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Supraventricular Tachycardia in Infancy and Childhood. Terrence Chun, MD Pediatric Electrophysiology and Pacing. Cardiac electrical anatomy. SVT - Overview. Rapid rhythm that involves or is driven by structures in the upper heart Incidence up to 1:250 children

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supraventricular tachycardia in infancy and childhood

Supraventricular Tachycardiain Infancy and Childhood

Terrence Chun, MD

Pediatric Electrophysiology and Pacing

svt overview
SVT - Overview
  • Rapid rhythm that involves or is driven by structures in the upper heart
  • Incidence up to 1:250 children
  • Generally well-tolerated, even fast rates
  • Risk of life-threatening arrhythmias is uncommon
narrow vs wide qrs
Narrow vs. Wide QRS
  • Not all narrow QRS complex tachycardia is supraventricular tachycardia
  • Not all wide QRS complex tachycardia is ventricular tachycardia
svt mechanisms overview
SVT Mechanisms - Overview
  • Reentrant rhythms
  • Automatic rhythms
svt mechanisms automatic rhythms
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)
svt mechanisms automatic rhythms1
SVT mechanisms –Automatic Rhythms
  • Left atrial focus
  • 2:1 AVN conduction
svt mechanisms reentrant rhythms
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
diagnostic methods
Diagnostic methods
  • 12-lead electrocardiogram ! ! !
  • Post-op atrial/ventricular pacing wires
  • Esophageal pacing leads
  • Adenosine can be diagnostic
  • Invasive electrophysiology study
diagnostic methods1
Diagnostic methods
  • Always
  • Always
  • Always record a rhythm strip during any intervention (adenosine, cardioversion, Valsalva, etc.)
diagnostic methods2
Diagnostic methods
  • Record a rhythm strip
ecg clues to diagnosis
ECG clues to diagnosis
  • Wide vs. narrow complex
  • Regular vs. irregular
  • Abrupt vs. gradual
  • P wave relationship to QRS
parade of rhythms
Parade of Rhythms

Automatic Arrhythmias

automatic rhythms sinus tachycardia
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
automatic rhythms sinus tachycardia1
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
automatic rhythms automatic atrial tachycardia
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”
automatic rhythms automatic atrial tachycardia1
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 2:1 at higher atrial rates)
    • Adenosine  P waves “march through” despite AV block
automatic rhythms automatic atrial tachycardia3
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
automatic rhythms junctional tachycardia
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
automatic rhythms junctional tachycardia1
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
automatic rhythms junctional tachycardia3
Automatic rhythms – Junctional Tachycardia
  • Tx
    • Reduce catecholamines
      • Decrease inotropic drips
      • Pain control and sedation
    • Cooling/hypothermia
    • Drugs (amiodarone)
    • ECMO
    • Catheter ablation(?)
parade of rhythms1
Parade of Rhythms

Reentrant Arrhythmias

reentrant rhythms pathway mediated tachycardia
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
reentrant rhythms pathway mediated tachycardia1
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
reentrant rhythms pathway mediated tachycardia2
Reentrant rhythms – Pathway Mediated Tachycardia
  • Dx
    • Electrocardiogram
    • Rhythm strips of start and stop of SVT
reentrant rhythms pathway mediated tachycardia3
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
reentrant rhythms wolff parkinson white syndrome
Reentrant rhythms – Wolff-Parkinson-White Syndrome
  • Electrocardiogram findings
    • Short PR interval
    • Wide QRS complex
    • Delta wave
reentrant rhythms wolff parkinson white syndrome2
Reentrant rhythms – Wolff-Parkinson-White Syndrome
  • Clinical symptoms
    • Palpitations
    • SVT
      • Note narrow QRS and lack of delta wave!
reentrant rhythms wolff parkinson white syndrome3
Reentrant rhythms – Wolff-Parkinson-White Syndrome
  • Sudden death(!)
    • Atrial fibrillation
    • Rapid conduction over bypass tract
    • Ventricular fibrillation
    • Risk 0.1-0.6% per year
reentrant rhythms wolff parkinson white syndrome4
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
reentrant rhythms av node reentry tachycardia
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
reentrant rhythms av node reentry tachycardia2
Reentrant rhythms – AV Node Reentry Tachycardia
  • Tx
    • Adenosine
    • Cardioversion
    • ±Pharmacotherapy
      • Beta blockers
      • Digoxin
      • Others
    • Catheter ablation
reentrant rhythms atrial flutter
Reentrant rhythms – Atrial Flutter
  • “Flutter” circuit around anatomic structures in atrium
    • Eustachian valve
    • Crista terminalis
    • Fossa ovalis
    • Surgical incisions
reentrant rhythms atrial flutter1
Reentrant rhythms – Atrial Flutter
  • Atrial rate ~300 (higher in neonates)
  • Ventricular rate depends on AV node conduction
    • 1:1  300/min
    • 2:1  150/min
    • 3:1  100/min
    • May be 3:1 then 2:1 then…
reentrant rhythms atrial flutter2
Reentrant rhythms – Atrial Flutter
  • Sawtooth “flutter” waves (may or may not be helpful)
reentrant rhythms atrial flutter3
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
threatening rhythms
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
adenosine
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
dc cardioversion
DC Cardioversion
  • Dose
    • Cardioversion 0.25-1 J/kg
    • Defibrillation 1-2 J/kg
  • Synchronized (avoids making worse)
  • Paddles – front+apex
  • Patches
    • Front+apex
    • Front+back
catheter ablation
Catheter Ablation
  • Multiple catheters
  • Size limitations
    • Ideally > 15 kg, but can be done in infants if necessary
  • Can be curative
    • ~95% success rate in children
record a rhythm strip
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)