What characteristic defines Selective QRS pacing?

Selective QRS pacing is characterized by a pacing spike that is followed by an isoelectric line and a narrow QRS complex. This method is designed to capture the heart’s native conduction system, particularly targeting the His-Purkinje system, which allows for a natural and efficient contraction of the ventricles. The narrow QRS complex indicates that the activation of the ventricles is occurring through the normal conduction pathways, which is essential for maintaining proper cardiac function.

The isoelectric line after the pacing spike suggests that the stimulus has successfully synchronized with the heart’s natural right and left bundle branch system, leading to a normal QRS morphology. This contrasts with other pacing techniques that may not utilize the natural conduction pathways, resulting in wider QRS complexes or irregular morphologies due to direct myocardial stimulation rather than conduction through the specialized conduction tissues.

In summary, the defining characteristic of selective QRS pacing is its ability to produce a narrow QRS complex following the pacing spike, indicating effective synchronization with the heart's native electrical conduction system.