An Optimally Energized Cardiac Pacemaker

Batteries that power implanted cardiac pacemakers deteriorate because of energy drain and permeation of body fluids. They must, therefore, be replaced periodically, most often by means of an operation. In this paper, the stimulating waveform that draws the least amount of energy from the battery and also delivers the minimum energy to a heart cell is derived. It is shown that a 31-percent reduction in energy (with respect to that required by the standard rectangular pulse) can be achieved if the pulse duration is about twice the cell time constant. Moreover, it is demonstrated that the required energy is insensitive to pulse-duration variations (due to component changes). An easily synthesized suboptimal approximation is developed and requires only slightly more energy than the optimal pulse.