Dr' Hany Abed

1
Dr. Hany Abed

• Bundles of Joy

2
The Case

• 14 year old ?
• 2005 presented with exertional palpitations and
  chest pain
• While walking to school
• Palpitations present for 8 hours
• Chest pain present since previous day
• Able to perform usual activities
• Nil other symptoms

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The Case

• PMH
• Premature birth 27/40
• Chronic lung disease requiring ventilation
• VLBW and anaemia
• Normal CV examination at the time
• SH
• Non-smoker, drinker. No illicit drug use. Year 8
• FH
• 6 siblings. No sudden deaths, drowning, single
  driver MVA. No CV history of note. Lebanese
  background

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The Case

• No medications
• Examination
• Anxious
• HR 205/min. 125/70. SaO2 100 RA
• Nil dysmorphic features. Descended testes
• Femoral pulses present
• Normal CV exam
• Other systems - NAD

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The Case ECG (arrhythmia)
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The Case ECG (Sinus Rhythm)
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The Case

• Ix Isolated hyperbilirubinaemia
• Rx
• IV Adenosine No effect
• IV Verapamil Reversion
• Remained in Sinus Rhythm during observation
• Discharged for O.P. Echo and follow-up

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Follow-up

• Normal echo. PASP 27mmHg
• Rx Sotalol and limitation on sporting activities
• Re-admission 2005
• Non-compliant
• IV sotalol failed
• 150J DC cardioversion
• Booked for diagnostic EPS (Dx RVOT VT) under GA

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Results

• Normal antegrade and retrograde conduction
• No evidence of accessory pathway or dual AV node
  physiology
• No VT inducible in presence of isoprenaline
• Re-presented 2006
• Conscious WCT during tennis
• Was off sotalol. No response to adenosine
• Failed 50Jx1, 100Jx1, 150Jx1, 200Jx3 DCCV
• Reverted with IV amiodarone

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Progress

• Re-admission 2007
• Associated TnI rise
• Rx Adenosine, Amiodarone, Metoprolol, Sotalol
• Dx BBR VT
• Re-booked EPS under LA
• Discharged on Sotalol
• MRI? SAECG?

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High Resolution Electrocardiography

• X,Y,Z Leads
• Analogue ? Digital Signal conversion
• QRS template
• Averaging successive QRS complexes
• Low frequency filtering
• Quantifying ventricular high frequency late
  potentials

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HR-ECG

• Late potentials
• Scar-related slow depolarizing currents within
  viable myocardial channels
• Inferoposterior ventricular regions
• Broad QRS
• Results of HR-ECG
• QRSd
• Root Mean Square Voltage at terminal
• Low Amplitude signal

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Signal Averaged ECG - SAECG

• Detects areas of microvolt slow conduction in
  re-entry circuit too low to observe on surface
  ECG
• Occur as late potentials after QRS
• Used as a stratifying tool in ICM/NICM/ARVD/Brugad
  a/Idiopathic VT, for risk of SCD

Mean Late Potential Voltages and Low Amplitude
signal
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SAECG

• Low amplitude, high frequency signals
• Reflect slow and fragmented myocardial conduction
• Critical components for re-entry heterogeneous
  tissue conduction velocity and refractoriness
• Predictive value for SCD and ventricular
  arrhythmias
• Post- MI
• Comparison to LVEF

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Re-Admission ECG

• Close analysis of ECG
• Rapid intriscoid deflections
• Likely circuit utilising rapidly conducting
  specialised cardiac tissue

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The His-Purkinje System

• Rapidly conducting network 1-4 m/sec.
• Penetrate inner 1/3 of endocardial surface
• Long refractory period
• Free running Purkinje fibres organised in series
  (false tendons) are capable of contraction
• Connexins play a role in apparent current-to-load
  mismatch

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Cellular characteristics of human Purkinje
tissue. 1982. Kenneth Dangman, et al.

• Micro-electrode testing of ex-vivo (transplant
  recipients) purkinje tissue
• Highest maximum phase 0 upstroke velocity (Vmax)
  of all cardiac tissue significantly greater
  than ventricular tissue

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Gap Junctions and Connexions Cx43

• Cx43 gap junction protein channel subunit
• Continuous IHC staining over entire purkinje
  cell-purkinje cell borders within fiber strand

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Cable Theory and Current-Load Mismatch

• Conduction Velocity 8 vRadius
• Circumferential gap junction channel distribution
  in purkinje fibres
• Functional increase in conducting fibre radius
• Rapid conduction velocity independent of any
  change in active membrane properties

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Role of subjacent collagen

• Collagen separates Purkinje bundles from
  subjacent ventricular tissue
• Prevents premature current dissipation

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HPS Site of Re-entrant Arrhythmias

• Fascicular VT
• Left anterior fascicle
• Left posterior fascicle
• Bundle Branch Re-entry
• Macro re-entrant circuit between the left and
  right bundles
• Inter-fascicular VT

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Fascicular Ventricular Tachycardia
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Fascicular Ventricular Tachycardia

• Idiopathic Ca-sensitive
• Macro re-entrant localised circuit
• Molecular abnormality Verapamil sensitive zone
  with slow conduction

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Fascicular VT

• Age 15-40 years, ?gt?
• No macro structural heart disease
• Paroxysmal catecholamine-dependent
• May be incessant ? Tachycardiomyopathy

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Left Posterior Hemi-Bundle Subtype
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Fascicular VT Anatomy and Physiology

