Differentiating Wide Complex Tachycardia_Saad

Differentiating Wide Differentiating Wide

Complex TachycardiaComplex Tachycardia

Noon Cardiology ConferenceNoon Cardiology Conference

Marc N. Saad, M.D.Marc N. Saad, M.D.

10/14/0810/14/08

ObjectivesObjectives

�� DefinitionsDefinitions

�� CausesCauses

�� Electrocardiographic featuresElectrocardiographic features

�� Diagnostic CriteriaDiagnostic Criteria

�� Brugada Brugada

�� Lead aVRLead aVR

DefinitionsDefinitions

�� Wide Complex Tachycardias (WCT) Wide Complex Tachycardias (WCT) -- QRS QRS

duration > 120 ms and heart rate > 100 duration > 120 ms and heart rate > 100

beats/minbeats/min

�� Ventricular Tachycardia (VT) Ventricular Tachycardia (VT) -- 3 or more 3 or more

consecutive ventricular beats with a rate of 100 consecutive ventricular beats with a rate of 100

beats/min or morebeats/min or more

�� Nonsustained VT (NSVT) Nonsustained VT (NSVT) –– tachycardia < 30 tachycardia < 30

seconds durationseconds duration


�� Sustained VT:Sustained VT:

�� Last > 30 secondsLast > 30 seconds

�� Causes significant hemodynamic symptomsCauses significant hemodynamic symptoms

�� Requires therapeutic intervention for terminationRequires therapeutic intervention for termination

�� Monomorphic VT Monomorphic VT –– uniform and stable QRS uniform and stable QRS appearance in any given leadappearance in any given lead

�� Polymorphic VT Polymorphic VT –– continuously varying QRS continuously varying QRS morphology and/or axis in a single lead during morphology and/or axis in a single lead during an episodean episode


�� Supraventricular tachycardia (SVT) Supraventricular tachycardia (SVT) –– any tachycardia any tachycardia

using the normal AV conduction system for ventricular using the normal AV conduction system for ventricular

excitation, w/ the tachycardia originating in the atria or excitation, w/ the tachycardia originating in the atria or

the AV node and requiring the AV node for its the AV node and requiring the AV node for its

maintenancemaintenance

�� Aberrant conduction (aberrancy) Aberrant conduction (aberrancy) –– conduction delay or conduction delay or

block in the Hisblock in the His--Purkinje system during antegrade Purkinje system during antegrade

conduction of impulses over the normal AV conduction of impulses over the normal AV

conduction system resulting in a wide, abnormal QRSconduction system resulting in a wide, abnormal QRS


�� PrePre--excitation syndrome excitation syndrome –– AV conduction can occur AV conduction can occur via the normal conduction system and via an accessory via the normal conduction system and via an accessory AV pathwayAV pathway�� The two pathways create the substrate for a reentrant circuit, The two pathways create the substrate for a reentrant circuit, facilitating AV reentrant tachycardia (AVRT)facilitating AV reentrant tachycardia (AVRT)�� Orthodromic AVRT Orthodromic AVRT –– antegrade conduction over the AV node and antegrade conduction over the AV node and retrograde conduction via the accessory pathway; QRS is narrow retrograde conduction via the accessory pathway; QRS is narrow unless there is aberrant conductionunless there is aberrant conduction

�� Antidromic AVRT Antidromic AVRT –– antegrade conduction over the accessory antegrade conduction over the accessory pathway and retrograde conduction over the AV node or a second pathway and retrograde conduction over the AV node or a second accessory pathway; QRS is wideaccessory pathway; QRS is wide

�� PrePre--excited tachycardias excited tachycardias –– ventricular activation occurs ventricular activation occurs predominately or exclusively via an accessory pathwaypredominately or exclusively via an accessory pathway

CausesCauses

�� VT VT -- most common cause of WCT (80% of cases in most common cause of WCT (80% of cases in unselected populations and more than 95% in pts w/ unselected populations and more than 95% in pts w/ structural heart disease)structural heart disease)�� Can originate anywhere below the AV node: His bundle, Can originate anywhere below the AV node: His bundle, bundle branches, fascicles, Purkinje fibers, and ventricular bundle branches, fascicles, Purkinje fibers, and ventricular myocardial tissuemyocardial tissue

