Cardiac implantable electronic devices

Last updated: May 24, 2023

Summarytoggle arrow icon

Cardiac implantable electronic devices (CIEDs) are battery-powered medical devices used to treat a variety of cardiac disorders and include permanent pacemakers (PPMs), automated implantable cardioverter defibrillators (AICDs), and cardiac resynchronization therapy devices (CRTs). CIEDs are used to monitor and control arrhythmias (PPMs, AICDs, CRTs) and improve systolic function (CRTs). Complications of CIEDs may result from implantation or device-related malfunctions. Device malfunctions are divided into pacing malfunctions (e.g., oversensing, undersensing) and cardioversion malfunctions (e.g., lack of appropriate shocks, inappropriate shocks). Management of CIED malfunctions typically involves CIED interrogation and treatment of underlying or resulting arrhythmias.

See also “Implantable loop recorders” and “Mechanical circulatory support devices.”

Overviewtoggle arrow icon

Types of CIEDs

Comparison of PPMs, ICDs, and CRTs

Comparison of PPMs, AICDs, and CRTs
Functions [1]
Basic types
  • Single chamber: usually RV
  • Dual chamber: RV and RA
Common indications

Technical backgroundtoggle arrow icon


Basic functions


Magnet placement

Permanent pacemakerstoggle arrow icon

A PPM is a CIED that contains a pulse generator and at least one pacing lead, preventing bradycardia and asystole. Other CIEDs (e.g., AICDs, CRTs) often include pacemaker functions. PPM implantation can be preceded by temporary cardiac pacing in acute cases.

Types of PPMs


  • All PPMs
    • Cardiac rhythm monitoring
    • Antibradycardia pacing
      • Pacing of the heart if the heart rate drops below a preset threshold
      • Achieved by delivering an electrical impulse to stimulate myocardial contraction
    • Both of the following requirements must be met for minimum PPM functioning:
  • Combination PPM and AICD devices: may also have antitachycardia pacing functions (see “AICDs”)

Indications for PPMs [5]

Pacemaker nomenclature [1][3][6]

  • NBG code: PPMs and CIEDs with pacemaker function are classified using a 5-letter system
    • 1st letter: chamber(s) that are paced, i.e., A = atrium, V = ventricle, D = dual
    • 2nd letter: chamber(s) that are sensed, i.e., A = atrium, V = ventricle, D = dual
    • 3rd letter: device's response to sensing native beats, i.e., I = inhibited, T = triggered, D = dual [6]
    • The 4th and 5th letters are less commonly communicated and denote device programmability and any antitachycardia pacing functions, respectively.
  • Examples
    • DDD pacemaker (most common): senses and paces both chambers; can inhibit impulses to either chamber if native atrial or ventricular beats are sensed
    • VVI pacemaker: senses and paces the ventricle; can inhibit impulses to the ventricle if a native ventricular beat is sensed

ECG findings of normal pacemaker function [1]

ECG findings depend on device type and the heart's intrinsic electrical activity.

ECG findings of electrical capture can vary depending on the type of CIED.

Automated implantable cardioverter defibrillatorstoggle arrow icon

An AICD (or ICD) is a CIED consisting of a pulse generator and leads that can sense VF and VT and deliver a shock to restore sinus rhythm.

Types of AICDs


Specific functions may vary by device depending on programming and patient needs.

All modern transvenous AICDs are capable of antibradycardia pacing in addition to synchronized cardioversion, defibrillation, and antitachycardia pacing.

Indications for AICDs [8]

The primary goal of AICDs is to prevent sudden cardiac death from ventricular tachyarrhythmias. Consult a cardiologist and/or electrophysiologist and use shared decision-making to determine if an AICD should be implanted, taking the patient's risk factors into account.

Primary prevention

Selected patients with an expected survival of > 1 year and any of the following:

Secondary prevention

All patients with an expected survival of > 1 year, an irreversible cause of ventricular tachyarrhythmias, and any of the following: [8]

Cardiac resynchronization therapytoggle arrow icon

A CRT device is a CIED that contains a pulse generator and leads to the atrium and both ventricles that pace the heart in a coordinated manner. Some CRTs also can deliver shocks to restore sinus rhythm.

