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

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.

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.

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