Module 1
Topic 4
Lesson 15

Eccentric activation

Piotr Buchta
Head of EP

What will you learn?

  • how to identify the eccentric antegrade activation / presence of preexcitation
  • interpretation of the changing morphology of the QRS complex with incremental atrial pacing
  • how to find maximum preexcitation and AV-node and accessory pathway refractoriness

About this scenario

  • The presence of preexcitation suggests the presence of an antegrade conducted accessory pathway (AP).
  • Typical WPW syndrome is characterized by short P-R interval below 120ms, a delta wave (slurred upstroke of the QRS complex) and wide QRS complex (wider than 120ms).
  • Most of the accessory pathways conduct both antegradly and retrogradly.
  • The degree of preexcitation it is always a competition - depends on the conduction velocity through the accessory pathway, the conduction velocity through the AV-node and His-Purkinje system and the mutual distance of these two structures. The slowing down of A-V node conduction at a constant AP conduction velocity results in the greater degree of preexcitation.
  • Remember to always test the retrograde conduction properties of the patient.
  • How to do it:
  1. Start testing with incremental atrial pacing, with at cycle length below that of sinus rhythm, with progressive, gradual shortening (-10ms) of the cycle length.
  2. Pacing at increased rates produces prolonged A-V conduction time over the A-V node, which allows preexcitation to be manifested.
  3. You will see a change in QRS morphology as a result of fusion of conduction through the A-V node and the AP. By IAP observe a shortening of PQ interval, AH interval increases whereas the A-V interval remains stable so the HV interval will be shortening.
  4. At A-V – node Wenckebach point, the conduction will be solely over the accessory pathway with maximal preexcitation.
  5. Also try to check these properties with programmed atrial stimulation.