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Cardiac implantable electronic devices

Last updated: December 6, 2021

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Cardiac implantable electronic devices (CIEDs) are insertable battery-driven medical devices that help control and/or monitor arrhythmias in individuals with arrhythmic conditions (due to dysfunctional heart conduction system) or heart failure. CIEDs include artificial cardiac pacemakers, implantable cardioverter-defibrillators (ICDs), cardiac resynchronization therapy devices (biventricular pacemakers), left ventricular assist devices for controlling arrhythmias, as well as implantable cardiac monitors/loop recorders for monitoring. This article focuses primarily on pacemakers stimulating myocardium for antibradycardia pacing, ICDs overstimulating/defibrillating for antitachycardia pacing, and biventricular pacemakers for cardiac resynchronization therapy between mismatched left- and right-ventricular contractions.

Technical information of CIEDs

  • Structure
    • A metal case (typically titanium) contains a battery-powered pulse generator with a computer (about 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 or stimulation probes connect the device with the myocardium.

  • Basic function
    • Electrodes detect the patient's ECG and transmit it to the device impulse generator unit.
    • The pacemaker unit identifies arrhythmias that trigger or inhibit electric impulses accordingly.
    • The electrodes then transmit electric impulses to the myocardium, which results in stimulation and contraction of the heart chamber (atrium and/or ventricle).
  • Implantation
    • In most cases, the generator is implanted on the nondominant side (right or left) between the pectoral muscle and its muscle fascia.
    • Electrodes are inserted into the right cardiac cavity usually transvenously via the subclavian and brachiocephalic vein.

Comparison of pacemakers, ICD, and CRT

Comparison of pacemakers, ICD, and CRT
Type of CIED Artificial cardiac pacemakers Implantable cardioverter-defibrillators (ICDs) Cardiac resynchronization therapy devices (biventricular pacemakers)
Basic function
  • Resynchronize ventricular dyssynchrony
Basic types
  • Single-chamber
  • Double-chamber
  • Triple-chamber (biventricular)
Common indications

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

Antitachycardia pacing can occur via cardioversion, which is achieved by mechanical (precordial thump), pharmacologic/chemical (antiarrhythmic drugs), or electrical means (implantable cardioverter-defibrillator, or ICD). Modern ICDs are capable of multiple forms of pacing and electrical cardioversion, either synchronized or unsynchronized (commonly known as defibrillation).

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

To distinguish an ICD from a pacemaker on a CXR, the leads can give a clue: In contrast to pacemaker leads, ICD leads have thick shock coils which are visible on the radiograph.

  • Placement complications:
  • Pacemaker syndrome
  • Pacemaker-induced reentry tachycardia: Excitation of the atrium as a result of retrograde conduction via the AV node, which then prematurely stimulates the ventricle again.
  • Pacemaker malfunction: Associated with symptoms ranging from bradycardia to asystole. Some causes include:
    • Electric fields
      • Short-wave (high-frequency) therapy: Electric fields occur during diathermy and interfere with pacemaker functionality.
    • Magnetic fields, e.g., MRI
    • Displacement of pacemaker electrodes, defect of battery or cable
      • Tingling sensations in the arm may be indicative of displaced electrodes.

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

  • Interference with MRI: Despite many devices being MRI-safe now, an electrophysiologist or the device maker should be consulted before scanning.
  • Surgical patients: Consider consulting an electrophysiologist regarding temporary deactivation, as surgery involving diathermy can trigger device activation. [4]
  • Patient education:
    • Driving advice
    • Education about interaction with medical procedures and (electronic) devices [5][6]
  • Discussions about device deactivation in 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.