Automatic Implantable Cardioverter Defibrillator (AICD)

Related Subjects: | Resuscitation - Adult Tachycardia Algorithm

Automatic Implantable Cardioverter Defibrillators are recommended as a possible treatment for people who have had a serious ventricular arrhythmia, who have an inherited heart condition linked to a high risk of sudden death, or who have had surgery to repair congenital heart disease. Implantable cardioverter-defibrillators, and cardiac resynchronisation therapy with defibrillation or pacing, are recommended as possible treatments for certain people with heart failure because of left ventricular dysfunction (see the guidance for more information).

About

• ICD is used to acutely treat ventricular tachycardia and ventricular fibrillation in those at high risk for these arrhythmias

Details

• The ICD is inserted just under your clavicle. It looks similar to a pacemaker and is a little bigger than a matchbox.
• It is made up of a pulse generator - a battery-powered electronic circuit and one or more electrode leads
• ICDs monitor the R-R interval. If an ICD detects too many short R-R intervals
• It decides between anti-tachycardia pacing (less battery use, more tolerable for the patient) or shock.
• Charging time is 6-15 seconds, after which many ICDs will reconfirm an arrhythmia prior to actually shocking.
• 10% of shocks are due to a non-VF non-VT rhythm, most commonly due to SVT
• Many ICDs also have antibradycardia pacing functions
• Batteries designed to last 4 to 5 years and deliver about 100 shocks

Actions

• Pacing - a series of low-voltage electrical impulses (paced beats) at a fast rate to try and correct the heart rhythm
• Cardioversion - one or more small electric shocks to try and restore the heart to a normal rhythm
• Defibrillation - one or larger electric shocks to try and restore the heart to a normal rhythm

Usual Types

• Single chamber ICD: Electrode in the right ventricle.
• Dual-chamber ICD with a RA and RV lead is implanted.
• The RV lead contains a coil +/- coil in the SVC (called the proximal coil).
• Shocks are delivered from <1 to 42 J between coil/device or other lead

Usual Indications

• Primary Prevention
  • Coronary disease, LV dysfunction (EF = 35%) and inducible VT
  • High-risk, inherited or acquired conditions, e.g. long QT syndrome, HCM, Brugada’s syndrome, ARVC
  • Chronic coronary disease, a history of MI + LVEF =30%: from MADIT II trial
• Secondary Prevention
  • Cardiac arrest due to VT/VF
  • Sustained VT with structural heart disease
  • Unexplained syncope with inducible sustained VT or VF with advanced structural heart disease and no other identifiable cause
• AICD + Biventricular pacing
  • QRS =130 ms, LV dilatation, LVEF =30% and advanced heart failure
  • Non-ischaemic cardiomyopathy: EF < 30% in NYHA II-IV

Devices

• ICD: Implantable cardioverter defibrillators (ICDs)
• (CRT-D) Cardiac resynchronisation therapy with defibrillator
• (CRT-P)Cardiac resynchronisation therapy with pacing are recommended as treatment options for people with heart failure with LVEF of 35% or less.

Monitoring

• After implantation of an implantable cardiac defibrillator (ICD) device there is usually follow up in the ICD clinic. Your ICD follow up will be carried out by cardiac physiologists.
• The physiologists will check the scar, whether the device is functioning correctly and that the battery is adequately charged.
• They also check if the ICD has detected and treated any fast heart rhythms since the last follow up. They may reset the device.
• The first follow up usually occurs one to three months after implantation of the ICD. A further check is carried out three to six months later.
• The battery life of an ICD can vary significantly from person to person. However, in many cases the ICD battery will need to be changed after approximately six to eight years depending on usage. This will require another minor operation

Patients receiving shocks

• Those who have received shocks need a full assessment of their clinical status and device function. Shocks are a red flag for clinical events. Even if inappropriate there is a related increased mortality.
• Shocks are unpleasant causing psychological distress, anxiety, and decreased quality of life. Catheter ablation of arrhythmias may be needed. Specialist assessment is needed.
• Ongoing SVT/AF/VT with haemodynamic compromise: Ignore presence of the ICD and treat. Consider external DC shock, iv Amiodarone and/or beta-blockers (if haemodynamically tolerated). To shock avoid placement of paddles in the skin area over the ICD pocket. If possible, attempt an anterior-posterior electrode position
• Repetitive ICD without a tachyarrhythmia or due to tachyarrhythmia (atrial or ventricular) that is haemodynamically well tolerated by the patient: Place a magnet over the device to inhibit further shock delivery
• Contact with the patient during ICD discharge: is harmless but gloves (1-2) decreases conductivity and attenuates potential discomfort.

Deactivation of ICD

• Place magnet on the patient skin over the bump of the ICD (usually left side of chest below collar bone) and tape in place
• Ensure patient is not dependent on ICD for pacing