This document discusses approaches for differentiating wide complex tachycardias (WCTs) on electrocardiograms (ECGs). It may indicate ventricular tachycardia (VT), supraventricular tachycardia (SVT) with abnormal conduction, or ventricular pacing rhythms. Diagnosis is important for acute and long-term management. The document outlines ECG criteria including QRS morphology, axis, concordance, AV dissociation, and the aVR algorithm that can help distinguish VT from SVT when the rhythm presents as a wide complex tachycardia. A stepwise differential diagnosis approach integrating these ECG features is recommended to determine if the underlying rhythm is VT or SVT.

1. GRAPHICS-WIDE
COMPLEX
TACHYCARDIAS-
APPROACH

2. Wide complex tachycardia
 Wide Complex Tachycardias (WCT) – QRS
duration > 120 ms and heart rate >
100beats/min
 Correct diagnosis is important for the acute as
well as long term management of patients
 Categories of WCTs include ventricular
tachycardia (VT), SVT with abnormal
intraventricular conduction, and ventricular
paced rhythms

3. DIFFERENTIAL DIAGNOSIS
 Ventricular tachycardia
 Supraventricular tachycardia with abnormal
interventricular conduction
1. Fixed( baseline) or Functional ( only during tachy)
2. Ventricular activation over anomalous AV
connections
3. Abnormal muscle muscle spread (RBBB type pattern
in TOF repair or LBBB in DCMP, non specific IVCD)
4. Drugs or electrolyte disturbances causing widening
of QRS(Na blocking agents 1A and
1C&Amiodarone)(Hyperkalemia-LBBB type
appearance)
 Ventricular paced rhythms(SVT or activity driven AV
pacing)

4. DIFFERENTIAL DIAGNOSIS

5. HISTORY AND EXAMINATION
 Majority of patients with VT have structural heart
disease (H/o MI, angina,CHF)
 Age VT>35yrs
 Previous history of arrhythmia , similar episodes over
past few years favours SVT
 Hemodynamic stability more with SVT
 Cannon A waves, variable SI, alteration in systolic
pressure,
 Carotid sinus massage, adenosine can unmask VT by
causing AV block
 Termination by adenosine and carotid sinus massage
favor SVT

6. ECG
 Rate: limited use in distinguishing VT from SVT as
there is too much overlap
 Consider Atrial flutter when HR is ~150 beats/min
 Regularity: VT is generally regular, though there can
be slight variation in the RR intervals
 Slight irregularity at the onset (“warm-up
phenomenon”) favours VT
 Grossly irregular WCT likely represents:
1) AF w/ aberrant conduction,,
2)AF w/ conduction over an accessory pathway,,
3) polymorphic VT
 Uniformity of the RR intervals favours SVT

7. ECG
 QRS Morphology: most approaches involve
 classifying the WCT as having RBBB—like
pattern or LBBB--like pattern
 RBBB-like pattern: QRS polarity is positive in
leadsV1 and V2
 LBBB-like pattern: QRS polarity is negative in
leads V1 and V2

8. ECG
 QRS duration (wellens et al)-LBBB>160msec
and RBBB>140msec( drugs and electrolytes
?)
 Axis-more leftward axis is VT(-90±180)
 Shift of axis >40 from sinus rhythm
 In RBBB--like WCT, axis to the left of -30°
suggest VT
 In LBBB--like WCT, axis to the right of +90°
suggests VT

9. ECG
 V1 RBBB-rSr’,rR’,rsr’ or rSR’(Triphasic ‘rabbit
ear’) suggest SVT, monophasic R wave or
broad R(>30 msec ) with terminal negative
QRS forces or qR suggest VT
 V6 RBBB-qRs,Rs or RS(R/S>1) SVT. VT
rS,Qrs,QS,QR or monophasic R (R/S<1)-
 RV activation with aberrancy produce smaller
s wave

11. ECG
 LBBB pattern associations:
 Lead V1 or V2: broad initial R wave of >30 msec duration
favors VT
 Slurred or notched downstroke of the S wave favors VT
 Duration from the onset of the QRS complex to the nadir of
the QSor S wave of > 60 msec favors VT
 Absence of an initial R wave or a small initial R wave of < 30
msec favors SVT
 A swift, smooth downstroke of the S wave in w/ a duration of
< 60 msec favors SVT
 LBBB-Lead V6: any Q or QS wave favors VT, RR’ or R wave
suggests SVT
 Absence of a Q wave favors SVT

