1. Purpose
Neonatal arrhythmia may first appear as an abnormally fast or slow heart rate detected on a monitor. The best test to confirm and classify the rhythm is a 12-lead ECG.
2. First Bedside Question: Stable or Unstable?
Before naming the rhythm, decide whether the baby is stable or unstable.
| Assess Immediately | Concerning Findings |
|---|
| Activity | Lethargy, irritability, decreased responsiveness |
| Breathing | Tachypnea, respiratory distress, apnea |
| Feeding | Poor feeding or inability to feed |
| Perfusion | Pallor, weak pulses, delayed capillary refill |
| Blood pressure | Hypotension or shock |
Unstable → Act immediately
Unstable tachyarrhythmia → synchronized cardioversion 0.5–1 J/kg. Do not delay to attempt vagal maneuvers or adenosine.
3. Supraventricular Tachycardia
- SVT is usually a narrow-complex tachycardia caused by re-entry through an accessory pathway or through the AV node
- Short SVT episodes may occur in otherwise asymptomatic neonates — but every infant should be assessed promptly for hemodynamic compromise
- Rate: typically 250–300 bpm with little or no R-R variability
SVT ECG pattern: narrow QRS | rate ≈ 250-300 bpm | regular R-R | P waves often absent or retrograde
4. AVRT (Atrioventricular Re-entrant Tachycardia)
AVRT is the most common neonatal SVT mechanism per the Baylor guideline. The re-entry circuit uses the AV node and an accessory pathway.
| Type | Baseline ECG Feature |
|---|
| WPW / overt pre-excitation | Delta wave, short PR interval, wide QRS in sinus rhythm |
| Concealed accessory pathway | Baseline ECG appears normal — pre-excitation not visible in sinus rhythm |
WPW Baseline ECG Clues
- Delta wave (slurred upstroke of QRS)
- Short PR interval
- Wide QRS complex (pseudo-bundle branch pattern)
5. AVNRT (AV Nodal Re-entrant Tachycardia)
- Caused by dual AV nodal pathways — one fast, one slow
- Regular rhythm; P waves may be hidden within or immediately after the QRS complex
- Less common than AVRT in neonates
- Treatment approach is the same as AVRT: vagal maneuver → adenosine → antiarrhythmics
6. Acute SVT Treatment
| Clinical Status | Treatment |
|---|
| Unstable SVT | Synchronized cardioversion 0.5–1 J/kg — do not delay |
| Stable SVT | Try vagal maneuver first if appropriate |
| Vagal maneuver fails | Give IV adenosine by rapid push using 2-syringe technique |
| Adenosine fails | Consider esmolol, sotalol, procainamide, or amiodarone with cardiology guidance |
7. Vagal Maneuvers
Goal: block AV nodal conduction and interrupt the re-entry circuit. Acceptable maneuvers:
- Gag stimulation with an NG tube
- Applying an ice bag over the face and ears for 15 seconds (diving reflex)
- Rectal stimulation
Time limit on vagal maneuvers
In ill neonates, do not continue vagal maneuvers for more than 5 minutes before moving to adenosine or another therapy.
Ocular pressure is contraindicated in neonates
Do not apply ocular pressure as a vagal maneuver in newborns or infants — risk of retinal injury.
8. Adenosine
Adenosine has a very short half-life of ~6–10 seconds. It must be given rapidly through IV access closest to the heart, followed immediately by a rapid normal saline flush (2-syringe technique).
| Dose | Use |
|---|
| 0.1 mg/kg IV rapid push | First dose |
| 0.2 mg/kg IV rapid push | Second dose if no response |
Have a code cart available before giving adenosine
- Potential adverse effects include: atrial or ventricular tachyarrhythmias, asystole, and bronchospasm
- Warn the family and bedside team before administration — the brief pause can be alarming
2-Syringe Technique
Draw adenosine in one syringe and normal saline flush in another. Connect both to a stopcock at the IV closest to the heart. Push adenosine as fast as possible, then immediately push the flush. Slow administration → drug is metabolized before reaching the AV node → no effect.
