Fusion beats

The rhythm strip in a patient with sustained ventricular tachycardia shows a fusion beat and a capture beat. The fusion beat occurs when a supraventricular impulse (following the first P wave) causes ventricular activation, which fuses with the complex originating in the ventricle, producing a hybrid complex. The complex following the second P wave has the appearance of a normal QRS complex and is known as a capture beat.

Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright.