Cardiac conduction devices

Last revised by Craig Hacking on 24 Jan 2024

Implantable cardiac conduction devices (also known as cardiac implantable electronic devices or CIEDs) are a very common medical device of the thorax, with over one million implanted in the United States of America alone.

There are two major types of cardiac conduction devices: pacemakers and automatic implantable cardioverter-defibrillators (AICD/ICD), and these may be co-implanted as an ICD-pacemaker combination. Both have two major components:

  1. pulse generator (battery pack and control unit): most commonly placed subcutaneously in the infraclavicular area

  2. lead wires with electrodes for contact with the endocardium or myocardium

Some models have an antenna to transmit data wirelessly, this should not be confused with a lead disconnection or fracture 8.


Cardiac pacemakers may be temporary or permanent, with the latter commonly known by the acronym PPM (permanent pacemaker). 

Categorization depends on the number of electrodes and location of pacing 7:

Automatic implantable cardioverter defibrillators

AICDs are common cardiac devices designed for both patient monitoring and therapy in case of ventricular tachycardia or fibrillation. AICDs consist of various combinations of sensing and shocking electrodes. They are frequently combined with a pacemaker as a bundled system for the patient, treating both the patient’s established arrhythmia and also acting as a fail-safe system should ventricular fibrillation or ventricular tachycardia occur.

Some types of AICD have leads that are implanted in the subcutaneous soft tissues (i.e. outside the thoracic cavity) 5


Complications can be early or late, and procedure-related or device-related 6.

Early or late

Differential diagnosis

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