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PRINCIPLES OF PRINCIPLES OF

ELECTROPHYSIOLOGY ELECTROPHYSIOLOGY

STUDIESSTUDIES

Albert Paul, RCISAlbert Paul, RCIS

Walter Reed Army Medical Walter Reed Army Medical

CenterCenter

Washington, D. C.Washington, D. C.

IntroductionIntroduction

•• Cardiac Electrophysiology Cardiac Electrophysiology

studies are becoming more studies are becoming more

common in the U.S. An common in the U.S. An

understanding of the basic understanding of the basic

principles of these studies is principles of these studies is

crucial for success as a Cardiac crucial for success as a Cardiac

Electrophysiology TechnicianElectrophysiology Technician

OverviewOverview

•• IndicationsIndications

•• AnatomyAnatomy

•• Catheter PlacementCatheter Placement

•• Normal IntervalsNormal Intervals

•• Programmed electrical Programmed electrical

StimulationStimulation

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Diagnostic Indications Diagnostic Indications

for EP Studyfor EP Study

•• Diagnose Sinus Node Diagnose Sinus Node

dysfunctiondysfunction

•• Define etiology of syncopeDefine etiology of syncope

•• Distinguish VT from SVT in wide Distinguish VT from SVT in wide

complex tachycardiascomplex tachycardias

•• Diagnose and define the level of Diagnose and define the level of

AV blockAV block

•• Define mechanism of VT/SVT Define mechanism of VT/SVT

and map originand map origin

Therapeutic Indications Therapeutic Indications

for EP Studyfor EP Study

•• Guide drug therapyGuide drug therapy

•• Select candidates for ICD Select candidates for ICD

implantationimplantation

•• Select candidates for Select candidates for

ablation/surgeryablation/surgery

Interventional Interventional

Indications for EP StudyIndications for EP Study

•• AVN ablation for AAVN ablation for A--fibfib

•• Atrial Atrial tachtach or Atrial flutter or Atrial flutter

ablationablation

•• AVN modification for AVNRTAVN modification for AVNRT

•• Accessory pathway ablation for Accessory pathway ablation for

WPWWPW

•• VT ablationsVT ablations

•• Pulmonary vein isolation for APulmonary vein isolation for A--

fib fib

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AnatomyAnatomy

•• Electrical impulse originates in Electrical impulse originates in the Sinus Nodethe Sinus Node

–– located in the high right atriumlocated in the high right atrium

•• Impulse spreads across the atria Impulse spreads across the atria at 1000mm/sec and is stopped at 1000mm/sec and is stopped at the AV ringat the AV ring

•• Travels through the AV node to Travels through the AV node to the ventriclesthe ventricles

AnatomyAnatomy

•• Conduction is slowed to Conduction is slowed to

200mm/sec in the AV node200mm/sec in the AV node

–– coincides with the PR interval on coincides with the PR interval on

ECGECG

–– allows for greater ventricular fillingallows for greater ventricular filling

•• Impulse travels at 4000mm/sec Impulse travels at 4000mm/sec

as it enters the Hisas it enters the His--Purkinje Purkinje

System and is dispersed to the System and is dispersed to the

ventriclesventricles

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Netter F. Atlas of Human Anatomy. 1989;Plate 208

AV Node PhysiologyAV Node Physiology

•• Electrical properties of the AVN Electrical properties of the AVN

cause slowing of impulsecause slowing of impulse

–– Allows for maximum ventricular Allows for maximum ventricular

fillingfilling

•• AVN tissue has AVN tissue has decremental decremental

conduction propertiesconduction properties

–– Conduction is slowed as HR Conduction is slowed as HR

increasesincreases

•• Occasionally individuals have Occasionally individuals have

two paths of conduction through two paths of conduction through

the AVNthe AVN

•• Fast and slow pathwaysFast and slow pathways

–– Fast pathway has fast conduction Fast pathway has fast conduction

and long refractorinessand long refractoriness

–– Slow pathway has slow conduction Slow pathway has slow conduction

and short refractoriness and short refractoriness

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Catheter PlacementCatheter Placement

