‘Channelopathy’ is a term used to describe a number of conditions affecting the electrical activation of the heart. The movement of electricity in the heart depends on salts (sodium, potassium and calcium) being pumped in and out of each individual cell. If some of these pumps are defective (either over or under active), this can affect how electrical signals move through the heart. This can increase your risk of palpitations or sudden death. There are several channelopathies, which are similar in many ways.
The most common channelopathy in Ireland is Long QT syndrome (LQTS). The term long QT syndrome describes a particular pattern of the electrical activation in the heart. It is usually diagnosed on a resting ECG, although treadmill exercise testing (or ‘Stress Test), or continuous heart rhythm monitoring (Holter monitoring) may be required. Occasionally a ‘provocation test’ may be suggested, where a medication (usually low doses of adrenaline) is given through a drip in your arm, and the doctors monitor closely for any alteration in the pattern of electrical activation on your ECG (also known as Epinephrine Stress Test). LQTS is often hereditary and genetic testing may identify the genetic variant causing the condition in up to 70% of affected patients.
Brugada syndrome is another channelopathy, which is due to a similar problem, but is recognisable to a specialist by a specific abnormal pattern on the ECG. It is more common in south-east Asia, particularly in males. A small number of affected individuals or families have been identified in Ireland. The diagnosis is usually made on the resting ECG. Milder cases (or ‘carriers’ of the condition) may need additional tests to diagnose it, such as a treadmill exercise test (‘Stress Test’) or continuous heart rhythm monitor (Holter monitor). If the condition is suspected in you or your family a drug provocation test may be suggested. In this test a medication (usually Ajmaline or Glutaramyl) is given through a drip in your arm and the doctor monitors your ECG closely for any changes in the electrical pattern that may suggest Brugada syndrome.
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is similar in many ways to long QT syndrome. It is however a much rarer condition. In CPVT the resting ECG may be normal or near-normal, and abnormalities usually appear during exercise or stress, when your heart rate rises above 110 beats per minute. Therefore if CPVT is suspected you will be asked to do the treadmill exercise test (stress test). Occasionally a drug provocation test may be suggested, using small doses of adrenaline through a vein in your arm to see if abnormal patterns develop on your ECG. This is performed under close supervision.