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Pediatric Arrhythmias & Device Therapy

Learning Objectives

For pediatric residents on cardiology rotation

Core Knowledge & Clinical Reasoning

  • [ ] Recognize SVT on ECG and differentiate from sinus tachycardia (rate, P waves, variability)
  • [ ] Identify WPW pattern on ECG (short PR <120 ms, delta wave, wide QRS)
  • [ ] Classify heart block: 1st degree, 2nd degree (Mobitz I vs II), 3rd degree (complete)
  • [ ] Recognize VT on ECG (wide complex, AV dissociation, fusion/capture beats)
  • [ ] Identify Torsades de pointes (polymorphic VT with twisting axis, long QT)
  • [ ] Know ECG features of VFib (chaotic, no organized QRS)

Acute Arrhythmia Management (Resident Scope)

  • [ ] Apply stepwise SVT management: vagal maneuvers → adenosine → synchronized cardioversion
  • [ ] Know adenosine dosing (0.1 mg/kg, max 6 mg; repeat 0.2 mg/kg, max 12 mg)
  • [ ] Manage unstable tachycardia: synchronized cardioversion 0.5-1 J/kg (SVT/VT with pulse)
  • [ ] Manage VFib/pulseless VT: defibrillation 2 J/kg → 4 J/kg + CPR + epinephrine
  • [ ] Treat Torsades: IV magnesium 25-50 mg/kg (max 2g) + defibrillate if unstable
  • [ ] Manage symptomatic bradycardia: atropine 0.02 mg/kg (min 0.1 mg), consider pacing

When to Call Cardiology Urgently

  • [ ] Wide complex tachycardia (presume VT until proven otherwise)
  • [ ] Hemodynamic instability with any arrhythmia
  • [ ] New complete heart block
  • [ ] Long QT with syncope or polymorphic VT
  • [ ] Post-operative arrhythmias (especially after CHD repair)

When to Refer to Cardiology/EP (Non-Urgent)

  • [ ] Asymptomatic WPW → EP study for risk stratification
  • [ ] Recurrent SVT despite medical therapy → ablation referral
  • [ ] Symptomatic bradycardia → pacemaker evaluation
  • [ ] Cardiac arrest survivors, sustained VT → ICD evaluation

Communication & Counseling

  • [ ] Explain arrhythmias to families in understandable terms
  • [ ] Discuss activity considerations for patients with devices
  • [ ] Ensure schools have emergency action plans for students with ICDs/arrhythmias

Systems-Based Practice

  • [ ] Coordinate with EP for device follow-up scheduling
  • [ ] Ensure medication compliance for patients on antiarrhythmics

Resident Scope Note: Device type selection, conduction system pacing decisions, and detailed ablation planning are EP/cardiology specialist responsibilities. Residents should focus on recognition, acute management, and appropriate referral.

Key Guidelines

2023 PACES/HRS/ACC/AHA Consensus Statement on Cardiac Implantable Electronic Devices in Pediatrics 130 recommendations covering all pediatric arrhythmias

2023 HRS/APHRS/LAHRS Guideline on Cardiac Physiologic Pacing Heart Rhythm. 2023 - Includes pediatric-specific section

2016 PACES/HRS Expert Consensus: Catheter Ablation in Children Heart Rhythm. 2016 - Remains current standard

Quick Reference: SVT Management Algorithm | Neonatal Arrhythmia

2023 CIED Guidelines: Key Updates

  • 130 recommendations covering all pediatric arrhythmias
  • 28% new recommendations from prior guidelines
  • Pacemaker: Heart rate criterion for AVB lowered (reduces too-early implantation)
  • ICD: Updated criteria for cardiomyopathies (DCM, HCM, ACM)
  • Emphasis on shared decision-making for complex cases

Pacemaker Indications

Class I (Definite Indication)

Indication Notes
Symptomatic sinus bradycardia Correlation with symptoms
Advanced 2nd degree or complete AVB with symptoms Syncope, HF, chronotropic incompetence
Post-surgical AVB >7 days Not expected to resolve
Congenital complete AVB with wide QRS, ventricular ectopy, or ventricular dysfunction
Sinus node dysfunction with symptoms Correlation required

