What is a fusion beat on an EKG?

• A. A blend of two normal beats in rapid succession
• B. A merging of a normal QRS complex with a PVC-like complex
• C. A beat originating solely from ectopic ventricular activity
• D. A solitary P wave followed by a wide QRS complex

Answer: (B)

A fusion beat is characterized by the merging of a normal QRS complex with a complex generated by a premature ventricular contraction (PVC). This occurs when a normal impulse from the atria simultaneously drives the ventricles, while an ectopic focus within the ventricles is also attempting to depolarize them. The result is a unique QRS complex that is distinct from both the normal beat and the PVC, reflecting the influence of both electrical activities.

In this context, other options do not accurately describe a fusion beat. A blend of two normal beats in rapid succession does not involve any ectopic activity, and therefore does not constitute a fusion beat. A beat originating solely from ectopic ventricular activity focuses exclusively on a PVC without the influence of a simultaneous normal contraction, thus failing to represent the fusion concept. The solitary P wave followed by a wide QRS complex describes a scenario where there is likely a block in conduction, rather than the fusion of two distinct electrical events.