�� Fixed conduction block Fixed conduction block –– when there is a baseline when there is a baseline block during sinus rhythm due to pathological lesions block during sinus rhythm due to pathological lesions in the conduction system in the conduction system �� Seen as baseline left bundle branch block (LBBB), right Seen as baseline left bundle branch block (LBBB), right bundle branch block (RBBB), or a nonspecific bundle branch block (RBBB), or a nonspecific intraventricular conduction delay (IVCD)intraventricular conduction delay (IVCD)

CausesCauses

�� Rate related (functional) aberration Rate related (functional) aberration –– conduction delay conduction delay

or block occurs due to rapidly generated impulses or block occurs due to rapidly generated impulses

reaching the conducting fibers before they have time to reaching the conducting fibers before they have time to

fully recover from the previous impulsefully recover from the previous impulse

�� May persist because the bundle branch blocked antegradely May persist because the bundle branch blocked antegradely

may be activated transseptally via its contralateral counterpartmay be activated transseptally via its contralateral counterpart

�� The delay in recovery may be due to underlying disease of the The delay in recovery may be due to underlying disease of the

HisHis--Purkinje system or the actions of antiarrhythmic drugsPurkinje system or the actions of antiarrhythmic drugs

�� Particularly the class 1A and 1C agentsParticularly the class 1A and 1C agents

CausesCauses

�� Orthodromic AVRT w/ aberrancyOrthodromic AVRT w/ aberrancy

�� PrePre--excitation tachycardiasexcitation tachycardias

�� Antidromic AVRTAntidromic AVRT

�� Relatively uncommon, occurring in about 6% of casesRelatively uncommon, occurring in about 6% of cases

�� Difficult to differentiate from VT because ventricular activatioDifficult to differentiate from VT because ventricular activation n

begins outside the normal intraventricular conduction system in begins outside the normal intraventricular conduction system in bothboth

�� Atrial fibrillation with an accessory pathwayAtrial fibrillation with an accessory pathway

�� Tachycardias w/ two accessory pathwaysTachycardias w/ two accessory pathways

�� Pacemakers and cardiac resynchronization therapyPacemakers and cardiac resynchronization therapy

ElectrocardiogramsElectrocardiograms

�� Can provide the probable diagnosis in many pts, but Can provide the probable diagnosis in many pts, but definitive diagnosis is not always possible and can be definitive diagnosis is not always possible and can be timetime--consumingconsuming

�� ECG can be carefully examined in HD stable pts, ECG can be carefully examined in HD stable pts, however, detailed evaluation should be deferred in however, detailed evaluation should be deferred in favor of urgent therapy in pts w/ questionable HD favor of urgent therapy in pts w/ questionable HD stabilitystability�� Pt should be treated as having VT if diagnosis unclearPt should be treated as having VT if diagnosis unclear

�� For adequate analysis, 12For adequate analysis, 12--lead ECG and rhythm strip lead ECG and rhythm strip should be obtainedshould be obtained�� If available, evaluation of ECG w/ pt in NSRIf available, evaluation of ECG w/ pt in NSR


�� Rate: limited use in distinguishing VT from SVT as Rate: limited use in distinguishing VT from SVT as there is too much overlapthere is too much overlap�� Consider Atrial flutter when HR is ~150 beats/minConsider Atrial flutter when HR is ~150 beats/min

�� Regularity: VT is generally regular, though there can be Regularity: VT is generally regular, though there can be slight variation in the RR intervalsslight variation in the RR intervals�� Slight irregularity at the onset (Slight irregularity at the onset (““warmwarm--up phenomenonup phenomenon””) ) favors VTfavors VT

�� Grossly irregular WCT likely represents: 1) AF w/ aberrant Grossly irregular WCT likely represents: 1) AF w/ aberrant conduction, 2)AF w/ conduction over an accessory pathway, conduction, 2)AF w/ conduction over an accessory pathway, or 3) polymorphic VTor 3) polymorphic VT

�� Uniformity of the RR intervals favors SVTUniformity of the RR intervals favors SVT