Class IIa (Reasonable)

  • Asymptomatic complete AVB with mean HR <50 or pauses >3x cycle length
  • Congenital AVB with prolonged QTc
  • CHD with impaired hemodynamics due to sinus bradycardia or loss of AV synchrony

Special Considerations

Congenital Complete Heart Block - Often diagnosed prenatally or in infancy - Frequently associated with maternal anti-Ro/La antibodies - Indications for pacing: - Symptoms - Ventricular dysfunction - Wide QRS escape rhythm - Ventricular ectopy - HR <55 (infant) or <50 (older child) - Long pauses

ICD Indications

Class I (Definite)

Indication Notes
Survivors of VF/sustained VT arrest After reversible causes excluded
Structural heart disease + spontaneous sustained VT Symptomatic or hemodynamically significant
High-risk conditions post risk stratification HCM, ARVC per specific criteria

Class IIa (Reasonable)

  • HCM with ≥1 major risk factor (see Topic 3)
  • LQTS with syncope/VT on beta-blockers
  • Brugada with syncope
  • CPVT with syncope on optimal therapy
  • DCM with significant LV dysfunction (pediatric-specific criteria evolving)

Class IIb (May Consider)

  • Unexplained syncope with inducible VT/VF on EPS
  • HCM without established risk factors but high-risk features

Conduction System Pacing

2023 Update

  • CRT and conduction system pacing section specific to pediatrics
  • PACES collaborated on guideline development

Options

  • His bundle pacing: More physiologic activation
  • Left bundle branch area pacing: Emerging in pediatrics
  • Preferred over traditional RV pacing when feasible

Catheter Ablation (2016 PACES/HRS)

Indications

Arrhythmia Class I Indications
SVT/AVNRT Recurrent, symptomatic, refractory to meds or patient preference
Accessory pathways WPW with symptoms; asymptomatic high-risk WPW
Atrial flutter Recurrent, symptomatic
JET Incessant with ventricular dysfunction
VT Recurrent symptomatic VT in structurally normal heart

Asymptomatic WPW

Risk Stratification: - EP study recommended for risk assessment - High-risk features: - SPERRI <250 ms - Multiple accessory pathways - Inducible AF with rapid conduction

Class I ablation for asymptomatic WPW with high-risk features

Considerations by Age

  • Infants: Avoid if possible; many arrhythmias resolve
  • Young children: Higher complication risk; consider waiting if stable on meds
  • Adolescents: Standard ablation approach
  • Cryoablation: Preferred near AV node (AVNRT) for reversibility

Tachyarrhythmias

Supraventricular Tachycardia (SVT)

Most common arrhythmia requiring treatment in children

Type Mechanism ECG Features Age Predominance
AVRT Accessory pathway Narrow QRS (usually), retrograde P after QRS Infants, WPW
AVNRT Dual AV nodal pathways Narrow QRS, P buried in QRS or just after Older children/teens
Atrial tachycardia Ectopic atrial focus Abnormal P wave axis, may have warm-up Any age

SVT vs Sinus Tachycardia:

Feature SVT Sinus Tachycardia
Onset Abrupt Gradual
Rate Fixed, often >220 (infant) or >180 (child) Variable with activity
P waves Absent/abnormal/retrograde Normal, upright in I, II
Rate variability None (fixed rate) Beat-to-beat variation
Response to adenosine Terminates Transient slowing, resumes

Acute Management: 1. Stable: Vagal maneuvers (ice to face in infants, Valsalva in older children) 2. If vagal fails: Adenosine 0.1 mg/kg rapid IV push (max 6 mg), may repeat 0.2 mg/kg (max 12 mg) 3. Unstable: Synchronized cardioversion 0.5-1 J/kg

Atrial Flutter

  • Less common than SVT in children (except post-Fontan/atrial surgery)
  • ECG: Sawtooth flutter waves (best seen II, III, aVF), regular or variable block
  • Typical rates: Atrial 300 bpm with 2:1 block → ventricular 150 bpm
  • Treatment: Cardioversion (often low energy effective), rate control, consider ablation

