Wide QRS

Key Features

• Sinus Rhythm
• Wide QRS
• Peaked T waves
• Flattened p waves

Interpretation = Hyperkalaemia

… 20 minutes post calcium gluconate:

• QRS narrows
• T waves decrease in amplitude

40 year old lady found unconscious in bed. Seen completely well 2 hours earlier by husband.

Key Features

• Irregular tachycardia ?AF
• Wide complex
• Prominent terminal R wave in aVR (Right axis deviation of the terminal QRS)

Interpretation

• Given history of sudden deterioration in consciousness from well state and these ECG findings – Sodium Channel Blockade from overdose

Sodium Channel Blocking Drugs include:

• TCA’s (tricyclic antidepressants): Amitriptyline, Desimipramine, Dothiepin, Imipramine, Nortripytline
• Class 1A anti-arrhythmics: Disopyramide, Procainamide, Quinidine
• Class 1C anti-arrhythmics: Flecanide
• Local Anaesthetics: Bupivacaine, Cocaine, Ropivacaine
  Antimalarials: Hydroxychloroquine/Chloroquine, Quinine
• Other: Phenothiazines (Thioridazine), Amantadine, Carbamazepine, Chloroquine, Diltiazem, Diphenhydramine, Propoxyphene/Dextropropoxyphene, Propanolol

Source: Toxicology Handbook, 3rd edition, Murray et al

Key Features

• Regular bradycardia
• Wide complex
• Baseline artefact (shivering)
• Osborne J waves (prominent notching at end of QRS)

Further history

• 80y.o lady fell over on way back to toilet in middle of night. Unable to get up and found on floor after 24hrs.

Interpretation

Hypothermia

…. After rewarming 2 degrees

Key Features

• Very slow rate
• Wide
• and…
• ECG 4(a)
  • Near total absence of atrial activity
• ECG (b)
  • Regular atrial activity without relationship to ventricular activity

Interpretation = Ventricular Escape Rhythms

• 4(a) Due to sinus arrest
• 4(b) Due to complete heart block

Key Features

• Wide regular rhythms
  • Unusually “normal” rate
    • Faster than usual ventricular escape rhythms
    • Slower than VT
• Nil other features to suggest a Tox/Metabolic cause

Interpretation – Accelerated IdioVentricular Rhythm (AIVR) due to

• 5(a) MI post reperfusion
• 5(b) Athlete’s heart (sinus beats with intermittent AIVR)

Key features

• Wide QRS
• Short PR
• Delta waves

Interpretation: Accessory Pathway – Wolf Parkinson White (WPW)

Key causes of a Wide QRS

• Bundle Branch Block
• Accessory Pathway
• Ventricular rhythm
  • Ventricular escape rhythm
  • AIVR – Accelerated Idioventricular Rhythm
  • Ventricular tachycardia
• Toxicology/Metabolic (Cellular poisoning
  • Hyperkalaemia
  • Sodium Channel Blockade
  • Hypothermia

Key Diagnostic Clues

• History:
  • Toxicological cause? Hypothermia? Reasons for hyperkalaemia?
• ECG findings
  • Heart rate:
    • Slow – think ventricular escape rhythms; think hypothermia if history/temp supports
    • Very fast – think VT
  • QRS Morphology
    • Features/appearance of RBBB or LBBB?
  • Other ECG abnormalities
    • Peaked T waves, Short PR/delta waves, Osborne J waves, Terminal R wave in aVR