Torsades de pointes

Background

• Torsades de Pointes is a form of polymorphic VTach, where there is a gradual change in the amplitude and twisting of the QRS complexes around the isoelectric line
• Associated with prolonged QT, which may be congenital or acquired.

Common Causes

POINTES mnemonic:

• Phenothiazines
• Other medications (ie TCAs)
• Intracranial bleed
• No known cause (idiopathic)
• Type I anti-arrhythmics (quinidine, procainamide, disopyramide)
• Electrolyte abnormalities (hypoK & hypoMag)
• Syndrome of Prolonged QT (aka Long QT Syndrome)

Clinical Features

• Syncope

Evaluation

Classic torsades in 12-lead

12-lead ECG of Torsades de Pointes (TdP) in a 56-year-old white female with a potassium of 2.4 mmol/L and a magnesium of 1.6mg/dL.

• ECG
• BMP, Mg, Phos

Differential Diagnosis

• Drug induced
• Congenital long QT
• Hypocalcemia
• Hypomagnesemia
• Hypokalemia
• Hypothermia
• POINTES as above

Management

Increasing HR decreases QT interval

1. Magnesium sulfate - decreases calcium influx
   • 1-2gm IV over 1-2 min, repeat in 5-15min; then 1-2gm/hr (3-10mg/min) drip
     • Danger of hypermagnesemia → depressed neuromuscular function, so monitor closely
     • Supplement with K+
2. Isoproterenol - Increases HR / AV conduction
   • 2-8 mcg/min
   • Target HR > 90 bpm
3. Overdrive Pacing - Atrial > Ventricular pacing
   • Goal HR 90-120
4. Defibrillation / synchronized cardioversion - Patient in extremis
5. AVOID amiodarone and procainamide, which may worsen prolonged QT

See Also

• Tachycardia (Wide)
• ACLS (2010 Guidelines)

References

Authors

Ross Donaldson