Differential Diagnosis of
Tachycardias
Differential diagnosis of broad complex tachycardias
Criteria for the diagnosis of the presence of a
broad complex tachycardia:
QRS >120ms = Broad Complex Tachycardia
QRS <120ms = Narrow Complex Tachycardia
Tachycardias
Narrow QRS
Sinus tachycardia
Atrial tachycardia
Atrial fibrillation
Atrial Flutter
AVRNT
AVRT
SVT
Broad QRS
Ventricular tachycardia
SVT with abnormal
conduction
Bundle branch block
Rate related
Ventricular pre- excitation
Differential diagnosis of broad complex tachycardias
The rhythm strip taken from a single lead is
generally insufficient to make a differential
diagnosis between an SVT with aberrancy
or VT. A 12 lead ECG is required for
making an accurate diagnosis.
Differential diagnosis of broad complex tachycardias
The presence of anyone of the following confirms the
diagnosis of VT:
Evidence of A.V.Dissociation….in the form of
independent atrial activity.
Presence of fusion beats
Presence of capture beats
AV dissociation

Atrioventricular dissociation in monomorphic
ventricular tachycardia (note P waves, arrowed)
Capture beat

Capture beat
Fusion Beat

Fusion beat
Differential diagnosis of broad complex tachycardias
In patients with IHD…. ….
90% of broad complex
tachycardias will be ventricular
in origin
QRS Contours Favouring Ventricular Tachycardia
V1
V1
V6
Wellens
Gulamhusein
15/15 (100%)
84/86 (98%)
7/7 (100%)
177/187 (95%)
27/31 (87%)
189/190(100%)
V6
17/17 (100%)
38/40(94%)
Wagner (2001) Marriotts Practical Electrocardiography 10th Ed.
Differential diagnosis of broad complex tachycardias
QRS Contours Favouring Ventricular Aberration
Wellens
V1
V6
Gulamhusein
38/41 (93%)
55/55 (100%)
44/47 (94%)
27/27 (100%)
Wagner (2001) Marriotts Practical Electrocardiography 10th Ed.
Differential diagnosis of broad complex tachycardias
Tachycardias presenting with a basically RBB pattern
R’
V1
SVT is more the likely
diagnosis where there is
a triphasic QRS…rSR’;
with the R’ wave taller
than the initial r.
Professor A.J Camm: “A Master Class in The Differential Diagnosis
of Broad Complex Tachycardias.
Differential diagnosis of broad complex tachycardias
Tachycardias presenting with a basically RBB pattern
V1
S
If the ‘S’ wave at least
reaches the isoelectric
line (or goes beyond it)
the tachycardia is most
likely to be supraventricular in origin.
Professor A.J Camm: “A Master Class in The Differential Diagnosis
of Broad Complex Tachycardias.
Differential diagnosis of broad complex tachycardias
Tachycardias presenting with a basically RBB pattern
NB: Proviso:
V1
S
If the ‘S’ wave is not
much more than a notch
on the down-stroke, then
the tachycardia is less
likely to be
supraventricular in origin.
Professor A.J Camm: “A Master Class in The Differential Diagnosis
of Broad Complex Tachycardias.
Differential diagnosis of broad complex tachycardias
Tachycardias presenting with a basically RBB pattern
V6
R:S >1
R:S <1
SVT
VT
Professor A.J Camm: “A Master Class in The Differential Diagnosis
of Broad Complex Tachycardias.
Differential diagnosis of broad complex tachycardias
Tachycardias presenting with a basically LBB pattern
V1
Kinwall Criteria:
The Presence of any one of these characteristics points
to the diagnosis of VT.
Initial ‘r’ wave in V1 > 30ms in duration.
Presence of a ‘notch’ on the down-stroke of the ‘S’
wave.
The duration of the complex from the start of the ‘r’
wave to the nadir of the ‘S’ wave = 60ms or more.
Differential diagnosis of broad complex tachycardias
Tachycardias presenting with a basically LBB pattern
30ms
‘notch’
V1
60ms
Professor A.J Camm: “A Master Class in The Differential Diagnosis
of Broad Complex Tachycardias.
Differential diagnosis of broad complex tachycardias
Tachycardias presenting with a basically LBB pattern
V6
‘q’
The presence of any ‘q’
wave points to the
likelihood that the
tachycardia is
ventricular in origin.
Professor A.J Camm: “A Master Class in The Differential Diagnosis
of Broad Complex Tachycardias.
Differential diagnosis of broad complex tachycardias
Brugarder et al Criteria:
‘rS’ patterns are usually present in one or more
precordial leads therefore:
A no ‘rS’ pattern most likely suggests that the
tachycardia is ventricular in origin.
If there are any ‘rS’ complexes; if the distance
from the start of the ‘r’ wave to the ‘nadir’ of the ‘S’
wave is 100ms or more it indicates that the
tachycardia is most likely to be ventricular in origin.
Differential diagnosis of broad complex tachycardias
V1 V6
100ms
Professor A.J Camm: “A Master Class in The Differential Diagnosis
of Broad Complex Tachycardias.
Differential diagnosis of broad complex tachycardias
Concordance of The QRS complexes in The Precordial Leads
“When all of the ventricular complexes from leads V1 to
V6 are either negative (concordant precordial negative) or
positive (concordant precordial positive), the diagnosis is
most likely VT, since these patterns would be atypical of
either RBBB or LBBB.”
Wagner (2001) Marriotts Practical Electrocardiography 10th Ed.
Differential diagnosis of broad complex tachycardias
Negative Concordance
Positive Concordance
Wagner (2001) Marriotts Practical Electrocardiography 10th Ed.
Cardiac Axis:
If the Cardiac axis is between -1500 and
-/+ 1800, this is clearly abnormal and is a
useful clue to the tachycardia being
ventricular in origin since the electrical axis
of neither RBBB or LBBB produce such
extreme axis deviation.
Broad complex Tachycardia
yes
Independent p waves visible
VT
no
Are QRS in V1 and V6 typical for left or
right BBB
yes
SVT a possibilty
no
VT