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Implantable Cardioverter Defibrillators

Tachyarrhythmias can be treated with either anti-arrhythmic drugs or an Implantable Cardioverter Defibrillator (ICD). The first ICD was implanted in 1980. ICDs sense and terminate life-threatening arrhythmias and reduce mortality.1
Implantable cardioverter defibrillators (ICDs) are battery powered, implantable devices that deliver an electrical shock to restore normal sinus rhythm when a life-threatening arrhythmia is detected.1
They are:

  • Similar in size to a pacemaker
  • Placed under the skin in the pectoral region
  • Have a lead in the right ventricular apex

Risk factors for sudden cardiac death include previous ventricular arrhythmia (VT), coronary artery disease, familial cardiac conditions (for example long QT syndrome) and poor cardiac function (low ejection fraction). People who survive a first episode of a life-threatening VT are at high risk of further episodes.1

Indications

By 2002, 2321 patients in the UK had received an ICD - less than half the expected rate compared to some other countries.
NICE Guidance (Implementation advice 2007) recommends that ICDs should be considered for patients in the following categories:1

  • Sustained VT causing syncope
  • Sustained VT with ejection fraction less than 35%
  • Ejection Fraction less than 30% without VT
  • After surgery for congenital heart disease (when there is a risk of VT)
  • Previous cardiac arrest (due to VT or VF)
  • MI complicated by non-sustained VT, or inducible VT on electrophysiological testing, or an ejection fraction less than 35%
  • Familial conditions (for example long QT syndrome, hypertrophic cardiomyopathy, Brugada syndrome)

The ICD leads are inserted via a vein under local anaesthesia. During implantation the unit is tested under conscious sedation. ECG storage provides a retrievable record of the onset and termination of arrhythmias. Programming changes are made with a unit placed over the defibrillator.

Device details

Current ICD devices use tiered pacing, recognizing cycle length and can initiate the following appropriate therapy, all via single lead:1

  • Anti-bradycardia pacing (like a normal pacemaker).
  • Pacing pulses (may cause brief palpitations or a feeling of dizziness) - adaptive bursts to end a VT.
  • Cardioversion shocks for persisting VT (if pacing pulses fail, low energy cardioversion shocks are given to terminate VT with the minimum of pain).
  • Defibrillation shocks (high energy shocks - feels like being kicked in the chest unless unconscious). Observers will notice the jolt. No harm comes to anyone touching the patient when they receive the shock.
Patient information

Postoperatively

  • It is safe to have a bath or shower after 3-4 days.
  • Keep the arm on the same side as the defibrillator below shoulder level until after first ICD check-up (there is a small chance the leads can move).
  • Do gentle arm and shoulder exercises to keep the arm mobile.
  • Following recovery (4-6 weeks) increase your level of activity if possible.
  • A programmer is used to check device settings (takes about 15 minutes).
  • Chest x-ray is used to check lead positions.
  • Battery length is 6-7 years.

More information

  • Change of ICD is like having a first ICD fitted, except new leads are not put in.
  • You may have some warning that your ICD is about to deliver a shock (palpitations, or feeling dizzy). Afterwards you should recover quite quickly.
  • After the first shock contact the implant centre to have the device checked.
  • It is not necessary to have the device checked after every shock unless you feel unwell.
  • If the device gives several shocks, dial 999 for an ambulance- the ICD will be checked to find out why.

Lifestyle changes

  • Keep your ICD card with you at all times (make, model and settings of the device).
  • Sexual activity - the device will not cause any harm, even if a shock is delivered to you during intercourse.
  • Electrical equipment (such as drills) can be safely used. Electromagnetic interference (radios, fridges, cookers, computers and microwaves) will not affect your ICD.
  • Travel: the ICD may set off the airport security alarm. Your ICD will be unharmed provided you walk briskly through the arch. Many ICD clinics carry a list of ICD-friendly insurance companies.
  • Arc welding - should be avoided.
  • Mobile phones - keep handsets 6 inches away from ICD (hold the phone over the ear on the opposite side to the device).
  • Driving - patients must notify DVLA following initial implantation and should not drive for 6 months. There are detailed guidelines, but in summary driving is curtailed:
    • 6 months off after a shock is delivered, with certain exceptions - agreed by DVLA
    • 1 month off following revision of the electrodes or alteration of anti-arrhythmic drug treatment
    • 1 week off after a defibrillator box change
    • Group 2 drivers (LGV/PCV) are permanently barred

Document references
  1. Arrhythmia - implantable cardioverter defibrillators (ICDs) (review), NICE Technology Appraisal (Jan 2006)
Acknowledgements EMIS is grateful to Dr Richard Draper for writing this article. The final copy has passed scrutiny by the independent Mentor GP reviewing team. ©EMIS 2007.
DocID: 187
Document Version: 21
DocRef: bgp25255
Last Updated: 30 Nov 2007
Review Date: 29 Nov 2009


















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