1、An Electrophysiologic OverviewVentricular TachyarrhythmiasModule Objectives Ventricular Tachyarrhythmias Identify the mechanisms for ventricular tachycardias Differentiate types of ventricular tachycardias using ECG and intracardiac electrogram recordings Discuss treatment options for ventricular ta
2、chycardiasAfter completion of this module,the participant should be able to:Module Outline Ventricular TachyarrhythmiasI.DescriptionII.CharacteristicsA.MechanismsB.Sustained vs.nonsustainedC.Premature ventricular contractionsModule Outline Ventricular TachyarrhythmiasIII.ClassificationA.Monomorphic1
3、.Idiopathica.Descriptionb.ECG recognitionc.Treatment ablation2.Bundle brancha.Descriptionb.ECG recognitionc.Treatment ablationModule Outline Ventricular TachyarrhythmiasIII.Classifications-continued3.Ventricular fluttera.ECG recognition4.Ventricular fibrillationa.ECG recognitionB.Polymorphic1.Torsad
4、es de pointesa.Descriptionb.ECG recognitionc.TreatmentIV.SummaryVentricular Tachycardia(VT)Originates in the ventricles Can be life threatening Most patients have significant heart diseaseCoronary artery diseaseA previous myocardial infarctionCardiomyopathyMechanisms of VT Reentrant Reentry circuit(
5、fast and slow pathway)is confined to the ventricles and/or bundle branches Automatic Automatic focus occurs within the ventricles Triggered activityEarly afterdepolarizations(phase 3)Delayed afterdepolarizations(phase 4)Reentrant Reentrant ventricular arrhythmiasPremature ventricular complexesIdiopa
6、thic left ventricular tachycardiaBundle branch reentryVentricular tachycardia and fibrillation when associated with chronic heart disease:Previous myocardial infarctionCardiomyopathyAutomatic Automatic ventricular arrhythmiasPremature ventricular complexesIschemic ventricular tachycardiaVentricular
7、tachycardia and fibrillation when associated with acute medical conditions:Acute myocardial infarction or ischemiaElectrolyte and acid-base disturbances,hypoxemiaIncreased sympathetic toneAutomaticityAbnormal Acceleration of Phase 4Fogoros:Electrophysiologic Testing.3rd ed.Blackwell Scientific 1999;
8、16.Triggered Triggered activity ventricular arrhythmiasPause-dependent triggered activityEarly afterdepolarization(phase 3)Polymorphic ventricular tachycardiaCatechol-dependent triggered activityLate afterdepolarizations(phase 4)Idiopathic right ventricular tachycardiaTriggeredFogoros:Electrophysiol
9、ogic Testing.3rd ed.Blackwell Scientific 1999;158.ECG recognitionIdiopathic Right Ventricular TachycardiaRhythm:Regular and uniformIncreased sympathetic toneMonomorphic VTCardioversionElectrolyte abnormalitiesCharacteristicsOriginates in the ventriclesPolymorphic ventricular tachycardiaSuccess large
10、ly depends on the etiology of the arrhythmiaBundle branch reentrySustained VTSustained VTIf the heart is paced from this region,the resulting ECG should be identical to the ECG taken during tachycardiaStable and uniform beat-to-beat appearanceRhythm:IrregularPause-dependent triggered activitySustain
11、ed vs.Nonsustained Sustained VTEpisodes last at least 30 secondsCommonly seen in adults with prior:Myocardial infarctionChronic coronary artery diseaseDilated cardiomyopathy Non-sustained VTEpisodes last at least 6 beats but 30 secondsPremature Ventricular Contraction PVCEctopic beat in the ventricl
12、e that can occur singly or in clustersCaused by electrical irritability Factors influencing electrical irritabilityIschemiaElectrolyte imbalancesDrug intoxicationClassification Ventricular TachycardiaMonomorphicIdiopathic VT Bundle branch reentry tachycardiaVentricular flutterVentricular fibrillatio
13、nPolymorphicTorsades de pointes(TdP)Monomorphic VTsMonomorphic VT Heart rate:100 bpm or greater Rhythm:Regular MechanismReentryAbnormal automaticityTriggered activity RecognitionBroad QRSStable and uniform beat-to-beat appearanceECG RecognitionECG used with permission of Dr.Brian Olshansky.Intracard
