Prolonged Q-T intervals may never cause any problems. However, physical or emotional stress may "trip up" a heart susceptible to prolonged Q-T intervals and cause the heart's rhythm to spin out of control, triggering life-threatening, irregular heart rhythms (arrhythmias) including:

  • Torsades de pointes — 'twists of the points.' This arrhythmia is characterized by your heart's two lower chambers (ventricles) beating fast, making the waves on an ECG monitor look twisted. When this arrhythmia occurs, less blood is pumped out from your heart. Less blood then reaches your brain, causing you to faint suddenly and, often, without any warning.

    If a torsades de pointes episode is short — lasting less than one minute — your heart can correct itself seconds later, and you regain consciousness on your own. However, if a torsades de pointes episode persists, it can lead to a life-threatening arrhythmia called ventricular fibrillation.
  • Ventricular fibrillation. This condition causes the ventricles to beat so fast that your heart quivers and effectively ceases pumping blood. Unless your heart is shocked back into a normal rhythm by a device called a defibrillator, ventricular fibrillation can lead to brain damage and death. It's thought that long QT syndrome may explain some cases of sudden death in young people who otherwise appear healthy.
Apr. 20, 2012

You Are ... The Campaign for Mayo Clinic

Mayo Clinic is a not-for-profit organization. Make a difference today.