Arrhythmias - Torsades de Pointes

Question 1

What is Torsades de Pointes?

Answer 1

A type of polymorphic ventricular tachycardia.

Question 2

ECG Representation of Torsades de Pointes (2).

Answer 2

1. QRS Complex twists around the baseline, getting progressively smaller and larger and smaller.
2. Prolonged QT Interval.

Question 3

Aetiology of Prolonged QT (4).

Answer 3

1. Long QT Syndrome - Inherited.
2. Medications.
3. Electrolyte Imbalances.
4. Acute MI, Myocarditis, Hypothermia, SAH.

Question 4

Medications that Prolong QT Interval (6).

Answer 4

1. Antipsychotics e.g. Haloperidol.
2. Citalopram, TCAs, SSRIs.
3. Flecainide.
4. Sotalol.
5. Amiodarone.
6. Macrolides e.g. Erythromycin.

Question 5

Electrolyte Disturbances that Prolong QT Interval (3).

Answer 5

LOW :
1. Hypokalaemia.
2. Hypocalcaemia.
3. Hypomagnesaemia.

Question 6

Why is the QT interval prolonged in Torsades de Pointes?

Answer 6

Prolonged repolarisation of myocytes - this can result in random spontaneous depolarisations (‘afterdepolarisations’) which lead to ventricular contraction prior to depolarisation.

Question 7

Acute Management of Torsades de Pointes (3).

Answer 7

1. Correct Underlying Cause.
2. IV Magnesium Sulphate Infusion (even if normal levels).
3. Defibrillation if VT.

Question 8

Long-Term Management of Long QT Syndrome (4).

Answer 8

1. Avoid Medications that prolong QT interval.
2. Correct electrolyte imbalances.
3. B-Blockers (not SOTALOL).
4. Pacemaker or Implantable Defibrillator.

Question 9

Prognosis of Torsades de Pointes.

Answer 9

1. Terminate spontaneously and revert to sinus rhythm.
2. Progression to Ventricular Tachycardia.