What is the procedure for insertion of an implantable cardioverter-defibrillator (ICD)?

Updated: Oct 11, 2019
  • Author: Daniel M Beyerbach, MD, PhD; Chief Editor: Jeffrey N Rottman, MD  more...
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Pacing systems consist of a pulse generator and pacing leads. With permanent systems, endocardial leads are inserted transvenously and advanced to the right ventricle and/or atrium, where they are affixed to the myocardial tissue, typically with a helical screw tip, most of which are extendable and retractable. The pulse generator is placed subcutaneously or submuscularly in the chest wall.

Pulse generators contain a battery, as well as sensing, timing, and output circuits. The battery (most commonly lithium-iodide) typically has a lifespan of around 10 years, although technologic advances are constantly improving performance. Pulse generators can be set to fixed-rate (asynchronous) or demand (synchronous) modes. In the asynchronous mode, impulses are produced at a set rate that is independent of intrinsic cardiac activity. This mode carries a small, but inherent, danger of initiating lethal arrhythmias should the impulse coincide with the vulnerable period of the T-wave. In the synchronous mode, the sensing circuit searches for an intrinsic depolarization potential. If this is absent, a pacing response is generated. This mode closely mimics intrinsic myocardial electrical activity.

At the time of pacemaker implantation, and at regular intervals afterward, signal amplitude and width are set high enough to reliably achieve myocardial capture, yet low enough to maximize battery life.

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