Treatments - Implantable Defibrillator

An implantable defibrillator or ICD is a special sort of pacemaker designed to treat dangerous fast heart beats. ICD implantation is recommended in two broad groups of patients. The first is those patients who have already experienced a potentially life-threatening arrhythmia, and no underlying cause has been identified that can be treated. The commonest arrhythmia is ventricular tachycardia occurring in patients months or years after a previous heart attack. This is called a ‘secondary prevention’ indication for an ICD. The other group of patients are those in whom investigations indicate may be at significantly increased risk for dangerous arrhythmias in the future. These patients may be offered an ICD for ‘primary prevention’ to protect them, even though they have not as yet experienced any problems. See diagnosis section, sudden death.

An ICD is implanted in a very similar way to a pacemaker, although the ICD is a larger device. Once again wires connect the defibrillator to the heart through a vein under the collar bone. Once the device is implanted, an abnormal heart rhythm is triggered, to confirm that ICD safely terminates the episode. As this usually involves the ICD delivering an electric shock, testing is carried out under very heavy sedation. An external defibrillator (such as those carried by ambulance) is always available so that in the very rare occasions that the ICD does not terminate the dangerous rhythm, effective treatment can be given immediately.

Once the ICD is successfully implanted, patients are usually fit for discharge within 24-48 hours. Care must be taken moving the arm on the same side as the implant for a few weeks and, like pacemaker patients, regular follow-up in a defibrillator clinic is organised. This is usually after 6-8 weeks and then every 6 months or so. Like a pacemaker, an ICD needs changing, typically every 5-7 years.

There are important implications for driving for patients with an ICD. They change regularly and the DVLA website should be consulted for the most up to date information (www.dvla.gov.uk). Currently, for an ICD implanted for primary prevention reasons driving must cease for one week. For secondary prevention, driving must cease for 6 months, and the DVLA must be informed. If dangerous arrhythmias occur after implantation, driving may be prohibited for even longer.

The ICD is able to terminate dangerous fast heart beats, such as ventricular tachycardia very effectively. Sometimes this is just by delivering very rapid pacing beats, which is completely painless. Very fast heart beats, including a rhythm called ventricular fibrillation (like ventricular tachycardia but much faster and a common cause of cardiac arrest), do not respond to pacing, and an electric shock must be given to restore a normal rhythm. This is painful, but very short lived.

The risks of an ICD implant are very similar to those of a pacemaker. See the section on pacemakers.