An Electrophysiologic Overview

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Ventricular Tachyarrhythmias

• An Electrophysiologic Overview

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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

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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

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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

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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)

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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

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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

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Automaticity

• Abnormal Acceleration of Phase 4

Fogoros Electrophysiologic Testing. 3rd ed.
Blackwell Scientific 1999 16.
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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

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Triggered
Fogoros Electrophysiologic Testing. 3rd ed.
Blackwell Scientific 1999 158.
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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

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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

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Classification

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

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Monomorphic VTs
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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

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ECG Recognition
ECG used with permission of Dr. Brian Olshansky.
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Intracardiac Recording of VT
EGM used with permission of Texas Cardiac
Arrhythmia, P.A.
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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

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ECG Recognition
Kay NG. Am J Med 1996 100 344-356.
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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

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Case History Idiopathic VT
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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

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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

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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

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Idiopathic VT Ablation in RVOT
RAO
RAO
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Idiopathic Left Ventricular Tachycardia

• RBBB/LAFB
• Involves the Purkinje network
• Treatment options
• RF ablation
• Pharmacologic therapy (verapamil, beta blockers)

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ECG Recognition
ECG used with permission of Kay NG.
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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

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VT Due to Bundle Branch Reentry
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Catheter Ablation of Right Bundle Branch
I
II
V1
RA
Current
Voltage
Courtesy of Dr. Warren Jackman
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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

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Ventricular Fibrillation

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

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ECG Recognition

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

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Polymorphic VT
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Polymorphic VT

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

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ECG Recognition
EGM used with permission of Texas Cardiac
Arrhythmia, P.A.
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Torsades de Pointes (TdP)

• Heart rate 200 - 250 bpm
• Rhythm Irregular
• Recognition
• Long QT interval
• Wide QRS
• Continuously changing QRS morphology

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Mechanism

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

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ECG Recognition

• QRS morphology continuously changes
• Complexes alternates from positive to negative

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Possible Causes

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

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Treatment

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

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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