Overview
- Occurs when a long RR interval is followed by a short RR interval, producing a wide QRS that mimics a PVC
- Most commonly seen in atrial fibrillation
- Represents aberrant supraventricular conduction, not a true ventricular ectopy
Mechanism
- The long cycle prolongs repolarization of the His-Purkinje system
- The following short-cycle beat arrives while part of the conduction system is still refractory
- Results in a wide, usually RBBB-pattern QRS
Key EKG Features
- Irregularly irregular rhythm (AF)
- Wide QRS following a long–short RR sequence
- Typically RBBB morphology
- No compensatory pause (distinguishes from PVC)
