What is the appropriate evaluation and management of tachycardia at rest in an 11-year-old with no cardiac history?

Evaluation and Management of Resting Tachycardia in an 11-Year-Old

Begin with a 12-lead ECG to document the rhythm and heart rate, then assess for underlying causes including fever, dehydration, anemia, hyperthyroidism, and cardiac structural abnormalities before attributing symptoms to a primary arrhythmia. 1

Initial Assessment

Define the Tachycardia

• Tachycardia in children is defined as heart rate >100 bpm at rest, though the clinical significance increases substantially when rates exceed 150 bpm 1
• For adolescents aged 12-19 years, orthostatic tachycardia specifically requires a sustained heart rate increase ≥40 bpm within 10 minutes of standing (compared to ≥30 bpm in adults) 1
• The upper limit of physiologic sinus tachycardia is approximately 220 minus the patient's age (209 bpm for an 11-year-old) 1

Critical History Elements

Determine whether the tachycardia is:

• Regular vs. irregular: Regular with abrupt onset/termination suggests paroxysmal supraventricular tachycardia (PSVT), while irregular suggests premature beats, atrial fibrillation, or multifocal atrial tachycardia 1
• Paroxysmal vs. continuous: Sinus tachycardia accelerates and decelerates gradually, whereas PSVT has sudden onset and termination 1
• Associated with exercise: Syncope with high-intensity physical activity raises concern for hypertrophic cardiomyopathy or catecholaminergic polymorphic ventricular tachycardia 1
• Accompanied by palpitations, chest pain, lightheadedness, dyspnea, or syncope: These symptoms warrant more urgent evaluation 2, 3
• Terminable by vagal maneuvers: This suggests reentrant tachycardia involving AV nodal tissue (AVNRT or AVRT) 1

Diagnostic Workup

Mandatory Initial Testing

• 12-lead ECG at rest: Look for pre-excitation (delta waves suggesting Wolff-Parkinson-White syndrome), prolonged QT interval, Brugada pattern, or other baseline abnormalities 1
• 12-lead ECG during tachycardia if possible: This is essential for definitive diagnosis and should be obtained before any treatment that terminates the rhythm 1
• Echocardiogram: Recommended to exclude structural heart disease including hypertrophic cardiomyopathy, dilated cardiomyopathy, valvular abnormalities, and coronary artery anomalies 1

Additional Evaluation Based on Presentation

• Laboratory testing: Thyroid function, complete blood count (for anemia), electrolytes (potassium, magnesium), and glucose to identify secondary causes 1
• Ambulatory monitoring: 24-hour Holter for frequent episodes (several per week), event recorder for less frequent episodes, or implantable loop recorder for rare but severe symptoms 1
• Exercise stress test: Indicated when symptoms occur with exertion to evaluate for exercise-induced arrhythmias or hypertrophic cardiomyopathy 1

Management Approach

Immediate Referral to Cardiology Required For:

• Pre-excitation (WPW syndrome) on ECG: Risk of sudden death from rapid conduction during atrial fibrillation mandates immediate electrophysiology evaluation 1, 2
• Syncope during tachycardia or with exercise: Suggests hemodynamic compromise or high-risk structural disease 1
• Wide complex tachycardia of unknown origin: Requires specialist evaluation to differentiate ventricular from supraventricular origin 1
• Documented sustained SVT: All patients should be referred to a cardiac arrhythmia specialist for definitive management options 1, 3

Sinus Tachycardia Management

• Identify and treat the underlying cause rather than the heart rate itself: fever, dehydration, anemia, hyperthyroidism, anxiety, or medications 1
• No specific antiarrhythmic therapy is indicated for physiologic sinus tachycardia 1
• Consider inappropriate sinus tachycardia if resting heart rate >100 bpm with mean 24-hour rate >90 bpm without identifiable physiologic cause 1

Paroxysmal SVT Management (If Documented)

• Teach vagal maneuvers as first-line acute treatment 1, 3
• Beta-blockers may be prescribed empirically if significant bradycardia (<50 bpm) has been excluded, but only after documented arrhythmia 1
• Do not initiate class I or III antiarrhythmics without documented arrhythmia due to proarrhythmic risk 1
• Catheter ablation is potentially curative and should be discussed with families, particularly for recurrent symptomatic episodes 2, 3

Critical Pitfalls to Avoid

• Do not dismiss as anxiety or panic disorder without proper cardiac evaluation, as this commonly delays diagnosis of true SVT 2
• Do not rely on automatic ECG interpretation systems, which are unreliable and frequently suggest incorrect diagnoses 1
• Do not use adenosine in WPW with atrial fibrillation, as it can precipitate ventricular fibrillation 4
• Recognize that persistent tachycardia (weeks to months) with fast ventricular response can cause tachycardia-mediated cardiomyopathy, which is reversible but requires careful long-term follow-up even after recovery 1, 5
• In pediatric patients, syncope with aortic stenosis is an ominous sign requiring urgent intervention 1