Types of CRTs

All CRT devices have leads implanted in the right atrium, right ventricle, and coronary sinus.

All CRTs are biventricular pacemakers.


Indication for CRTs

Complicationstoggle arrow icon

During implantation [10][11]

After implantation [10][11]

  • Lead displacement: the migration of a CIED lead away from its intended position, leading to dysfunction
  • Lead fracture: fragmentation and discontinuity of a CIED lead, leading to dysfunction
  • Upper extremity DVT
  • Venous stenosis
  • Infection (see “Device-related infections”)
  • Twiddler syndrome (uncommon)
    • Caused by the accidental or deliberate manipulation of the pulse generator, resulting in lead coiling and retraction
    • Consequences
      • Failure to detect abnormal rhythms
      • Failure to capture
      • Stimulation of noncardiac structures (e.g., the diaphragm, pectoral muscle)
  • Tricuspid valve dysfunction

Lead displacement and lead fracture are common underlying causes of various CIED malfunctions.

CIED malfunction [1][3]

Pacemaker syndrome

Can occur in patients with single-chamber pacemakers (e.g., VVI pacemakers)

CRT complications [11]

  • Coronary sinus dissection or perforation during placement of the LV pacing lead
  • Displacement of the left ventricular pacing lead, resulting in loss of pacing

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

Managementtoggle arrow icon

Management approach [1][3]

All patients

Unstable patients

Consider magnet placement for unstable patients with undersensing, oversensing, pacemaker-related tachycardia, or inappropriate shocks due to AICD malfunction.

Begin transcutaneous pacing for unstable patients with failure to capture or pacemaker output failure.

Sensing problems [3]

Pacing problems [3]

Pacemaker-related tachycardias [12][13][14][15]

  • Pacemaker-mediated tachycardia: typically occurs in dual-chamber pacemakers with atrial sensing
  • Sensor-driven tachycardia: typically occurs in rate-responsive dual-chamber pacemakers
    • Sensors track and conduct false stimuli, leading to inappropriate tachycardia.
    • Heart rates remain under maximum device limit.
  • Runaway pacemaker: typically occurs in older-generation single-chamber pacemakers; rare in modern devices
    • Very low battery states can result in potentially lethal rapid misfiring.
    • Heart rates can surpass the maximum device limit due to programming malfunction.
  • Management of unstable patients: magnet placement

Cardioversion problems

Overview of acute AICD complications [3]
Causes to consider Emergency intervention
Lack of appropriate shocks
  • Battery depletion
  • Component failure
  • Undersensing
  • Lead malfunction
  • Programming problems
Inappropriate shocks (i.e., oversensing)

Repeated AICD shocks may be appropriate, e.g, in patients with recurrent VT or electrical storm. Begin initial management of Vtach in these patients.



Chest x-ray

In contrast to pacemaker leads, AICD leads have thick shock coils that are visible on x-ray.

Laboratory studies

CIED interrogation [1][3]

  • Definition: placement of an external device over a CIED pulse generator to check device function and retrieve diagnostic data
  • Indications
    • All symptomatic patients: e.g., those with worsening cardiac function
    • Suspected device malfunction
    • Evidence of intrinsic dysrhythmia on ECG
    • Repeated AICD shocks
    • Before and after procedures with a risk of electromagnetic interference (e.g., MRI)
  • Management: The device can be reprogrammed as required.

Disposition [1]

  • PPMs
  • AICDs
    • Admit patients with multiple shocks confirmed by interrogation or single shocks thought to be secondary to myocardial infarction or heart failure.
    • Discharge all other patients with a single shock confirmed by interrogation after discussion with cardiology and expedited follow-up.

Special considerationstoggle arrow icon

  • 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. [17]
  • Patient education
    • Driving advice
    • Education about possible interactions during medical procedures and with electronic devices [18][19]
  • 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.

