Approach to Wide QRS Complex Tachycardia covering mainly the ECG and algorithm part for differentiating VT from SVT.

1. APPROACH TO WIDE QRS COMPLEX
TACHYCARDIA
Dr Mohit Goyal
PG Medicine

2. CCU Bed 7
Old IHD/ P/PTCA+S/
P/ICD/ a/w VT
- Meanwhile PG Medicine
seeing here & there
ICD Technician: कौन कह रहा है कक यह SVT –VT है?
Dr Nasir humbly walks in: “Braunwald says, Any wide QRS
Complex tachycardia (QRS> 0.12 sec) with IHD &
haemodynamic instability should be considered VT until
proved otherwise.”

3. DEFINATION
Wide QRS complex tachycardia is a rhythm with a rate of
more than 100 b/m and QRS duration of more than 120 ms
SVT (20%)

4. Wide Complex Tachycardia Diagnostic Possibilities

5. APPROACH TO THE EVALUATION OF WIDE
COMPLEX TACHYCARDIAS
1. History
2. Physical Examination
3. ECG
4. Algorithms
5. Electrophysiologic T
esting

6. 1. POINTS IN HISTORY DIAGNOSIS
H/O MI VT
H/0 CHF VT
H/OANGINA VT
Recurrent episodes SVT
Duration of illness >3 years SVT
Minimally symptomatic events including
palpitations and light headedness without syncope
SVT
Each has a
PPV of 95%

7. 2. Physical Examination (SVT vs VT)
• VT- AV dissociation (cannon A waves – Frog Sign,
variable-intensity S1,variation in BP unrelated to
respiration)
• SVT- Haemodynamic stability; Termination of WCT in
response to maneuvers like Valsalva, carotid sinus
pressure, or adenosine

8. 3. ECG Features:
1. QRS Duration: wider QRS duration favors VT.
i. In RBBB-like WCT, QRS >140 msec &
ii. LBBB-like WCT, QRS >160 msec favour VT.
o Rarely, VT can have a relatively narrow QRS duration (less than
120 to 140 milliseconds) can be observed in fascicular
(verapamil-sensitive) VT.

9. 2. QRS Axis:
o Asignificant axis shift (more than 40 degrees) between the
baseline NSR and WCT is suggestive of VT.
o A right superior (northwest) is rare in SVT and strongly suggests
VT – Dominant R wave in aVR (Vereckei)!
o In a patient with an RBBB-like WCT, a QRS axis to the left of
- 30 degrees suggests VT.
o in a patient with an LBBB-like WCT, a QRS axis to the right of
+90 degrees suggests VT.
o RBBB with a normal axis is uncommon in VT (less than 3°
/o)
and is suggestive of SVT

10. 3. Precordial QRS Concordance:
Concordance is present when QRS complexes in all 6 precordial
leads (V1 through V6) are either all positive in polarity (tall R
waves) or all negative in polarity (deep QS complexes).
Because concordant patterns are present in <20% of all VTs,
this criterion has low sensitivity.
In some cases of LBBB aberration, R waves may not be seen
until V7 or later, leaving a concordant negative pattern.
A more recent analysis found that a negative concordant pattern
had virtually no capacity to distinguish SVT-A from VT, but a
positive concordant pattern remained a strong differentiator.
MillerJM, DasMK. YadavAV, et al.: Valueof the 12.Jead ECG in wide ORStschycardia. Cardiol CNn. 24:439-451 2006 1§939835

11. 4. Atrioventricular Dissociation:
AV dissociation is the hallmark of VT (specificity is 100%;
sensitivity is 20% - 50%
).

