Cardiac implantable electronic devices

Last updated: July 18, 2022

Summarytoggle arrow icon

Cardiac implantable electronic devices (CIEDs) are battery-powered medical devices that help control and/or monitor arrhythmias in patients with conduction disorders or heart failure. CIEDs include artificial cardiac pacemakers, implantable cardioverter defibrillators (ICDs), cardiac resynchronization therapy (CRT) devices (biventricular pacemakers, sometimes called CRTs), and left ventricular assist devices for controlling arrhythmias, as well as implantable cardiac monitors (loop recorders) for monitoring. This article focuses primarily on pacemakers stimulating the myocardium for antibradycardia pacing, ICDs overstimulating or defibrillating for antitachycardia pacing, and biventricular pacemakers for cardiac resynchronization therapy between mismatched left and right ventricular contractions.

Technical information for CIEDs

  • Structure
    • A metal case (typically titanium) contains a battery-powered pulse generator with a computer.
      • ∼ 5 cm across, although newer, much smaller versions exist
      • The battery life depends heavily on the working mode and underlying disease: Newer models last between 5 and 15 years.
    • Leads with electrodes connect the device to the myocardium.

  • Basic functions
    • Electrodes detect the heart's electrical activity and transmit it to the device impulse generator unit.
    • The impulse generator unit identifies arrhythmias.
    • The electrodes then transmit electric impulses to the myocardium, which results in contraction of the respective heart chamber (atrium and/or ventricle).
  • Implantation
    • In most cases, the generator is implanted on the patient's nondominant side between the pectoral muscle and the muscle fascia.
    • Electrodes are inserted into the right cardiac cavity, usually transvenously, via the subclavian and brachiocephalic veins.

Comparison of pacemakers, ICDs, and CRTs

Comparison of pacemakers, ICDs, and CRTs
Artificial cardiac pacemakers Implantable cardioverter defibrillators (ICDs) Cardiac resynchronization therapy devices (biventricular pacemakers)
Basic function
  • Resynchronization of ventricular dyssynchrony
Basic types
  • Single chamber
  • Double chamber
  • Triple chamber (biventricular)
Common indications

Antibradycardia pacing can be achieved using an artificial cardiac pacemaker, which is capable of monitoring the cardiac rhythm and delivering electrical impulses to maintain an adequate heart rate (e.g., in severe bradycardia) or synchronize the ventricles (e.g., in atrioventricular block) when needed. While there are various types of pacemakers, most modern pacemakers have multiple functions and can be combined with a cardioverter defibrillator (i.e., an ICD).

Antitachycardia pacing can be achieved via cardioversion, e.g., mechanical cardioversion (precordial thump), pharmacological cardioversion (antiarrhythmic drugs), or electrical cardioversion (ICD). Modern ICDs are capable of multiple forms of pacing, as well as electrical cardioversion, both synchronized and unsynchronized (commonly known as defibrillation).

Cardiac resynchronization therapy (CRT) aims to synchronize left- and right-ventricular contractions using a biventricular pacemaker, which improves cardiac function.

X-rays should be conducted to assess for lead displacement and complications such as myocardial perforation, pneumothorax, and disconnection between the device and leads.

Proper CIED positioning

In contrast to pacemaker leads, ICD leads have thick shock coils that are visible on the radiograph.

Lead displacement

  • Placement complications
  • Pacemaker syndrome
    • May occur with VVI pacemakers
    • Causes include:
      • Atrioventricular dyssynchrony or retrograde atrial excitation that leads to atrial contraction against a closed AV valve
      • Interventricular dyssynchrony
    • Clinical features: hypotension, dizziness, dyspnea, palpitations, and syncope
  • Pacemaker-induced reentry tachycardia: excitation of the atrium as a result of retrograde conduction via the AV node, which prematurely restimulates the ventricle
  • Pacemaker malfunction is associated with symptoms ranging from bradycardia to asystole; causes include:
    • Electric fields (short-wave, high-frequency): produced during diathermy and interfere with pacemaker functionality
    • Magnetic fields: e.g., produced by MRI
    • Displacement of pacemaker electrodes, or battery or cable defect: Tingling sensations in the arm may indicate displaced electrodes.

We list the most important complications. The selection is not exhaustive.

  • Interference with MRI: Despite many CIEDs now being MRI safe, an electrophysiologist or the device manufacturer should be consulted before scanning.
  • Surgical patients: Consider consulting an electrophysiologist regarding temporary CIED deactivation, as surgery involving diathermy can trigger the device to stimulate the heart unnecessarily. [4]
  • Patient education
    • Driving advice
    • Education about possible interactions during medical procedures and with electronic devices [5][6]
  • Discussions about device deactivation during end-of-life care
  • Provision of a cardiac device wallet card and medical alert bracelet
  • Regular follow-up is essential.

Reference: [1]

  1. Yancy CW, Jessup M, Bozkurt B, et al. 2013 ACCF/AHA Guideline for the Management of Heart Failure. J Am Coll Cardiol. 2013; 62 (16): p.e147-e239. doi: 10.1016/j.jacc.2013.05.019 . | Open in Read by QxMD
  2. Brignole M, Auricchio A, Baron-Esquivias G, Bordachar P et al. 2013 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy. Eur Heart J. 2013; 34 (29): p.2281-2329. doi: 10.1093/eurheartj/eht150 . | Open in Read by QxMD
  3. Peal J, Mathews I, Runnett C, Thomas H, Ripley D. An update on cardiac implantable electronic devices for the general physician. J R Coll Physicians Edinb. 2018; 48 (2): p.141-147. doi: 10.4997/jrcpe.2018.208 . | Open in Read by QxMD
  4. Donnelly P, Pal N, Herity NA. Perioperative management of patients with implantable cardioverter defibrillators.. Ulster Med J. 2007; 76 (2): p.66-7.
  5. Can I use an induction hob if I have a pacemaker?. . Accessed: October 22, 2020.
  6. Devices that May Interfere with ICDs and Pacemakers. Updated: September 30, 2016. Accessed: October 22, 2020.

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