It is fortunate that most issues we encounter in the Pediatric ED are not due to the child’s heart! Sure there are numerous other odd entities to consider, like Necrotizing Enterocolitis, Omphalitis, and Hamman’s Syndrome but even in the critically ill child, their heart is usually working extra hard to help us have time to figure things out. Unfortunately, when a child with a cardiac issue does enter our ED, it can cause tachycardia in everyone. We have discussed some basic concepts previously, like Pediatric ECGs, Murmurs, and Adenosine dosing. We have also confronted SVT, Atrial Fibrillation, Heart Failure, and Fontan procedures (hmm… it almost seems like the first sentence was inaccurate). Now, let’s make sure we can mitigate our own palpitations with respect to Atrial Flutter in Children:

Atrial Flutter in Children: Basics

Atrial Flutter is a cardiac arrhythmia with fast and regular atrial depolarization.

In children, the atrial rate is faster than than seen in adults. [Kedziora, 2020]
- Most often with atrial rates from 250 to 350 beats/min.
  - Up to 400 beats/min in children !
  - Up to 500 beats/min in neonates!
- Often too fast for the AV node, so a physiologic AV block develops.
- 2:1, 3:1, 4:1 blocks occur leading to slower, regular ventricular rhythm.

The ECG should have: [Kedziora, 2020]
- Flutter (F) waves is a “sawtooth” shape.
- Absence of isoelectric line between F Waves in limb leads.
- F wave frequency of > 250 beats/min.
- Regular QRS that is slower than F waves.

The F waves may be difficult to see initially on ECG, due to accelerated ventricular response. [Kedziora, 2020]
- Adenosine will “uncover” the F Waves.
- Adenosine will not slow the atrial rate, but will affect the ventricular response.

Atrial Flutter requires abnormal structure and conduction.

Atrial Flutter needs a reentry loop.
- In adults, this loop may develop from ischemic heart disease or heart surgery. [Dieks, 2021]
- In children, the reentry loop is often associated with an abnormal atrial architecture. [Kedziora, 2020]
  - The reentry loop can create a closed-loop circuit if there is unidirectional block within it and conditions disrupt conduction.
  - Electrolyte disturbances and abnormal myocardium may exacerbate this mechanism.

Atrial abnormalities may be due to: [Kedziora, 2020]
- Hypoxia
- Inflammatory Process
- Scarring
- Increased Atrial size (from increased pressures)

Atrial Flutter is rare in children WITHOUT organic heart disease.

Atrial Flutter in Children: Presentations

While rare, Atrial Flutter can be seen in fetuses, neonates, and adolescents. [Kedziora, 2020]

Fetus/Neonate: [Kedziora, 2020; Wojtowicz-Marzec, 2020; Yilmaz-Semerci, 2018]
- Atrial Flutter can be diagnosed in utero.
  - May lead to non-immune fetal hydrops.
  - Perinatal atrial flutter is associated with ~9% mortality.
- Atrial Flutter in neonates usually is noted within first ~7 days of life.
  - Accounts for ~20% of supraventricular arrhythmias in this age group.
  - Often detected in the newborn nursery, but…
  - Could develop shortly after discharge from the nursery and then present to the ED.
- 80% will be “Asymptomatic.”
  - If ventricular response is near physiologic normal, newborns will tolerate the arrhythmia.
  - Usually have no organic heart disease.
  - Detected during normal newborn assessments.
- 20% will have Moderate to Severe Heart Failure.
  - The efficient AV conduction system in children can allow for very fast ventricular response (although can also see bradycardia).
  - May lead to quickly evolving symptoms of heart failure:
    - Fatigue with feeding
    - Pale, mottled skin with poor Cap Refill
    - Faint pulses
  - May develop dilated cardiomyopathy if arrhythmia continues.

Older Children: [Kedziora, 2020]
- Presentations may be related to concurrent exacerbating factors.
- Typically will present with cardio-pulmonary symptoms:
  - Palpitations
  - Chest Pain
  - Shortness of Breath / Dyspnea

Atrial Flutter in Children: “Lone A-Flutter?”

Atrial Flutter in children is usually associated with another condition. [Kedziora, 2020; Wojtowicz-Marzec, 2020]
- Congenital Heart Disease
  - Transposition of Great Vessels
  - Ebstein’s anomaly
  - Tricuspid valve disease
  - Atrial septal defects
- Post-operative (ex, after surgery involving the atrium)
- Myocarditis
- Cardiomyopathy
- Channelopathies (ex, Brugada)
- WPW
- Endocrine problems (ex, Hyperthyroidism)
- Obesity
- Familial genetic mutation

Like Atrial Fibrillation, Atrial Flutter may also occur WITHOUT any obvious cardiac abnormality = “Lone A-Flutter” [Dieks, 2021]
- Very Rare – less than 10% of cases.
- Most often associated with the neonate, not the older child.
- Recent study [Dieks, 2021] found that “true incidence” of “lone A-Flutter” to be 0.3%.
  - Further testing (ex, Biopsy) showed more had defined etiology in those thought to be without abnormality.
  - Some cases due to:
    - Myocarditis
    - Cardiomyopathy
    - Channelopathy

Atrial Flutter in Children: Management

Management is often determined by clinical experience.
- There are no evidence-based guidelines.
- Management depends on age, symptoms, and anatomy. [Kedziora, 2020]
- Make sure to involve your friendly pediatric cardiologist early!

Both electrical cardioversion and chemical cardioversion have been successfully used. [Kedziora, 2020]
- Unstable / ill patients warrant cardioversion.
  - Synchronized cardioversion
    - Increasing dose from 0.5 to 2 J/kg
    - Used in the hemodynamically unstable
    - May also be needed in those unresponsive to medical therapy.
  - Medications that have been used in infants: [Kedziora, 2020]
    - Sotalol
    - Digoxin
    - Amiodarone
  - Medications that have been used in older children: [Kedziora, 2020]
    - Beta blockers
- Atrial Flutter may spontaneously resolve in neonates.
  - Resolves spontaneously in 25% of newborns.
  - A period of investigation and monitoring in the asymptomatic neonate may be reasonable.

Risk of recurrence of Atrial Flutter is low after conversion. [Kedziora, 2020]
- Older children and adolescents may need catheter ablation or prolonged anti-arrhythmic medication.
- Management tailored for individual case.

Moral of the Morsel

The Younger they are, the Faster they can go! That atrial rate can be heroically fast!
Adenosine is helpful to diagnose, but not to resolve. Narrow complex tachycardia concerning for SVT? Adenosine may uncover F-waves.
A Flutter is unusual and warrants concern. Talk about further investigation with Cardiology as “Lone A-Flutter” is very rare.