Cardiac ion channelopathies (also sometimes referred to as inherited arrhythmic syndromes) affect the electrical functioning of the heart without affecting the heart’s structure. They are a group of rare genetic conditions that are caused by abnormalities of the DNA known as mutations. They are usually inherited from parents although they can occur for the first time in a person. If they occur for the first time they are described as sporadic or ‘de novo’ meaning ‘from new’.
The mutations affect certain genes – specific segments of the DNA that are responsible for the production of cardiac ion channels. An ion is a chemical substance – such as sodium, potassium or calcium – that carries an electrical charge and forms the basis of the movement of electricity through the heart muscle. Each heart muscle cell is surrounded by a membrane that separates the inside from the outside of the cell. An ion channel is the route (the gate) that the ions take in and out of the heart muscle cells to allow the movement of electricity. The ion channels regulate the flow of electrical charge. If these channels do not behave normally, the electrical function of the heart becomes abnormal. The person can then be prone to arrhythmias (disturbances in the heart’s rhythm) that may cause blackouts or cardiac arrest.
Since these channels are microscopic and are not visible to the naked eye, the heart appears normal during post-mortem examination.
The following are the common disorders that affect ion-channels: