Differentiating Between an ICD and a Pacemaker
Introduction
Cardiac implantable electronic devices (CIEDs) - pacemakers, implantable cardioverter‑defibrillators (ICDs) and cardiac resynchronisation devices (CRT‑P / CRT‑D) - are common in emergency practice.
Rapid recognition of the device type guides resuscitation, immediate safety actions (magnet use, pad placement), and the need for urgent device interrogation or specialist involvement.
UK guidance from the Resuscitation Council, NICE and the MHRA summarises indications and practical ED management (Resuscitation Council UK; NICE TA314; NICE TA88/TA324; MHRA).
Definitions
- Pacemaker: Delivers low‑energy pacing pulses to treat symptomatic bradycardia and atrioventricular block; can be single‑, dual‑ or biventricular (CRT‑P) (NICE TA88/TA324).
- ICD (implantable cardioverter‑defibrillator): Detects and treats life‑threatening ventricular arrhythmias with high‑energy shocks and usually provides pacing capabilities; indicated to reduce sudden cardiac death in high‑risk patients (NICE TA314).
- CRT‑D: Cardiac resynchronisation device that also provides defibrillation therapy.
Why the distinction matters in the ED
- Recognising device type influences resuscitation strategy because ICDs may deliver internal shocks, and external defibrillation must not be withheld if a shockable arrest is present or if the device is inhibited.
- ICDs contain high‑voltage leads/coils and pose risks during extraction, autopsy or incisions unless deactivated.
- After return of spontaneous circulation (ROSC) or after a delivered shock, device interrogation by the device team is required to review therapy and lead integrity.