12. 5. QRS Morphology:
If WCT is d/t SVT with aberration, then QRS complex must
be compatible with some form of BBB causing that QRS
configuration. Otherwise think of VT
Normal
Conduction
SVT with
Aberration
VT

13. WCTs with LBBB-like pattern; points favouring VT:
• Negative QRS polarity in lead V1
• Broad initial R wave of >30 millisec in lead V1 or V2
• Notching in the down stroke of S wave >60 millisec in lead V1 or V2
• Any Q wave in V6 favors VT
Normal
Conduction
SVT with
Aberration
VT

14. WCTs with RBBB-like pattern; points favouring VT:
• Positive QRS polarity in lead V1
• Monophasic R, biphasic qR complex, or broad R (more than 40
milliseconds) in lead V1
• A double-peaked R wave in lead V1 if the left peak is taller than the
right peak (the rabbit ear sign)
• An rS complex in lead V6 is a strong predictor of VT (likelihood ratio
more than 50 : 1)
Normal
Conduction
SVT with
Aberration
VT

15. 6. Algorithms

16. Wellens HJ, Bär FW, Lie KI. The value of the electrocardiogram in the differential diagnosis of a tachycardia
with a widened QRS complex. Am J Med. 1978;64:27–33. [PubMed] [Google Scholar]
WELLENS, Criteria favouring VT

17. KINDWALL'S CRITERIA FOR VT IN LBBB
Kindwall KE, Brown J, Josephson ME. Electrocardiographic criteria for ventricular tachycardia in wide complex left
bundle branch block morphology tachycardias. Am J Cardiol. 1988;61:1279–83. [PubMed] [Google Scholar]

18. Brugada P, Brugada J, Mont L et al. A new approach to the differential diagnosis of a regular tachycardia
with a wide QRS complex. Circulation. 1991;83:1649–59. [PubMed] [Google Scholar]

19. GRIFFITH Criteria for Aberrant SVT
VT UNLESS OTHERWISE PROVED!
• SVT is diagnosed only if QRS morphology is typical of
bundle branch block :
• RBBB: rSR' in V1 & RS in V6
with R/S > 1
• LBBB: rS or QS in V1 and V2 and delay to S wave nadir < 10
msec, R wave and no Q wave in V6
Griffth MJ, Garratt CJ, Mounsey P, Camm AJ. Ventricular tachycardia as default diagnosis in broad
complex tachycardia. Lancet. 1994;343:386–8. [PubMed] [Google Scholar]

20. Application of a new algorithmin the differential diagnosis of wide QRS
complex tachycardia
New aVR algorithm
o Vereckeiet al;Heart Rhythm 2008
o 483 WCT (351 VT, 112 SVT, 20 preexcited
tachycardia) analysed
o Greater sensitivity for VT diagnosis than
Brugada algorithm(96.5% vs 89.2%, P .001)
o Greater specificity for diagnosing SVT compared with
Brugada criteria
Andras Vereckei, MD et al Heart Rhythm, Vol 5, No 1, January 2008

21. o Vereckei proposed two algorithms incorporating lead aVR.
Reasons for using aVR:
• 'During SVT w/ BBB, the initial rapid septal activation and the later
main ventricular activation wavefront move away from lead aVR,
creating a negative QRS complex in lead aVR
• Initial dominant R wave in aVR is incompatible w/ SVT, its presence
suggest VT, typically originating from the inferior or apical region
• The first had four steps (a positive result at any step makes a VT
diagnosis, with the remaining ECGs categorized as SVT-A)

22. Vereckei Algorithm
Vereckei A, Duray G, Szénási G et al. Application of a new algorithm in the differential diagnosis of wide
QRS complex tachycardia. Eur Heart J. 2007;28:589–600. [PubMed] [Google Scholar]

23. VENTRICULAR ACTIVATION VELOCITY RATIO Vi/Vt
o Vi - initial ventricular activation velocity
o Vt - terminal ventricular activation velocity
o Measured by the excursion (in mV) during the initial (Vi) and terminal
(Vt) 40 msec of the QRS complex
• Vi/Vt <= 1, supports VT
• Principle: Rapidity of initial septal activation with SVT as
compared to VT
O SVT with abernncy-initial activation is rapid
O VT-initial ventricular activation slow due to muscle to muscle spread of activation

24. o This algorithm performed well in initial testing but is
somewhat cumbersome, and it is difficult to remember
how to make the measurements.
o The second proposed algorithm involves only aVR
and thus is generally simpler.

