Question 30.2

A 36-year-old female with history of alcohol abuse presents with nausea, vomiting and palpitations. Her ECG is shown on page 12 (ECG 30.2).

a)    What is the major abnormality in this ECG?    (20% marks)

b)    List three differential diagnoses for the ECG abnormality.    (20% marks)

ECG 30.2

long qt

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College answer

a)    What is the major abnormality in this ECG (20% marks)
Prolonged QT

b)    List 3 differential diagnoses for the ECG abnormality (20% marks – 5% marks each)
-    Electrolyte abnormality
o    Hypokalaemia
o    Hypocalcaemia
o    Hypomagnesaemia
-    Drugs (many)
o    E.g. Amitriptyline, amiodarone, erythromycin, droperidol, haloperidol, risperidone,
-    Thyroid – hypo/hyper
-    Myocardial – heart failure, ischaemia, myocarditis
-    Congenital


This ECG is on loan from the Jill Squires collection, with many thanks to her.  The QTc of this patient was 585 msec according to the automated QT-correcting algorithm. 

Differentials, according to Harrigan & Chan (2009), include:

Non-drug-related causes

  • Hypokalemia
  • Hypocalcemia
  • Hypomagnesemia
  • Hypothermia
  • Thiamine deficiency
  • Cardiac ischaemia

Drugs (also see

  • Cardiac agents
    • Anti-arrhythmics (Type Ia, Ic, and III)
    • Calcium channel-blockers (some) (e.g. bepridil, isradipine, nicardipine)
  • Anti-psychotic agents
    • Phenothiazines (some) (e.g. thioridazine, mesoridazine)
    • Butyrophenones (e.g. haloperidol, droperidol)
  • Anti-depressants (some) (e.g. tricyclics, fluoxetine, sertraline, venlaflaxine)
  • Anti-infective agents
  • Fluoroquinolones (some) (e.g. sparfloxacin, gatifloxacin, moxifloxicin)
  • Macrolides (some) (e.g. erythromycin, clarithromycin)
  • Miscellaneous (pentamidine, amantadine, tetracyclines, foscarnet, quinine, chloroquine)
  • Neurologic agents
    • Carbamazepine, fosphenytoin, sumatriptan, zolmitriptan, naratriptan
  • Organophosphates
  • Gastrointestinal agents (e.g. cisapride, ipecac, octreotide, dolasetron)
  • Other (e.g. cocaine, diphenhydramine, methadone, tacrolimus, tamoxifen, probucol, tizanidine, salmeterol)


Harrigan, Richard A., and Theodore C. Chan. "| What is the ECG differential diagnosis of a prolonged QT interval?." Critical Decisions in Emergency and Acute Care Electrocardiography. Oxford, UK: Wiley‐Blackwell, 2009. 479-482.