In a Ventricularly Paced rhythm, where does the spike appear?

In a Ventricularly Paced rhythm, the spike appears before the QRS complex, which is confirmed by the wide QRS that follows. This is characteristic of ventricular pacing because the pacemaker generates an electrical impulse that triggers the ventricles to contract. The spike is indicative of the pacing output, which occurs right before the QRS complex, as the electrical impulse travels through the ventricles causing depolarization.

In this scenario, the QRS is wide due to the abnormal pathway of conduction—specifically because the pacing occurs in the ventricles rather than through the normal conduction pathway. This results in a delayed depolarization, producing a wide QRS complex. Understanding this timing is crucial for identifying pacing rhythms on an ECG, distinguishing them from other types of rhythms.