TOC | Cardiology   

Long QT Syndromes  


  1. Both acquired and congenital forms of long QT Syndromes exist
  2. Usually defined as a corrected QT (QTc) interval of >0.45 seconds
  3. Increasing concerns due to risk for serious morbidity and death
  4. Ion Channels and the QT Interval
    The QT interval represents the repolarization phase of action potential
    Repolarization is due primarily to voltage dependent outward rectifying K+ currents
    The prolonged length of the QT interval in normal persons is due to inward K+ channels
    These inward rectifying potassium currents are also voltage dependent
    Hypocalcemia can prolong QT because Ca2+ can modulate a K+ channel

Drugs Associated with Prolongation of QT Interval

  1. Antihistamines - Terfenadine (Seldane®) ,  Astemizole (Hismanal®)
  2. Tricyclic Antidepressants
  3. Phenothiazines and other Typical Neuroleptics
  4. Cisapride (Propulsid®)
  5. Drugs Contributing to QT Prolongation -
  6. Hypomagnesemia and hypocalcemia may precipitate TDP in susceptible patients
  7. Bradycardia with atrioventricular (AV) block can precipitate TDP

Back to top |  Home Page

Congenital Prolonged QT Syndromes

Long QT Syndrome 1

Long QT Syndrome 2

Long QT Syndrome 3

Romano-Ward Syndrome [4]

Back to top |  Home Page