Basics of Electrophysiologic study, part 1 (2020)

ppt at the scientific meeting of the EP club of the Cardiology department of Assiut University

1. Part I Dr. Salah Atta, MD Professor of Cardiology, Assiut University. Electrophysiologic Study Basics

2. AGENDA What is Electrophysiologic Study ? (EPS) Why to do it? What is needed ? How to read an EP tracing How to perform the EP study and its basic components Role of EPS in decision making and management of Cardiac Arrhythmias ----(Brady Arrhythmias)

3. What is EPS ?! A cardiac electrophysiologic study (EPS) is an invasive cardiac procedure which involves the percutaneous introduction and positioning of electrode catheters under fluoroscopic guidance in certain locations inside the heart, in good contact with the cardiac tissues, so that: 1- each catheter can show the real-time local electrical activity (intracardiac electrogram) on the display screen, as if we are doing intracardiac ECG. 2- stimulate and evaluate automaticity, conduction and also induction, termination so diagnose the mechanism and moreover manage arrhythmias by ablation.

4. Aims of an EPS procedure: A) Diagnostic purposes : Evaluation of bradycardias: sinus node functions, level and severity AV block (needs PPM or not) Evaluation of unexplained syncope: recurrent unexplained syncope with –ve non invasive monitoring tests, -ve tilt test specially in the prsence of structural heart disease. Why to do?!

5. Evaluation of cardiac arrest survivors: with no myocardial infarction (MI) or 48 hs after MI or with no reversible aetiology. Evaluation of palpitation with rapid pulse but no ECG documentation. Risk stratification for sudden cardiac death as in heritable cardiomyopathies, suspected channelopathies, asymptomatic WPW, etc. Electrophysiologic study

6. B) Therapeutic (Ablation) Evaluation of tachycardias: Narrow and Wide QRS complex tachycardia for diagnostic and therapeutic purposes. Ablation catheter is placed at area of source of arrhythmia, and energy is applied to destroy tissue. It can be done by Radiofrequency (RF) or Cryo or other forms of energy as Microwave.. Ablative therapy is beneficial in SVT, WPW, atrial tachycardia, A-flutter, AF and some VTs. Success rate is above 95% in SVTs, but less in AF and VTs… Complication rate is around 1%, including vascular or cardiac injuries as heart block in rare cases…

7. Requirements: Cath Lab. Electrode Catheters. Stimulator. Displaying and recording system. Junction Box. Well trained and knowledged Personnel. What is needed ?!

8. CATH LAB with EP system

9. Electrode Catheters

10. Preprocedure check list: written consent, stop antiarrhythmics 5 half-lives before, stop warfarin 3-5 days before and check INR on the day or DOACs for 36 hs , insure patient fasting, IV access, blood pressure monitoring, emergency equipment available, check drugs available ( isoprenaline, atropine, adenosine, sedatives and analgesics). What to do ?!

11. How do we reach there

12. Basically, Catheters are placed transvenously mainly via femoral veins in four positions: HRA (high right atrium). RV (right ventricle). His : across the superior aspect of the tricuspid ring. CS (coronary sinus) Where to land ?!

13. Bipolar Recordings The recorded bipolar cardiac electrograms: are generated by the potential (voltage) differences between two recording electrodes during the cardiac cycle. So each channel represents an area between the two electrodes as one electrode that is connected to the anodal (positive) input of the recording amplifier and the second source that is connected to the cathodal (negative) input.

14. Unipolar Recordings Unipolar recordings are obtained by positioning the exploring electrode in the heart and the second electrode (referred to as an indifferent electrode) distant (theoretically an infinite distance) from the heart so the signal represents the very local signal at the tip electrode. The morphology of the unipolar recording indicates the direction of wave front propagation

15. Unipolar Recordings for Identifying the Site of Earliest Activation in Focal arrhythmias When the exploring electrode is located at the site of initial activation, the depolarization produces a wave front that spreads away from the electrode generating a monophasic QS-complex.