9. Long-Term SVT Management
- Long-term management depends on frequency, severity, and how easily SVT terminates
- When chronic treatment is needed, beta-blockers (commonly propranolol) are first-line
- Accessory pathway ablation is generally performed later in childhood rather than in neonates
10. Antiarrhythmic Medication Summary
| Medication |
Main Use |
Dose (Baylor) |
Key Caution |
| Propranolol |
First-line enteral therapy for uncomplicated neonatal SVT or atrial tachycardia |
4 mg/kg/day divided q6h PO |
Hypoglycemia, hyperkalemia, increased airway resistance (rare but important) |
| Esmolol |
IV beta-blocker for recurrent or sustained SVT when rapid onset and short half-life are useful |
Institution-specific continuous infusion |
Bradycardia and hypotension |
| Sotalol |
Second-line when propranolol fails; can terminate arrhythmia IV |
PO 120–150 mg/m²/day ÷ q8h; IV 1 mg/kg over 1 hour for active arrhythmia |
QTc prolongation — daily ECGs during initiation |
| Flecainide |
Second-line for SVT and atrial tachycardia |
PO 120–150 mg/m²/day ÷ q8h |
Milk affects absorption — give consistently with or without feeds; daily ECGs to monitor QRS duration |
| Amiodarone |
Class III antiarrhythmic when beta-blockade fails |
IV bolus 5 mg/kg over 20–60 min (with pulse); Loading 20 mg/kg/day → Maintenance 5–10 mg/kg/day |
Hypotension, thyroid toxicity, pulmonary fibrosis, hepatotoxicity, corneal deposits, dermatologic effects, arrhythmias |
| Ivabradine |
Reserved for automatic tachycardias (JET, atrial ectopic tachycardia) |
0.05 mg/kg q12h PO |
Bradycardia; no serum level or ECG monitoring marker required |
11. Amiodarone Practical Notes
- IV amiodarone commonly causes hypotension after administration — monitor BP closely during infusion
- IV amiodarone is incompatible with many solutions, including heparin
- Use a dedicated IV line for amiodarone — avoid heparinized saline flushes on that line
- Long-term amiodarone requires monitoring of thyroid function, liver function, chest X-ray, and ophthalmology exams
12. Atrial Flutter
- Rapid atrial rhythm caused by a macro-reentry circuit in the atria
- Atrial rate usually >250/min with variable AV conduction and usually narrow QRS
- ECG: classic sawtooth flutter waves (F waves), most visible in II, III, aVF, V1
- Associated with CHD in older children — but may occur in structurally normal neonates
- Most neonatal atrial flutter presents in the first 48 hours of life
Atrial Flutter: sawtooth F-waves | atrial rate ≥250/min | 2:1, 3:1, or variable block | narrow QRS
Treatment
- Synchronized cardioversion 0.5–1 J/kg is the treatment of choice
- Transesophageal pacing or IV sotalol may also be considered for conversion
- In structurally normal hearts, neonatal atrial flutter usually does not recur — long-term medication is usually not needed
Key distinction from SVT
In atrial flutter, adenosine may transiently slow the ventricular rate and reveal sawtooth F-waves, but it will not terminate flutter (unlike AVRT/AVNRT). Cardioversion is definitive.
13. Congenital Complete AV Block
Complete AV block means there is no electrical communication between atria and ventricles.
