Long QT Syndrome

Long QT syndrome (LQTS) is one of several cardiac arrhythmias (changes in heartbeat), characterized by an abnormal duration and shape of the Q to T interval on an electrocardiogram (EKG). Heart muscles contract and fire an impulse through the ventricles, a chamber of the heart that receives blood and from which blood is forced into an artery. QT is the time it takes for the heart muscle to contract and recover. When the interval is erratic, there is an increased risk for a serious form of ventricular tachycardia.


Some people with LQTS have no symptoms while others experience:

  • A fast, irregular heartbeat
  • Fainting
  • Seizures

LQTS is rare, occurring in approximately one in 5,000 people. Since not everyone with LQTS has a dangerous heart rhythm or other symptoms, the team of experienced cardiologists at the Cedars-Sinai Heart Institute are skilled at recognizing this syndrome on an electrocardiogram.


Causes and Risk Factors

LQTS may be inherited or can be caused by certain medications. Hereditary LQTS is classified according to whether one or two parents have the defective gene, though not necessarily the condition. Two forms of inherited LQTS are:

  • Romano-Ward syndrome, which occurs when people inherit one defective gene.
  • Jervell & Lange-Nielsen syndrome, which is seen in children who are born deaf and inherit other genetic mutations found in LQTS.

Many people experience an irregular heartbeat during or after exercise, during emotional excitement or upon awakening suddenly. If the heartbeat does not return to normal quickly, the person’s risk of sudden death increases because the heart may be unable to pump blood effectively throughout the body. If the arrhythmia lasts more than a few minutes, call 9-1-1 for emergency treatment.

Risk factors may include:

  • Blood relatives with the condition: It is recommended that family members of all ages get tested to determine if the gene or condition is present.
  • Medications: Some medications are known to increase the risk of an arrhythmia. Check with your doctor about the medications and supplements you take and before starting any new medications or supplements.


LQTS is usually seen on an electrocardiogram, where the heart's electrical activity and distance between the heart rhythm waves can be measured. Other diagnostic tests include exercise stress tests and a Holter monitor. An evaluation by your doctor of your current medication(s) is important. Make sure to give your doctor a complete list of all medications and supplements you take, the dosage and how long you’ve been taking them.


Your doctor will work with you to determine a treatment plan, which can include:

  • Pacemaker: An implantable device that regulates heart. Pacemakers may be adjusted to be suitable for the top or bottom heart chambers and, since it works only when needed, it does not work all the time.
  • Defibrillator: An implantable cardioverter defibrillator (ICD) shocks the heart into normal rhythm when it detects a life threatening rhythmic disturbance from the lower chambers of the heart. It is there to prevent cardiac arrest. ICD’s have pacemakers built into them.
  • Lifestyle: Check with your doctor before resuming exercise. Some exercise may be allowed but not strenuous physical activity.
  • Manage stress: Reduce the stress in your life and avoid, if possible, being startled by sudden noise or activity. Talk with your family members to discuss ways they can help and make sure they understand what to do in the event of any arrhythmia.
  • Medications: An evaluation by your doctor of all of your medications is important. In some cases, beta-blockers can effectively treat LQTS.