What is the initial step in managing a child with palpitations and tachycardia, likely an infant or young child with a possible underlying medical condition or history of heart problems, presenting with a heart rate of 250 beats per minute (bpm)?

Initial Management of Pediatric Tachycardia at 250 bpm

The initial step is to obtain an electrocardiogram (ECG) immediately to differentiate the type of tachyarrhythmia and guide appropriate treatment. 1, 2

Rationale for ECG as First-Line

A heart rate of 250 bpm in a child is extremely concerning and requires immediate rhythm identification before any other diagnostic or therapeutic intervention. 3 The American Heart Association recommends that a 12-lead ECG should be performed in all pediatric patients presenting with paroxysmal symptoms to exclude cardiac arrhythmias. 1 This is critical because:

• Supraventricular tachycardia (SVT) represents more than 70% of tachyarrhythmias in children, and approximately half of pediatric SVT cases present in the first 4 months of life. 2

• A heart rate of 250 bpm strongly suggests SVT or atrial flutter rather than sinus tachycardia, as the upper normal limit for sinus tachycardia in infants is 179 bpm in the first month and declines to approximately 160 bpm after six months. 3

• Extremely rapid rates over 200 bpm suggest the presence of an accessory pathway (Wolff-Parkinson-White syndrome), which has critical treatment implications. 3

• Misdiagnosis as ventricular tachycardia (VT) can be fatal, as digoxin or verapamil should never be used when VT has not been excluded, particularly in infants. 2

Critical Diagnostic Distinctions on ECG

The ECG will immediately reveal:

• Regular vs. irregular rhythm: Regular narrow-complex tachycardia at 250 bpm suggests SVT or atrial flutter with 2:1 conduction, while irregular rhythm suggests atrial fibrillation (rare in children without structural heart disease). 3

• QRS width: Narrow QRS confirms supraventricular origin, while wide QRS (>120 ms) suggests either SVT with aberrancy, preexcitation, or VT. 3

• P wave morphology and relationship to QRS: Visible P waves with saw-tooth pattern suggest atrial flutter (typically 240-320 bpm atrial rate), while absent or retrograde P waves suggest SVT. 3

Why Echocardiogram is NOT the Initial Step

While echocardiography is important in the workup of pediatric arrhythmias, it should not precede ECG because:

• Echocardiography does not identify the rhythm mechanism and therefore cannot guide acute treatment decisions. 3

• Congenital heart disease is more common in infants with preexcitation (prevalence up to 45% with right-sided accessory pathways), but this assessment is performed after rhythm identification and stabilization. 3

• The European Society of Cardiology recommends complete 2-dimensional echocardiographic work-up in patients with preexcitation pattern on surface ECG, but this follows the initial ECG diagnosis. 3

Immediate Management Algorithm After ECG

Once the ECG confirms the rhythm:

1. Assess hemodynamic stability: Check for altered mental status, chest pain, heart failure, hypotension, or shock. 3

2. For hemodynamically stable SVT: Attempt vagal maneuvers first, followed by adenosine if unsuccessful. Initial adenosine doses in children are higher than adults (150-250 mcg/kg). 2

3. For hemodynamically unstable tachycardia: Proceed immediately to synchronized cardioversion. 2

4. If preexcitation is identified: Avoid digoxin and verapamil, as these agents shorten the antegrade effective refractory period of the accessory pathway and can precipitate ventricular fibrillation or sudden death. 3, 2

Common Pitfall to Avoid

Never assume this is sinus tachycardia and order an echocardiogram to look for structural causes of compensatory tachycardia. A heart rate of 250 bpm exceeds the physiologic capacity of sinus tachycardia in children and represents a primary arrhythmia requiring immediate rhythm identification via ECG. 3, 4