What is an ICD?
An implantable cardioverter defibrillator (ICD) is an artificial device that is implanted in the chest to regulate an abnormal heartbeat. It consists of a battery which can last around 8-10 years depending on how much the device is used, a pulse generator that generates the electrical impulses to stimulate the heart and leads which carry the electrical impulses to the correct chambers of the heart. The ICD continually senses the heartbeat and if it detects that your heart has missed a beat or is beating too slowly, it sends signals at a steady rate to stimulate the heart. If, however, the ICD detects that the heart is beating too fast or chaotically, it gives defibrillation shocks to stop the abnormal rhythm. ICDs also have a special sensor that recognises body movement or your breathing rate and allows the device to pace the heart faster during periods of increased demand.
What are the reasons for needing an ICD?
The main reason for requiring an ICD is if you are at risk of a life-threatening ventricular arrhythmia, which could cause sudden cardiac death, from ventricular tachycardia (VT) or ventricular fibrillation (VF). In this case, a pacemaker alone is not sufficient as it would not provide the defibrillation shocks required when the heart beats too fast or erratically.
How is an ICD implanted?
The implantation of an ICD is a relatively low risk and straightforward procedure. Along with the fitting of a pacemaker it is the most common type of heart surgery in the UK. The procedure is usually performed under local anaesthetic and conscious sedation. The ICD leads (flexible wires) 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 pacemaker device which is usually smaller than the size of a small matchbox, 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. Once implanted the ICD can be checked using programmers which communicate with the devices and allow the doctor and technicians to adjust the device settings to optimise the performance of the ICD. Most patients can return to normal activities within 4 weeks of the implant and will require regular ongoing follow up and ICD checks to ensure correct functioning of the device. Although ICD implantation is straightforward, there is a low rate of risks related to the procedure including bruising at the site of the wound, infection or movement of the leads after insertion which may require further surgery to reposition and correct this.