Complete AV Block: P waves completely dissociated from QRS | atrial rate ~120-150 bpm | ventricular rate ~50-80 bpm
| Feature | Detail |
|---|
| Atrial rate | Usually 120–150 bpm |
| Ventricular escape rate | Usually 50–80 bpm |
| Most common cause | Maternal autoimmune disease (anti-Ro/SSA, anti-La/SSB antibodies) — lupus or Sjögren syndrome |
| Associated structural CHD | Heterotaxy syndrome, congenitally corrected TGA (ccTGA) |
| Important mimic | Long QT syndrome — measure QTc whenever AV block is suspected |
Management
- Some infants are asymptomatic with an adequate escape rhythm — observe
- Temporary heart rate support: isoproterenol infusion or epinephrine
- Emergency transcutaneous pacing if acutely unstable
- Permanent pacemaker is definitive therapy for clinically significant complete AV block
Measure QTc — long QT syndrome can mimic complete AV block
2:1 AV block in long QT syndrome may resemble complete heart block on the monitor. Obtain a 12-lead ECG and measure QTc before concluding the rhythm is congenital complete AV block.
14. Pacemaker Implantation
- Permanent pacemaker decisions should follow pediatric pacing guidelines with cardiology/electrophysiology involvement
- In neonates: epicardial pacemaker placement through sternotomy is the usual approach (transvenous leads are too large)
- Neonates often need to weigh ~3 kg before implantation can be considered
Postoperative Concerns
- Infection or bleeding in the pacemaker pocket
- Cardiac strangulation from leads as the heart grows
- Pacemaker malfunction or lead dislodgment
Pacing Modes
| Mode | Description |
|---|
| VVI — Single-chamber ventricular | Paces and senses ventricle; inhibited by intrinsic ventricular activity; does NOT preserve AV synchrony |
| DDD — Dual-chamber | Paces and senses both atrium and ventricle; allows AV synchrony and better heart-rate response |
15. NASPE/NBG Pacemaker Code
| Code Letter | Meaning |
|---|
| A | Atrium |
| V | Ventricle |
| D | Dual (atrium + ventricle) |
| O | None |
| T | Triggered response to sensing |
| I | Inhibited response to sensing |
| R | Rate response (when used as 4th letter) |
Reading the code
The 3-letter code reads: Chamber Paced – Chamber Sensed – Response to Sensing. Example: VVI = ventricle paced, ventricle sensed, inhibited by intrinsic beat. DDD = dual paced, dual sensed, dual response (triggered or inhibited).
16. Bedside Algorithm — Tachyarrhythmia
Neonatal Tachyarrhythmia — Bedside Approach
STEP 1 — Confirm rhythm with ECG (12-lead preferred)
↓
STEP 2 — Assess stability: perfusion, pulses, respiratory status, feeding, pallor, activity
↓
STEP 3a —
UNSTABLE narrow-complex tachycardia → Synchronized cardioversion 0.5–1 J/kg immediately
↓
STEP 3b — STABLE SVT → attempt vagal maneuver (ice/face, gag, rectal) for up to 5 minutes
↓
STEP 4 — Vagal maneuver fails → rapid IV adenosine 0.1 mg/kg (2-syringe technique); second dose 0.2 mg/kg if no response
↓
STEP 5 — Adenosine fails → involve cardiology; consider esmolol, sotalol, procainamide, or amiodarone
↓
STEP 6 — Recurrent SVT → choose long-term therapy based on frequency, severity, and ease of termination (propranolol first-line)
17. Bedside Algorithm — Bradyarrhythmia
Neonatal Bradyarrhythmia — Bedside Approach
STEP 1 — Confirm rhythm with ECG; look for AV dissociation
↓
STEP 2 —
Measure QTc — long QT syndrome can mimic complete AV block
↓
STEP 3 — Assess perfusion, feeding, respiratory status, BP, lactate, activity
↓
STEP 4 — Evaluate maternal autoimmune disease history (anti-Ro/SSA, anti-La/SSB); screen for associated CHD
↓
STEP 5 — If unstable → temporary support: isoproterenol infusion, epinephrine, or emergency transcutaneous pacing
↓
STEP 6 — Consult cardiology/electrophysiology early for pacemaker planning when complete AV block is clinically significant
18. Common Mistakes
| Mistake | Better Action |
|---|
| Treating monitor heart rate without ECG confirmation |
Obtain ECG — it is the preferred method for rhythm diagnosis; monitor alone is insufficient |
| Continuing vagal maneuvers too long in an ill neonate |
Do not continue vagal maneuvers beyond 5 minutes before escalating to adenosine |
| Giving adenosine slowly |
Use rapid IV push with immediate flush through access closest to the heart; slow delivery is ineffective |
| Giving adenosine without emergency readiness |
Have code cart available — asystole, bronchospasm, and tachyarrhythmias can occur |
| Starting sotalol without QTc monitoring |
Obtain daily ECGs during initiation because sotalol can prolong QTc and cause Torsades de Pointes |
| Giving flecainide inconsistently with feeds |
Give consistently with or without feeds — milk impairs absorption and inconsistent timing causes variable drug levels |
| Forgetting complete AV block mimics |
Measure QTc — long QT syndrome can present with 2:1 AV block resembling complete heart block |
| Assuming atrial flutter always requires chronic medication |
In structurally normal hearts, neonatal atrial flutter usually does not recur — long-term medication is usually not needed |
19. Parent Explanation
What to Tell Families
"An arrhythmia means the baby's heartbeat is too fast, too slow, or irregular. The ECG — a painless test that reads the heart's electrical activity — tells us exactly what rhythm is present and guides treatment."
