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Polymorphic VT

critical
Lead II
25 mm/s10 mm/mV
Heart rate
72bpm
RR
833ms
QT
378ms
Type

Bidirectional VT

A form of ventricular tachycardia with beat-to-beat alternation of QRS axis, typically by 180°. Classically associated with digitalis toxicity and familial catecholaminergic polymorphic VT (CPVT).

Mechanism

A form of ventricular tachycardia with beat-to-beat alternation of QRS axis, typically by 180°. Classically associated with digitalis toxicity and familial catecholaminergic polymorphic VT (CPVT).

Findings· 2
  • Regular wide-complex tachycardia with alternating QRS morphology — typically right-axis and left-axis deviation alternating beat-to-beat.
  • Rate 140–200 bpm.
Clinical Impact

Strongly suggests digitalis toxicity or CPVT. Treat underlying cause. Digitalis toxicity: stop digoxin, give digoxin-specific antibody fragments. CPVT: beta-blockers, avoid catecholamines.

Differential· 2
Monomorphic VT

Both wide-complex tachycardias. Bidirectional has alternating QRS axis beat-to-beat.

Ventricular Bigeminy

Alternating morphology may resemble bigeminy. Bigeminal pattern has sinus beats between PVCs.