US Patent 7751881 Acoustically-powered wireless defibrillator

An acoustic transmitter produces a pulsed ultrasound waveform which is transmitted through body tissues to an implanted receiver-stimulator device. The waveform has an acoustic amplitude, pulse width, and pulse repetition period, which corresponds to a pacing pulse electrical amplitude, pacing pulse width, and pacing cycle length, respectively. The receiver-stimulator device intercepts at least a portion of the transmitted acoustic energy and coverts that acoustic energy into electrical energy using piezoelectric or other devices. This electrical energy is applied to circuitry, which produces a desired stimulating pulse waveform, which is then applied to tissue-contacting electrodes.