Cardiac Electrophysiology basics

1. Dr. Salah Atta, MDDr. Salah Atta, MD
Consultant Electrophysiolgist, SBCCConsultant Electrophysiolgist, SBCC
Professor of CardiologyProfessor of Cardiology,,
Assiut UniversityAssiut University..

2. Electrophysiologic studyElectrophysiologic study
An electrophysiologic study (EPS) entails theAn electrophysiologic study (EPS) entails the
percutaneous introduction and positioning ofpercutaneous introduction and positioning of
multiple special electrode catheters in strategicmultiple special electrode catheters in strategic
sites in the heart in order to:sites in the heart in order to:
1-1- Record, explore intracardiac sequence ofRecord, explore intracardiac sequence of
impulse formation and activation.impulse formation and activation.
2-2- Stimulate and evaluate automaticity,Stimulate and evaluate automaticity,
conduction and refractoriness.conduction and refractoriness.
3-3- Initiate, terminate, diagnose and manageInitiate, terminate, diagnose and manage
arrhythmias.arrhythmias.

3. Indications of EPS:Indications of EPS:
• Evaluation of bradycardias:Evaluation of bradycardias: sinus nodesinus node
functions, level and severity AV blockfunctions, level and severity AV block
• Evaluation of tachycardias:Evaluation of tachycardias: Narrow andNarrow and
Wide QRS complex tachycardia for diagnostic andWide QRS complex tachycardia for diagnostic and
therapeutic purposes.therapeutic purposes.
• Evaluation of unexplained syncope:Evaluation of unexplained syncope:
recurrent unexplained syncope with –ve tilt test orrecurrent unexplained syncope with –ve tilt test or
with structural heart disease and failure of nonwith structural heart disease and failure of non
invasive tests.invasive tests.
Electrophysiologic studyElectrophysiologic study

4. • Evaluation of cardiac arrest survivors:Evaluation of cardiac arrest survivors: with nowith no
myocardial infarction (MI) or 48 hs after MI with no acutemyocardial infarction (MI) or 48 hs after MI with no acute
ischaemia.ischaemia.
• Evaluation of palpitation:Evaluation of palpitation: specially palpitationspecially palpitation
preceding syncope or with rapid pulse but nopreceding syncope or with rapid pulse but no
ECG documentation.ECG documentation.
• Risk stratification in suspectedRisk stratification in suspected
channelopathies, asymptomatic WPW.channelopathies, asymptomatic WPW.
Electrophysiologic studyElectrophysiologic study

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

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

12. Basically, Catheters are placedBasically, Catheters are placed
transvenously in four positions:transvenously in four positions:
• HRA (high right atrium).HRA (high right atrium).
• RV (right ventricle).RV (right ventricle).
• His : across the superior aspect ofHis : across the superior aspect of
the tricuspid ring.the tricuspid ring.
• CS (coronary sinus)CS (coronary sinus)
Where to go ?!

23. Bipolar Recordings
• Cardiac electrograms are generated by
the potential (voltage) differences
recorded at two recording electrodes
during the cardiac cycle. All clinical
electrogram recordings are differential
recordings from one source that is
connected to the anodal (positive) input of
the recording amplifier and a second
source that is connected to the cathodal
(negative) input.

25. 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 such that it has little or no cardiac
signal.
• The pre-cordial ECG leads are unipolar
recordings that use an indifferent
electrode (Wilson central terminal),
created by connecting the arms and left
leg electrodes through high impedance
resistors.

26. • Most clinical recording systems have the option
for selecting a unipolar recording mode that
connects the negative input of the recording
amplifier to the Wilson central terminal.
• We may use an alternative to the Wilson central
terminal to reduce electrical noise. The amplifier
is left in the bipolar configuration, but the
negative input is connected to an intravascular
electrode that is remote from the heart, in the
inferior vena cava.

28. • By convention the exploring electrode that is in
contact with the myocardium is connected to the
positive input of the recording amplifier. In this
configuration a wavefront of depolarization that
is propagating toward the exploring electrode
generates a positive deflection.
• As the wavefront reaches the electrode and
propagates away, the deflection sweeps steeply
negative. Thus an R/S complex is generated. In
a sheet of uniformly conducting tissue, the
maximum negative slope (–dV/dt) of the signal
coincides with the arrival of the depolarization
wavefront directly beneath the electrode.

29. Unipolar Recordings for Identifying the
Site of Earliest Activation
• The morphology of the unipolar recording
indicates the direction of wave front
propagation, provided that the corner
frequency for the high pass filter is kept
low; we usually use 0.5 Hz. When the
exploring electrode is located at the site of
initial activation depolarization produces a
wavefront that spreads away from the
electrode generating a monophasic QS-
complex.

31. Reading An EP tracing:
(Identify the channels and correlate
electrograms)
•Ist correlate the intracardiac electrogram
with surface ECG:
•Electrogram coincident with P wave
represents atrial activity (A),
•Electrogram coincident with QRS wave
represents ventricular activity (V).
•Electograms in between represent the
conduction system: His, Bundle B, AP.

32. • Identify if any pacing stimulus, then from
which channel is it done and in which
manner.
• Can measure the intervals using the
system or the tracing using the ruler and
knowing the recording speed:
• the duration in ms = distance in mm x
1000/speed in mm
• e.g if speed is 100 mm/sec, then 100 mm
=1000 msec and a distance of 20 mm=
20x1000/100=200 msec

36. The key to understanding an EPThe key to understanding an EP
tracing is the simpletracing is the simple
understanding of the activationunderstanding of the activation
sequence of the heart.sequence of the heart.
During EPS the activationDuring EPS the activation
sequence is examined insequence is examined in
several settings.several settings.
How to
know ?!

37. During normal sinus rhythm:During normal sinus rhythm:
Normal sequence of activation inNormal sequence of activation in
the atrium and in the ventricles.the atrium and in the ventricles.
How to
know ?!

38. Impulse propagation

41. Sequence of Activation
• Determination of the sequence of antegrade and
retrograde atrial and ventricular activation during
spontaneous rhythms, atrial pacing, ventricular
pacing, and induced rhythms is essential in
differentiating ventricular tachycardia from
supraventricular tachycardia and in defning the
reentrant circuit in supraventricular tachycardia.

42. Sequence of Antegrade
Activation
• The atrial activation normally begins in the
high right atrium and spreads to the low
right atrium and His bundle, with left atrial
activation recorded from the coronary
sinus catheter occurring signifcantly
later.

46. Sequence of Retrograde
Activation
When ventriculoatrial conduction is present
during ventricular pacing, the earliest retrograde
atrial activity is recorded in the His bundle
electrogram followed by the RA and coronary
sinus recordings.
Abnormal or eccentric sequences of retrograde
atrial activation occur in the presence of AV
accessory pathways. This is discussed in more
detail in subsequent sections dealing with
supraventricular tachycardia and catheter
ablation.

48. Till next time InshaALLAH
Thank you