Paradoxical response during Para-Hisian pacing in a case with fasciculo-ventricular pathway: What is the mechanism?

Abstract

Causes of paradoxical response include Pure His capture and inadvertent intermittent direct atrial capture. In the index case , we postulate that the likely mechanism of paradoxical prolongation could be due to decrement in the AV node due to the shortening of HH interval which happened as a result of a narrower H + Vc beat following a wider Vc beat during decremetal pacing output.