16. Basics of Reading An EP tracing (I) Ist Identify the channels: ECG Leads HRA: High right atrium HBE: His bundle electrogram HBE P: “ “ “ proximal HDE D: “ “ “ distal CS: Coronary sinus (p: proximal, D, distal) and the numbers between RVA: right ventricular apex RVO: right ventricular outflow tract Abl. D: ablation distal, and p. proximal

17. Reading An EP tracing

18. Reading An EP tracing (II) Learn how to measure the basic intervals : using the system or using the ruler and the tracing and knowing the recording speed: the duration in ms = distance in mm x1000/speed in mm/sec e.g if speed is 100 mm/sec and a distance of 20 mm then the duration is = 20 x1000/100=200 msec.

19. How to know ?! Measurement of basic intervals: PA interval: 20-40ms, from the onset of the earliest P wave on the surface ECG to the earliest rapid deflection of the atrial electrogram from the His Catheter, measures intra-atrial conduction. AH interval: 50-140ms, represents conduction through the AV node to the His bundle, measured in the His Catheter, HV interval: 30-55 ms, represents conduction from proximal His bundle to the ventricular myocardium. Cycle Length (Heart rate): from peak to peak to measure the R-R interval or the V-V interval (CL < 600 ms  Tachycardia) VA interval during any tachycardia: from V to A in the His channel as an essential measurement in the diagnostic elements…

20. Measurement of basic intervals:

21. Reading An EP tracing (II) - 2nd Identify the rhythm and decide whether in tachycardia or not : If no tachycardia i.e CL < 500-600): Identify relation between the atrial electrograms and ventricular electrogram to identify the rhythm : If 1:1 with A separated from the V , and the normal atrial activation with earliest A is in HRA and spreads to the low right atrium and His bundle, with left atrial activation recorded from the CS catheter occurring later and from proximal to distal CS this is sinus rhythm . if confluent A and V in all channels , this is junctional rhythm (slow or accelerated)…

22. Identify the sequence of activation in the tracing: Normal sequence of activation in the atrium and in the ventricles or Abnormal...!. Reading An EP tracing

23. Impulse propagation

24. Assess Sequence of Antegrade Activation The normal ventricular activation sequence conducting via the AV node-His; begins in HBE followed by RVA and CS from proximal to distal ( concenteric ). If it starts anywhere away from this, then it is conducting through an Accessory pathway (AP) and called eccentric activation.

25. Reading An EP tracing during pacing (III) Identify if any pacing stimulus, then from which channel: Atrial or CS or Ventricular or ablation catheter . Identify the whether it is capturing the atrium or the ventricle or not capturing….. from the activity following the stimulus.

26. Sequence of Retrograde Activation When ventriculo -atrial conduction is present during ventricular pacing, the normal earliest retrograde atrial activity should be recorded in the His bundle electrogram (concentric) followed by the RA and coronary sinus recordings. Abnormal or eccentric sequences of retrograde atrial activation occur in the presence of AV accessory pathways.

27. -during ventricular pacing, When ventriculo -atrial conduction is present the normal earliest retrograde atrial activity is recorded in the His bundle electrogram (concentric) followed by the RA and coronary sinus recordings. Assess Sequence of Retrograde Activation

28. Normal sequence of retrograde activation earliest at the His bundle electrogram-(1st), otherwise accessory pathway exists e.g if earliest in the CS (2nd,3rd).

29. Eccenteric Retrograde Conduction

30. Positions of Accessory pathways According to earliest antegrade V (during SR or atrial pacing) or retrograde earliest A activation site during VP or tachycardia APs are termed as follows: HRA: right lateral Ap PCS (CS 9,10): right posteroseptal AP CS 7,8: Left posteroseptal AP, CS 5,6-3,4: Lt posterior and posterolateral AP, CSD (CS1,2) : Lt Lateral AP If earliest at His channel as normal but with confluent A-V and QRS showing delta wave: then this is right anteroseptal.

31. IF CL < 600 msthen pt has tachycardia with , then: identify whether A-V relationship is 1:1, if yes then identify the timing relation to each other: If V-A confluent in all channels and V-A <70 ms in His channel AV nodal re-entrant tachycardia (AVNRT)…. Reading An EP tracing in Tachycardia (IV)

32. IF tachycardia with CL < 600 ms , then: If A-V relationship is 1:1, and A and V are not superimposed: if A is followed shortly by His then by V, with longer V-A and earliest in HRA : Sinus tachycardia, But if A is earliest in other channel then this is PAT with1:1 conduction. If each V is followed shortly by A then long A-V in each cycle i.e V-A---V-A---V: this is Atrio- venricular re-entrant tachycardia (AVRT)….(earliest retrograde A defines the site of AP.) . Reading An EP tracing in Tachycardia

