1. Differential diagnosis of broad complex tachycardia
Dr.Deepak Raju

2. Definitions
Wide Complex Tachycardia(WCT)-a rhythem with QRS duration ≥ 120 ms and heart rate > 100 bt/min
Ventricular tachycardia-a WCT originating below the level of His bundle
SVT-tachycardia dependent on participation of structures at or above the level of His bundle
LBBB morphology-QRS complex duration ≥ 120 ms with a predominantly negative terminal deflection in lead V1

3. RBBB morphology-QRS complex duration ≥ 120 ms with a predominantly positive terminal deflection in V1
LBBB&RBBB morphology denote morphological appearance of QRS complex-result from direct myocardial activation

4. Causes of regular WCT Ventricular tachycardia-
Most common cause of WCT in general population(80%)
95% of WCT in pts with structural heart disease
Supraventricular tachycardia with abnormal interventricular conduction(15% to 30% of WCT)
SVT with BBB aberration;
fixed(present during normal rhythem)
functional(present only during WCT)

6. Functional aberration results from sudden change in cycle length when parts of the His-Purkinje system are partially or wholly inexcitable
Functional RBBB commoner because of longer refractoriness
Linking phenomenon -Functional BBB may persist for several successive impulses because the bundle branch that is blocked antegradely may be activated trans-septally via its contralateral counterpart

7. AV reentrant tachycardia (AVRT)
Orthodromic AVRT – antegrade conduction over the AV node and retrograde conduction through accessory pathway.WCT occurs in aberrant conduction,either rate related or preexisting
Antidromic AVRT – antegrade conduction over the accessory pathway and retrograde conduction over the AV node result in WCT
Pre-excited tachycardia- SVT with ventricular activation occurs predominantly via accessory pathway

9. Mahaim pathway mediated tachycardia
antegrade conduction through mahaim(nodoventricular) pathway and retrograde through AV node
Tachycardia with LBBB morphology and left axis
episodes of pre-excited tachycardia without exhibiting pre-excitation during sinus rhythm
Wide QRS complex tachycardia occur because absence of retrograde conduction over accessory pathway

10. SVT with a wide complex due to abnormal muscle spread of impulse
RBBB in pts undergone rt.ventriculotomy
LBBB in pts with DCM
SVT with wide complex due to drug or electrolyte induced changes
Ι A, Ι C,amiodarone,tricyclic antidepressants
Hyperkalemia
Ventricular paced rhythems
LBBB with left axis

11. Causes of irregular WCT
Any irregular supraventricular rhythem(AF,EAT or atrial flutter with varying conduction) with aberrant ventricular conduction
AF with ventricular preexcitation-if the ventricular rate in AF is >220/min or shortest R-R int is <250 msec bypass tract should be considered
Polymorphic VT
Torsade de pointes

12. SVT Vs VT- history and physical examination
History of prior heart disease favour VT
Prior MI,angina or CCF
Each factor -95% PPV for VT
H/o similar episodes for >3 yrs-SVT more likely
First episode of WCT after MI-VT more likely
Older age grp>35 yrs-VT more likely

13. Findings of AV dissociation-favour VT
Cannon a waves
Variable intensity of S1
AV dissociation can be brought out by carotid sinus massage,adenosine
Termination in response to CSM, adenosine,valsalva-suggest SVT

14. ECG features-QRS morphology
SVT with aberrancy-QRS complex must be compatible with some form of BBB or FB
If not,diagnosis by default is VT

15. Specific morphologies of QRS
V1 with RBBB
SVT with aberration-
initial portion of QRS not affected by RBBB aberration
Triphasic complex (rabbit ear sign)with rt peak taller
r S R (r-septal activation,S-activation of LV,R-activation of RV)
pattern s/o VT
Monophasic R
Broad(>30 msec)initial R qR
Triphasic complex with lt.peak taller

17. V6 with RBBB SVT with aberration pattern s/o VT qRs,Rs,RS(R/S>1)
Delayed RV activation produces a small S wave in V6
pattern s/o VT
rS,QS,Qrs,QR
RS with R/S<1
Large S due to RV component of ventricular activation+depolarisation of some portion of LV as activation propagates away from V6

19. V1 -LBBB SVT with aberrancy VT r S, QS
Rapid initial forces(narrow r&rapid smooth descent to nadir of S)
Initial forces are relatively preserved VT
Broad R/deep S
QS with a slow descent to S wave nadir
Initial R >30 msec s/o VT,wider the R greater likelihood
Notch in downstroke of S
Interval from onset of QRS to nadir of S >60 msec
Taller R during WCT than sinus rhythem

21. V6 -LBBB SVT with aberrancy VT Lacks initial Q wave
Monophasic R or RR’ VT
QR,QS,QrS,Rr’
Patterns consistent with SVT may be seen

24. QRS complex duration
69% of VT had QRS duration >140 ms-Wellens et al
VT probable when QRS duration >140 ms with RBBB morphology ,>160 ms with LBBB morphology
QRS duration > 160 msec-a strong predictor of VT regardless of bundle--branch block morphology
QRS duration < 140 msec does not exclude VT