�� Axis: mean QRS axis in the normal range favors SVT Axis: mean QRS axis in the normal range favors SVT

w/ aberrationw/ aberration

�� Right superior axis of Right superior axis of --90 to 90 to ±± 180180°° strongly suggests VT strongly suggests VT

(sometimes called (sometimes called ““northwestnorthwest”” or extreme right axis)or extreme right axis)

�� Should compare the axis during SR, an axis shift during WCT Should compare the axis during SR, an axis shift during WCT

of > 40of > 40°° favors VTfavors VT

�� In RBBBIn RBBB--like WCT, axis to the left of like WCT, axis to the left of --3030°° suggest VTsuggest VT

�� In LBBBIn LBBB--like WCT, axis to the right of +90like WCT, axis to the right of +90°° suggests VTsuggests VT


�� QRS duration: generally, a wider QRS favors VTQRS duration: generally, a wider QRS favors VT

�� In RBBBIn RBBB--like WCT, duration > 140 msec suggests VTlike WCT, duration > 140 msec suggests VT

�� In LBBBIn LBBB--like WCT, duration > 160 msec suggest VTlike WCT, duration > 160 msec suggest VT

�� QRS duration > 160 msec is a strong predictor of VT QRS duration > 160 msec is a strong predictor of VT

regardless of bundleregardless of bundle--branch block morphologybranch block morphology

�� Except in cases of SVT w/ an AV accessory pathway and the Except in cases of SVT w/ an AV accessory pathway and the

presence of drugs capable of slowing intraventricular conductionpresence of drugs capable of slowing intraventricular conduction

�� Such as class 1A or class 1C agents or amiodarone Such as class 1A or class 1C agents or amiodarone

�� QRS duration < 140 msec does not exclude VTQRS duration < 140 msec does not exclude VT

�� VT originating from the septum or w/in the HisVT originating from the septum or w/in the His--Purkinje systemPurkinje system


�� Concordance: present when QRS complexes in all 6 Concordance: present when QRS complexes in all 6 precordial leads (V1precordial leads (V1--V6) are monophasic w/ the same V6) are monophasic w/ the same polarity (90% specificity for VT)polarity (90% specificity for VT)�� Positive concordance Positive concordance –– All entirely positive w/ tall, All entirely positive w/ tall, monophasic R wavesmonophasic R waves�� Most often due to VT but can also occur in rare cases of antidroMost often due to VT but can also occur in rare cases of antidromic mic AVRT w/ a left posterior accessory pathwayAVRT w/ a left posterior accessory pathway

�� Negative concordance Negative concordance -- All entirely negative w/ deep All entirely negative w/ deep monophasic QS complexesmonophasic QS complexes

�� Concordance is not present if any of the 6 leads has a Concordance is not present if any of the 6 leads has a biphasic QRS (qR or RS complexes)biphasic QRS (qR or RS complexes)�� Absence of concordance is not diagnostically helpfulAbsence of concordance is not diagnostically helpful

ConcordanceConcordance

Antidromic AVRT w/ a left Antidromic AVRT w/ a left

posterior accessory pathwayposterior accessory pathway


�� AV dissociation: atrial activity that is AV dissociation: atrial activity that is independent of ventricular activity; occurs in 20independent of ventricular activity; occurs in 20--50% of VT and almost never in SVT50% of VT and almost never in SVT

�� When the atrial rate is slower than the ventricular When the atrial rate is slower than the ventricular rate, this strongly suggest VTrate, this strongly suggest VT

�� Atrial rate faster than the ventricular rate suggests a Atrial rate faster than the ventricular rate suggests a SVT, such as atrial flutter or AT w/ 2:1 AV SVT, such as atrial flutter or AT w/ 2:1 AV conductionconduction�� There is a consistent relationship between the P waves There is a consistent relationship between the P waves and the QRS complexesand the QRS complexes

AV dissociationAV dissociation

�� Presence of this largely establishes the diagnosis Presence of this largely establishes the diagnosis

of VT but its absence is not helpfulof VT but its absence is not helpful

�� May sometimes not be evident on ECGMay sometimes not be evident on ECG

�� Some cases of VT, the ventricular impulses conduct Some cases of VT, the ventricular impulses conduct

retrograde through the AV node and capture the retrograde through the AV node and capture the

atrium, preventing dissociationatrium, preventing dissociation

AV DissociationAV Dissociation

AV dissociationAV dissociation

�� Echo beat Echo beat –– VT impulse conducted retrogradely VT impulse conducted retrogradely through the AV node to produce atrial capture that, on through the AV node to produce atrial capture that, on return to the ventricles, produces a narrow QRS return to the ventricles, produces a narrow QRS complexcomplex

