Methods and apparatus for cardiac pacing, cardioversion and defibrillation rely on delivering ultrasonic or other vibrational energy in combination with electrical energy to the heart, usually after the onset of an arrhythmia. A vibrational transducer and suitable electrical contacts may be combined in a single housing or distributed among various housings, and will usually be implantable so that the vibrational transducer can be directed at a target portion of the heart. Alternatively, external systems comprising the vibrational transducer and electrical contacts are also described.