林口長庚醫院內科
Grand Round
Idiopathic ventricular tachycardia
心內一科 葉勇信 醫師
2011-6-17 Am 7:30-8:30
Idiopathic Ventricular Tachycardia
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Ventricular tachycardia that occurs in the
absence of clinically apparent structural
disease.
Clinical evaluation
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VPC/VT 12-lead ECG morphology
Exclude structural heart disease (coronary
artery angiography, cardiac
echocardiography)
No metabolic/electrolyte abnormalities or
long QT syndrome can be identified.
24-hour Holter recording
Exercise stress test
MRI?
Holter report
Idiopathic Ventricular Tachycardia
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In 10% of patients with VT
Young (20-50 years, range, 6 to 80 years)
Palpitation, dizziness, presyncope or syncope (rare)
Sudden cardiac death is rare
Excellent prognosis
Can be a cause of tachycardia-mediated
cardiomyopathy
Certain anatomic locations with manifest specific
ECG patterns which help identify their site of
origin.
RBBB pattern, superior axis  low LV
LBBB pattern, inerior axis  from RVOT or LVOT
Mechanism of tachyarrhythmia
(1) Automaticity
(2) Triggered activity:
Delayed afterdepolarization (DAD)
Early afterdepolarization (EAD)
Mechanism of tachyarrhythmia
(3) Reentry
Mechanism of tachyarrhythmia
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Automaticity
1. focal origin
2. may become incessant during isoproterenol
3. cannot be initiated or terminated by programmed electrical
stimulation
4. sometimes suppressed by calcium or β blockers
5. adenosine transiently suppresses but does not terminate it.
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Triggered activity
1. focal origin
RVOT VT: DAD, adensine sensitive
2. EAD or DAD ([Ca2+]i overload due to HR↑, β adrenergic effect
(cAMP↑) or digoxin)
3. Induced by burst pacing, isoproterenol infusion or atropine
Mechanism of tachyarrhythmia
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Reentry
1. a large circuit (macroreentry) or focal
(microreentry)
2. slow conduction zone: small diastolic potential
3. can be initiated and terminated by programmed
electrical stimulation
4. can be entrained from multiple sites
Idiopathic left VT: macroreentry, verapamil sensitive
Classification of idiopathic VT relative to the
mechanism
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Adenosine-sensitive VT (triggered activity)
Propranolol-sensitive VT (automaticity)
Verapamil-sensitive VT (reentry)
Classification of idiopathic VT relative to the
location
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Outflow tract ventricular tachycardia (OTVT)
1. RVOT VT (90%)
above pulmonary valves rarely
2. LVOT VT (10%): above/below AVs, mitral annulus
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Idiopathic left ventricular tachycardia (ILVT)
1. Left posterior fascicular VT (most common)
2. Left anterior fascicular VT (rare)
3. Upper septal fascicular VT (rare)
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Others…….
Purkinje fibers, epicardium…..
RVOT VT
1.
1.
Nonsustained, repetitive, monomorphic VT.
# Most common form (60-90%)
# Characterised by frequent VPCs, couplets and salvos of non
sustained ventricular tachycardia (NSVT)
# LBBB morphology and inferior QRS axis.
# Occurs at rest or following a period of exercise
# Transiently suppressed by sinus tachycardia. They may
diminish with exercise during stress testing.
Paroxysmal, exercise-induced sustained VT.
# This VT may be initiated during exercise or recovery.
# Exercise stress testing is frequently uses to initiate and
evaluate
RVOT VT, but is not clinically helpful in most cases.
I
II
III
aVR
aVL
aVF
V1
V2
V3
V4
V5
V6
RVOT VT
Signal transduction schema for initiation and termination of
cAMP-mediated DAD (triggered activity)
Adenosine
cAMP↓
DAD↓
Outflow tract ventricular tachycardia
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90% of outflow tract VT comes from the RVOT
- may above the pulmonary valves (rare)
10% may arise from LVOT
- superior basal region of LV septum, free wall
- aortic sinuses of Valsava
- aortic cusps
- the aorto-mitral continiuty
- mitral annulus
- His bundle area
Epicardium
Management of OTVT
1.
2.
Acute termination: vagal maneuver or adenosine (6
mg until 24 mg), IV verapamil (10 mg given over 1 min.
These drugs may suppress triggered rhythms;
electrical cardioversion.
Long term treatment options
# Medical therapy: β-blockers, verapamil, diltiazem
(efficacy: 20 to 50%); Alternatively class IA, IC and III
agents.
# Radiofrecuency ablation has cure rates of 90% with
a recurrence rate of 5%.
Indications for catheter ablation of idiopathic
ventricular tachycardia
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Monomorphic VT that is causing severe
symptoms
Monomorphic VT when antiarrhythmic
drugs are not effective, not tolerated, or not
desired
Tachycardia-induced cardiomyopathy
Contraindication for catheter ablation of
idiopathic ventricular tachycardia
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Presence of a mobile ventricular thrombus
Asymptomatic PVCs and/or non-sustained
VT that are not suspected of causing or
contributing to ventricular dysfunction
VT due to transient, reversible causes, such
as acute ischemia, hyper-/hypokalemia, or
drug-induced torsade de points
How to ablate VT
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Mapping
 Basic electrophysiologic study
 Pace mapping (identical 12-lead ECG
morphology)
 Activation mapping (earliest activation site)
 Electroanatomic mapping (Carto, Navx, Enside
Array, Magnetic remote control) (voltage,
anatomy)
Ablation successful rate: 90 %
Mapping Tool for OT-VT
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ECG morphology:
Could be non-inducible
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Pacing morphology
could be large area 2 cm2: different chamber, scar,
or epicardium
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Activation map
More accurate: remain unsuccess: more mapping
sites, epicardium
RVOT VT
1
4
7
2
5
8
3
6
9
Dixit et al, JCE 2003
Dixit et al, JCE 2003
Septum
Free wall
•↑QRS duration
• Notching in
inferior lead
• Smaller amplitude
In inferior lead
• Large S wave
in V2 > 3 mV
• Later QRS
transition
Dixit et al, JCE 2003
Spontaneous PVC
Pace Mapping
1. Important overlapping
nature of the outflow tract
course!
