Feedback Controlled Resonant Drift

The phenomenon of resonant repulsion makes it clear that it may not be the best strategy to keep stimulation frequency constant or to change it according to a prescribed program, but this change should be determined by actual events via feedback. The feedback may be realized by monitoring activity at a point in the medium with a recording electrode. Since the frequency of real rotation of a drifting vortex is close to and changes together with the resonant frequency, the simplest control...

Inappropriate Detection Due to Oversensing

ICD sensing circuits are designed to be highly sensitive so that low amplitude EGM waveforms during fibrillation can be sensed adequately.5 As a result, oversensing of cardiac and noncardiac signals in ICDs occurs and is one of the major sources of inappropriate ICD therapy. Oversensing on the ventricular sensing channel of an ICD (ventricular oversensing) causes inappropriate VT VF detection due to overestimation of the true cardiac rate. Oversensing on the atrial sensing channel (atrial...

The Long List of Inventions and Observations that Led to the Pacemaker

Pulse Theory and Observations that Bradycardia Leads to Syncope Today physicians and athletes routinely measure the pulse. Although it is fairly simple to measure, especially compared to our now sophisticated imaging tools like magnetic resonance imaging, the pulse is still considered one of the vital signs. The knowledge that the pulse was a critical sign of health goes back to the ancient Egyptians. In 1875 George Ebers purchased an Egyptian scroll written in 1553 BC that described the...

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...