14. ECG
 LBBB+RAD almost always VT
 RBBB with normal axis –suggests SVT
 Concordant pattern( predominantly)
 Usually seen in VT
 Exception –pre excited tachycardia in which
ventricular activation occurs over accessory
pathway
 Concordance specificity is high(>90%),
sensitivity is low (20 % of all VTs)

16. ECG
 Concordance in limb leads I,II,III
(predominantly negative QRS)
 Q waves- Q waves during WCT suggest
presence of MI, in post MI VT Q waves are
seen in both Normal rhythm and tachycardia
 Exceptions include DCMP, pseudo –Q waves
in SVT retrograde P wave deforming the
onset of QRS

17. ECG-AV DISSOCIATION
 Complete AVD occurs in 20-50% of all VTs
 15-20% VTs have second degree AV block
 30% of VTs have 1:1 retrograde conduction
 QRS complex amplitude variation,T wave changes
 Transient retrograde blocks can be induced by carotid sinus
massage
 Prevalence varies due to
1. Tachycardia rate
2. Amount of ECG recording available
3. Observer experience
4. Observer confidence
 Use lewis leads, echocardiography, oesophageal electrode,
transvenous electrode

19. FUSION, CAPTURE AND ECHO
BEATS

20. FUSION AND CAPTURE
BEATS

21. ECHO BEAT

22. PRECORDIAL RS ABSENT
 Absence of RS in any precordial lead in any
lead suggests VT
 In a analysis of 554 WCTs (384 VTs and 170
SVTs) RS was absent in 83 (15%) all were VTs
 In the presence of RS, interval between R
wave onset to S wave nadir >100msec VT
diagnosed (37%

23. ECG
 QRS complex narrower during VT than Normal
rhythm
 Occurs in <1% of VTs, occurs when there is
baseline BBB
 Contralateral BBB in NR and WCT suggests VT
 Rarely contralateral BBB can occur in SVTs when
block is at peripheral purkinje level or myocardial
delay
 QRS alternans equally seen with both but slightly
more with SVT
 Multiple QRS configurations suggest VTs

24. QRS morphology change

25. UNDERLYING BBB
 Many of morphologic criteria less reliable with
underlying BBB or axis shift
 Precordial concordance,right ward superior axis,
R wave in V1, precordial RS pattern still reliable
predictors of VT
 Comparison between previous ECG in normal
rhythm and WCT, configuration will be similar in
SVT and different in VTs
 Rarely morphology may be similar in VTs,
demonstrate non 1:1 conduction in such a case
 Mostly seen with RBBB at baseline( VTs)

26. BRUGADA CRITERIA
 Stepwise approach in which four criteria for VT
are sequentially evaluated and if any are
satisfied, the diagnosis off VT is made;; if none
are fulfilled then diagnosis off SVT is made by
exclusion
1)Lead V1-V6 are inspected for an RS complex,
if none then concordance is present
2)If an RS complex is present, the longest
interval in any lead between the onset of the R
wave and the nadir of the S wave (RS interval)
is measured
 VT if the RS interval is > 100 msec

27. BRUGADA CRITERIA
3)If the RS interval is < 100 msec, then evaluate
for the presence of AV dissociation to diagnose
VT
4)If the RS interval is < 100 msec and AV
dissociation is not evident, then evaluate the
QRS morphology for V1-positive and V1-
negative WCT If either the V1-V2 or the V6
criteria are not consistent w/ VT, then SVT is
assumed

28. BRUGADA CRITERIA

31. aVR algorithm

32. aVR algorithm

33. aVR patterns

34. aVR algorithm
1) Evaluate for the presence of an initial R wave
2) Evaluate for the presence of an initial r or q
wave with width > 40 msec
3)Evaluate for notching on the descending limb
of a negative onset, predominately negative
QRScomplex

35. aVR algorithm
 4)Evaluate for Vi/Vt (ventricular activation
velocity ratio) < 1
 Vi – initial ventricular activation velocity
 Vt – terminal ventricular activation velocity
 Both are measured by the excursion (in mV)
recorded on the ECG during the initial (Vi) and
terminal (Vt) 40 msec of the QRS complex

36. aVR algorithm