Cardioverter Defibrillators

Implantation of Cardioverter Defibrillators

Sometimes things go wrong in the heart’s electrical system causing an abnormal, often irregular heart beat called an arrhythmia. When the heart beat is too fast it is called a tachyarrhythmia. When this electrical impulse has started in the lower chambers of your heart (the ventricles), instead of the sinus node, the heart rhythm is called ventricular tachycardia (VT). This fast heart rate might feel as though the heart is pounding or skipping beats.

Another type of tachyarrhythmia is ventricular fibrillation (VF). VF may develop when VT continues and it becomes unstable and irregular. The heart muscle quivers and your heart no longer pumps any blood at all. Your body quickly becomes starved of oxygen and you usually pass out within a few seconds. This situation is called cardiac arrest.

Emergency teams try to revive people from cardiac arrest by using machines called defibrillators to send electrical impulses, or shocks, through the heart. The electrical current or shock from the defibrillator passes through the heart, stops the erratic electrical activity, and allows the heart to return to a more regular rhythm. An Implantable Cardiac Defibrillator (also known as an ICD) is an internal defibrillator and pacemaker. When your heart goes into a tachyarrhythmia, the defibrillator can pace or shock your heart out of VT or VF within those first crucial seconds.

Sometimes the heart beats too slowly. This is called bradycardia, and can be caused by the sinus node not working properly or by a condition called heart block. Some medications that are used to treat tachyarrhythmias may cause the heart to beat too slowly at times. During bradycardia, the heart may beat so slowly that the body and brain may not receive enough oxygen. A person with bradycardia may feel tired or have blackouts. Bradycardia may also be controlled via an implantable cardiac defibrillator

An ICD consists of a pulse generator and leads. The pulse generator or defibrillator is like a small computer that runs on a battery. The battery and circuitry are sealed inside a titanium case. The leads are insulated wires that connect the defibrillator to your heart. There are 3 types of ICDs to suit individual needs.

The defibrillator continually monitors your heart rhythm. It has been programmed by your doctor to respond in specific ways to treat your arrhythmia. Your cardiologist will have a programmer that communicates with your ICD via radio frequency waves. It is used to program the settings of your ICD so that it is fine-tuned to your specific needs. The programmer also reads information from your ICD, such as the date and time of any rapid rhythms you have had and how they were treated by the device.

In preparation for the implantation, your doctor will perform some tests to gather information about your heart rhythms, such as an Electrocardiograph (ECG), blood tests and an electrophysiology study (EPS).

Your ICD will be implanted in the Cardiovascular Theatre. The ICD leads are introduced into a vein in the left upper chest region. The lead is then threaded through the vein to the appropriate chamber in the heart. After the leads are in position they are secured and connected to the pulse generator which is positioned on the left side of your upper chest.

During the procedure, the ICD is tested to ensure it can detect and successfully treat VF. During this time you will be given a light anaesthetic.

Your Doctor will give you advice on what you should and should not do when you return home. Once you have fully recovered you should be able to confidently resume your normal activities of daily life. You can safely use common household appliances including microwave ovens, televisions, video and computer games, gardening machinery and portable phones etc.