Fusion Beats

Fusion beats due to VT - the first of the narrower complexes is a fusion beat (the next two are capture beats)

Definitions

• 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.

Causes

Fusion beats are seen with:

• Ventricular tachycardia
• Accelerated idioventricular rhythm (AIVR)

Related Topics

• VT versus SVT with aberrancy

Further Reading

• ECG Basics
• ECG Clinical Cases
• Eponymous Cardiac Syndromes