25. QRS axis Mean QRS axis in the normal range favors SVT with aberrancy
Right superior axis -90 to ± 180° suggests VT
Axis shift during WCT of > 40° favors VT
LBBB morphology with rt axis deviation-almost always due to VT
RBBB with a normal axis-uncommon in VT

26. Concordant pattern
Concordant precordial R wave progression pattern(all precordial leads predominantly positive or predominantly negative)
High specificity for VT (90%)
Low sensitivity(observed in only 20%of VTs)
Exception –antidromic AVRT w/ a left posterior accessory pathway-positive concordance

29. Concordance of the limb leads-predominantly neg QRS complex in limb leads s/o VT

30. A V dissociation Most useful ECG feature
Complete AV dissociation seen in 20 to 50 % of VT(sensitivity .2 to .5,specificity 1)
15 to 20% of VT has 2nd degree V A block
Lewis leads-p waves seen better with arm leads at various levels on opposite sides of sternum
Psudo p waves-contour of terminal portion of QRS may resmble p-inspect simultaneous recording in other leads

31. Variation in QRS complex altitude during WCT-due to summation of p wave on the QRS complex –clue to presence of AVD
30% of VT has 1:1 retrograde conduction-CSP or adenosine used to block retrograde conduction to diagnose VT
When the atrial rate<ventricular rate-s/o VT
Atrial rate>ventricular rate s/o SVT with conduction block

32. Evidences of AV dissociation
Fusion beat – when one impulse originating from the ventricle and a second supraventricular impulse simultaneously activate the ventricular myocardium
Morphology intermediate b/w sinus beat&pure ventricular complex
Capture beat – normal conduction momentarily captured control of ventricular activation from the VT focus

34. Onset of tachycardia Episode initiated by a premature p wave-SVT
If begins with a QRS-can be ventricular or supraventricular
If first wide QRS preceded by a sinus p with a shorter PR int.-usually VT

35. Presence of Q waves during a WCT –s/o old MI-s/o VT
Patients with post MI VT maintain Q wave in the same territory as in NR
DCM-Q waves during VT,which was not there in sinus rhythem
Psudo Q –retrograde p deforming the onset of QRS

36. QRS complex during WCT narrower than NR
In presence of BBB during NR,a WCT with a narrower complex indicate VT
Contralateral BBB in NR and in WCT s/o VT
QRS alternans-
alternate beat variation in QRS amplitude>0.1 mV
occurs with equal frequency in WCT due to VT &SVT,but grter no.of leads show this (7 Vs 4) in SVT with aberrancy(Kremer et al;Am J Cardiol)

37. Multiple WCT configurations-
More than one QRS configuration during a WCT –VT more likely
51% of pts with VT,8% with SVT in one series

39. Importance of sinus rhythem ECG
Differentiation between VT and SVT with antegrade conduction over accessory pathway
Aberrancy is rate related or pre existing
Presence of premature complexes in sinus rhythem
Old MI
QT interval
ECG clues to any other structural heart disease

40. rule out ECG artifacts which may be misdiagnosed as WCT

42. VT Vs preexcited tachycardia
Characteristics specific for VT
Predominantly negative QRS complexes in V4-V6
Presence of a QR complex in one or more leads V2-V6
More QRS complex than P
75% sensitivity&100%specificity for VT(Stierer et al)

43. Criteria for diagnosis
Griffith et al;1991
QRS morphology in V 1&aVF,change in QRS axis grter than 40 from normal rhythem&h/o MI
Predictive accuracy greater than 90% in detecting VT
Kremer et al ;1988
Precordial concordance,NW axis,monophasic R in lead V1

44. Brugada criteria
Brugada et al analysed 554 cases of WC tachycardias with a new algorithm(circulation 1991)
Sensitivity of the four consecutive steps was 98.7%&specificity was 96.5%
Four criteria for VT sequentially evaluated
If any satisfied diagnosis of VT made
If none are fulfilled-SVT

46. Evaluation of RS complexes

47. Measurement of RS interval

51. New aVR algorithm Vereckei et al;Heart Rhythm 2008
483 WCT (351 VT, 112 SVT, 20 preexcited tachycardia)analysed
Greater sensitivity for VT diagnosis than Brugada algorithm(96.5% vs 89.2%, P .001)
Greater specificity for diagnosing SVT compared with Brugada criteria

52. Reasons for using a VR
Duriing SVT with aberrancy,initial septal activation and main ventricular activation directed away from lead aVR, so negative complex
Exception-inferior MI-initial r wave (rS complex) during NSR or SVT
Initial dominant R suggest VT typically originating from inferior or apical region

53. VT originating from other sites-show a slow initial upward vector f/b main vector pointing downward and creates a predominantly negative QRS in lead aVR.
Exception-VT originating from the most basal septum or free wall

57. Vi/Vt (ventricular activation velocity ratio)
Vi –initial ventricular activation velocity
Vt –terminal ventricular activation velocity
Both measured by the excursion (in mV) ECG during initial (Vi) and terminal (Vt) 40 msec of QRS complex

61. Thank you