updated thanks to Vassili from Epicardio.com for the images contact if any questions or comments

1. Troy Watts
Cardiac Physiologist
troy.watts@mh.org.au
melbourneheartrhythm.com.au
@Troy_The
How to perform an EP study &
diagnostic pacing during sinus rhythm

2. • 1 -catheters
• 2 -baseline measurements
• 3 -evaluate conduction
– EP properties of A, V, AV node & AP
– tachycardia induction
• 4 –diagnostic pacing during sinus rhythm
• 5-special circumstances for EP

3. Catheters
• No of caths
• Full arsenal vs minimal
approach
• Position CS proximal at
ostium initially
• His placement
• Atrial signal on same bipole
as His

4. Baseline intervals – normal values
• Cycle length, QRSd, QT
• PA interval 25-55ms
– intra-atrial conduction time (IACT)
• AH 55-120ms
– conduction through AV node
• HV 35-55ms
– His through purkinje to V activation

5. Measuring intervals

6. PA interval
• P wave onset/earliest
AEGM to sharp AEGM
deflection on His (not THIS
one it’s not local signal)
epicardio.com

7. AH interval
• Sharp A on His to beginning of His deflection

8. HV interval
• Beginning of His to earliest V onset (ECG or EGM)

9. Refractory periods
• Effective RF-the longest S2 that doesn’t
conduct or capture local tissue
• Functional RP-the shortest S2 that conducts
• Relative RP-the longest S2 that shows latency

10. Retrograde testing
• Retrograde testing – why?
– V refractory period
– Assess atrial activation
• Concentric
• Eccentric
– Assess properties of AV node and/or AP
• Decremental conduction
– VA Wenckebach point
– Induce tachycardia

11. Retro how
Synchronised fixed pacing of 8 beats (S1) at 600ms &
400ms with extrastimulus (S2)
1 2 3 4 5 6 7 8
600

12. • S2 down to VERP
•
• If VERP longer than AV node ERP can use shorter S1
• Add S3, S4 if necessary
No capture
with V stim

13. • Incremental ventricular pacing
increase the rate of V pacing until VA block occurs =
VA W’Bach cycle length
360ms 350ms360ms
VA

14. Retro things to look out for
• VA ‘jump’ due to retrograde RBBB
AVH AV H
H H
A
A
H A time the same,
no AV nodal jump

15. • Repetitive Ventricular Response (RVR)
AHV V’
V’

16. Anterograde testing why?
• Determine atrial effective refractory period
• Atrial & ventricular activation sequence
• Assess properties of AV conduction
– AV node duality
– Assess properties if accessory pathway
• Induce tachycardia

17. Anterograde testing how?
• Synchronised drive cycle (S1) of 8 beats at
600ms & 400ms with extrastimulus (S2)
• S2 down to AERP
• If AERP longer than AV node ERP can use
shorter S1
• Add S3, S4 if necessary
• Incremental atrial pacing
– Gradually increase the rate of A pacing until AV
Wenckebach occurs

18. Antero to look out for
• Measurement of AH interval
– Measure from AEGM on His cath, NOT stim spike
• AH jump may be present in up to 30%
• Intra-atrial re-entry
– ‘Junk’
• gap phenomenon
Block occurs with long S1S2 interval but resumes after a
‘gap’ at shorter S1S2 coupling intervals due to proximal
delay

19. Antero things to look out for
• gap phenomenon
• Block occurs with long S1S2 interval but resumes after a
‘gap’ at shorter S1S2 coupling intervals
• Long S1S2
H1 H2V1 V2

20. Antero things to look out for
• gap phenomenon
• Block occurs with long S1S2 interval but resumes after a
‘gap’ at shorter S1S2 coupling intervals
• Shorter S1S2 = block
H1 V1 H2

21. Antero things to look out for
• gap phenomenon
• Block occurs with long S1S2 interval but resumes after a
‘gap’ at shorter S1S2 coupling intervals
• Shortest S1S2 = conduction resumes
Resumes due to proximal delay
H1 H2V1 V2

22. Pacing to induce tach
• Pace from different
sites (on AP)
• Stim from 2 sites
simultaneously
Will often require
• Isuprel
• Atropine

23. • Short(S2) – long(S3) – short(S4)
• Burst pacing (triggered activity)
• 1x/2x/3x ectopics during SR (FP →SP)
sense sense