�� Fusion beat Fusion beat –– when one impulse originating from the when one impulse originating from the ventricle and a second supraventricular impulse ventricle and a second supraventricular impulse simultaneously activate the ventricular myocardiumsimultaneously activate the ventricular myocardium�� Morphology is intermediate between that of a sinus beat and Morphology is intermediate between that of a sinus beat and a purely ventricular complexa purely ventricular complex

�� Capture beat Capture beat –– normal conduction momentarily normal conduction momentarily ““capturedcaptured”” control of ventricular activation from the control of ventricular activation from the VT focusVT focus

Fusion and Capture BeatsFusion and Capture Beats

Echo BeatEcho Beat


�� QRS Morphology: most approaches involve QRS Morphology: most approaches involve

classifying the WCT as having RBBBclassifying the WCT as having RBBB--like like

pattern or LBBBpattern or LBBB--like patternlike pattern

�� RBBBRBBB--like pattern: QRS polarity is positive in leads like pattern: QRS polarity is positive in leads

V1 and V2V1 and V2

�� LBBBLBBB--like pattern: QRS polarity is negative in leads like pattern: QRS polarity is negative in leads

V1 and V2V1 and V2

QRS MorphologyQRS Morphology

�� RBBB pattern associations:RBBB pattern associations:

�� Lead V1: monophasic R or biphasic qR complex Lead V1: monophasic R or biphasic qR complex

favors VTfavors VT

�� Triphasic RSRTriphasic RSR’’ or RsRor RsR’’ complex (complex (““rabbitrabbit--earear”” sign) favors sign) favors

SVT, except if the left peak of the RsRSVT, except if the left peak of the RsR’’ complex is taller complex is taller

than the right peakthan the right peak

�� Lead V6: rS complex (R wave smaller than S wave) Lead V6: rS complex (R wave smaller than S wave)

favors VTfavors VT

�� Rs (R wave larger than S wave) complex favors SVTRs (R wave larger than S wave) complex favors SVT



�� LBBB pattern associations:LBBB pattern associations:

�� Lead V1 or V2: broad initial R wave of >30 msec duration Lead V1 or V2: broad initial R wave of >30 msec duration

favors VTfavors VT

�� Slurred or notched downstroke of the S wave favors VTSlurred or notched downstroke of the S wave favors VT

�� Duration from the onset of the QRS complex to the nadir of the QDuration from the onset of the QRS complex to the nadir of the QS S

or S wave of or S wave of ≥≥ 60 msec favors VT60 msec favors VT

�� Absence of an initial R wave or a small initial R wave of < 30 mAbsence of an initial R wave or a small initial R wave of < 30 msec sec

favors SVT favors SVT

�� A swift, smooth downstroke of the S wave in w/ a duration of < A swift, smooth downstroke of the S wave in w/ a duration of < 60 60

msecmsec favors SVTfavors SVT

�� Lead V6: any Q or QS wave favors VTLead V6: any Q or QS wave favors VT

�� Absence of a Q wave favors SVTAbsence of a Q wave favors SVT




Brugada CriteriaBrugada Criteria

�� Stepwise approach in which four criteria for VT Stepwise approach in which four criteria for VT are sequentially evaluated and if any are satisfied, are sequentially evaluated and if any are satisfied, the diagnosis of VT is made; if none are fulfilled the diagnosis of VT is made; if none are fulfilled then diagnosis of SVT is made by exclusionthen diagnosis of SVT is made by exclusion

�� 1)Lead V11)Lead V1--V6 are inspected for an RS complex, if V6 are inspected for an RS complex, if none than concordance is presentnone than concordance is present

�� 2)If an RS complex is present, the longest interval in 2)If an RS complex is present, the longest interval in any lead between the onset of the R wave and the any lead between the onset of the R wave and the nadir of the S wave (RS interval) is measurednadir of the S wave (RS interval) is measured�� VT if the RS interval is > 100 msecVT if the RS interval is > 100 msec

