Incremental pacing, retrograde Wenckebach and ventriculo-atrial ERP

• the utility of performing ventricular stimulation
• what is incremental ventricular pacing and how it is performed
• what is retrograde Wenckebach point
• what is programmed ventricular pacing and how it is performed
• what is ventriculo-atrial effective refractory period

How to stimulate and analyse:  Incremental ventricular pacing (IVP)

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1. Pick RVA channel.
2. Measure BCL (i.e. 600 msec).
3. Set stimulation mode to incremental pacing with pacing CL just lower than BCL (i.e. 500 msec) - you want to be faster than NSR.
4. Stimulate from RVA.
5. Decrease pacing CL by 10-20 msec (do not pace faster than 250 msec because ventricular tachycardia or fibrillation may be induced at higher rates).
6. Observe when the ventricular beat is not followed by an atrial response – observe RVA catheter, HRA catheter, CS catheter and His catheter. There will be a moment when no A signal is visible after stimulation of ventricle - 1:1 ventriculo-atrial (VA) conduction is no longer maintained.
7. Once noted, you have reached the retrograde Wenckebach point, the lowest value of paced CL at which signal was still conducted.

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How to stimulate and analyse: Programmed ventricular pacing (Extra-stimulus pacing)

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1. Pick RVA channel.
2. Set stimulation mode to programmed (S1-S2) pacing in an 8-beat train starting with a drive (S1) of 600 msec and an extrastimulus (S2) lower than the drive CL (e.g. 400 msec).
3. Set rest time to 3 sec - you determine how long the stimulator should wait after delivery of S2 pacing prior to new S1 drive train.
4. Set S2 limit to 200 msec - you want to have a safety limit and avoid S2 stimulation below 200 msec.
5. Set Pre-Int -10 msec - this means simulator will decrease S1-S2 coupling interval by 10 msec every new S1-S2 train.
6. Stimulate from RVA.
7. Observe VH/VA interval becoming longer as you shorten the S1-S2 coupling interval.
8. There will be a moment when no A/HA signal is visible on the HRA catheter, CS catheter, His catheter.
9. Once noted, you have reached the retrograde ventriculo-atrial effective refractory period, the longest premature coupling interval (S1-S2) that fails to capture the tissue or propagate through a tissue.