- A fusion beat occurs when a supraventricular and a ventricular impulse coincide to produce a hybrid complex.
- It indicates that there are two foci of pacemaker cells firing simultaneously: a supraventricular pacemaker (e.g. the sinus node) and a competing ventricular pacemaker (source of ventricular ectopics).
- The fusion beats are of intermediate width and morphology to the supraventricular and ventricular complexes.
Fusion beats are seen with: