In Non-Selective QRS pacing, what happens immediately after the pacing spike?

In Non-Selective QRS pacing, immediately after the pacing spike, a Pseudodelta wave appears. This phenomenon occurs because the pacing stimulus activates myocardial tissue in a way that can cause premature depolarization, leading to an alteration in the usual ventricular conduction pattern. The Pseudodelta wave is indicative of the pacing impulse's effect and shows that the ventricular myocardium is responding to the pacing.

This is significant in clinical settings, as recognizing the Pseudodelta wave on the ECG can help practitioners distinguish between paced and intrinsic ventricular activity. Other options, such as a flat isoelectric line or a normal intrinsic QRS, do not occur in the context of Non-Selective QRS pacing. A flat isoelectric line would suggest absence of depolarization and no visible QRS complex would indicate that there is no myocardial response to pacing, which is atypical in this scenario. Normal intrinsic QRS complexes would imply that the natural conduction system is firing without the influence of the pacing spike, which again does not occur in this specific timing after pacing.