Tachyarrhythmias can be treated with either anti-arrhythmic drugs or an implantable cardioverter defibrillator (ICD) and anti-arrhythmic drugs.

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 tend to be used in conjunction with anti-arrhythmic drugs. The first ICD was implanted in 1980.
ICDs 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

These include:

• Previous ventricular arrhythmia (ventricular tachycardia - VT)
• Coronary artery disease
• Familial cardiac conditions (for example, long QT syndrome)
• Poor cardiac function (low ejection fraction)

Indications

By 2002, 2,321 patients in the UK had received an implantable cardioverter defibrillator (ICD) - less than half the expected rate compared with some other countries.

National Institute for Health and Clinical Excellence (NICE) Guidance (Implementation advice 2007) recommends that ICDs should be considered for patients in the following categories:¹

• Sustained ventricular arrhythmia (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 ventricular fibrillation (VF)
• Myocardial infarction (MI) complicated by nonsustained 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 implantable cardioverter defibrillator (ICD) devices use tiered pacing, recognising 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 implantable cardioverter defibrillator (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.

Further patient 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).

DVLA

• 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

Adverse events

Serious adverse events due to implantable cardioverter defibrillators (ICDs) are reported infrequently. However, recorded complications include:¹

• Inappropriate ICD discharge²
• Infection
• Haematomas and bleeding
• Leads may dislodge and migrate
• Cardiac perforation
• Pleural effusion and pneumothorax
• Device dysfunction/malfunction of the generator

Additionally, some people for whom defibrillation is initiated while they remain conscious report that they become fearful of the severe jolt to the thorax occasioned by device activation.

Prognosis

In a Canadian study the mortality rate at two years among patients with heart failure who accepted and were waiting for an ICD implant was 18.8%. After receiving an ICD, the mortality rate was 12.2% at two years.³

Document references

1. Arrhythmia - implantable cardioverter defibrillators, NICE Technology Appraisal (January 2006)
2. Jodko L, Kornacewicz-Jach Z, Kazmierczak J, et al; Inappropriate cardioverter-defibrillator discharge continues to be a major Cardiol J. 2009;16(5):432-9. [abstract]
3. Ghosh N, Mangat I, O'Donnell SS, et al; Outcomes in heart failure patients referred for consideration of implantable Can J Cardiol. 2009 Oct;25(10):e342-246. [abstract]

Internet and further reading

• Guidelines for the perioperative management of patients with implantable pacemakers or implantable cardioverter defibrillators, MHRA (2006); (where the use of surgical diathermy/electrocautery is anticipated)
• Guidelines for follow up of implantable cardiac devices for cardiac rhythm management, Society for Cardiological Science & Technology (October 2008)
• British Heart Foundation. Implantable Cardioverter Defibrillators (ICDs) In Patients Who Are Reaching The End Of Life (Factfile) (2009).

Acknowledgements