Long QT Syndrome

Basic Facts

  • “QT” refers to the measurement between certain waves on an electrocardiogram (ECG) 
  • In this disorder, the heart takes longer to “recharge” electrically after a heart beat and the QT measurement prolongs.
  • It can potentially cause fast, chaotic heartbeats or sudden cardiac arrest. 

Long QT Syndrome can be seen on an ECG, but it usually does not produce symptoms unless an abnormal heart rhythm occurs. Symptoms could then include:

  • Palpitations
  • Fainting, or feeling like you are going to faint
  • Sudden cardiac arrest

There are two main types of Long QT Syndrome:

  1. Congenital- born with it; caused by a specific change in a gene
  2. Acquired- happens later in life, can be caused by medications or mineral imbalances, such as having too little potassium or magnesium (especially in those with poor liver or kidney function, due to decreased drug clearance).

Electrocardiogram (ECG)- Non-invasive test that provides a snapshot of the heart's electrical activity.

Treatment depends on the cause:

  1. Congenital- Beta-blockers are used to help keep the heart from beating too fast.
  2. Acquired- Stop the medicine and/or correct the electrolyte imbalance causing it.

All with known long QT should avoid the use of medicines that are likely to lengthen the QT interval.

ICD is indicated for all in whom sudden cardiac arrest occurs.