•• HRA catheter placed on high lateral HRA catheter placed on high lateral

wall near SVC junctionwall near SVC junction

•• His catheter is placed across His catheter is placed across

posterior TV posterior TV

•• CS CS ostiumostium is located posterior and is located posterior and

inferior to the tricuspid valveinferior to the tricuspid valve

•• RV catheter is placed in the RV apexRV catheter is placed in the RV apex

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CS CATHETER ANTERIOR VIEW

CS CATHETER LATERAL VIEW

RVCATHETER ANTERIOR VIEW

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RV CATHETER LATERAL VIEW

HRA CATHETER ANTERIOR VIEW

HRA CATHETER LATERAL VIEW

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HIS CATHETER ANTERIOR VIEW

HIS CATHETER LATERAL VIEW

Normal IntervalsNormal Intervals

•• Intervals are measured from Intervals are measured from

onset to onsetonset to onset

•• QRS 80QRS 80--100 ms100 ms

•• PP--R 120R 120--200 ms200 ms

•• QQ--T 250T 250--400 ms400 ms

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Normal IntervalsNormal Intervals

•• AA--H 50H 50--130 ms (may vary 130 ms (may vary

throughout study)throughout study)

•• HH--V 35V 35--55 ms (remains constant 55 ms (remains constant

throughout study)throughout study)

–– measured from onset of His measured from onset of His

potential to earliest surface Rpotential to earliest surface R--

wave wave

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Programmed Programmed

Electrical StimulationElectrical Stimulation

•• Sinus Node Recovery TimeSinus Node Recovery Time

•• Rapid Atrial PacingRapid Atrial Pacing

•• Rapid Ventricular PacingRapid Ventricular Pacing

•• Atrial ExtraAtrial Extra--stimulusstimulus

•• Ventricular Extra StimulusVentricular Extra Stimulus

Sinus Node Recovery Sinus Node Recovery

TimeTime

•• Atrial Atrial pacing for at least 30 pacing for at least 30

secondsseconds

•• Gradually reduce PCL until Gradually reduce PCL until

approximately 300msapproximately 300ms

Sinus Node Recovery Sinus Node Recovery

TimeTime

•• SNRT measured from last paced SNRT measured from last paced

beat to first intrinsic beatbeat to first intrinsic beat

•• > 1500 ms considered abnormal> 1500 ms considered abnormal

•• CSNRT= SNRTCSNRT= SNRT--BCLBCL

•• CSNRT > 525 ms considered CSNRT > 525 ms considered

abnormal abnormal

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Rapid Atrial PacingRapid Atrial Pacing

•• Assesses antegrade conductionAssesses antegrade conduction

•• Begin pacing at 600 ms Begin pacing at 600 ms

•• Decrement by 10 ms every 2 Decrement by 10 ms every 2

beats beats

•• WenckebachWenckebach Cycle Length when Cycle Length when

1:1 conduction is lost 1:1 conduction is lost

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Rapid Ventricular Rapid Ventricular

PacingPacing

•• Assesses retrograde conductionAssesses retrograde conduction

•• Begin pacing at 600 ms Begin pacing at 600 ms

•• Decrement by 10 ms every 2 Decrement by 10 ms every 2

beatsbeats

•• 1:1 conduction is lost 1:1 conduction is lost

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Atrial ExtraAtrial Extra--StimulusStimulus

•• Used to assess AV node Used to assess AV node

effective refractory periodeffective refractory period

•• Determines dual AV node Determines dual AV node

physiologyphysiology

•• Drive train of 8 beats (S1) Drive train of 8 beats (S1)

followed by PAC (S2)followed by PAC (S2)

•• S2 is decremented by 10S2 is decremented by 10--20 ms20 ms

Atrial ExtraAtrial Extra--StimulusStimulus

•• Note is made when ANote is made when A--H interval H interval

is increased by 50 ms after 10 is increased by 50 ms after 10

ms decrease in S1ms decrease in S1--S2 intervalS2 interval

•• AVNERP is longest S1AVNERP is longest S1--S2 S2

interval that does not conduct to interval that does not conduct to

the ventriclesthe ventricles

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Ventricular ExtraVentricular Extra--

StimulusStimulus

•• Used to assess retrograde AV Used to assess retrograde AV

node effective refractory periodnode effective refractory period

•• Also used to induce VT Also used to induce VT

•• Drive train of 8 beats (S1) Drive train of 8 beats (S1)

followed by PAC (S2)followed by PAC (S2)

•• S2 is decremented by 10S2 is decremented by 10--20 ms20 ms

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ConclusionConclusion

•• Watch V1 and HRAWatch V1 and HRA

•• Understand anatomyUnderstand anatomy

•• Understand AV node physiologyUnderstand AV node physiology

Questions????Questions????