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Implantable cardioverter-defibrillators

Implantable cardioverter-defibrillators

An implantable cardioverter-defibrillator (ICD) reduces sudden cardiac death by detecting and treating ventricular tachycardia (VT) and ventricular fibrillation (VF).

How ICDs work
  • antitachycardia pacing (ATP) can terminate VT without a shock
  • shocks terminate VT or VF; transvenous devices also provide bradycardia pacing
  • appropriate treatment of underlying heart disease remains essential

Indications

Secondary prevention: after excluding reversible causes
  • cardiac arrest due to VT/VF
  • sustained VT causing syncope or haemodynamic compromise
  • sustained VT without syncope/arrest if LVEF ≤35% and NYHA class I–III

Primary prevention
  • selected patients with cardiomyopathy and LVEF ≤35% despite usually ≥3 months of optimised treatment
  • high-risk inherited conditions, including hypertrophic/arrhythmogenic cardiomyopathy, long QT and Brugada syndromes
  • generally defer until ≥40 days after myocardial infarction
  • assess individual arrhythmic risk, symptoms and comorbidities; meaningful survival >1 year is generally required

Device types
  • transvenous ICD: intracardiac lead; provides shocks, ATP and bradycardia pacing
  • subcutaneous ICD: no intravascular lead; standalone devices cannot provide ATP, ongoing pacing or resynchronisation
  • CRT-D: resynchronisation plus defibrillation; selection depends on LVEF, NYHA class, QRS duration and LBBB
    • CRT-P provides resynchronisation without defibrillation

Complications
  • haematoma, infection, pneumothorax, perforation/tamponade
  • lead displacement/fracture, inappropriate shocks and psychological distress
  • regular device checks and remote monitoring are required

Driving: DVLA rules
  • notify DVLA following implantation
  • group 1:
    • primary prevention: stop for 1 month; resume if asymptomatic without ICD therapy
    • secondary prevention: usually stop for 6 months
    • appropriate shock or appropriate ATP causing/likely to cause incapacity: stop for 6 months
    • inappropriate therapy: resume 1 month after complete control of the cause, subject to cardiologist approval
  • group 2: permanent disqualification

Deactivation
  • ICD therapies may be suspended for procedures involving electromagnetic interference, recurrent inappropriate shocks, or end-of-life care
  • a medical magnet usually temporarily suspends shocks and ATP without affecting bradycardia pacing
    • response depends on device/programming; removing the magnet usually restores therapies
  • planned deactivation or reprogramming is performed by the device team; pacing can be preserved
  • temporary suspension during active treatment requires cardiac monitoring and access to external defibrillation
  • discuss permanent deactivation near the end of life to prevent distressing shocks
    • DNACPR does not automatically deactivate an ICD
+PassMedicine Notes

An implantable cardioverter-defibrillator (ICD) reduces sudden cardiac death by detecting and treating ventricular tachycardia (VT) and ventricular fibrillation (VF).

How ICDs work
  • antitachycardia pacing (ATP) can terminate VT without a shock
  • shocks terminate VT or VF; transvenous devices also provide bradycardia pacing
  • appropriate treatment of underlying heart disease remains essential

Indications

Secondary prevention: after excluding reversible causes
  • cardiac arrest due to VT/VF
  • sustained VT causing syncope or haemodynamic compromise
  • sustained VT without syncope/arrest if LVEF ≤35% and NYHA class I–III
Primary prevention
  • selected patients with cardiomyopathy and LVEF ≤35% despite usually ≥3 months of optimised treatment
  • high-risk inherited conditions, including hypertrophic/arrhythmogenic cardiomyopathy, long QT and Brugada syndromes
  • generally defer until ≥40 days after myocardial infarction
  • assess individual arrhythmic risk, symptoms and comorbidities; meaningful survival >1 year is generally required
Device types
  • transvenous ICD: intracardiac lead; provides shocks, ATP and bradycardia pacing
  • subcutaneous ICD: no intravascular lead; standalone devices cannot provide ATP, ongoing pacing or resynchronisation
  • CRT-D: resynchronisation plus defibrillation; selection depends on LVEF, NYHA class, QRS duration and LBBB
    • CRT-P provides resynchronisation without defibrillation
Complications
  • haematoma, infection, pneumothorax, perforation/tamponade
  • lead displacement/fracture, inappropriate shocks and psychological distress
  • regular device checks and remote monitoring are required
Driving: DVLA rules
  • notify DVLA following implantation
  • group 1:
    • primary prevention: stop for 1 month; resume if asymptomatic without ICD therapy
    • secondary prevention: usually stop for 6 months
    • appropriate shock or appropriate ATP causing/likely to cause incapacity: stop for 6 months
    • inappropriate therapy: resume 1 month after complete control of the cause, subject to cardiologist approval
  • group 2: permanent disqualification
Deactivation
  • ICD therapies may be suspended for procedures involving electromagnetic interference, recurrent inappropriate shocks, or end-of-life care
  • a medical magnet usually temporarily suspends shocks and ATP without affecting bradycardia pacing
    • response depends on device/programming; removing the magnet usually restores therapies
  • planned deactivation or reprogramming is performed by the device team; pacing can be preserved
  • temporary suspension during active treatment requires cardiac monitoring and access to external defibrillation
  • discuss permanent deactivation near the end of life to prevent distressing shocks
    • DNACPR does not automatically deactivate an ICD


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