If spikes fall before the QRS complex, what is the rhythm?

When spikes appear before the QRS complex, it indicates that there is pacing coming from the atria. This is typically seen in A-Pacing, where a pacemaker is being used to stimulate the atria, leading to ventricular contraction following atrial depolarization. The presence of these spikes signifies that the pacing is functioning adequately, initiating the electrical impulse that will eventually lead to the QRS complex.

In the case of V-Pacing, spikes would reflect ventricular pacing, which would not appear prior to the QRS complex. Nodal rhythm would indicate impulses being generated from the AV node and may not exhibit pacing spikes as prominently as atrial pacing would. Atrial Flutter is characterized by rapid atrial rates with specific flutter waves, rather than distinct pre-QRS pacing spikes. Thus, the identification of spikes appearing before the QRS complex clearly signals that the rhythm is a result of A-Pacing.