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An Electrophysiologic Overview

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Title: An Electrophysiologic Overview


1
Ventricular Tachyarrhythmias
  • An Electrophysiologic Overview

2
Module Objectives Ventricular Tachyarrhythmias
After completion of this module, the participant
should be able to
  • Identify the mechanisms for ventricular
    tachycardias
  • Differentiate types of ventricular tachycardias
    using ECG and intracardiac electrogram recordings
  • Discuss treatment options for ventricular
    tachycardias

3
Module Outline Ventricular Tachyarrhythmias
  • Description
  • Characteristics
  • Mechanisms
  • Sustained vs. nonsustained
  • Premature ventricular contractions

4
Module Outline Ventricular Tachyarrhythmias
  • Classification
  • Monomorphic
  • Idiopathic
  • Description
  • ECG recognition
  • Treatment ablation
  • Bundle branch
  • Description
  • ECG recognition
  • Treatment ablation

5
Module Outline Ventricular Tachyarrhythmias
  • Classifications - continued
  • Ventricular flutter
  • ECG recognition
  • Ventricular fibrillation
  • ECG recognition
  • Polymorphic
  • Torsades de pointes
  • Description
  • ECG recognition
  • Treatment
  • Summary

6
Ventricular Tachycardia (VT)
  • Originates in the ventricles
  • Can be life threatening
  • Most patients have significant heart disease
  • Coronary artery disease
  • A previous myocardial infarction
  • Cardiomyopathy

7
Mechanisms of VT
  • Reentrant
  • Reentry circuit (fast and slow pathway) is
    confined to the ventricles and/or bundle branches
  • Automatic
  • Automatic focus occurs within the ventricles
  • Triggered activity
  • Early afterdepolarizations (phase 3)
  • Delayed afterdepolarizations (phase 4)

8
Reentrant
  • Reentrant ventricular arrhythmias
  • Premature ventricular complexes
  • Idiopathic left ventricular tachycardia
  • Bundle branch reentry
  • Ventricular tachycardia and fibrillation when
    associated with chronic heart disease
  • Previous myocardial infarction
  • Cardiomyopathy

9
Automatic
  • Automatic ventricular arrhythmias
  • Premature ventricular complexes
  • Ischemic ventricular tachycardia
  • Ventricular tachycardia and fibrillation when
    associated with acute medical conditions
  • Acute myocardial infarction or ischemia
  • Electrolyte and acid-base disturbances, hypoxemia
  • Increased sympathetic tone

10
Automaticity
  • Abnormal Acceleration of Phase 4

Fogoros Electrophysiologic Testing. 3rd ed.
Blackwell Scientific 1999 16.
11
Triggered
  • Triggered activity ventricular arrhythmias
  • Pause-dependent triggered activity
  • Early afterdepolarization (phase 3)
  • Polymorphic ventricular tachycardia
  • Catechol-dependent triggered activity
  • Late afterdepolarizations (phase 4)
  • Idiopathic right ventricular tachycardia

12
Triggered
Fogoros Electrophysiologic Testing. 3rd ed.
Blackwell Scientific 1999 158.
13
Sustained vs. Nonsustained
  • Sustained VT
  • Episodes last at least 30 seconds
  • Commonly seen in adults with prior
  • Myocardial infarction
  • Chronic coronary artery disease
  • Dilated cardiomyopathy
  • Non-sustained VT
  • Episodes last at least 6 beats but

14
Premature Ventricular Contraction
  • PVC
  • Ectopic beat in the ventricle that can occur
    singly or in clusters
  • Caused by electrical irritability
  • Factors influencing electrical irritability
  • Ischemia
  • Electrolyte imbalances
  • Drug intoxication

15
Classification
  • Ventricular Tachycardia
  • Monomorphic
  • Idiopathic VT
  • Bundle branch reentry tachycardia
  • Ventricular flutter
  • Ventricular fibrillation
  • Polymorphic
  • Torsades de pointes (TdP)

16
Monomorphic VTs
17
Monomorphic VT
  • Heart rate 100 bpm or greater
  • Rhythm Regular
  • Mechanism
  • Reentry
  • Abnormal automaticity
  • Triggered activity
  • Recognition
  • Broad QRS
  • Stable and uniform beat-to-beat appearance

18
ECG Recognition
ECG used with permission of Dr. Brian Olshansky.
19
Intracardiac Recording of VT
EGM used with permission of Texas Cardiac
Arrhythmia, P.A.
20
Idiopathic Right Ventricular Tachycardia
  • Right ventricular idiopathic VT
  • Focus originates within the right ventricular
    outflow tract
  • Ventricular function is usually normal
  • Usually LBBB, inferior axis
  • Treatment options
  • Pharmacologic therapy (beta blockers, verapamil)
  • RF ablation

