This document discusses techniques for localizing the site of origin of ventricular tachycardia based on electrocardiogram characteristics. It describes that right ventricular outflow tract tachycardias typically present with left bundle branch block morphology while left ventricular sites may present with either right or left bundle branch block depending on exit site. Specific leads are discussed that can provide clues about anterior vs posterior, septal vs free wall origin within the outflow tracts. Other areas like fascicles, papillary muscles and mitral/tricuspid annuli are also summarized.

1. Localisation of ventricular
tachycardia

2. • VT exit site -point from which rapidly
expanding endocardial systolic
activation occurred on the isopotential
map synchronous with or just prior (up
to 40 msec) to surface QRS onset.

3. • >>70–80% of idiopathic VTs or VPCs
originate from RVOT

4. General Considerations
1. Left ventricular free wall VT =RBBB
2. VT exiting from the interventricular septum or right
ventricle =LBBB
3. Septal exits =narrower QRS complexes
4. Basal sites - positive precordial concordance
5. negative concordance == apical sites of origin

6. Anatomic Considerations
• anteroseptal aspect of
RVOT is located in close
proximity to the LV
epicardium, adjacent to
the AIV and the LAD.
• posteroseptal aspect
of RVOT is adjacent to
the region of the RCC,
• anterior septal surface is
adjacent to the anterior
margin of the RCC or the
medial aspect of
theLCC.

7. • Simultaneous mapping
on the posterior RVOT
and the anterior wall of
the LVOT should be
performed to identify
the true earliest site of
origin.
• The top of RVOT may
be crescent shaped,
with the posteroseptal
region directed
rightward and the
anteroseptal region
directed leftward

8. •anteroseptal aspect of RVOT is
located in close proximity to the
LV epicardium, adjacent to the
AIV and the LAD.
•The posteroseptal aspect of
RVOT is adjacent to the region of
the RCC, and the anterior septal
surface is adjacent to the anterior
margin of the RCC or the medial
aspect of the LCC

9. •RVOT tachycardia
– LBBB
– inferior axis (R waves in II,III,aVF)
– QS complexes in aVR and aVL.
•Lead V1 : negative (LBBB)
•posterior RVOT or origin near or above the pulmonic valve (left side
of the body) = initial R wave in lead V1.
•R wave in lead V1 : potential anatomic sites of origin

10. Anterior RVOT (1) : LBBB morphology
• (2), (3) : between the posterior RVOT and the anterior right coronary cusp
(RCC) of the aortic valve. A small but variable R wave is seen in lead V1.
• (4) : more posteriorly in the region of the left coronary cusp (LCC)/aortic mitral
continuity(AMC) /noncoronary cusp(NCC) characterized with a distinct R wave in
V1.
• Even more posterior and leftward origin (the posterior mitral annulus) : RBBB
morphology.

11. Lead I
•The focus near or above the pulmonic valve (leftward in the body): typically all
negative (QS complex)
•Origin on the right side of the RVOT (free wall): positive lead I
•Origin posterior portion of the RVOT : positive lead I
•Origin anterior portion of the RVOT : biphasic pattern

12. Leads aVR and aVL (Both leads are superior leads.)
•Outflow tract VT (right or left) in a superior location : negative (QS
complexes) deflections in aVL and aVR
•Peri-His bundle region in the RVOT (most rightward and inferior portion) :
lead aVL (a left-sided lead) becomes isoelectric or slightly positive, lead aVR
(a right-sided lead) remains negative
•Suprapulmonary VT (anatomic location of the site in the left side of the
body) : greater amplitude negatively in the aVL compared to aVR

13. • Leads II, III, and aVF
• All outflow tract arrhythmias show a positive deflection in leads II, III,
aVF.
• The ratio of positivity (R-wave amplitude) : a clue to the site of origin.
• Suprapulmonary valve arrhythmia : a taller R wave in lead III than in II.
(the anatomic leftward location of the PV and lead III being an inferior and
rightward lead)

14. Localisation
• LV or RV?
• VTs arising from the LV have a RBBB like
morphology because the LV is activated before the
RV.
• VTs arising on or adjacent to the LV septum can
have a LBBB morphology if VTs exit from the septum
to the RV.
• Similarly, most VTs arising from the RV will have a
LBBB-like morphology.
• The anterior aspect of the LVOT is closely located to
the posterior aspect of the RVOT and the ECG
morphologies are similar each other

15. • RV origin VT
• RVOT
• Para hisian
• TA
• PA
• VT arising from other sites like PPM.

16. • RVOT VT
• LBBB
• inferiorly directed axis
• deeply negative QS - leads aVL and aVR.
• Septal sites on the RVOT -- narrower LBBB with
earlier precordial transition (positive QRS by V3 or
earlier) and higher amplitudes in the inferior leads.
• Free wall sites -- later precordial transitions (≥V4),
with broader QRS complexes and notching in the
inferior leads

17. • Posterior sites in the RVOT - leftward initial vector
( positive QRS complex in limb lead I)
• Anterior sites -- isoelectric or negative, often
multiphasic, forces in lead I.
• majority of RVOT VT foci lie at the top of the RVOT
within a 1–2-cm craniocaudal band subjacent to the
pulmonic valve=negative QS pattern in lead aVL.
• Isoelectric or positive forces in aVL =more caudal site
of origin at the base of the RVOT, potentially adjacent
to the His bundle.

