Question 30.2

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
 

Discussion

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 www.qtdrugs.org)

• 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)