An In Vivo Study of Cardiac Pacemaker Optimization by Pulse Shape Modification

This paper is an experimental extension of theoretical work previously published by one of the authors. Results of pacing a canine heart using four different increasing exponential and ramp-like waveforms are presented. It is shown that these waveforms reduce the cardiac threshold energy by as much as 14 percent when compared with a pure rectangular pulse shape and by about 21 percent when compared with a standard cardiac pacer pulse. It is also found that above threshold energy is reduced by 50-60 percent. These results offer promise of increasing the life of certain new pacer power sources currently being tested. In addition, it may now be possible to pace at lower energy levels, thereby reducing tissue damage near the stimulating electrode, without running as much of a risk of exit block as with a comparable rectangular pulse pacer.