What causes long QT syndrome?

To understand the underlying cause of long QT syndrome, it's important to know how the heart cells work.

On the surface of each heart muscle cell are tiny pores, or ion channels. These open and close to let electrically charged sodium, calcium and potassium atoms (ions) flow into and out of the cells.

This passage of ions generates the heart's electrical activity. The electrical signal spreads from the top of the heart to the bottom, causing the heart to contract and pump blood.

In most cases of long QT syndrome, the flow of potassium ions out of the heart muscle's cells is delayed. This means that after each heartbeat, your heart can take longer to reset itself.

Inherited long QT syndrome

Long QT syndrome is often inherited from a parentas afaulty gene.The abnormal gene affects the proteins that make up the ion channels in the heart cells. The ion channels may not work well, or there may not be enough of them, which disrupts the heart's electrical activity.

Drug-induced long QT syndrome

Certain commonly used medicines can also trigger long QT syndrome, including some types of:

  • antibiotics
  • antihistamines
  • antidepressants
  • antipsychotics
  • diuretics
  • heart medications

Cardiac Risk in the Young has published a list of medications that people with long QT syndrome should avoid .

Drug-induced long QT syndrome usually happens in people with an inherited higher risk of developing it, such as those with slight genetic heart defects.

For more information, you can read the Sudden Arrhythmic Death Sydrome's (SADS UK) guide about acquired, drug-induced long QT syndrome (PDF, 158kb) .

Content supplied by the NHS Website

Medically Reviewed by a doctor on 21 Dec 2018