20. Parahisian
•lower R-wave amplitude (III, aVF)
•shorter QRS duration (II, III, aVF)
•Larger R-wave amplitude in leads I, V5, and V6
•a QS pattern in V1.
•close anatomical proximity of the aortic root
• may overlap with OT VT arising from the NCC or RCC
of the aortic valve
•no specific ECG criteria reliably differentiate these sites.

21. Tricuspid Annulus (TA)
•LBBB
•inferior axis
•Lead aVL =monophasic positive or multiphasic
and of low amplitude.
•Free wall of the valve ring off the septum-
similar configuration is seen but with notching in
the limb leads.

22. Pulmonary Artery
•sleeves of myocardium extending above the semilunar
valves
•Typical RVOT VT, sometimes with taller R waves in the
inferior leads.
•pulmonary trunk is a more leftward structure than the
infundibulum,
•earlier precordial transition
•deeper QS in aVL than in aVR.

23. • Increased R-wave amplitudes on the inferior leads in
PA VT
• Lead I polarity: QS (rS) pattern in the PA VT, whereas
RVOT VT shows an R(Rs) pattern
• Early precordial transition at V3.
• The R/S amplitude ratio on lead V2 was significantly
larger than that in the RVOT.
• The average aVL/aVR ratio of Q-wave amplitude is >1
in PA VT.

24. VT Arising from Other Sites of RV(PPM)
•LBBB
•inferior in septal PPM origin or superior in ant. & post. PPM
•QRS width: 160 msec
•Presence of a notch in V1–V6,
•R-wave pattern in V1 (rS, QS), and
•Transition point from a predominantly negative S wave to a positive
R-wave deflection in the precordial leads
•Transition in <V4 in septal > V4 in ant. & post. PPM origin.

25. LV Origin Idiopathic VT
• LVOT
• 15–25% of OT
LCC/RCC/NCC& AMC AIV/GCV
LCC RCC JN. SEPTO PARA HISIAN
Supra valvular Infra valvular Epicardial

26. • more common –LCC than the right, rarely arises from
the NCC,
• LCC
• earlier precordial transition with broader and taller R
waves in V1 or V2
• taller inferior R waves, an S wave in lead I
• characteristic absence of S waves in V5 and V6.
• R-wave duration of >50% of the total QRS duration or
an R/S ratio of more than 30% =LCC origin.
• Characteristic multiphasic notched pattern in V1 with
an M” or “W” pattern, presumably due to transseptal
activation after initial LV activation from the LCC.

28. • RCC
• left bundle-type pattern
• broad small R wave in V2
• precordial transition generally at V3.
• NCC: no pathognomonic ECG pattern
• LCC/RCC junction
• significant overlap between this group
• multiphasic notched V1 pattern seen in standard LCC
foci
• QS morphology in lead V1 with notching on the
downward deflection with precordial transition at lead
V6

29. • LCC/RCC junction
• • QS morphology in
lead V1 with notching on
the downward deflection
• • precordial transition at
lead V3
• • presence of late
potentials in sinus
rhythm at the site of
successful ablation

30. • Monomorphic ventricular tachycardia with LBBB morphology and
an inferior axis : DDx of RVOT and ASC origin

31. • LBBB morphologies with
right inferior axis
• VT arising from the anterior
septal side of the RVOT, from
the right or left coronary
cusp, and from the
pulmonary artery.
• R-wave progression : LV or the
aortic cusp
• R waves in V1 and V2 and a
transition by lead V3
• Left-sided outflow tract VT,
• Later transitions at V3 and V4 :
RVOT or the pulmonary artery

32. Infravalvular
• basal LVOT VT = VT
arising from the AMC that
characteristically displays a
qR pattern in V1
VT originating further leftward across
the anterior mitral annulus : the R
wave in lead I diminishes and a
broad, positive R wave is seen in lead
V1.

33. • Result of the left fibrous trigone deflecting
initial electrical activation leftward
• Depending the position and extent of the
trigone, AMC VT may not display this ECG
signature and may instead have an RBBB
pattern with positive concordance and no late
precordial S waves.
• Early transition and longer intrinsicoid
deflection.

34. • Septal-parahisian sites. ECG features.
• LBBB configuration more akin to RV foci and have a
dominant R in lead I, usually with left inferior axis
• A QS pattern in lead V1 and R wave in lead aVL also
were observed more often in the His group than that in
the RVOT.
• Narrow QRS, and small r wave in LII,LIII, aVF.

36. Epicardial
•no specific ECG feature
•LBBB configuration
•inferior axis and transition usually around
V3

37. • shortest RS interval
• Maximum deflection index (MDI: interval from
the earliest ventricular activation to the peak
of the largest amplitude deflection in any
precordial lead divided by the QRS duration)
• larger in epicardial VT.

