Atrio‐Hisian block precludes preexcitation—What is the mechanism?

[...]more preexcitation, a larger delta wave and a broader QRS complex are noted when there is an AVP. Pacing manoeuvres that increase preexcitation and shorten the HV interval in AVP fail to do so in FVP as it occurs distal to the AVN. [...]incremental atrial pacing which relies on faster pacing rate to increase preexcitation, pacing from multiple sites which relies on increased preexcitation while pacing closer to the site of atrial insertion site of the AVP all yield a constant degree of preexcitation in FVP. [...]preexcitation FVP may cause intermittent preexcitation though the exact mechanism is unknown.