His-Synchronous RV Pacing – Properly interpreting a Common Manoeuvre

Answer:

Positive Zipes/His-Synchronous RV Pacing with AA advancement & subsequent VV perturbation indicating Accessory pathway mediated tachycardia (AVRT).

• This tachycardia appears to visually be a mid RP tachycardia. Althought not mesured here, it measures as a short RP tachycardia, suggestive of AVJRT or AVRT.
• The VA time appears visually >70ms, making typical slow/fast AVJRT unlikely and suggesting AVRT or atypical fast/slow AVJRT.

His-Synchronous RV Pacing/Zipes

Also known as “Zipes,” is a valuable maneuver for confirming the presence of accessory pathway-mediated tachycardia (AVRT). This technique is particularly useful when an accessory pathway is suspected and needs confirmation.

Ensuring His-Synchronicity:

Crucially, we must ensure the RV paced stimulus is “His-Synchronous,” as the maneuver is invalid otherwise.

To ensure the RV paced stimulus is “His-Synchronous” (crucial for a valid maneuver), follow these steps:

1. Measure the preceding HH interval and the His-Stim interval.
2. The difference between these intervals should be less than 55ms, ideally 0ms.

In the example below, H-Stim – HH interval = +10ms, so we can be fairly certain that our RV paced beat is TRULY “His Synchronous”.

Side note: I admit that our “His” signal in this example is pretty dodgy. That is no criticism of the operator; it happens to the best of them. Ideally, you have a clearer His signal than this. You’re going to have to trust me that HH measurement is really measuring a sneaky His signal.

 

What to measure?

We are interested in measuring just x2 things:

1. The immediate AA interval (highlighted below)
2. The Subsequent VV interval (highlighted below).

There are x3 possible outcomes & conclusions – many forget to differentiate the 2nd & 3rd result 

1.     No perturbation of either immediate AA interval or subsequent VV interval.

Conclusion: No evidence of Accessory pathway. NOTE: The absence of evidence is NOT evidence of absence.

2.     Perturbation of immediate AA interval >10ms (advancement or delay), with no change in subsequent VV interval.

Conclusion: Indicates an accessory pathway, but not its participation in tachycardia. This could suggest a bystander pathway.

3.     Perturbation of both immediate AA & subsequent VV interval by >10ms.

Conclusion: This confirms both the presence AND participation of the accessory pathway in tachycardia. Diagnostic of AVRT.

In the example above, we observe a 20ms AA Advancement, confirming the presence of an accessory pathway. Furthermore, the subsequent VV interval advances by 20ms, indicating participation in SVT.

My Two Cents:

Thanks for tuning in
Cheers
Mitch & CPP Team

Some extra pitfalls mentioned below :)

We have more detailed explanations on SVT differentiation manoeuvres in our EP in Practice Program 2: SVT in EP.