What will you learn?
- correct position of diagnostic electrodes for best interpretation of the signals
- how to identify the eccentric retrograde activation
- interpretation of changing atrial activation sequence by incremental ventricle pacing by presence of retrograde conducting accessory pathway
- the first steps in finding the location and signals of the accessory pathway
About this scenario
- Physiologically, retrograde conduction through the A-V node is concentric and decremental.
- Check retrograde conduction during incremental ventricular pacing from right ventricular apex (RVA), starting at a cycle length lower than the actual sinus rhythm rate, or for example from CL 600ms.
- A change in atrial activation to eccentric usually indicates the presence of a retrograde conducting accessory pathway (AP). Continue pacing to CL 300-280ms. Faster pacing in the ventricle will increase the risk of ventricular malign arrhythmia induction.
- Conduction through the AP has mostly constant velocity, so - except for some posteroseptal APs - you won't see the decrement / prolongation of the VA interval by IVP in this case.
- By constant AP velocity conduction, the slowing in AV node conduction during your stimulation will result in “banana shape” activation in CS, caused by fusion of conduction over both structures. The fully eccentric VA conduction occurs by functional A-V node block.
- Test these properties during programmed ventricular stimulation. Start with a sequence of 500-450ms, decrease S2 by -10ms, measuring the VA interval after each sequence – observe the slowing AV node conduction and activation sequence changes.
- By careful – changing the position of coronary sinus catheter will change the shown observed retrograde activation pattern. For the proper interpretation of the signals, you should always know what the position of the catheter is.
- Advancing or pulling back the catheter will finally help you find the site of AP potential with the shortest VA / local VA-signals fusion.
