What Are the Signs and Symptoms of Long QT Syndrome?

Major Signs and Symptoms

If you have long QT syndrome (LQTS), you're prone to developing a sudden and dangerous arrhythmia (abnormal heartbeat). Signs and symptoms of LQTS-related arrhythmias often first appear during childhood and include:

• Unexplained fainting. This happens because your heart isn't pumping enough blood to your brain. Fainting may occur when you're under physical or emotional stress. Some people will have fluttering feelings in their chests before they faint.
• Unexplained seizures. Those around you may mistake your fainting from LQTS as a seizure due to epilepsy. In children, fainting may be seen as a hysterical reaction to a stressful situation.
• Unexplained drowning or near drowning. This may be due to fainting while swimming.
• Unexplained sudden cardiac arrest (SCA) or death. This means that your heart suddenly stops beating for no obvious reason. People who have SCA will die within minutes unless they receive treatment. Most people who have SCA die. In about 1 out of 10 patients, SCA or sudden death is the first sign of LQTS.

Other Signs and Symptoms

Often, people who have LQTS 3 will develop an abnormal heartbeat during sleep. This may cause them to have noisy gasping while sleeping.

Long QT Syndrome Without Symptoms

People who have LQTS may not have any signs or symptoms (silent LQTS). Doctors often advise family members of people who have the condition to be tested for it, even if they have no symptoms.

Medical and genetic tests may reveal whether they have LQTS and what type of the condition they have.