interact with each other only in one desired direction and every impulse except the desired DGEW decays.