Idiopathic ventricular fibrillation (IVF) describes the group of conditions responsible for life-threatening, rapid rhythm disturbances without any signs of the heart diseases described above. In some of these patients, changes on their ECG known as early repolarisation, have been seen. This has become known as early repolarisation syndrome and in a few cases mutations of potassium and calcium ion channel genes have been found. Early repolarisation can, however, be seen on the ECGs of many normal healthy people. The diagnosis and treatment of this condition is therefore still unclear but an ICD is needed in patients who have suffered a cardiac arrest.