Torsades de pointes vs Other polymorphic ventricular tachycardia
How to tell Torsades de pointes and Other polymorphic ventricular tachycardia apart when a board question makes them look alike.
Torsades is polymorphic VT plus prolonged QT; polymorphic VT with normal QT is not torsades.
Side by side
Polymorphic VT with prolonged QT and twisting QRS amplitude around the baseline, often from drugs or low potassium/magnesium.
Polymorphic VT without prolonged QT is often acute ischemia-driven and does not use the torsades label.
Delayed repolarization promotes early afterdepolarizations and triggered polymorphic VT.
Ischemia or scar-related electrical instability creates changing ventricular activation without long-QT mechanism.
Long QT, QT-prolonging drug, hypomagnesemia, or response to magnesium points torsades.
Normal QT with acute ischemia points non-torsades polymorphic VT.
The trap
The twisting morphology alone does not make it torsades. Torsades is polymorphic VT in the setting of a long baseline QT (congenital long QT, hypokalemia, hypomagnesemia, hypocalcemia, or QT-prolonging drugs like macrolides, fluoroquinolones, antipsychotics, methadone, ondansetron); polymorphic VT during acute ischemia with a normal QT is not torsades and needs ACS treatment plus standard antiarrhythmic management, not magnesium.
Watch it explained
The repair move
For any polymorphic VT, do three things before naming and treating: (1) measure the baseline QT on a prior or interictal ECG (corrected QT over 500 ms supports torsades); (2) check magnesium, potassium, and calcium plus a full medication review for QT-prolonging agents; (3) treat torsades with IV magnesium 2 g bolus first regardless of magnesium level, then correct other electrolytes, withdraw offending drugs, and consider overdrive pacing; treat ischemic polymorphic VT with revascularization and antiarrhythmic management.
Try a free question
CoreA patient on a QT-prolonging medication develops polymorphic ventricular tachycardia whose QRS complexes appear to twist around the baseline. Which rhythm is most likely?
Show answer and explanation
Answer: A. Torsades de pointes. Torsades is polymorphic VT associated with prolonged QT and twisting QRS amplitude around the baseline.
Why the other choices are tempting
- B. Polymorphic VT can occur with acute ischemia without QT prolongation; the long-QT twisting clue points torsades.
- C. Atrial flutter is a supraventricular rhythm with sawtooth waves.
- D. AF with WPW is irregular wide-complex tachycardia from accessory pathway conduction.
- E. Monomorphic VT has a consistent QRS morphology.
Flashcards
Tap a card to flip it.
What is the fastest separator for Torsades de pointes vs Other polymorphic ventricular tachycardia?
Torsades is polymorphic VT plus prolonged QT; polymorphic VT with normal QT is not torsades.
What clue should make you choose Torsades de pointes?
Polymorphic VT with prolonged QT and twisting QRS amplitude around the baseline, often from drugs or low potassium/magnesium.
Quick answers
What is the fastest way to tell Torsades de pointes from Other polymorphic ventricular tachycardia?
Torsades is polymorphic VT plus prolonged QT; polymorphic VT with normal QT is not torsades.
What is the key clue for Torsades de pointes?
Polymorphic VT with prolonged QT and twisting QRS amplitude around the baseline, often from drugs or low potassium/magnesium.
What is the key clue for Other polymorphic ventricular tachycardia?
Polymorphic VT without prolonged QT is often acute ischemia-driven and does not use the torsades label.
What is the common trap with Torsades de pointes vs Other polymorphic ventricular tachycardia?
The twisting morphology alone does not make it torsades. Torsades is polymorphic VT in the setting of a long baseline QT (congenital long QT, hypokalemia, hypomagnesemia, hypocalcemia, or QT-prolonging drugs like macrolides, fluoroquinolones, antipsychotics, methadone, ondansetron); polymorphic VT during acute ischemia with a normal QT is not torsades and needs ACS treatment plus standard antiarrhythmic management, not magnesium.