0. EP Studies in Bradyarrhythmias
BIOTRONIK Training & Education Electrophysiology
EP Studies in Bradyarrhythmias

1. EP Studies in Bradyarrhythmias
Sinus node functionality
AV node functionality

2. Tests of Sinus Node Function
Sinus Node Recovery Time = SNRT
Test of intrinsic function
Atrial overdrive pacing (30 sec)
Time from last paced to first spontaneous complex after cessation of pacing in HRA
Varies with sinus rate, correction: CSNRT = SNRT – sinus cycle length

3. Sinus Node Recovery Time
HRA
HRA = High Right Atrium
SCL = Sinus Cycle Length
SNRT = Sinus Node Recovery Time
Murgatroyd, Krahn: Handbook of Cardiac Electrophysiology 2002

4. Tests of Sinus Node Function
Repeated measurements at different cycle length
Longest values to be used
Normal: max SNRT <1500 ms max CSNRT <550 ms

5. Sinus Node Recovery Time
Prior to start of pacing
End of 30-s pacing train
CL = 930, S1S1 = 700, SNRT = 1175, CSNRT = 245 ms
Murgatroyd, Krahn: Handbook of Cardiac Electrophysiology 2002

6. EP Studies in Bradyarrhythmias
Sinus node functionality
AV node functionality

7. Evaluation of AV Conduction with EP
First Degree AV Block
ECG H
HBE A V
HV interval prolonged = distal block

8. Evaluation of AV Conduction with EP
First Degree AV Block V A H
HBE
AH interval prolonged = block in AV node

9. Evaluation of AV Conduction with EP
Second Degree AV Block Type Wenckebach
ECG V H H
HBE V
180
210 A A A
Gradual prolongation of AH interval before blocked beat, no exit from the AV node

10. Evaluation of AV Conduction with EP
Second Degree AV Block Type Mobitz ? A V H
HBE
Dropped beat after H spike
No prior prolongation in AH or HV intervals
Subnodal block

11. Evaluation of AV Conduction with EP
Third-Degree AV Block V H A
HBE V H A
HBE
Above: H prior to escape V, block in AV node
Below: H follows each A, distal block

12. Atrial Extrastimulus Testing
Aim - Investigation of the dynamic properties of the conduction over the AV node and the His-Purkinje system - Refractory periods of AV node and right atrium
Method - Drive train of 5-8 atrial paces with fixed cycle length followed by an atrial extrastimulus - Progressive decrease of coupling interval until atrial non capture
Observations - Gross abnormalities of intra-atrial conduction - Presence of dual AV node physiology - Abnormal conduction structures (accessory pathways) - Arrhythmia induction

13. Antegrade Conduction over AV Node
Atrial Extrastimuli
Long coupling intervals - fairly constant conduction
Shorter coupling intervals - increasing AH delay, HV constant
Progressively shorter - AV nodal block, atrial refractoriness

14. Atrial Extrastimuli with Long Coupling
A1H1 ≈ A2H2
Murgatroyd, Krahn: Handbook of Cardiac Electrophysiology 2002

15. Atrial Extrastimuli with Long Coupling
S1S1 = 500 ms, S1S2 = 400 ms
S1A1 ≈ S2A2 ≈ 55 ms, H1V1 ≈ H2V2 ≈ 50 ms
A1H1 = 78 ms, A2H2 = 97 ms
Murgatroyd, Krahn: Handbook of Cardiac Electrophysiology 2002

16. Atrial Extrastimuli with Shorter Coupling
A1H1 < A2H2
Murgatroyd, Krahn: Handbook of Cardiac Electrophysiology 2002

17. Atrial Extrastimuli with Shorter Coupling
S1S1 = 500 ms, S1S2 = 300 ms
H1V1 ≈ H2V2 ≈ 50 ms
Atrial escape: inverted P in aVF, earliest in CS*
A1H1 = 78 ms, A2H2 = 140 ms
Murgatroyd, Krahn: Handbook of Cardiac Electrophysiology 2002

18. Atrial Extrastimuli Very Short Coupling
AV nodal refractoriness
Murgatroyd, Krahn: Handbook of Cardiac Electrophysiology 2002

19. Atrial Extrastimuli Very Short Coupling
S1S1 = 500 ms, S1S2 = 280 ms
A1A2 = 280 ms, no His after A2
AV nodal effective refractory period (AVN-ERP): 280 ms
Murgatroyd, Krahn: Handbook of Cardiac Electrophysiology 2002

20. AV Nodal Refractory Periods
Effective Refractory Period (AVN-ERP) - longest A1A2 interval on HBE that fails to be conducted to the His bundle - normal values: 250 – 400 ms
Functional Refractory Period (AVN-FRP) - shortest H1H2 interval that can be elicited by any A1A2 interval - normal: 330 – 550 ms

21. Incremental Atrial Pacing
Method - Pacing at constant cycle length slightly shorter than spontaneous rhythm - Pacing cycle length decrease in small steps - Analysis of rhythm for several seconds at each step (steady-state)
Observations - Cycle length at which 1:1 conduction over the AV node ceases ( Wenckebach cycle length) - Sudden increase in the AH interval ( dual AV nodal physiology) - Ventricular pre-excitation ( accessory pathway) - Arrhythmia induction

22. Incremental Atrial Pacing
1:1 Conduction
Wenckebach
WCL = Wenckebach Cycle Length
Murgatroyd, Krahn: Handbook of Cardiac Electrophysiology 2002

23. Incremental Atrial Pacing
Murgatroyd, Krahn: Handbook of Cardiac Electrophysiology 2002

24. EP Studies in Bradyarrhythmias
BIOTRONIK Training & Education Electrophysiology
EP Studies in Bradyarrhythmias