24. Diagnostic pacing in
sinus rhythm

25. Differential pacing
• Used to confirm presence of retrogradely
conducting posteroseptal pathway
• Useful if tach irregular or non-sustained
• Determine VA index=VA(apex) – VA(base)
• If VA index = >10ms = accessory pathway
• 100% sensitivity & 100% specificity
– Martinez-Alday etal Circulation. 1994 Mar;89(3):1060-7

26. No AP present: VAI = VA apex – VA base = <10ms

27. AP present: VAI = VA apex – VA base = >10ms
Avoid atrial capture
when pacing basally
Not useful in slowly
conducting APs

28. Parahisian pacing
• Used to confirm presence of retrogradely
conducting septal pathway
• Pace at high output from distal His cath
– Ensure capture of His & RV myocardium
– Lower output to achieve RV myocardial capture only
• Measure stim to A interval
Hirao K, Otomo K, Wang X et al. Para-Hisian pacing. A new method for differentiating retrograde
conduction over an accessory AV pathway from conduction over the AV node. Circulation 1996;94(5):1027–35

29. Parahisian pacing – NO septal accessory pathway
Hirao ,K et al Circulation 1996; 94:1027-1035
His bundle
High output:
Stim->A interval with His & V capture = short VA
High output pacing

30. Low output pacing
Parahisian pacing – NO septal accessory pathway
Hirao ,K et al Circulation 1996; 94:1027-1035
His bundle
Low output:
Stim-A with V only capture = longer VA
No AP; Stim-A increases >50ms with loss of His capture

31. Parahisian pacing–WITH septal accessory pathway
High output pacing
Trace modified from Obeyesekere M et al. Circ Arrhythm Electrophysiol 2011;4:510-514

32. Low output pacing
Parahisian pacing–WITH septal accessory pathway
AP present stim-A change with loss of His capture <40ms
Trace modified from Obeyesekere M et al. Circ Arrhythm Electrophysiol 2011;4:510-514

33. Parahisian pacing
• Avoid atrial capture
– Stim-A <60ms in CSp, stim-A >90ms no A capture
• May get His only capture
– Narrow complex matching QRS in sinus rhythm
– Stim-V interval ≈ HV in sinus rhythm
• No good for slowly conducting Aps
OBEYESEKERE, M. N., LEONG-SIT, P., GULA, L. J. and KLEIN, G. J. (2012), Seven Manifestations of Para-Hisian Pacing.
Journal of Cardiovascular Electrophysiology, 23: 1035–1036.

34. Other reasons
• Myotonic dystrophy
• HV >70ms
• VT stim – Wellens protocol
• Test ATP effectiveness of device
programming
• Evaluate drugs on tachy
• EP study though PPM/ICD/CRT

35. Take home
• Measure all intervals correctly
• Determine AV node conduction properties
• Will often need drugs to induce tach
• Make sure you’re capturing what you think
you’re capturing
• Use differential pacing/para-Hisian pacing
• Be prepared for the unexpected
• Enjoy EP!!

36. Thank you

37. Further reading
• Handbook of Cardiac Electrophysiology: A Practical Guide to Invasive EP Studies and Catheter Ablation
• Francis Murgatroyd, Andrew D. Krahn, Raymond Yee, Allan Skanes, George J. Klein
• Martínez-Alday etal. Identification of concealed posteroseptal Kent pathways by comparison of ventriculoatrial intervals
from apical and posterobasal right ventricular sites. Circulation. 1994 Mar;89(3):1060-7.
• Obeyesekere M etal. Determination of inadvertent atrial capture during para-hisian pacing. Circ Arrhythm Electrophysiol
2010;4:510-514.
• Liew et al. A randomized-controlled trial comparing conventional with minimal catheter approaches for the mapping and
ablation of regular supraventricular tachycardias. Europace (2009) 11, 1057–1064
• Single-catheter approach to radiofrequency current ablation of left-sided accessory pathways in patients with Wolff-
Parkinson-White syndrome
• K H Kuck and M Schlüter Circulation. 1991;84:2366-2375
• Hirao K, Otomo K, Wang X et al. Para-Hisian pacing. A new method for differentiating retrograde conduction over an
accessory AV pathway from conduction over the AV node. Circulation 1996;94(5):1027–35.