38. 1. pseudodelta wave in any precordial leads of
RBBB VTs- time from the QRS onset to the
earliest rapid deflection of ≥34 ms.
2. delayed intrinsicoid deflection=time from
QRS onset to the peak of the R wave in V2
of ≥85 ms.
3. shortest RS interval= time from the first
ventricular activation to the nadir of the first S
wave in any precordial leads of ≥120 ms

39. • Precordial MDI= shortest time to maximal positive or
negative deflection in any precordial lead divided by
the QRS duration.
• cut-off value of 0.55 = epicardial foci and other OT
sites of origin
• “Pattern break,” R-wave regression/progression-
abrupt loss of R wave in V2 followed by resumption in
R waves from V3 to V6

40. • Valles et al. described a four-step algorithm for
identifying epicardial origin VT from basal superior
and lateral LV in the setting of nonischemic
cardiomyopathy using the presence of inferior q
waves, pseudo-delta ≥ 75 ms, MDI ≥ 0.59, and
presence of q wave in lead I.
•

41. VA from LV summit( AIV/GCV):
• LVS - triangular
portion of the
epicardial LVOT
bounded by the
bifurcation between
the LAD and the LCX
• transected laterally by
the great cardiac vein
(GCV) at its junction
with the anterior
interventricular vein
(AIV).

42. • RBBB
• transition zone: early in V2
• R-wave amplitude ratio in leads III to II:
• Qwave amplitude ratio in leads aVL to aVR: >1.1
• S wave in lead V6 all accurately predicted the site of
origin of the idiopathic VAs originating from the LV summit
• Accessible area/ ablation succesful from GCV/AIV
• When LV summit VAs exhibit a III/II amplitude ratio of > 1.25
and an aVL/aVR amplitude ratio of > 1.75, those VAs are
likely to require a pericardial approach for ablation

43. • VT Arising from Other LV Sites
• Mitral annulus:
• delta wave-like beginning of the QRS complex.
• MA is located in the posterior portion of the LV and anterior,
and anterolateral sites have more predominant occurrence
than posteromedial sites.
• RBBB
• Early transition in V2
• Long QRS duration
• Negative QRS complex in LI

44. • Late notching in the inferior leads or an S wave in lead I, which are
found usually in both anterolateral MA and posterior MA VT, may be
absent in anterior or posteroseptal MA VT

45. PPM
•RBBB
•refractoriness to verapamil and Na+ channel blockers
•tendency for VPCs rather than VT
•inducibility with exertion
• lack of inducibility with programmed ventricular or atrial stimulation
•earliest ventricular activation at the base or middle portion of the
LV PPM
• absence of highfrequency potentials at the site of origin
•requirement of high RF power to achieve longterm ablation
success

46. • Anterolateral PPM:
• VTs exhibit RBBB pattern and right inferior axis QRS
morphology with an early precordial transition, generally before
V1. qR or qr pattern in lead aVR and rS pattern in lead V6 (R/S
ratio < 1) are useful features to differentiate from other LV sites.
The mean QRS duration during VT or VPCs is 168 ms.
• (b)Posteromedial PPM. VT with a posterior PPM origin showed
RBBB and right or left superior axis QRS morphology.
• The mean QRS duration during VT was within 160 ms.
• Monophasic R and qR pattern predominate in lead I. R/S
amplitude ratio <1 in V6

47. • Crux:
• On the epicardial surface of
the heart.
• JN of MCV with CS
• Ecg
• LBBB
• Early transition
• Left superior axis
• MDI >0.55
• Q in LII,LIII,aVF.

48. Fascicular VT:
»LPF VT
»LAF VT
»USF VT
RBBB, left superior axis, RS in
V5,V6.
VTs exhibit an RBBB configuration
with right axis deviation
its narrow QRS complex with
normal or rightward axis
deviation

50. • The steps to finding the exit site are:
• What is the bundle branch block (BBB)
configuration?
• What is the inferior lead QRS complex
polarity?
• What is the lead I QRS complex polarity?
• What is the lead aVL QRS complex polarity?
• What is the lead aVR QRS complex
polarity?
• Where is the R-wave transition point?

52. Take Home Messages
•Anatomic relationship between RVOT and LVOT : RVOT is anterior and to
the left of the LVOT
•ECG recognition of outflow tract tachycardia location
•R wave in lead V1 : clue to the potential anatomic sites of origin
•Precordial QRS transition: RVOT vs LVOT (RCC, LCC)
•Lead I : right vs left side of RVOT site QRS width: free wall vs septum of
RVOT Leads aVR and aVL : peri-His bundle region and suprapulmonary
VT Leads II, III, and aVF: suprapulmonary VT
•R-wave duration index ≥50% and R/S ratio ≥30% in lead V1 or V2 :
LVOT (RCC, LCC)
•Precordial MDI >0.55, delayed pattern of initial QRS activation, pseudo-
delta wave : epicardial LV VT