An implantable cardiac defibrillator (ICD) is very similar to a pacemaker but in addition to regulating a slow heartbeat, an ICD can regulate dangerous rapid heartbeats that arise from the main pumping chamber of the heart.
These rhythms, referred to as ventricular tachycardia (VT) or ventricular fibrillation (VF), are usually life threatening and the ICD can treat these by either rapidly stimulating the heart to override the fast heart beats or deliver an electrical shock to restore the heart to a normal rhythm.
ICD’s have been proven in a number of trials to save lives of patients who are at risk of cardiac arrest who without the device would have otherwise not survived.
Patients who benefit from an ICD are usually those who are known to have had a history of fast heartbeats or in those in whom there has been significant damage to the heart muscle that increases their risk of cardiac arrest.
This is a very difficult area and requires specific expertise from Cardiologists to fully assess the risks of patients to ensure the right patients receive the right treatment.
An ICD is implanted in a similar method to a pacemaker although an ICD is a little larger in size. Similar to a pacemaker, the implantation of an ICD is a relatively low risk and straightforward procedure usually performed under local anaesthetic and conscious sedation.
An ICD consists of a generator and leads (flexible wires). The leads are advanced to the heart through a large vein under the collarbone and carefully positioned into the correct chambers of the heart with the aid of X-rays and firmly secured into place. The leads are then connected to the ICD device and then placed in a small pocket just under the skin.
The wound, which is usually only 5cm long, is carefully sutured and patients can be discharged usually the same day. ICDs are checked using programmers which communicate with the devices and allow the doctor and technicians to adjust the device settings to optimise their performance.
Most patients can return to normal activities within 4 weeks of the implant and will require regular ongoing follow up and checks to ensure correct functioning of the ICD.
Although, ICD implantation is straightforward there is a low rate of risks related to the procedure including:
requiring further surgery to reposition and correct this.
There are newer ICDs available where the device is implanted entirely under the skin and the lead does not have to be inserted into a cardiac chamber. This type of device is not suitable for everyone but can be a better option for some patients.
Once implanted an ICD continually senses the heart beat and if it senses that the heart has developed a rapid potentially dangerous heart rhythm, the ICD will try and override this fast heartbeat. If this is not successful, then the ICD will deliver a shock to return the heart to a normal rhythm.
All ICDs operate as pacemakers as well and therefore if the device senses that your heart has missed a beat or is beating too slowly, it sends signals at a steady rate to stimulate the heart.