Long QT Syndrome

Long QT syndrome is a disorder of the heart's electrical system. Long QT syndrome affects the process that allows the heart to recharge itself after each heartbeat (repolarization). In long QT syndrome, the heart takes longer to recharge, which can lead to:

  • A very fast heart rhythm (arrhythmia).

  • Fainting (syncope).

  • Sudden death.

Long QT syndrome can be either acquired or present at birth (congenital). Congenital long QT syndrome is either associated with deafness at birth (Jervell and Lang-Nielsen syndrome), which is rare, or not associated with deafness (Romano-Ward syndrome), which is the most common type.


  • Deafness at birth.

  • Family history of experienced unexplained fainting or sudden cardiac death.

  • Use of certain medicines.


Acquired long QT syndrome can be caused by abnormal electrolyte levels, such as low potassium levels and low magnesium levels. It can also be caused by the use of certain medicines. These medicines can include:

  • Antihistamines.

  • Antidepressants and psychotropic drugs.

  • Antiarrhythmics.

  • Antibiotics, antifungals, and antivirals.

  • Gastrointestinal medicines.

  • Diuretics.

  • High blood pressure medicines.

  • Cholesterol-lowering medicines.

  • Migraine medicines.


Different kinds of tests can be used to diagnose long QT syndrome. These include:

  • Electrocardiography, which records the heart's electrical activity.

  • Holter monitor, which records your heartbeat and can help diagnose heart arrhythmias.

  • Stress tests by exercise or by giving medicine that makes the heart beat faster.

  • Genetic tests.


Treatment of long QT syndrome may involve:

  • Stopping the use of medicines that may be the cause.

  • Correcting abnormal electrolyte levels.

  • Correcting abnormal thyroid levels.

  • Use of heart medicines such as beta blockers.

  • An implantable cardioverter-defibrillator. This is a device that can shock a fast heart rate into a normal heart rhythm.


  • You have chest pain that feels like squeezing or pressure.

  • You feel faint or like you are going to pass out.

  • You feel your heart racing or skipping beats.

  • You have shortness of breath.


  • Understand these instructions.

  • Will watch your condition.

  • Will get help right away if you are not doing well or get worse.