SAQ 368 – Cardiology – prolonged QT with torsades de pointes

Cardiology – prolonged QT with torsades de pointes.

a. ECG abnormality

• Prolonged QT interval.
• QT interval greater than 0.6 seconds.

b. Drug causes

• Antiarrhythmics, such as sotalol, amiodarone, quinidine, or procainamide.
• Antipsychotics, such as haloperidol, droperidol, or quetiapine.
• Antidepressants, such as tricyclic antidepressants, citalopram, or venlafaxine.
• Antibiotics, such as macrolides or fluoroquinolones.
• Antiemetics, such as ondansetron.
• Methadone is also an accepted example.

c. Non-drug causes/risk factors

• Age and female sex.
• Congenital long QT syndrome.
• Left ventricular failure.
• Recent cardioversion.
• Metabolic abnormalities: hypomagnesaemia, hypokalaemia, or hypocalcaemia.
• Hepatic dysfunction.

d. Rhythm strip

• Torsades de pointes, a polymorphic ventricular tachycardia.

e. Management

• Resuscitate using an ABC approach.
• Correct contributing abnormalities and give electrolytes.
• Administer IV magnesium sulphate at an appropriate dose.
• Treat hypokalaemia if present.
• Consider acute cardiac pacing.
• Continue monitoring.