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.