Supraventricular Tachycardia in Infancy and Childhood

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Supraventricular Tachycardiain Infancy and
Childhood

• Terrence Chun, MD
• Pediatric Electrophysiology and Pacing

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Cardiac electrical anatomy
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SVT - Overview

• Rapid rhythm that involves or is driven by
  structures in the upper heart
• Incidence up to 1250 children
• Generally well-tolerated, even fast rates
• Risk of life-threatening arrhythmias is uncommon

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Narrow vs. Wide QRS

• Not all narrow QRS complex tachycardia is
  supraventricular tachycardia
• Not all wide QRS complex tachycardia is
  ventricular tachycardia

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SVT Mechanisms - Overview

• Reentrant rhythms
• Automatic rhythms

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SVT mechanisms Automatic Rhythms

• Originate from a particular focus
• Warm-up and cool-down behavior
• Respond to drugs and maneuvers that affect
  myocardial automaticity
• May be suppressed by faster rates
• Usually do not respond to cardioversion
  (typically pause, then restart)

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SVT mechanisms Automatic Rhythms

• Left atrial focus
• 21 AVN conduction

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SVT mechanisms Reentrant rhythms

• Requires a circuit of tissue to create
  repetitive activation
• Must have appropriate conditions to perpetuate
  reentrant rhythm
• Usually abrupt onset and termination
• Regular, with little variation in rate
• Often will respond to cardioversion

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SVT mechanisms Reentrant rhythms
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Diagnostic methods

• 12-lead electrocardiogram ! ! !
• Post-op atrial/ventricular pacing wires
• Esophageal pacing leads
• Adenosine can be diagnostic
• Invasive electrophysiology study

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Diagnostic methods

• Always
• Always
• Always record a rhythm strip during any
  intervention (adenosine, cardioversion, Valsalva,
  etc.)

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Diagnostic methods

• Record a rhythm strip

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ECG clues to diagnosis

• Wide vs. narrow complex
• Regular vs. irregular
• Abrupt vs. gradual
• P wave relationship to QRS

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Parade of Rhythms

• Automatic Arrhythmias

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Automatic rhythms Sinus Tachycardia

• Sinus node fish-shaped structure with head at
  SVC-RA junction and tail extending along RA
  wall
• S-tach usually due to increased sympathetic
  discharge, fever, anemia, hypovolemia,
  hyperthyroidism, etc.
• Inappropriate sinus tachycardia - rare

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Automatic rhythms Sinus Tachycardia

• Dx
• Rate greater than normal range, but usually less
  than 200
• P wave axis normal (0 90)
• PR interval normal
• Tx
• Treat the cause

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Automatic rhythms Automatic Atrial Tachycardia

• Originates from a focus in either the right or
  left atrium, or atrial septum
• Commonly from atrial appendages, crista
  terminalis, pulmonary veins
• Can also be due to central lines, etc.
• Also called ectopic atrial tachycardia
• although any automatic rhythm other than sinus
  rhythm is technically ectopic

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Automatic rhythms Automatic Atrial Tachycardia

• Dx
• Speeds-up and slows-down, rates vary
• P wave axis abnormal
• PR interval may be abnormal (it is a function of
  distance from focus to AVN)
• May see 2 AV block (e.g. Wenckebach or 21 at
  higher atrial rates)
• Adenosine ? P waves march through despite AV
  block

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Automatic rhythms Automatic Atrial Tachycardia
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Automatic rhythms Automatic Atrial Tachycardia

• Tx
• Remove source (check CXR and pull back PICC)
• Beta-blockers
• Esmolol infusion in ICU setting
• propranolol, atenolol
• Amiodarone, others
• Catheter ablation

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Automatic rhythms Junctional Tachycardia

• Originates from around the AV junction
• Also called JET (Junctional Ectopic
  Tachycardia), because it sounds cool
• Rate 170-200
• Most commonly seen post-operatively, usually
  self-limited
• Congenital forms, more persistent

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Automatic rhythms Junctional Tachycardia

• Dx
• AV dissynchrony
• Sinus P wave at different rate than narrow QRS
• Atrial wire ECG (in post-op with pacing wires)
• Cannon a-waves on CVP monitor
• Retrograde P waves (abnormal Pw axis)
• May be on top, before, or after QRS

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Automatic rhythms Junctional Tachycardia

• Cannon a-waves

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Automatic rhythms Junctional Tachycardia

• Tx
• Reduce catecholamines
• Decrease inotropic drips
• Pain control and sedation
• Cooling/hypothermia
• Drugs (amiodarone)
• ECMO
• Catheter ablation(?)

