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Ventricular Tachyarrhythmias. An Electrophysiologic Overview. Module Objectives – Ventricular Tachyarrhythmias. After completion of this module, the participant should be able to:. Identify the mechanisms for ventricular tachycardias

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ventricular tachyarrhythmias

Ventricular Tachyarrhythmias

An Electrophysiologic Overview

module objectives ventricular tachyarrhythmias
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
module outline ventricular tachyarrhythmias
Module Outline – Ventricular Tachyarrhythmias
  • Description
  • Characteristics
    • Mechanisms
    • Sustained vs. nonsustained
    • Premature ventricular contractions
module outline ventricular tachyarrhythmias1
Module Outline – Ventricular Tachyarrhythmias
  • Classification
    • Monomorphic
      • Idiopathic
        • Description
        • ECG recognition
        • Treatment – ablation
      • Bundle branch
        • Description
        • ECG recognition
        • Treatment –ablation
module outline ventricular tachyarrhythmias2
Module Outline – Ventricular Tachyarrhythmias
  • Classifications - continued
      • Ventricular flutter
        • ECG recognition
      • Ventricular fibrillation
        • ECG recognition
    • Polymorphic
      • Torsades de pointes
        • Description
        • ECG recognition
        • Treatment
  • Summary
ventricular tachycardia vt
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
mechanisms of vt
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)
reentrant
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
automatic
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
automaticity
Abnormal Acceleration of Phase 4Automaticity

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

triggered
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
triggered1
Triggered

Fogoros: Electrophysiologic Testing. 3rd ed. Blackwell Scientific 1999; 158.

sustained vs nonsustained
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 < 30 seconds
premature ventricular contraction
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
classification
Classification
  • Ventricular Tachycardia
    • Monomorphic
      • Idiopathic VT
      • Bundle branch reentry tachycardia
      • Ventricular flutter
      • Ventricular fibrillation
    • Polymorphic
      • Torsades de pointes (TdP)
monomorphic vt
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
ecg recognition
ECG Recognition

ECG used with permission of Dr. Brian Olshansky.

intracardiac recording of vt
Intracardiac Recording of VT

EGM used with permission of Texas Cardiac Arrhythmia, P.A.

idiopathic right ventricular tachycardia
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
ecg recognition1
ECG Recognition

Kay NG. Am J Med 1996; 100: 344-356.

case history idiopathic vt
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
case history idiopathic vt2
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
endocardial activation mapping
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
pace mapping
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
idiopathic left ventricular tachycardia
Idiopathic Left Ventricular Tachycardia
  • RBBB/LAFB
    • Involves the Purkinje network
  • Treatment options:
    • RF ablation
    • Pharmacologic therapy (verapamil, beta blockers)
ecg recognition2
ECG Recognition

ECG used with permission of Kay NG.

bundle branch reentry
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
catheter ablation of right bundle branch
Catheter Ablation of Right Bundle Branch

I

II

V1

RA

Current

Voltage

Courtesy of Dr. Warren Jackman

ventricular flutter
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
ventricular fibrillation
Ventricular Fibrillation
  • Heart rate: Chaotic, random and asynchronous
  • Rhythm: Irregular
  • Mechanism: Multiple wavelets of reentry
  • Recognition:
    • No discrete QRS complexes
  • Treatment:
    • Defibrillation
ecg recognition3
P waves and QRS complexes not present

Heart rhythm highly irregular

Heart rate not defined

ECG Recognition
polymorphic vt1
Polymorphic VT
  • Heart rate: Variable
  • Rhythm: Irregular
  • Mechanism:
    • Reentry
    • Triggered activity
  • Recognition:
    • Wide QRS with phasic variation
    • Torsades de pointes
ecg recognition4
ECG Recognition

EGM used with permission of Texas Cardiac Arrhythmia, P.A.

torsades de pointes tdp
Torsades de Pointes (TdP)
  • Heart rate: 200 - 250 bpm
  • Rhythm: Irregular
  • Recognition:
    • Long QT interval
    • Wide QRS
    • Continuously changing QRS morphology
mechanism
Mechanism
  • Events leading to TdP are:
    • Hypokalemia
    • Prolongation of the action potential duration
    • Early afterdepolarizations
    • Critically slow conduction that contributes to reentry
ecg recognition5
QRS morphology continuously changes

Complexes alternates from positive to negative

ECG Recognition
possible causes
Possible Causes
  • Drugs that lengthen the QT:
    • Quinidine
    • Procainamide
    • Sotalol
    • Ibutilide
  • Physical
    • Ischemia
    • Electrolyte abnormalities
treatment
Treatment
  • Pharmacologic therapy:
    • Potassium
    • Magnesium
    • Isoproterenol
    • Possibly class Ib drugs (lidocaine) to decrease refractoriness/shorten length of action potential
  • Overdrive ventricular pacing
  • Cardioversion
summary
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