Long QT Syndrome

Symptoms

Symptoms of either inherited or acquired long QT syndrome depend on the type of abnormal heart rhythm that occurs and how long the abnormal rhythm lasts. The severity of symptoms depends on whether or not the heart returns to a normal rhythm.

About half of people with LQTS don't have any signs or symptoms. These people may learn of their condition only from results of an ECG performed for an unrelated reason, because they have a family history of long QT syndrome or from genetic test results.

Others may have one or two fainting spells as children and no symptoms after that. In about 5 percent of people with inherited LQTS, the first symptom is sudden cardiac death.

The most common symptom is fainting (syncope). Usually, there is no warning before syncope. Symptoms are caused when the heart rhythm becomes so fast that the heart cannot pump blood effectively and blood flow to the brain is decreased. Symptoms may begin at any time.

Another symptom is seizure. If the heart beats erratically over time, the brain may be deprived of oxygen. This can cause generalized seizures.

Symptoms usually occur during physical activity or emotional upset or after being startled by sudden noises such as sirens or alarm clocks. Symptoms also may occur during sleep or upon waking up. The specific trigger that provokes symptoms depends on the specific gene defect.