2. RVOT and PA lie anterior and
to the left of the LVOT and
aorta.
How to D/D RVOT and LVOT VT in origin?
LVOT VT Morphology
P=0.007
Survival curve
of VT patients (N=200)
Fascicular VT (ILVT)
RVOT
ARVC
CPVT, idiopathic VF
Ischemic VT
DCM
Management of RVOT VT
1.
2.
3.
CAG and 2D echo are usually normal, but MRI may show
abnormalities of the RV in up to 70% of patients (focal
thinning, diminished systolic wall thickening and
abnormal wall motion).
RVOT VT should be distinguished from ARVD: ECG
morphologic features similar to RVOT VT but DOES NOT
terminate with adenosine.
It should be strongly considered for the following
patients with a potentially malignant form of OT VT:
a) a history of syncope; b) very fast VT; c) ventricular
premature beats with a short coupling interval.
coupling interval
Requirement of non-contact mapping
system for VT mapping
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Pacing mapping may not sensitive to locate the
sites of foci in certain patients with focal VT, in
the presence of large scar area.
VT could be non-sustained and unstable. It is
difficult to map the entire chamber
One beat analysis of dynamic substrate by NCM
may be useful to treat these patients.
Ensite Array Location
ＲＡＯ
ＬＡＯ
RVOT VPC recorded by enside array
(Higa S: University of the Ryukyus, Okinawa, Japan)
Classification of idiopathic VT relative to the
location
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Outflow tract tachycardia
1. RVOT VT (most common)
2. LVOT VT
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Idiopathic left ventricular tachycardia
(fascicular ventricular tachycardia, intrafascicular
verapamil-sensitive VT)
1. Left posterior fascicular VT (most common)
2. Left anterior fascicular VT (rare)
3. Upper septal fascicular VT (rare)
Others……. (focal origin in the Purkinje system,
triggered activity or automaticity, rare)
Fascicular ventricular tachycardia
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Left posterior fascicular VT (most common)
RBBB, superior axis
Left anterior fascicular VT (rare)
RBBB, right axis deviation, inferior axis
Upper septal fascicular VT (rare)
A narrow QRS, normal or right axis deviation, inferior
axis
Posterior Fascicular VT
Mechanism of fascicular VT
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The most likely mechanism of idiopathic left
ventricular tachycardia is reentry with an
excitable gap and a zone of slow conduction
since can be initiated and terminated with
programmed stimulation as well as the
demonstration of entrainment of the
tachycardia with rapid pacing
Verapamil sensitive
Diastolic potential & Purkinje potential
P2
P1=LDP=DP
P2=PP
P1
P2
Management of fascicular VT
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The long-term prognosis of patients with
fascicular VT without structural heart disease is
very good.
Arrhythmias in patients with sporadic, welltolerated episodes of idiopathic left ventricular
tachycardia may not progress despite absence of
pharmacologic therapy.
Treated with oral verapamil (120 to 480 mg/day).
Ablation successful rate: >95%
Posterior Fascicular VT
Where to Target
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Diastolic potential (P1) in the midseptum of
LV. P1-QRS=28-130 msec
If P1 could not be identified, target the fused
and earliest Purkinje potential (P2)
Successful ablation revealed P1 during SR
could be a marker of successful ablation.
Ablation successful rate: >95%
Complication: trivial
Role of electroanatomic mapping systems
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Refers to point by point (contact) mapping combined with the
ability to display the location of each point in 3-dimensional
space.
Carto, Navx, Ensite array, Magnetic remote system
Functions:
1. non-fluoroscopic localization of the ablation catheter
2. display of intracardiac electrograms (scar, low voltage zone)
3. interpretation of mechanism of arrhythmia (focal or
macroreentry)
Always useful in scar-related VTs; can be useful in idiopathic
VTs.
ARVC
Classification of idiopathic VT relative to the location,
judged by 12-lead ECG morphology
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Outflow tract tachycardia
1. RVOT VT (most common)
2. LVOT VT: below/above aortic valves, mitral annulus
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Idiopathic left ventricular tachycardia (fascicular
VT)
1. Left posterior fascicular VT (most common)
2. Left anterior fascicular VT (rare)
3. Upper septal fascicular VT (rare)
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Others……. epicardium, focal origin in the Purkinje system
(triggered activity or automaticity, rare)
Summary
Conclusion
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Idiopathic VT concerns a small subgroup of patients
with VT. Depending on tachycardia mechanism,
idiopathic VT may respond to β-blockers, Ca2+ channel
blockers or to vagal manueuvers, although
radiofrequency ablation is curative in most patients.
Patients usually continue to follow up to rule out
latent progressive heart disease such as
arrhythmogenic right ventricular dysplasia (ARVD) or
other forms of cardiomyopathies.
Thank you for your attention!