RBBB: Paced Fusion Rhythm

Report:

Sinus tachycardia 107/min 1

Atrial-sensing ventricular pacemaker, 100% capture 2

Presumptive right bundle branch block 5

Fusion complexes throughout 2

Comment:

This is similar to the delectable deduction in Case 38, except that the pacemaker’s contribution to fusion beats is not as marked. All the complexes are of normal duration, less than 0.10”. The unit is in DDD mode. If its sensing AV interval (0.18” here) were extended, native QRSs would emerge and there would be no sign of a pacemaker presence.

Below is the patient’s native ECG, unremarkable except for the borderline frontal lead voltage and the RBBB.

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