What are pacemakers and implantable cardioverter-defibrillators (ICD)?

Updated: Oct 11, 2019
  • Author: Daniel M Beyerbach, MD, PhD; Chief Editor: Jeffrey N Rottman, MD  more...
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An implantable cardioverter-defibrillator (ICD) is a specialized device designed to directly treat many dysrhythmias, and it is specifically designed to address ventricular tachyarrhythmias. ICDs have revolutionized the treatment of patients at risk for sudden cardiac death due to ventricular tachyarrhythmias. A permanent pacemaker is an implanted device that provides electrical stimuli, thereby causing cardiac contraction when intrinsic myocardial electrical activity is inappropriately slow or absent. See the image below. All modern ICDs also function as pacemakers. 

100% ventricular paced rhythm. 100% ventricular paced rhythm.

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