An electrical lead system includes a shaft to which a series of expandable ring electrodes are attached that follows the contour of the vascular or muscular structures of the heart, such as cardiac veins, arteries, atrial appendages and trabeculae, and provides sensing of electrical cardiac impulses, pacing and high voltage shock or defibrillation. The lead system uses a variety of energy sources to stimulate the heart, such as ultrasound, electromagnetic and electric impulses.
