There are many types of heart rhythm; some can be tolerated by the body reasonably and others cannot. 2 types of rhythm which are not well tolerated are Ventricular tachycardia (VT) and Ventricular fibrillation (VF).
VT is a rhythm whose origin is initiated somewhere in the ventricles, instead of the atria. This causes the heart to beat very rapidly. The heart cannot fill adequately in this rhythm, making the patient feel light headed and weak. This can lead to fainting if not corrected promptly.
It can also lead to death if not treated at all. VF is more serious than VT. In VF, the heart has no coordinated activity. There are a multitude of signals sent out in all directions across the heart. Due to the chaotic activity, the pumping mechanism is totally ineffective. This is a medical emergency, and if not treated promptly, results in death.
The ICD is a device, similar to a pacemaker, which can be fully implanted within the body under local anesthetic taking approximately an hour. The procedure is similar to that of a pacemaker implantation but the patient will have some additional ECG electrodes connected before the procedure and they may receive slightly more sedative medication. A wire electrode is inserted in a vein near the shoulder, in a similar way to a pacemaker wire. This is introduced into the correct position in the heart by a cardiologist. A small pocket is then made underneath the muscle high up on the chest, commonly the pectoral muscle. The ICD is placed here and the electrode tunneled from its insertion point and attached.
The ICDs can be programmed specifically to suit the patient's individual needs and are used in some patients who are at risk of developing the life threatening arrhythmias VT or VF. The ICD can terminate some rapid heart rhythms by use of the pacemaker function of the device, which is painless and is successful in 80% of cases. But when the heart is so rapid or irregular that it has stopped pumping, (VF) the device will deliver a shock to reset the heart and restore a normal rhythm.
Patients undergoing ICD implantation should have consulted a Cardiac Rhythm Specialist who will fully assess the suitability and benefit of such a device.