Fusion beat
From Self-sufficiency
Fusion beat and Capture beat.
In some cases of VT with AV dissociation the SA node may transiently "capture" the ventricles, producing a capture beat, which has a normal QRS duration, or a fusion beat, in which the sinus and ventricular beats coincide to produce a hybrid complex.
Ref:Goldberger: Clinical Electrocardiography: A Simplified Approach, 6th edn P 210
Marriot et al. Ventricular Fusion Beats. Circulation 26 (5): 880. 1962 ; http://circ.ahajournals.org/cgi/reprint/26/5/880
