how to perform an ep study properly & diagnostic pacing during sinus rhythm
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How to perform an EP study properly & diagnostic pacing
during sinus rhythm
Troy Watts Chief Cardiac Physiologist
St Bartholomew’s Hospital London Troy.watts@bartshealth.nhs.uk
• 1 -catheters • 2 -baseline measurements • 3 -evaluate conduction
– EP properties of A, V, AV node & AP – tachycardia induction – diagnostic pacing during sinus rhythm
• 4 -special circumstances for EP
Catheters
• No of caths – Full arsenal vs. minimal approach
• His placement – atrial signal on same bipole as His
• CS position 9/10 at ostium initially
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
Image of baseline measurements
Measuring intervals
HV – Beginning of His to earliest V onset (ECG or EGM)
AH – Sharp A on His to beginning of His deflection
PA - P wave onset/earliest AEGM to sharp AEGM deflection on His (not THIS one it’s not local signal)
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
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
Retro how – Synchronised fixed pacing of 8 beats (S1) at 600ms &
400ms with extrastimulus (S2)
1 2 3 4 5 6 7 8
600
• 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
• Incremental ventricular pacing – Gradually increase the rate of V pacing until VA
block occurs = VA W’Bach cycle length
360ms 350ms 360ms
VA
Retro things to look out for • VA ‘jump’ due to retrograde RBBB
A VH A V H
• Repetitive Ventricular Response (RVR)
A H V V’
V’
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
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
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’
Antero things to look out for 2
• gap phenomenon • Block occurs with long S1S2 interval but resumes after a
‘gap’ at shorter S1S2 coupling intervals.
• Commonly occurs in AV node
Pacing to induce tach • Pace from different
sites (on AP) • Stim from 2 sites
simultaneously
AV node
AP
• Short(S2) – long(S3) – short(S4) • Burst pacing (triggered activity) • Single/double/triple ectopics during sinus
rhythm (FP SP) sense sense
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.
No AP present: VAI = VA apex – VA base = <10ms
AP present: VAI = VA apex – VA base = >10ms
• Avoid atrial capture when pacing basally
• Not useful in slowly conducting APs
Parahisian pacing
• Used to confirm presence of retrogradely conducting anteroseptal 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.
Parahisian pacing – no septal accessory pathway No AP; Stim-A increases >50ms with loss of His capture
Hirao ,K et al Circulation 1996; 94:1027-1035
Stim-A with His & V capture
Stim-A with V only capture
Parahisian pacing – septal AP present AP present stim-A change with loss of His capture <40ms
Obeyesekere M et al. Circ Arrhythm Electrophysiol 2011;4:510-514
Stim-A with V only capture
Stim-A with His & V capture
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.
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
Be aware of previous procedures
• Know where previous ablation has occurred or surgical scars are present
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!!
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.
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