• Relatively narrow WCT
• 90 originate from left posterior fascicle
• Anatomic substrate LV false tendon or
  postero-inferior fibromuscular band to basal
  septum
• Diagnostically may require isoprenaline to
  facilitate induction

Purkinje Tissue running in false tendon
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Three Subtypes
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Fascicular VT - Circuit
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Purkinje and Pre-Purkinje Potentials
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The Circuit - Electrograms
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Diagnostic Pitt falls

• Robust VA conduction may cloud VA dissociation
• Circuit may be entered via atrial pacing and
  cycle length of circuit re-set (entrained)
• 25 have concomitant inducible A-V accessory
  pathways with inducible SVT

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Rapid atrial pacing required to dissociate A from
V
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Fascicular VT Rare mimics

• Inter-fascicular VT
• RBBB and right or leftward axis
• Structurally abnormal heart Previous anterior
  infracts and LAFB or LPFB
• A subtype of BBR VT
• Idiopathic mitral annular VT
• RBBB and rightward axis
• Variable verapamil-sensitivity
• Ill-defined

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Fascicular VT - Treatment

• Treatment is cure 80 in single procedure
• RF ablation during VT
• Ablation at PP
• Ablation at Pre-PP
• RF ablation during sinus rhythm
• Pace mapping
• Electro anatomic mapping

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RF Ablation During VT

• Purkinje potential target
• Mapping the posterior LV septum, 1/3 distance
  from apex over 3 sq. cm.
• PP identified and ablated
• PP-QRS interval 186 msec. for success
• Entrainment from ablation site Concealed fusion
  and
• Post Pacing Interval VT Cycle Length lt 30msec.

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Ablation at Pre-Purkinje Potential site

• Higher risk of AV block or LBBB
• Requires higher RF applications compared to a
  strategy targeting Purkinje potential

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Ablation During Sinus Rhythm

• Tachycardia may be non-inducible or non-sustained
• Pace mapping technique
• A perfect pace map may not be essential for
  success
• Successful ablation still occurred in
  (9.62.1)/12 ECG leads matched
• Electro Anatomic mapping
• Useful in those with recurrences

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Bundle Branch Re-Entry Ventricular Tachycardia
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BBR VT

• Macro re-entrant (?Ventricular flutter) circuit
  employing
• Both bundle branches
• Ramifications of the left bundle
• Hallmark His-Purkinje system disease
  functional or structural
• Acquired heart disease or apparently normal
  hearts
• Ischemic (6) vs. non-ischemic (40) cardiac
  disease

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Purkinje fibre Connexion Cx43 and Cardiomyopathy

• Quantitative electro micrograph and
  immuno-labelling
• Selective gap junction Cx43 remodelling
• Decreased density (33) in bordering scar and
  hibernating myocardium
• Exquisite vulnerability of His-Purkinje system
• Slowed conduction and fragmented depolarizing
  waveform

1998. Kaprielian, Gunning, et al
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• Akhtar and Damato 1973 antecubital vein
  approach
• Ventricular extra-stimulus with a critical V-H
  delay blocked in the right bundle and activated
  the His via the left bundle
• A V3 response conducted down via the right
  bundle with an H-V interval longer than that of
  sinus beat
• Importantly complete RBBB abolished the V3
  response

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HPS integral to VT mechanism

• Critical V-H interval to initiate (HPS conduction
  delay)
• Prolonged H-V
• H-RB/LB-V-LB/RB activation sequence consistent
  with VT QRS morphology
• H-H oscillations precede changes in V-V during VT

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His Catheter
RB Catheter
LB Catheter
V Catheter
44
BBR VT and valve surgery

• Early (3 weeks) post-operative state
• Correlates with historical literature on post-op
  peak sudden death time-course
• 30 as sole VT mechanism (spontaneous, sustained
  monomorphic. Non-VF)
• Systolic function usually preserved

Proximity of valve annuli to bundle branches
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(No Transcript)
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BBR VT Pitt Falls

• Exclusion of SVT with aberrancy
• Need to prove A-V dissociation
• Need to prove active HPS participation in the VT
  mechanism rather than passive participation
• For BBR VT, entrainment from RV apex
• Post Pacing Interval Tachycardia Cycle Length
  lt 30 msec.

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BBR VT Differentials and Management

• Differentials
• Intra-myocardial re-entry VT (ICM vs NICM)
• Interfascicular VT (form of BBRVT) RBBB and
  LPFB
• Intrafascicular VT (Idiopathic LV VT)
• 11 Supraventricular tachycardia with aberrancy
• Atrio-fascicular re-entry (Mahaim)
• Management

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Issues

• His-Purkinje network
• Sophisticated system
• Pathology begets specific but diverse arrhythmic
  syndromes
• Recognition is critical
• Specific management
• Terminology is crucial

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Management1

• Patient developed AF and hemodynamically stable
  VT during study
• VT had RBBB and, after AF cardioversion, 11 V?A
  conduction
• Atrial and ventricular programmed stimulation
  could not re-initiate VT

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Management2

• 3-D left ventricular map constructed using Ensite
  NavX electroanatomic mapping
• Pace mapping revealed earliest (pre-systolic)
  activation in mid posterior LV septum
• 4 x RF applications terminated VT without further
  recurrence

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Summery

• Diagnosis
• Idiopathic Left Ventricular Verapamil-sensitive
  VT arising from left posterior hemi-bundle
• Management
• Purkinje potential mapped between mid and apico
  posterior LV septum. Abnormal tissue ablated with
  subsequent cure

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Outcome