14、iac Recording of VTEGM used with permission of Texas Cardiac Arrhythmia,P.A.Idiopathic Right Ventricular Tachycardia Right ventricular idiopathic VTFocus originates within the right ventricular outflow tractVentricular function is usually normalUsually LBBB,inferior axis Treatment options:Pharmacolo
15、gic therapy(beta blockers,verapamil)RF ablation Kay NG.Am J Med 1996;100:344-356.ECG RecognitionCase History:Idiopathic VT First episode9 hours of palpitationsIn ER,found to be in wide-complex tachycardia of LBBB,inferior axis,at 205 bpmConverted with IV lidocaine;placed on tenormin Second episodeWh
16、ile on tenormin,patient had onset of palpitations at airportIn ER,converted with IV lidocaine Patient underwent EP study39 y.o.female with no prior cardiac historyCase History:Idiopathic VTCase History:Idiopathic VT At EP study,tachycardia focus was mapped and localized to right ventricular outflow
17、tract The focus was successfully ablatedusing radiofrequency energy,with no subsequent inducible or clinical VTEndocardial 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 compl
18、ex during tachycardia This area identifies the site of earliest activation,and possibly the“site of origin”of the arrhythmiaPace 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 i
19、dentical to the ECG taken during tachycardia Delivering RF energy to this site usually eliminates ventricular tachycardiaIdiopathic VT Ablation in RVOTRAORAOIdiopathic Left Ventricular Tachycardia RBBB/LAFBInvolves the Purkinje network Treatment options:RF ablationPharmacologic therapy(verapamil,bet
20、a blockers)ECG used with permission of Kay NG.ECG RecognitionBundle Branch Reentry Reentry circuit is confined to the left and right bundle branches Usually LBBB,during sinus rhythm Presents with:SyncopePalpitationsSudden cardiac death Treatment:RF ablation of right bundleReentry circuit(fast and sl
21、ow pathway)is confined to the ventricles and/or bundle branchesDifferentiate types of ventricular tachycardias using ECG and intracardiac electrogram recordingsP waves and QRS complexes not presentVentricular TachycardiaMechanisms of VTIf the heart is paced from this region,the resulting ECG should
22、be identical to the ECG taken during tachycardiaDifferentiate types of ventricular tachycardias using ECG and intracardiac electrogram recordingsReentrant ventricular arrhythmiasIdiopathic VTRF ablationConverted with IV lidocaine;placed on tenorminPossible CausesPharmacologic therapy(beta blockers,v
23、erapamil)Rhythm:IrregularSustained VTRF ablationVT Due to Bundle Branch ReentryCatheter Ablation of Right Bundle BranchCourtesy of Dr.Warren JackmanIIIV1RACurrentVoltageVentricular Flutter Heart rate:300 bpm Rhythm:Regular and uniform Mechanism:Reentry Recognition:No isoelectric intervalNo visible T
24、 waveDegenerates to ventricular fibrillation Treatment:CardioversionVentricular Fibrillation Heart rate:Chaotic,random and asynchronous Rhythm:Irregular Mechanism:Multiple wavelets of reentry Recognition:No discrete QRS complexes Treatment:DefibrillationECG Recognition P waves and QRS complexes not
25、present Heart rhythm highly irregular Heart rate not definedPolymorphic VTPolymorphic VT Heart rate:Variable Rhythm:Irregular Mechanism:ReentryTriggered activity Recognition:Wide QRS with phasic variationTorsades de pointesECG RecognitionEGM used with permission of Texas Cardiac Arrhythmia,P.A.Torsa
26、des de Pointes(TdP)Heart rate:200-250 bpm Rhythm:Irregular Recognition:Long QT intervalWide QRSContinuously changing QRS morphologyMechanism Events leading to TdP are:HypokalemiaProlongation of the action potential durationEarly afterdepolarizationsCritically slow conduction that contributes to reen
27、tryECG Recognition QRS morphology continuously changes Complexes alternates from positive to negative Possible Causes Drugs that lengthen the QT:QuinidineProcainamideSotalolIbutilide PhysicalIschemiaElectrolyte abnormalitiesTreatment Pharmacologic therapy:PotassiumMagnesiumIsoproterenolPossibly clas
28、s Ib drugs(lidocaine)to decrease refractoriness/shorten length of action potential Overdrive ventricular pacing CardioversionSummary 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