Atrial Fibrillation

  • Rare in children without structural heart disease
  • Associations: WPW (dangerous!), post-operative, cardiomyopathy
  • WPW + AF: Life-threatening - rapid conduction via accessory pathway → VFib
  • Treatment: Rate control (avoid AV nodal blockers in WPW), anticoagulation, cardioversion

Ventricular Tachycardia (VT)

Definition: ≥3 consecutive ventricular beats at rate >120 bpm

Type ECG Features Etiology
Monomorphic VT Wide QRS, single morphology Scar, cardiomyopathy, idiopathic
Polymorphic VT Wide QRS, changing morphology Ischemia, channelopathy
Torsades de pointes Polymorphic, twisting axis Long QT syndrome

VT Recognition: - Wide QRS (>120 ms, or >90 ms in infants) - AV dissociation (P waves marching through) - Fusion beats, capture beats - Extreme axis deviation - Concordance (all precordial leads same direction)

ASSUME WIDE COMPLEX TACHYCARDIA IS VT UNTIL PROVEN OTHERWISE

Acute Management: - With pulse, stable: Amiodarone 5 mg/kg IV over 20-60 min, cardioversion if fails - With pulse, unstable: Synchronized cardioversion 0.5-1 J/kg - Pulseless VT: Defibrillation 2 J/kg → CPR → 4 J/kg + epinephrine

Torsades de Pointes

Polymorphic VT with characteristic "twisting" morphology

  • Always associated with prolonged QT (acquired or congenital)
  • Triggers: Bradycardia, hypokalemia, hypomagnesemia, drugs (see QT-prolonging drugs)
  • ECG: QTc usually >500 ms before episode

Treatment: 1. IV Magnesium 25-50 mg/kg (max 2g) over 10-20 min - FIRST LINE 2. Correct K+ to >4.0 mEq/L 3. Increase heart rate (shortens QT): Isoproterenol or pacing 4. Defibrillate if unstable/pulseless 5. Stop all QT-prolonging drugs

Ventricular Fibrillation (VFib)

  • Chaotic ventricular rhythm - no organized QRS, no pulse
  • Rare primary arrhythmia in children (more common: respiratory arrest → asystole)
  • Causes: Channelopathy (LQTS, CPVT, Brugada), cardiomyopathy, commotio cordis, drowning

Treatment (2025 AHA/AAP PALS): 1. Defibrillation 2 J/kg immediately 2. High-quality CPR × 2 minutes (minimize interruptions <10 sec) 3. Defibrillation 4 J/kg 4. Epinephrine 0.01 mg/kg IV/IO (give ASAP for nonshockable; after 2nd shock for shockable) 5. Defibrillation 4 J/kg 6. Amiodarone 5 mg/kg or Lidocaine 1 mg/kg 7. Continue cycle: shock → CPR → epi every 3-5 min

2025 Update: Physiology-directed resuscitation now emphasized. If arterial line present, target DBP ≥25 mmHg (infants) or ≥30 mmHg (children) during CPR.

Bradyarrhythmias & Heart Block

Sinus Bradycardia

Normal Pediatric Heart Rates (Awake):

Age Lower Limit Concerning
Newborn 100 <80
1-12 months 100 <80
1-3 years 90 <70
3-5 years 80 <60
5-10 years 70 <50
>10 years 60 <50

Causes: - Physiologic (athletes, sleep) - Hypoxia (most common pediatric cause) - Increased vagal tone - Hypothyroidism, hypothermia - Medications (beta-blockers, digoxin) - Sick sinus syndrome

Heart Block Classification

First-Degree AV Block

  • ECG: Prolonged PR interval (>200 ms adult, age-dependent in children)
  • Mechanism: Delayed conduction through AV node
  • Clinical significance: Usually benign, no treatment needed
  • Causes: Vagal tone, myocarditis, digoxin, congenital

Normal PR Intervals by Age:

Age Upper Limit PR
<1 year 160 ms
1-3 years 160 ms
3-5 years 170 ms
5-12 years 180 ms
>12 years 200 ms

Second-Degree AV Block - Mobitz Type I (Wenckebach)

  • ECG: Progressive PR prolongation until dropped QRS, then cycle repeats
  • Mechanism: AV nodal fatigue (above His bundle)
  • Clinical significance: Usually benign, rarely progresses
  • Common in: Athletes, high vagal tone, sleep
  • Treatment: Usually none; atropine if symptomatic

