simplified approach to different pacing maneuvers to reach to the diagnosis of narrow QRS tachycardia

1. Narrow QRS tachycardia
diagnostic
maneuvers
Ahmed Taha Abdelwahed
MD Cardiology, EHRA-certified
EP-specialist
Fellowship of Cardiac electrophysiology-Tampere Finland

2. features

3. AVNRT simple D.D
SVT has :
• a septal VA interval <70 ms (excluding AVRT)
• HH interval changes precede and predict AA interval
changes
• the SVT stops with a nonpremature terminal atrial
electrogram (excluding AT, repetitively and reproducibly )
--> slow pathway can be targeted for ablation

4. VOP
• Overdrive pacing from the right ventricle (RV) at a cycle
length (CL) that is 10–40 ms shorter than the TCL
provides a rapid tool:
• a post-VOP response that is atrial-atrial-ventricular (A-A-
V) rules in AT.
• a post-VOP response that is atrial-ventricular (A-V) rules
out AT (effectively ruling in AVRT or AVNRT).

5. Post VOP: V-A-A-V

6. AT post VOP

7. AVRT

8. AVNRT

9. ~“AVRT<115ms<AVNRT ”
Decremental pacing of VA with VOP

10. SA-VA < 85 ms
SA-VA > 85 ms
Stimulus-A: ventricle-A

11. Differential entrainment
The PPI-TCL interval was
longer at the base than at the apex in AVNRT
The PP-TCL interval
shorter at the base than the apex in AVRT

12. Differential entrainment
The SA-VA interval
shorter at the base than the apex in AVRT
The SA-VA interval was
longer at the base than at the apex in AVNRT

13. Differential entrainment
• The PPI–TCL interval was longer at the base than at the
apex in AVNRT but shorter at the base than the apex in
AVRT

14. PVC-His refractory

15. results
• Termination of Tachycardia by block in A -> AVRT
• Atrial activation is delayed without a change in the atrial
activation sequence -> AVRT employing decremental AP.
• Atrial activation is advanced without a change in the
atrial activation sequence -> AVRT
• No change in the A sequence or timing -> rule out AVRT
“AP” “but not confident”

16. AOP AT vs. AVNRT
VA
linking

17. APC-His refractory
affects the timing of the next His potential in any way (i.e. that advances or delays the
next His potential, or that terminates the SVT) is consistent with a diagnosis of
-> AVNRT

18. APC-His refractory
AVNRT JT

19. In VOP response
Pitfalls

20. Non-interpretable
• The main shortcoming of this pacing maneuver is that, in
50–80% of cases of AT, the atria are not accelerated to
the pacing CL
• (the ventricles are dissociated from the tachycardia), “VA
dissociation” so the response is technically not
interpretable (though this particular response still
excludes AVRT).
•  AT is most common diagnosis

21. Pseudo- V-A-A-V response

22. Pseudo- V-A-A-V response
• the HV interval exceeds the HA interval in AVNRT.

23. IsoRhythm
• When the pacing CL is not short enough, or when the
TCL shortens “accelerate” just before or during pacing,
• so that 1:1 VA conduction during pacing is not present
• the tachycardia and the pacing train are just
isorhythmically dissociated from each other.

24. Overcome
• 1) performing the maneuver repeatedly and
decrementing the pacing CL by 10–20 ms after each
apparently successful attempt to accelerate the atria to
the pacing CL.
• 2) checking to see that after pacing has stopped, the
TCL immediately returns to the longer pre-pacing TCL,
or at least a CL that is longer than that to which the atria
were accelerated during pacing.