Evaluation for RS complexesEvaluation for RS complexes

RS IntervalRS Interval


�� 3)If the RS interval is < 100 msec, then evaluate for 3)If the RS interval is < 100 msec, then evaluate for

the presence of AV dissociation to diagnose VTthe presence of AV dissociation to diagnose VT

�� 4)If the RS interval is < 100 msec and AV 4)If the RS interval is < 100 msec and AV

dissociation is not evident, then evaluate the QRS dissociation is not evident, then evaluate the QRS

morphology for V1morphology for V1--positive and V1positive and V1--negative WCTnegative WCT

�� If either the V1If either the V1--V2 or the V6 criteria are not consistent V2 or the V6 criteria are not consistent

w/ VT, then SVT is assumedw/ VT, then SVT is assumed


New aVR AlgorithemNew aVR Algorithem

�� Hypothesized reasons for using aVR:Hypothesized reasons for using aVR:

�� During SVT w/ BBB, the initial rapid septal activation and During SVT w/ BBB, the initial rapid septal activation and

the later main ventricular activation wavefront move away the later main ventricular activation wavefront move away

from lead aVR, creating a negative QRS complex in lead aVRfrom lead aVR, creating a negative QRS complex in lead aVR

�� Exception to this generalization is occurs in inferior myocardiaException to this generalization is occurs in inferior myocardial l

infarction where there is the loss of the initial inferiorly dirinfarction where there is the loss of the initial inferiorly directed ected

forces creating an initial r wave (rS complex) during NSR or SVTforces creating an initial r wave (rS complex) during NSR or SVT

�� Because an initial dominant R wave in aVR is incompatible Because an initial dominant R wave in aVR is incompatible

w/ SVT, its presence suggest VT, typically originating from w/ SVT, its presence suggest VT, typically originating from

the inferior or apical regionthe inferior or apical region

New aVR AlgorithmNew aVR Algorithm

�� Useful for detecting VT originating from sites other Useful for detecting VT originating from sites other

than the inferior or apical wall, but would not show than the inferior or apical wall, but would not show

an initial R wave in aVRan initial R wave in aVR

�� Would rather show a slow, initial upward vector of Would rather show a slow, initial upward vector of

variable size pointing toward aVR even if the main vector variable size pointing toward aVR even if the main vector

of the VT points downward and creates a predominately of the VT points downward and creates a predominately

negative QRS in lead aVRnegative QRS in lead aVR

�� Exceptions would be VT originating from the most basal Exceptions would be VT originating from the most basal

sites of the interventricular septum or free wallsites of the interventricular septum or free wall

ECG Patterns in aVRECG Patterns in aVR

ECG Patterns in aVRECG Patterns in aVR


�� Stepwise approach similar to the Brugada criteria Stepwise approach similar to the Brugada criteria

used to analyze monophasic WCT:used to analyze monophasic WCT:

�� 1) Evaluate for the presence of an initial R wave1) Evaluate for the presence of an initial R wave

�� 2) Evaluate for the presence of an initial r or q wave 2) Evaluate for the presence of an initial r or q wave

with width with width ≥≥ 40 msec40 msec

�� 3)Evaluate for notching on the descending limb of a 3)Evaluate for notching on the descending limb of a

negative onset, predominately negative QRS negative onset, predominately negative QRS

complexcomplex



�� 4)Evaluate for Vi/Vt (ventricular activation velocity 4)Evaluate for Vi/Vt (ventricular activation velocity

ratio) ratio) ≤≤ 11

�� Vi Vi –– initial ventricular activation velocityinitial ventricular activation velocity

�� Vt Vt –– terminal ventricular activation velocityterminal ventricular activation velocity

�� Both are measured by the excursion (in mV) recorded on Both are measured by the excursion (in mV) recorded on

the ECG during the initial (Vi) and terminal (Vt) 40 msec the ECG during the initial (Vi) and terminal (Vt) 40 msec

of the QRS complexof the QRS complex

Evaluation of Vi/VtEvaluation of Vi/Vt

New aVR AlgorithemNew aVR Algorithem

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Differentiating Wide Complex Tachycardia_Saad