Second-Degree AV Block - Mobitz Type II

  • ECG: Fixed PR interval with sudden dropped QRS (no progressive prolongation)
  • Mechanism: Infranodal (His bundle or below) - MORE DANGEROUS
  • Clinical significance: HIGH risk of progression to complete heart block
  • Treatment: Pacemaker typically indicated
  • Key point: May have wide QRS (indicates infranodal disease)

Mobitz I vs Mobitz II - Critical Distinction:

Feature Mobitz I (Wenckebach) Mobitz II
PR interval Progressively prolongs Fixed
QRS Usually narrow Often wide
Level of block AV node Below AV node
Prognosis Benign May progress to CHB
Pacemaker Rarely needed Usually needed

Third-Degree (Complete) Heart Block

  • ECG: No relationship between P waves and QRS; atrial rate > ventricular rate
  • Mechanism: Complete dissociation of atria and ventricles
  • Escape rhythm: Junctional (narrow QRS, 40-60 bpm) or ventricular (wide QRS, 20-40 bpm)

Causes in Children:

Type Etiology
Congenital Maternal anti-Ro/La (SLE, Sjögren's), structural CHD (L-TGA, AVSD)
Acquired Post-surgical (VSD repair, valve surgery), myocarditis, Lyme disease

Congenital Complete Heart Block: - Often diagnosed prenatally (fetal bradycardia) - Associated with maternal autoantibodies in ~60% - May be well-tolerated if adequate junctional escape rate - Monitor for: symptoms, ventricular dysfunction, wide QRS, ectopy

Sick Sinus Syndrome (Sinus Node Dysfunction)

  • Definition: Dysfunction of SA node causing bradycardia, pauses, or chronotropic incompetence
  • Tachy-brady syndrome: Alternating bradycardia and atrial tachyarrhythmias
  • Common after: Fontan, Mustard/Senning, atrial surgery
  • Treatment: Often requires pacemaker

Premature Beats

Premature Atrial Contractions (PACs)

  • Common, usually benign
  • ECG: Early P wave with abnormal morphology, usually conducted
  • Frequent in newborns, typically resolve

Premature Ventricular Contractions (PVCs)

Assessment: - Burden: <1% typically benign; >10-20% may cause cardiomyopathy - Morphology: Unifocal (single origin) vs multifocal (concerning) - Timing: Suppression with exercise = reassuring; increase with exercise = concerning

Concerning Features: - Symptoms (syncope, presyncope, palpitations with exercise) - High burden (>10-20%) - Polymorphic/multifocal - Couplets, triplets, runs of NSVT - Exercise-induced PVCs - Structural heart disease - Family history of sudden death

Benign PVCs: - Unifocal, LBBB morphology (RVOT origin) - Suppress with exercise - Structurally normal heart - Low burden (<5%) - Asymptomatic

Board Pearls

Pearl: SVT vs Sinus Tachycardia

SVT: Abrupt onset, fixed rate, no P waves or retrograde P. Sinus tach: Gradual onset, variable rate, normal upright P waves

Pearl: Wide complex tachycardia = VT until proven otherwise

Safer to treat as VT. SVT with aberrancy is uncommon in children

Pearl: Mobitz I vs Mobitz II

Mobitz I (Wenckebach): Progressive PR prolongation, benign. Mobitz II: Fixed PR then dropped beat, needs pacemaker

Pearl: Torsades treatment = Magnesium first

IV Mg 25-50 mg/kg (max 2g). Also correct K+, increase HR, stop QT-prolonging drugs

Pearl: Post-surgical AVB >7 days = pacemaker

Block persisting >7 days after cardiac surgery unlikely to resolve

Pearl: Congenital CHB - pacemaker indications

HR <50, wide QRS escape, ventricular ectopy, LV dysfunction, symptoms

Pearl: WPW + AFib = avoid AV nodal blockers

Digoxin, verapamil, diltiazem can accelerate conduction via accessory pathway → VFib

Pearl: Asymptomatic WPW requires risk stratification

EP study recommended; ablate if high-risk features (SPERRI <250 ms)

Self-Assessment

Q1: A 12-year-old has asymptomatic WPW on ECG. Parents want to know if ablation is needed. What is the recommended approach?

