introduction to electrophysiology - pennsylvania · introduction to electrophysiology wm. w....

Introduction to

Electrophysiology

Wm. W. Barrington, MD, FACC

University of Pittsburgh Medical

Center

Objectives

• Indications for EP Study

• How do we do the study

• Normal recordings

• Abnormal Recordings

• Limitations of EP Study

Indications for EP Study

• Characterization of an arrhythmia with the intent of performing ablation therapy.

• Characterization of the conduction system to determine the need for permanent pacing.

• Stratify the patient’s risk of developing a symptomatic or life threatening arrhythmia.

• Characterization of the effectiveness of therapy.

"Guidelines for Clinical Intracardiac Electrophysiological and Catheter Ablation

Procedures“ Circulation. 1995;92:673-691.)

Ablation is a large part of the current indications

for EP Study

Am J Cardiol (2009)104:671-77

The authors examined published results from

1990 to 2007 that were cited in Medline or

EMBASE:

• 18 Primary Studies of Atrial Flutter ablation

• 39 Primary Studies of SVT ablation

Study examined reentrant SVT’s

Am J Cardiol (2009)104:671-77

Atrial Flutter

Ablation Line

Ablation site

AV Node Reentry

Accessory Pathways

Ablation

Site

Meta-Analysis of Ablation of Atrial Flutter and SVT’s

Atrial Flutter

Single procedure success

Am J Cardiol (2009)104:671-77

Accessory Pathways

AV Node Reentry

91.7% 90.9% 94.3%

Multi-procedure success 97.0% 93.3% 96.0%

Repeat ablation procedure 8.0% 8.0% 5.6%

Procedure related mortality 0.0% 0.1% 0.0%

Hematoma 0.0% 0.3% 0.3%

Cardiac Tamponade 0.0% 0.4 % 0.1%

Need for Pacemaker 0.2% 0.3 % 0.7%

Complications

1. Am J Cardiol (2009)104:671-77

• “studies of RFA for treatment of patients with atrial flutter

and SVT report high efficacy rates and low rates of

complications1.”

• “the 2003 consensus guidelines for SVT management2

recommend radiofrequency ablation as a class I

intervention in all cases except:

• First episode of well tolerated atrial flutter

• SVT patients who do not desire ablation or

• Asymptomatic patients with WPW.”

Meta-Analysis of Ablation of Atrial Flutter and SVT’s

2. J Am Coll Card (2003) also available at www.acc.org

The authors concluded:

Furthermore:

• Electrophysiologist will place 1, 2, 3 or more catheters into the heart.

• Access will be from femoral vein, antecubital vein, subclavian vein or internal jugular vein.

• Catheters generally at least “quadrapolar” (4 electrodes) in configuration.

• Pacing and recording usually done in “bipolar” configuration (one electrode + and the other -)

How to do an EP Study

High Right Atrial

Location

HRA

His Bundle

Location

His

Right Ventricular Apical

Location

RVA


Typical Catheter

Locations

• Intracardiac recordings are “filtered” to

allow visualization of signals

• Band pass filter from 30 or 40 Hz to

400 or 500 Hz

• Gain settings to optimize viewing

• Clipping as needed

• Screen display shows surface ECG and

appropriate intracardiac channels



P

QRS

A

H

V

• Sinus cycle length (SCL or AA

interval)

• PR interval (120 – 200 ms)

• QRS duration (< 100 ms)

• QT interval (QTc < 440)

• AH interval (60 – 125 ms)

• HV interval (35 – 55 ms)


Baseline Measurements

SCL (AA) = 830 ms

PR = 170 ms

QRS = 80 ms

QT = 380 ms

AH = 90 ms HV = 40 ms

AA = 880 ms

PR = 140 ms

QRS = 140 ms

AH = 100 ms HV = -30 ms

Ventricular Pre-excitation

(Wolff- Parkinson-White)

12 Lead ECG of patient with short HV interval

• Pace HRA at fixed rate for at least 30

seconds.

• Measure interval from last paced atrial

signal to first sinus atrial signal – this is

the sinus node recovery time (SNRT).

• Generally this is repeated for a variety of

pacing cycle lengths.


Atrial pacing – examining SA nodal function or

Sinus Node Recovery Time (SNRT)

Last “paced” A First “sinus” A

SNRT = 1320 ms

Paced at 600 ms (100 bpm)

for > 30 sec

Sinus Node Recovery Times

(SNRT)

• Normal is < 1.3 x sinus cycle length

(<1600 ms)

• Can “correct” by several methods:

• CSNRT = SNRT – SCL

( Normal <525 ms)

• Ratio of SNRT/SCL (Normal < 1.5)

• Limitation of SNRT is that while it is very

specific – it is not very sensitive!


• Pace the HRA at gradually increasing

rates.

• Look for gradual prolongation in the AH

interval (“decremental” conduction).

• Determine the AV nodal wenkebach

cycle length.