"If the baby is unstable, we treat right away with a controlled electrical shock to reset the heart rhythm, or with a pacemaker if the rate is too slow."
"If the baby is stable, we may first try safe bedside maneuvers — like briefly applying ice to the face — or a rapid medicine called adenosine, which works for just a few seconds but is enough to stop the abnormal rhythm."
"Some babies need longer-term medicine or a pacemaker, depending on the type of rhythm and how well the baby tolerates episodes. Most neonatal SVT responds well to treatment, and many babies eventually outgrow it."
Key Takeaways — Chapter 3.5
- Confirm all arrhythmias with ECG — monitor rate alone is not enough
- Assess stability first: unstable tachyarrhythmia → synchronized cardioversion 0.5–1 J/kg immediately
- AVRT (most common) vs. AVNRT (less common) — both cause narrow-complex SVT at 250–300 bpm
- WPW: delta wave + short PR + wide QRS in sinus rhythm
- Stable SVT: vagal maneuver (≤5 min) → adenosine 0.1 mg/kg (then 0.2 mg/kg) by 2-syringe rapid push
- Have code cart at bedside before giving adenosine — asystole and bronchospasm can occur
- Long-term SVT: propranolol first-line; sotalol/flecainide second-line (daily ECGs during initiation)
- Flecainide: give consistently with/without feeds — milk affects absorption
- Amiodarone: use dedicated line; incompatible with heparin; watch for hypotension during infusion
- Atrial flutter: cardioversion 0.5–1 J/kg; adenosine slows rate but does not terminate; usually no long-term meds in normal hearts
- Complete AV block: measure QTc first — long QT can mimic; maternal anti-Ro/SSA/La/SSB; check for heterotaxy and ccTGA
- Pacemaker: epicardial in neonates (~3 kg); VVI = no AV synchrony; DDD = dual-chamber with AV synchrony
References
- Baylor College of Medicine — Guidelines for Acute Care of the Neonate, current edition: Chapter 3.5
- Brugada J, et al. Management of pediatric arrhythmias. Circulation. 2019
- Lapage MJ, Bradley DJ. Supraventricular tachycardia in children. Pediatr Ann. 2019
- Perry JC, Garson A Jr. Supraventricular tachycardia due to Wolff-Parkinson-White syndrome in children: early disappearance and late recurrence. J Am Coll Cardiol. 1990
- Villain E. Indications for pacing in patients with congenital heart disease. Pacing Clin Electrophysiol. 2008
- Baruteau AE, et al. Congenital and childhood atrioventricular blocks. Eur J Pediatr. 2016
- Moodley S, et al. Neonatal atrial flutter: a case series and literature review. Pediatr Cardiol. 2011
- Manolis AS, et al. Amiodarone in cardiac arrhythmias: review of efficacy and safety. Curr Med Res Opin. 2020