Internal Pacemakers

William Bigelow and John Callaghan in Toronto used cold temperatures to slow the heart down enough to perform open heart surgery. Although, this made surgery easier, they struggled with the problem of how to start the heart if it stopped and on how to restart the heart at the end. John Hopps, an electrical engineer, built an external device of vacuum tubes that was powered by 60 Hz wall current. The generator was hooked up to a lead attached to the right atrium...

Time Dependence of the Anodal and Cathodal Refractory Periods

Mehra et al.27 observed that immediately following implantation of a pacemaker the anodal refractory period was shorter than the cathodal refractory period, but after several weeks the cathodal refractory period became shorter than the anodal refractory period. Figure 14 suggests one hypothesis to explain this observation.28 After a pacemaker electrode is implanted, tissue adjacent to the electrode is healthy and excitable. However, within a few weeks a region of inexcitable scar tissue...

References

Marchlinski FE, Callans DJ, Gottlieb CD, et al. Benefits and lessons learned from stored electrogram information in implantable defibrillators. J Cardiovasc Electrophys-iol 1995 6(10 Pt 1) 832-851 2. Israel CW, Barold SS. Pacemaker systems as implantable cardiac rhythm monitors. Am J Cardiol 2001 88(4) 442-445 3. Weretka S, Becker R, Hilbel T, et al. Far-field R wave oversensing in a dual chamber arrhythmia management device predisposing factors and practical implications. Pacing Clin...