Long Q-T syndrome

What is Long Q-T Syndrome?

Long Q-T syndrome (LQTS) is a disorder of the heart’s electrical system that can happen in otherwise healthy people. Its name comes from the way the heart’s electrical activity is recorded during an electrocardiogram (ECG or EKG). The electrical activity that is recorded produces a characteristic pattern and the different parts of the pattern are labelled with the letters P, Q, R, S and T. The space between the Q and the T (the Q-T interval) represents the time it takes for the electrical signal to pass through the lower chambers of the heart (the ventricles) until the heart is ready for its next beat. If it takes longer than normal, it is diagnosed as a prolonged or long Q-T interval.

People with LQTS do not necessarily have a prolonged Q-T interval at all times. It is possible for patients with this syndrome to have an ECG with a normal or borderline Q-T interval. People with this syndrome may show prolongation of the Q-T interval during physical exercise, while experiencing intense emotion or when startled. In one type of inherited LQTS, a person is born hearing impaired.

LQTS is often inherited and present from birth (congenital). It can also be caused by certain medications that prolong the Q-T interval and disrupt heart rhythms.


Some people with LQTS often have no symptoms. If there are symptoms, they may include unexplained fainting, unexplained seizures, and abnormal rate and rhythm of the heartbeat (arrhythmia). If not detected and treated, LQTS can lead to sudden death in a small proportion of patients.

If you have a family history of diagnosed LQTS or unexplained fainting, unexplained seizures, or sudden death in young people you should advise your family doctor or healthcare provider as you may be at risk of LQTS or other Inherited Rhythm Disorders.


The first step in diagnosing LQTS is by identifying prolonged QT intervals using an electrocardiogram (ECG or EKG). This is a printed record of your heart’s electrical activity that provides information about its rhythm, chambers, heart damage and other abnormalities.

However, LQTS is a difficult condition to diagnose because sometimes patients with LQTS do not have a visibly prolonged QT interval on an electrocardiogram test. If LQTS is suspected, it is important that a family physician refer their patient to a cardiologist who specializes in cardiac rhythm disorders for further testing. Additional tests may include exercise stress testing and genetic testing.


LQTS is a treatable condition and your doctor may prescribe medication, surgery or recommend lifestyle changes.


Beta-blockers are the most commonly prescribed medication and they work by slowing your heart rate by reducing the effect of adrenaline on your heart. It is important to discuss with your doctor the medications that work best for you and to follow instructions carefully.

In certain circumstances, you may be required to have surgery on nerves that regulate your heartbeat or you may need an implantable cardioverter defibrillator (ICD) if LQTS causes abnormal heart rhythms.



If properly treated and controlled, many people with LQTS require very few changes to their normal lifestyle. However, a diagnosis of LQTS may require the patient to make some adjustments to their lifestyle. For instance certain sports or activities increase the risk of fainting or more serious events in patients with LQTS. It is important for the patient to discuss this matter with their cardiologist to determine how best to live a healthy, active lifestyle while minimizing the risk of further complications.