missed long QT syndrome

longqt

Misdiagnosis of Long QT Syndrome as Epilepsy at First Presentation. Ann Emerg Med. 2009;54:26-32

This retrospective review of 31 patients (median age 21) with proved long QT syndrome found 39% experienced diagnostic delay after presenting with syncope or seizure, with a median delay of 2.4 years. A third of patients had EEGs and a sixth of patients were diagnosed with epilepsy–which prolonged their diagnostic delay (due to diagnostic momentum). During diagnostic delay four unexplained sudden deaths occurred in young relatives, which could potentially have been prevented had long QT been diagnosed and the relatives screened.

The cases were

  1. 27yo diagnosed as epilepsy,
  2. 4yo diagnosed as breath-holding spells, QTc not recorded
  3. 10yo diagnosed as fall, QTc not recorded
  4. 12yo diagnosed as arrhythmias, QTc not recorded
  5. 43yo diagnosed as hyperventilation, QTc not recorded
  6. 11yo unknown diagnosis QTc recorded as upper limits
  7. 29yo diagnosed as epilepsy, QTc miscalculated
  8. 35yo diagnosed as epilepsy, QTc not recorded
  9. 37yo diagnosed as epilepsy
  10. 35yo diagnosed as epilepsy
  11. 31yo diagnosed as vasovagal, QTc miscalculated
  12. 41yo diagnosed as sleep dissociation state, QTc miscalculated
  13. 25yo diagnosed as vasovagal, QTc as 0.44

Take home points:

  1. get an ECG on all “seizure” and syncope patients to rule out long QT, including patients with a longstanding diagnosis of “seizure”
  2. calculate the interval correctly: QT divided by square root of RR

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