Polymorphic VT

Question 1

Polymorphic VT (PVT)
Definition

Answer 1

VT with varying QRS complexes & axis so that they appear to “twist” around the baseline.
HR > 200/min

Question 2

Causes

Answer 2

Various aetiologies:
* Ischaemia / acute MI
* Dilated CMP
* Hypertrophic CMP
* Takotsubo
* Congenital long QT
* Acquired QT prolongation (drugs, electrolyte abnormalities, medications)

Question 3

Torsades de Pointes

Answer 3

->Subset of PVT with QT prolongation.
-Congenital or acquired.
-Worse as QTc becomes more prolonged.
-QTC often >500msec
-U waves often present

**High risk of degeneration into VF.**

Diagnosis
* After defibrillation/spontaneous termination → Obtain ECG in sinus rhythm.
* QT prolongation → clue for Torsades.
-R/V previous ECGs–> if QT prolonged–>congenital long QT syndrome
- If no prolongation–>Echo->?ischemia;ECG- ?Brugada/early depolarization

Question 4

Differential Diagnosis

Answer 4

-> Digoxin toxicity → bidirectional VT (can mimic PVT).
-> Hyperkalaemia
-> WPW with AF (irregular, polymorphic appearance)
-> Coarse VF
-> PVT without QT prolongation → catecholaminergic polymorphic VT (CPVT), Takotsubo, etc.

Question 5

Treatment

Answer 5

1). Breaking active PVT
2). Prevent recurrence of VT
3). Treat precipitating factors
4) Cease all QT prolonging drugs

Question 5

Breaking active PVT

Answer 5

=>Unstable:Immediate defib-200j biphasic, unsynchronised

=>Stable PVT-
->*Polymorphic VT is never truly stable → usually degenerates into VF.
* IV MgSO₄ 1–2 mmol over 10 min → repeat if rhythm persists.
* Defibrillator pads ready applied (ready to shock if degeneration into VF).

Question 6

Prevent recurrence of Torsades

Answer 6

• Magnesium infusion: 20 mmol MgSO4 (≈ 2–4 mmol/hr).
• Target Mg²⁺: 1.0–1.5 mmol/L.
• Continue ECG monitoring for bradycardia & QT prolongation.
• Stop Mg after 24 hrs.
• Treat other predisposing factors:
  
  • Hypokalaemia
  • Hypocalcaemia
  • Hypomagnesaemia
• Hypothermia

Question 7

Avoid QT-prolonging drugs

Answer 7

• Antimicrobials: erythromycin, fluoroquinolones, fluconazole.
• Antiarrhythmics:
• Class IA: quinidine
• Class IC: flecainide
  
  • Class III: sotalol
• Antipsychotics: haloperidol
  
  • Antidepressants: TCAs
  • Anti-emetics: ondansetron
  • Sedatives: propofol
  • Others: cocaine, methadone

Question 8

Refractory Torsades Storm
Management

Answer 8

->Reload Mg²⁺ if needed (target max 1.5–2.0 mmol/L).
* Treat other predisposing factors (K⁺, Ca²⁺, Mg²⁺, ischaemia).

->Chronotropy (increase HR, reduce QTc)
* If hypotensive → adrenaline, isoprenaline.
* If normotensive →dobutamine, isoprenaline or pacing.
* Beta agonists-: CI in patients with congenital long QT, catecholamines can be proarrhythmic–> can trigger Torsades

->Lignocaine- Antiarrhythmic of choice in Torsades
Amiodarone/ Procainamide/Beta blockers- Contraindicated.

->Electrical pacing
* Transcutaneous pacing or transvenous pacing to increase HR.
* Aim device rate ~ 90–110 bpm.