33. IF the A-V relation is not 1:1 i.e one of them is leading or dissociated: if atrial is leading  atrial arrhythmia (regular: A flutter, PAT with regular block, irregular : Atrial fibrillation … if Ventricular activity is leading then  Ventricular tachycardia … Reading An EP tracing in Tachycardia

34. How to know ?! EP Assessment by pacing: Pacing concept: If an electronic stimulator applies electrical pulses „Stimulus“ to the ventricular or atrial electrode tissue interface, the electrical field radiates from the electrode, triggers rapid depolarization of few cells which spreads by cell-to-cell conduction throughout the entire myocardial mass initiating a cardiac impulse.

35. Capture can be observed as a depolarization observed immediately after the stimulus artifact.

36. Pacing methods in EPS: A pulse duration of 1 or 2 milliseconds at double the pacing threshold is most commonly used. Both atrial and ventricular pacing can be done in any of the following ways: Pacing with extrastimulation Fixed rate pacing (at a fixed drive cycle). Incremental pacing : with progressive shortening of the pacing cycle length.

37. The major purposes of programmed electrical stimulation are to 1- characterize the electrophysiologic properties of cardiac tissues (Refractory periods) 2- assess sequence of activation both antegrade and retrograde to rule out AP. 3- induce and analyze the mechanism of arrhythmias and to terminate tachyarrhythmias. How can pacing help us during EPS ?!

38. Atrial or Ventricular pacing with extrastimulation: Pacing with a train of 8 beats at a fixed cycle length followed by an extrastimulus at a shorter cycle length which is shortened each time.

39. Determination of Refractory Periods The refractoriness of cardiac tissue is defined by the response of the tissue to the introduction of premature stimuli. For most routine EPS, the ERP is defined as the longest coupling interval between the basic drive and the premature stimulus that fails to stimulate or to propagate through the tissue. Normal values for AV nodal, atrial, and ventricular refractory periods have been established ).

40. Atrial extrastimulus testing Atrial extrastimulus testing can determine the properties of the AV node ( antegrade) and of the atrium . As the S2 atrial extrastimulus cycle length decreases, the conduction over the AV node (represented by the A-H interval) progressively increases, known as the decremental conduction over the AV node

41. Refractory periods By further decreasing the S2 interval, the ERP of the AV node will be achieved when the atrium A2 is no longer followed by the His or the V, this indicated RP of the AVN. Here it is important to notice whether block is supra-His or infra-His.

42. Finally, the S2 spike will no longer capture the atrium (atrial ERP, also called atrial refractoriness). Doing the same with ventricular pacing till S2 is not capturing determines the VRP as in this tracing. Refractory Periods

43. Pacing with extra-stimulus may end by refractory period determination as shown above or by induction of tachycardia as shown here

44. Incremental Atrial pacing: means continuos pacing the atrium with progressive shortening of the pacing cycle length, shows: - the wenckebach point and excludes infra His block, -may show pre-excitation, may induce a tachycardia . Incremental Atrial pacing:

45. Normal Antegrade decremental conduction with gradual prolongation of the AH interval, till the wenckebach point.

46. Sinus node function tests 1-Sinus node recovery time (by fixed rate atrial pacing) : The HRA catheter is paced faster than the sinus rate by at least 30 ms at a fixed rate without ES for 30-60 seconds, then abruptly stopped. Sinus node recovery time (SNRT) is the interval between the last paced beat and the first returning sinus beat. Normal range < 1500ms. Corrected SNRT=SNRT-sinus cycle length which is normaly less than 525 ms.

47. 2-Sinoatrial conduction time: How to calculate: A single paced atrial stimulus is delivered just before the next spontaneous sinus cycle, thereby resetting the sinus node. SACT is calculated from the interval between the paced stimulus to the next sinus beat (return interval) and equals half the difference between the spontaneous cycle length and the return cycle length. Normal range 50-125 ms. Prolonged SACT indicates susceptibility to exit block.

48. Burst pacing Burst pacing for tachycardia induction: Stimuli are delivered at a constant fast rate for a relatively short duration but at successively faster rates with each burst. Bursts for termination of tachycardia: This is similar to the technique used for induction. The initial pacing rate is faster than that of the tachycardia.

49. Thank you