Medications / electrolytes and their effect on ECG

Question 1

ECG changes suggestive of tricyclic overdose

Answer 1

QRS widening

Question 2

ECG in hypokalaemia

Answer 2

U waves
small or absent T waves (occasionally inversion)
prolong PR interval
ST depression
long QT

Question 3

ECG in hypercalcaemia

Answer 3

Short QT

Question 4

Effect of digoxin on ECG

Answer 4

• Down-sloping ST depression (‘reverse tick’, ‘scooped out’)
• Flattened/inverted T waves
• Short QT interval
• Arrhythmias e.g. AV block, bradycardia

Question 5

Hypocalcaemia on ECG

Answer 5

QT prolongation

Question 6

Hyperkalaemia on ECG

Answer 6

• Absent P waves
• Prolonged QRS
• Peaked or ‘tall tented’
  T waves
• Sine wave pattern

Question 7

ECG changes seen in hypomagnesaemia

Answer 7

• Prolonged PR interval
• Prolonged QT interval
• Atrial and ventricular ectopy
• Predisposition to ventricular tachycardia and torsades de pointes