Symptoms of long QT syndrome

There are usually no physical signs of long QT syndrome, and some people don't experience any symptoms.

The most common symptoms are blackouts or seizures caused by the interruptions to the heart's rhythm.

Some people with long QT syndrome find that their heart sometimes suddenly beats in an abnormally fast, uncontrollable way. This type of arrhythmia is called"torsade de pointes".

When this happens, the heart can't pump blood properly and the brain is temporarily starved of oxygen, causing the person to temporarily pass out. The heart's rhythm usually returns to normal within a minute or so and the person regains consciousness.

These episodes can start at any age and may be triggered by:

  • stress
  • a sudden noise such as an alarm bell
  • strenuous exercise particularly swimming
  • a slow heart rate during sleep

However, there isn't always a trigger.

Sometimes, the abnormal heart rhythm persists, leading to ventricular fibrillation (a rapid, uncoordinated series of contractions). This rarely reverts to normal without medication and, if it isn't electrically corrected, usually causes the heart to stop pumping (cardiac arrest) and death.

Dial 999 to request an ambulance if someone with long QT syndrome suddenly collapses. Perform cardiopulmonary resuscitation (CPR) until medical help arrives.

Long QT syndrome is a leading cause of sudden cardiac death in young, otherwise healthy people, and is often thought to be an underlying cause of sudden infant death syndrome(SIDS) .

Content supplied by the NHS Website

Medically Reviewed by a doctor on 21 Dec 2018