Referencestoggle arrow icon

  1. Kusumoto FM, Schoenfeld MH, Barrett C, et al. 2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay. J Am Coll Cardiol. 2019; 74 (7): p.e51-e156.doi: 10.1016/j.jacc.2018.10.044 . | Open in Read by QxMD
  2. Walls R, Hockberger R, Gausche-Hill M, Erickson TB, Wilcox SR. Rosen's Emergency Medicine 10th edition- Concepts and Clinical Practice E-Book. Elsevier Health Sciences ; 2022
  3. Bernstein AD, Daubert JC, Fletcher RD, et al. The Revised NASPE/BPEG Generic Code for Antibradycardia, Adaptive-Rate, and Multisite Pacing. Pacing Clin Electrophysiol. 2002; 25 (2): p.260-264.doi: 10.1046/j.1460-9592.2002.00260.x . | Open in Read by QxMD
  4. Roberts JR. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. Elsevier ; 2018
  5. Safavi-Naeini P, Saeed M. Pacemaker Troubleshooting: Common Clinical Scenarios. Texas Heart Institute Journal. 2016; 43 (5): p.415-418.doi: 10.14503/thij-16-5918 . | Open in Read by QxMD
  6. Alasti M, Machado C, Rangasamy K, et al. Pacemaker‐mediated arrhythmias. Journal of Arrhythmia. 2018; 34 (5): p.485-492.doi: 10.1002/joa3.12098 . | Open in Read by QxMD
  7. Ortega D, Sammartino M, Pellegrino G, et al. Runaway pacemaker: A forgotten phenomenon?. EP Europace. 2005; 7 (6): p.592-597.doi: 10.1016/j.eupc.2005.06.004 . | Open in Read by QxMD
  8. Gul A, Sheikh MA, Rao A. Runaway pacemaker. BMJ Case Reports. 2019; 12 (3): p.e225411.doi: 10.1136/bcr-2018-225411 . | Open in Read by QxMD
  9. Heidenreich PA, Bozkurt B, Aguilar D, et al. 2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2022; 145 (18).doi: 10.1161/cir.0000000000001063 . | Open in Read by QxMD
  10. Shepard RK, Ellenbogen KA. Leads and longevity: how long will your pacemaker last?. Europace. 2008; 11 (2): p.142-143.doi: 10.1093/europace/eun359 . | Open in Read by QxMD
  11. Ozkartal T, Demarchi A, Caputo ML, Baldi E, Conte G, Auricchio A. Perioperative Management of Patients with Cardiac Implantable Electronic Devices and Utility of Magnet Application. J Clin Med. 2022; 11 (3): p.691.doi: 10.3390/jcm11030691 . | Open in Read by QxMD
  12. Mulpuru SK, Madhavan M, McLeod CJ, Cha YM, Friedman PA. Cardiac Pacemakers: Function, Troubleshooting, and Management. J Am Coll Cardiol. 2017; 69 (2): p.189-210.doi: 10.1016/j.jacc.2016.10.061 . | Open in Read by QxMD
  13. Walls R, MD R, Hockberger R, et al. Rosen's Emergency Medicine: Concepts and Clinical Practice. Elsevier ; 2022
  14. Fong KY, Ng CJR, Wang Y, et al. Subcutaneous Versus Transvenous Implantable Defibrillator Therapy: A Systematic Review and Meta‐Analysis of Randomized Trials and Propensity Score–Matched Studies. J Am Heart Assoc. 2022; 11 (11).doi: 10.1161/jaha.121.024756 . | Open in Read by QxMD
  15. Al-Khatib SM, Stevenson WG, Ackerman MJ, et al. 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death. J Am Coll Cardiol. 2018; 72 (14): p.e91-e220.doi: 10.1016/j.jacc.2017.10.054 . | Open in Read by QxMD
  16. 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
  17. Donnelly P, Pal N, Herity NA. Perioperative management of patients with implantable cardioverter defibrillators.. Ulster Med J. 2007; 76 (2): p.66-7.
  18. Can I use an induction hob if I have a pacemaker?. . Accessed: October 22, 2020.
  19. Devices that May Interfere with ICDs and Pacemakers. Updated: September 30, 2016. Accessed: October 22, 2020.

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