Incremental atrial pacing – examining AV nodal

function

PCL = 600 ms

AH = 160 ms

PCL = 500 ms

AH = 195 ms

Normal Decremental Function

AH

Inte

rval

S1 Interval

Normal Decremental

AV Nodal Conduction

Faster Rate

AV Nodal Function Curve

A A H

V

A

PCL = 410 ms

Wenkebach CL = 410 ms

AH = 220 ms

Wenkebach Block – Mobitz type I (above His bundle)

No V

No H

Atrial PCL = 500 ms or 120 bpm

A H V A H

Mobitz type II block

(below the bundle of His)

A H V A H V A H V A H A H A H

• Pace the atrium at a fixed CL (typically

600, 500, 400 ms) for 8 beats then

introduce 1,2 or 3 extrastimuli

• Useful in determining:

• Refractory periods

• Change in conduction

• Dual AV nodal physiology

• Initiation of an arrhythmia


Atrial extra stimulus techniques

Drive Train of 8 beats at 500 ms (S1)

and one premature S2 310 ms after S1

S1 S2 310 ms

A H V

Drive Train of 8 beats at 500 ms (S1)

and one premature S2 300 ms after S1

AH=160 ms

S1 S2

300 ms

A H V

AH=280 ms

AH

In

terv

al

S1S2 Interval

Dual AV Nodal

Physiology

• AH Interval “jumps” suggest

conduction moved from one

conduction pathway to another.

• A > 50 msec jump in AH

interval with a 10 msec

decrease in S1S2 interval is

called

More Premature

AV Nodal Function Curve

Right Atrial Anatomy

Superior Input Inferior

Input

Left Atrial

Input

Atrial depolarization

can reach the AV

node by several

“paths.”

When activation

changes from the

“fast” conducting

Superior input to

the “slower” Inferior

input – we see an

AH interval jump.

S1 S2

240 ms

A H V

AH=250 ms SVT at 200 bpm

AV Node Reentry

S1 S2

310 ms

A H V

QRS = 120 ms

PR = 210 ms

HV = 45 ms

Functional LBBB

• Pace the RVA at gradually increasing

rates.

• Look for gradual prolongation in the VA

interval (decremental conduction)

• Concentric activation (via AV node)

• Eccentric activation (via AP).

• Determine the VA wenkebach cycle length.


Incremental Ventricular pacing – examining

retrograde AV nodal function

PCL = 500 ms

His A is earliest

Concentric retrograde conduction

V A

Concentric (AV nodal) retrograde Activation

V A

Earliest A

In His

V A

Earliest A

In CS

(left side)

Eccentric (AP) retrograde Activation

S1 = 600 ms

VA = 80 ms VA = 210 ms

Retrograde “Jump”

V V A V A A

• Pace the ventricle at a fixed CL (typically

600, 500, 400 ms) for 8 beats then

introduce 1,2 or 3 extrastimuli

• Useful in determining:

• Refractory periods

• Change in conduction

• Dual retrograde AV nodal physiology

• Initiation of an arrhythmia


Ventricular extra stimulus techniques

S1 = 600 ms S1S2 = 260 ms

Single Ventricular extra stimuli

No retrograde conduction No repetitive

response

S1 = 600 ms S1S2 = 240 ms

ERP of the RVA


No ventricular

response

S1= 400 ms S1S2 = 240 ms

Single induced

beat


S1 = 400 ms S1S2 = 250 ms

S2S3 = 200 ms

Multiple Ventricular extra stimuli

No repetitive

response

Multiple Ventricular extra stimuli

400/260/230 Sustained Monomorphic VT

Induced Ventricular Tachycardia

Sustained Monomorphic VT Rate = 220 bpm

• EP Study has not been widely used in

patients with nonischemic

cardiomyopathy

• Sensitivity and specificity is likely

decreased

Limitations of the EP Study

• EP study may not be able to “reproduce” a

non-reentrant arrhythmia

• The EP study tries to cause “block” in

one limb while exciting the other limb to

induce the arrhythmia

• Pharmacologic maneuvers may help

induce non reentrant arrhythmias

Limitations of the EP Study

• Electro-anatomic mapping (CARTO)

• Catheter mapping

• Pacing maneuvers

Allow us to localize the arrhythmia circuit to facilitate diagnosis and treatment with ablation.


These techniques along with

Ablation is a large part of the current indications

for EP Study

so lets look at a few examples

Baseline ECG for 17 year old with palpitations

AP Potential

Pacing from HRA

Wide QRS

(130 ms)

Negative HV

His “cloud”

Ablation

Location

4 cm

Successful RF Ablation

Wide QRS

(130 ms)

AV = 50 ms AV = 180 ms

QRS = 80 ms

Loss of antegrade

AP function

Post Ablation ECG

ECG of SVT in 67 year old

I

aVF

V1

V6

hRA

His p

His m

His d

Abl d

Abl p

Cs 4

Cs 3

Cs 2

Cs d

RVa

Stim

Intracardiac in SVT

Eccentric Activation

Concentric Activation

Ventricular Pacing

Why are these

different?

I

aVF

V1

V6

hRA

His p

His m

His d

Abl d

Abl p

Cs 4

Cs 3

Cs 2

Cs d

RVa

Stim

Eccentric

Activation

In SVT

Concentric

Activation

RV pacing

Termination of SVT with RF

I

aVF

V1

V6

hRA

His p

His m

His d

Abl d

Abl p

Cs 4

Cs 3

Cs 2

Cs d

RVa

Stim

Termination with

Block in AP

SVT

Questions

or

Comments?

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