The Amplifier: Sensing the Depolarization

  • Dennis A. Brumwell
  • Kai Kroll
  • Michael H. Lehmann
Part of the Developments in Cardiovascular Medicine book series (DICM, volume 188)


THE ROLE of the sense amplifier in an ICD is to register the occurrence of successive cardiac depolarizations, and, thereby allow measurement of the consecutive time intervals demarcated by these events. This is accomplished in a similar fashion to the familiar external heart monitor that relies on electrocardiogram waveforms. Depolarization of heart muscle is the source of the electrical signals for both the ICD and the external heart monitor, but the waveforms are slightly different due to the location and size of the sense electrodes. Surface electrodes sense voltage waveforms (ECG) of a far-field average of the dynamic voltages from the heart muscle. In contrast, typical intracardiac bipolar electrodes sense a waveform generated by the passage of a depolarization wave through a nearby region of the heart. The intracardiac ventricular electrogram (EGM), as recorded by the ICD, shows a much reduced P-wave amplitude and a narrower QRS complex (R-wave) compared to the surface ECG. The sense amplifier must detect this R-wave and mark each occurrence with a digital pulse suitable for rate counting by other circuitry.


Ventricular Fibrillation Automatic Gain Control Lead System Direct Current Voltage Sense Amplifier 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer Science+Business Media New York 1996

Authors and Affiliations

  • Dennis A. Brumwell
  • Kai Kroll
  • Michael H. Lehmann

There are no affiliations available

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