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Parade of Rhythms

• Reentrant Arrhythmias

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Reentrant rhythms Pathway Mediated Tachycardia

• Bypass tract of conductive tissue connects atrium
  to ventricle
• Most common mechanism of SVT in children
• Rate 180-240
• May be manifest (e.g. WPW) or concealed (no
  preexcitation)
• Pathway can be anywhere on mitral or tricuspid
  annuli, usually left-sided

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Reentrant rhythms Pathway Mediated Tachycardia

• Orthodromic reciprocating tachycardia
• Runs correctly with normal conduction
• Down AV node (narrow QRS)
• Up accessory pathway (retrograde)
• Retrograde P waves may be visible after QRS
• Antidromic reciprocating tachycardia
• Runs against normal conduction
• Down accessory pathway (wide QRS)
• Up AV node (retrograde)
• Less common

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Reentrant rhythms Pathway Mediated Tachycardia

• Dx
• Electrocardiogram
• Rhythm strips of start and stop of SVT

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Reentrant rhythms Pathway Mediated Tachycardia

• Tx
• Valsalva maneuvers, Ice to face
• Adenosine (technique matters!)
• Antiarrhythmic drugs
• Beta blockers (watch blood glucose in infants!)
• Digoxin (limited value digitalization only in
  difficult situations)
• Others (Verapamil, Flecainide, Sotolol, etc.)
• Catheter ablation

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Reentrant rhythms Wolff-Parkinson-White
Syndrome

• Electrocardiogram findings
• Short PR interval
• Wide QRS complex
• Delta wave

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Reentrant rhythms Wolff-Parkinson-White
Syndrome
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Reentrant rhythms Wolff-Parkinson-White
Syndrome

• Clinical symptoms
• Palpitations
• SVT
• Note narrow QRS and lack of delta wave!

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Reentrant rhythms Wolff-Parkinson-White
Syndrome

• Sudden death(!)
• Atrial fibrillation
• Rapid conduction over bypass tract
• Ventricular fibrillation
• Risk 0.1-0.6 per year

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Reentrant rhythms Wolff-Parkinson-White
Syndrome

• Tx
• Tachycardia control
• Recognition
• Drugs (patient/family choice)
• Digoxin generally contraindicated
• Risk stratification
• Holter
• Exercise testing
• Invasive electrophysiology testing
• Catheter ablation

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Reentrant rhythms AV Node Reentry Tachycardia

• More common in teens and adults
• Tachycardia circuit contained within
  atrioventricular node
• Activates atria at the top of the circuit,
  ventricles at bottom of circuit, nearly
  simultaneously
• Rate 200-250
• Usually cannot see retrograde P waves

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Reentrant rhythms AV Node Reentry Tachycardia
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Reentrant rhythms AV Node Reentry Tachycardia

• Tx
• Adenosine
• Cardioversion
• Pharmacotherapy
• Beta blockers
• Digoxin
• Others
• Catheter ablation

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Reentrant rhythms Atrial Flutter

• Flutter circuit around anatomic structures in
  atrium
• Eustachian valve
• Crista terminalis
• Fossa ovalis
• Surgical incisions

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Reentrant rhythms Atrial Flutter

• Atrial rate 300 (higher in neonates)
• Ventricular rate depends on AV node conduction
• 11 ? 300/min
• 21 ? 150/min
• 31 ? 100/min
• May be 31 then 21 then

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Reentrant rhythms Atrial Flutter

• Sawtooth flutter waves (may or may not be
  helpful)

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Reentrant rhythms Atrial Flutter

• Dx
• Electrocardiogram
• Adenosine blocks AV node flutter waves continue
• Tx
• Rate control digoxin, beta blockers, etc.
• Overdrive pacing
• DC cardioversion
• Catheter ablation

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Threatening Rhythms

• Atrial fibrillation in high-risk WPW
• Danger of ventricular fibrillation
• Persistent prolonged SVT
• Tachycardia induced cardiomyopathy (reversible)
• SVT in compromised cardiac status
• Syncope or cardiovascular collapse

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Treatment Pearls
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Adenosine

• 0.1-0.4 mg/kg/dose
• Very short half-life (seconds)
• Central administration can be helpful, but not
  necessary
• Rapid saline bolus (5-10 ml) essential
• Stopcock on venous access is helpful

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DC Cardioversion

• Dose
• Cardioversion 0.25-1 J/kg
• Defibrillation 1-2 J/kg
• Synchronized (avoids making worse)
• Paddles frontapex
• Patches
• Frontapex
• Frontback

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Catheter Ablation

• Multiple catheters
• Size limitations
• Ideally gt 15 kg, but can be done in infants if
  necessary
• Can be curative
• 95 success rate in children

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Record a Rhythm Strip!

• Especially during interventions
• Most SVT in infants and children is
  hemodynamically well-tolerated
• Proper diagnosis can guide appropriate therapy
• RA/LA/RL/LL limb leads give 6 electrograms (I,
  II, III, aVL, aVR, aVF)