Let's jump!

• clear understanding of dual AV-node physiology
• ready to go recipe for triggering jump
• ability to train with different patients and observing different responses
• basic skills you need to deal with AVNRT

• The extrastimulus testing is a good way to demonstrate dual AV nodal physiology. The compact AV node is composed of fast and slow conducting tissues.
• In a sinus rhythm, the electrical signal from the atrium enters the AV node through the fast pathway.
• An atrial extrastimulus may be blocked in the fast pathway being conducted to the ventricle through a slow pathway, which takes more time as the conduction velocity of the slow pathway is lower than fast pathway. Consequently, the AH interval suddenly prolongs.
• We can replicate this phenomenon in the EP lab. The extrastimulus testing (S1S2) includes a drive train of 7 paced beats at a fixed CL (called S1), followed by extrastimulus (called S2). On the consecutive stimulations the drive train is kept the same (constant S1) while the coupling interval of the extrastimulus is decreasing, usually by 10 ms.
• In case the AH interval prolongs by > 40-50 ms during S1S2 stimulation, we call it the AH jump.
• AH jump is highly indicative for the AVNRT as dual AV nodal physiology is essential for this arrhythmia. However, the presence of AH jump itself is not sufficient to start ablation. Always try to get reproducible induction of the AVNRT or presence of atrial echos (after S1S2 stimulation you can recognize atrial activation).

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HOW TO SECTION:

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1. Pick a channel with a good quality atrial signal – usually CS 9-10 or HRA.
2. Measure baseline cycle length (BCL).
3. Set extrastimulus pacing.
4. Set S1 pacing CL to 500 ms.
5. Set S2 pacing CL to 350 ms.
6. Set decrement (shortening of the S1S2 coupling interval during consecutive stimulations) to 10 ms.
7. Look for sudden increase in the AH interval (≥ 40-50 ms) at the His catheter.