25. AVR ALGORITHM
Andn ls Vored<ol. MD ot al HeanRhythm. VolS, No 1.January 2008

26. CAVEATS OF Vi/Vt CRITERIA
o A scar situated at a late activated ventricular site can
result in a decreased Vt in the presence of VT, leading
to the misdiagnosis of SVT
o In fascicular VT, the Vi is not slower than the Vt

27. MODIFIED BRUGADA/
PAVA CRITERIA
SENSITIVITY 93.2%
SPECIFICITY 99.3%
POSITIVE PREDICTIVE VALUE 98.2%
NEGATIVE PREDICTIVE VALUE 93.3 %
o Pava et al proposed another simple,
one-step criterion: the interval from
QRS onset to peak amplitude (positive
or negative) in lead 2.
o Using a cutoff of 50 ms, almost all
WCTs with a shorter time to peak
amplitude in lead 2 were SVT,
whereas almost all WCTs with
intervals >50 ms were VT.
o The proposed rationale to analyze
lead II is that it is a lead that is easy
to obtain and is commonly
represented as a rhythm strip on
ECG or ECG monitors.
J Brugada/Pava et al Heart Rhythm
2010;7:922- 926

28. CAVEATS OF PAVA CRITERIA
o Inability to accurately define the initiation and peak of QRS
complexes
o Fascicular VT and Bundle branch re-entry VT may have a
shorter RWPT due to their origin within or in close proximity to
the His-Purkinje network.
o Although this criterion appears to have many desirable
features-simplicity, ease of application, accuracy-its
performance in the hands of other investigators has been less
impressive (sensitivity 0.60, specificity 0.83).

30. ACC/AHA ALGORITHM

31. IRREGULAR WCT
o AF + BBB
• Consistent QRS morphology
• Rate limited byAV node (usually < 200bpm)
o Atrial flutter with variable block + BBB
• Flutter waves present, some not conducted
• Consistent QRS morphology
Consistent R-R interval in groups
o AF + WPW
• QRS morphology variation
• Rates can approach 300bpm

32. o MAT + BBB
• Irregular P waves of different morphology
• Consistent QRS morphology
• Inconsistent R-R interval
o Polymorphic VT
• QRS morphology variation (more chaotic than
WPW)
• Rates consistently rapid (often > 300bpm)
• Unstable

33. 5. ELECTROPHYSIOLOGICAL TESTING
o When His bundle-ventricular (HV) interval is positive
(i.e., His potential precedes QRS onset), an HV interval
during the WCT shorter than that during NSR (HVWCT
less than HVNSR) indicates VT or preexcited SVT
o an HVWCT equal to or longer than HVNSR
indicates SVT with aberrancy.
o When HV interval is negative (i.e., His potential
follows QRS onset), SVT with aberrancy are
excluded.

34. SUMMARY
o Arriving at the correct diagnosis of tachycardia has obvious
clinical importance, in that current therapies can cure many
disorders thereby preventing further episodes.
o In cases of WCT, many algorithms have been proposed to
differentiate between the two major causes: VT and SVT-A.
Although each algorithm is introduced with great promise, each
has its limitations.
o The ideal algorithm would be one that is (1) easy to remember,
(2) universally applicable to all WCTs, (3) easy to apply with
unequivocal results, and (4) 1OOo/o sensitive and specific for VT
(or SVT).
o Until such a tool is developed, it is safest to treat the
patient with WCT that cannot be readily classified for
whatever reason as though the rhythm is VT, until proven
otherwise.

35. TAKE HOME MESSAGE
o VT>>SVT
o When in doubt treat as VT
o Oo not hesitate to shock if hemodynamic instability is
present
o Brugada 's is not the only criteria, it's time to move on!!
o Never make the mistake of rejecting VT because the broad
QRS tachycardia is haemodynamically well tolerated.