21
ECG Recognition
Kay NG. Am J Med 1996 100 344-356.
22
Case History Idiopathic VT
39 y.o. female with no prior cardiac history
  • First episode
  • 9 hours of palpitations
  • In ER, found to be in wide-complex tachycardia of
    LBBB, inferior axis, at 205 bpm
  • Converted with IV lidocaine placed on tenormin
  • Second episode
  • While on tenormin, patient had onset of
    palpitations at airport
  • In ER, converted with IV lidocaine
  • Patient underwent EP study

23
Case History Idiopathic VT
24
Case History Idiopathic VT
  • At EP study, tachycardia focus was mapped and
    localized to right ventricular outflow tract
  • The focus was successfully ablatedusing
    radiofrequency energy, with no subsequent
    inducible or clinical VT

25
Endocardial Activation Mapping
  • Using an ablation catheter, map the area around
    and inside of the right ventricular outflow tract
  • Find the electrograms that precede the onset of
    the QRS complex during tachycardia
  • This area identifies the site of earliest
    activation, and possibly the site of origin of
    the arrhythmia

26
Pace Mapping
  • Pace mapping helps to localize the site of
    origin after endocardial mapping has been
    performed
  • If the heart is paced from this region, the
    resulting ECG should be identical to the ECG
    taken during tachycardia
  • Delivering RF energy to this site usually
    eliminates ventricular tachycardia

27
Idiopathic VT Ablation in RVOT
RAO
RAO
28
Idiopathic Left Ventricular Tachycardia
  • RBBB/LAFB
  • Involves the Purkinje network
  • Treatment options
  • RF ablation
  • Pharmacologic therapy (verapamil, beta blockers)

29
ECG Recognition
ECG used with permission of Kay NG.
30
Bundle Branch Reentry
  • Reentry circuit is confined to the left and right
    bundle branches
  • Usually LBBB, during sinus rhythm
  • Presents with
  • Syncope
  • Palpitations
  • Sudden cardiac death
  • Treatment RF ablation of right bundle

31
VT Due to Bundle Branch Reentry
32
Catheter Ablation of Right Bundle Branch
I
II
V1
RA
Current
Voltage
Courtesy of Dr. Warren Jackman
33
Ventricular Flutter
  • Heart rate 300 bpm
  • Rhythm Regular and uniform
  • Mechanism Reentry
  • Recognition
  • No isoelectric interval
  • No visible T wave
  • Degenerates to ventricular fibrillation
  • Treatment Cardioversion

34
Ventricular Fibrillation
  • Heart rate Chaotic, random and asynchronous
  • Rhythm Irregular
  • Mechanism Multiple wavelets of reentry
  • Recognition
  • No discrete QRS complexes
  • Treatment
  • Defibrillation

35
ECG Recognition
  • P waves and QRS complexes not present
  • Heart rhythm highly irregular
  • Heart rate not defined

36
Polymorphic VT
37
Polymorphic VT
  • Heart rate Variable
  • Rhythm Irregular
  • Mechanism
  • Reentry
  • Triggered activity
  • Recognition
  • Wide QRS with phasic variation
  • Torsades de pointes

38
ECG Recognition
EGM used with permission of Texas Cardiac
Arrhythmia, P.A.
39
Torsades de Pointes (TdP)
  • Heart rate 200 - 250 bpm
  • Rhythm Irregular
  • Recognition
  • Long QT interval
  • Wide QRS
  • Continuously changing QRS morphology

40
Mechanism
  • Events leading to TdP are
  • Hypokalemia
  • Prolongation of the action potential duration
  • Early afterdepolarizations
  • Critically slow conduction that contributes to
    reentry

41
ECG Recognition
  • QRS morphology continuously changes
  • Complexes alternates from positive to negative

42
Possible Causes
  • Drugs that lengthen the QT
  • Quinidine
  • Procainamide
  • Sotalol
  • Ibutilide
  • Physical
  • Ischemia
  • Electrolyte abnormalities

43
Treatment
  • Pharmacologic therapy
  • Potassium
  • Magnesium
  • Isoproterenol
  • Possibly class Ib drugs (lidocaine) to decrease
    refractoriness/shorten length of action potential
  • Overdrive ventricular pacing
  • Cardioversion

44
Summary
  • VT ablation is not an FDA-approved indication
  • RF catheter ablation can be a useful technique in
    patients with ventricular tachycardia
  • Success largely depends on the etiology of the
    arrhythmia
  • Unstable sustained VT, polymorphic VT and
    ventricular fibrillation are not ablatable
  • Improved catheters and imaging techniques may
    change this in the future
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