Long QT Syndrome

Long QT syndrome refers to an issue with your heart’s electrical system taking longer than normal to recharge between heartbeats.

The QT interval is the section on an electrocardiogram (ECG) report that represents the time it takes your heart muscle to contract and then recover. Put another way, it’s the time it takes for your electrical system to fire an impulse through your ventricles (lower heart chambers) and then recharge.

Ions (electrically charged particles of sodium, calcium, potassium and chloride) produce electrical activity in your heart. Long QT syndrome happens when you have an issue with the ion channels that control the flow of ions in and out of your heart muscle cells.

When these ion channels aren’t working well or you don’t have enough of them, it delays the time it takes your electrical system to recharge after each heartbeat. When the QT interval is longer than normal, it increases the risk for Torsades de Pointes, a life-threatening form of ventricular tachycardia.

Long QT syndrome types

Long QT syndrome has acquired and inherited forms. The types you can inherit (congenital forms) include:

• Ion channel abnormalities. The most common of these types include LQT1, LQT2, LQT3, LQT4 and LQT5. Researchers classify them by the type of channel that causes the syndrome. Different types have different risk levels for future cardiac events.
• Jervell and Lange-Nielsen Syndrome. Both parents carry this abnormal gene, but they may not have symptoms of long QT syndrome. This syndrome is extremely rare, as there’s a small chance that both parents would carry the long QT syndrome gene. Each child has a 25% chance of inheriting it. People with this syndrome may be deaf at birth.
• Romano-Ward Syndrome. One parent has long QT syndrome and the other parent usually doesn’t. Each child has a 50% chance of inheriting the abnormal gene. The abnormal gene may be present in all the couple’s children, some of them or none at all. In this syndrome, hearing abilities are typical.
• Timothy Syndrome. This is a very rare form of long QT syndrome that affects other parts of your body as well as your heart.