Answer **Answer**: Recommend EP study for risk stratification **Rationale**: Per 2016 PACES/HRS guidelines, asymptomatic WPW should undergo risk assessment. EP study determines SPERRI and presence of multiple pathways. If high-risk features present (SPERRI <250 ms), ablation is Class I recommended even without symptoms.

Q2: A newborn is diagnosed with congenital complete heart block. HR is 58 bpm with narrow QRS and no ventricular ectopy. Echo shows normal function. What is the recommendation?

Answer **Answer**: Close monitoring; pacemaker not immediately indicated **Rationale**: Per 2023 guidelines, asymptomatic CCHB with HR >50, narrow QRS, no ectopy, and normal ventricular function may be observed. Pacemaker becomes Class I if: symptoms develop, HR <50, ventricular dysfunction, wide QRS escape, or significant ectopy.

Q3: A 6-month-old presents with HR 280, narrow QRS, no visible P waves, and poor perfusion. What is the immediate management?

Answer **Answer**: Synchronized cardioversion 0.5-1 J/kg **Rationale**: This is SVT with hemodynamic instability (poor perfusion). Unstable patients require immediate synchronized cardioversion. In stable SVT, try vagal maneuvers (ice to face) then adenosine first.

Q4: An 8-year-old collapses during soccer. Monitor shows wide complex tachycardia with changing QRS morphology and "twisting" axis. QTc was 520 ms on prior ECG. What is the arrhythmia and first-line treatment?

Answer **Answer**: Torsades de pointes; IV Magnesium 25-50 mg/kg (max 2g) **Rationale**: Polymorphic VT with twisting morphology in setting of prolonged QT = Torsades. First-line treatment is IV magnesium. Also correct electrolytes (K+ >4.0), increase heart rate (shortens QT), and defibrillate if pulseless/unstable.

Q5: A 10-year-old has ECG showing regular rhythm at 75 bpm. Every PR interval is 240 ms (fixed). Occasionally a P wave is not followed by QRS (dropped beat), but the PR of conducted beats is always 240 ms. What type of heart block is this?

Answer **Answer**: Second-degree AV block, Mobitz Type II **Rationale**: Fixed PR interval with intermittent dropped beats = Mobitz II. This is infranodal block with high risk of progression to complete heart block. Mobitz I (Wenckebach) would show progressive PR prolongation before the dropped beat. Mobitz II typically requires pacemaker.

Q6: A 3-year-old with repaired AVSD is post-op day 5. Telemetry shows complete heart block with ventricular rate 45 bpm. Echo shows good biventricular function. What is the management?

Answer **Answer**: Continue temporary pacing; if block persists beyond day 7, permanent pacemaker is indicated **Rationale**: Post-surgical complete heart block that persists >7 days is unlikely to resolve and is a Class I indication for permanent pacemaker. Continue temporary pacing support and observe. If AV conduction does not recover by day 7-10, proceed with pacemaker implantation.

Q7: A teenager is found unresponsive. Monitor shows chaotic rhythm with no discernible QRS complexes. No pulse. What is the rhythm and immediate action?

Answer **Answer**: Ventricular fibrillation; Defibrillation 2 J/kg immediately **Rationale**: VFib is a shockable rhythm. Per PALS, immediate defibrillation at 2 J/kg is first priority. Then CPR × 2 min, repeat shock at 4 J/kg, epinephrine, shock, amiodarone or lidocaine, continuing the cycle. Unlike pulseless VT or SVT, VFib requires unsynchronized defibrillation.

References

  • 2023 PACES/HRS/ACC/AHA CIED Consensus Statement. Heart Rhythm. 2023
  • Crosson JE, et al. Heart Rhythm. 2016 (Ablation guidelines)
  • 2023 HRS Physiologic Pacing Guidelines
  • 2025 AHA/AAP Pediatric Advanced Life Support Guidelines. Circulation. 2025. Part 8: PALS
  • Brugada J, et al. 2019 ESC Supraventricular Tachycardia Guidelines