What are the next steps for an 8-year-old child with tachycardia who is taking Clonidine (clonidine) and Strattera (atomoxetine)?

Immediate Medication Hold and Cardiovascular Assessment

Hold the clonidine immediately if the heart rate is below 50 bpm or systolic blood pressure is below 90 mmHg, and obtain a 12-lead ECG to determine the tachycardia mechanism before proceeding with any treatment. 1

Initial Assessment and Stabilization

• Assess hemodynamic stability first: Check for signs of shock, altered mental status, or cardiovascular compromise. If present, proceed directly to synchronized cardioversion at 0.5-1 J/kg rather than attempting pharmacologic management. 2

• Obtain a 12-lead ECG immediately while establishing continuous cardiac monitoring and IV access. The ECG determines the entire management pathway by answering three critical questions: QRS duration (narrow vs. wide complex), P-wave morphology and relationship to QRS, and presence of pre-excitation (delta waves). 2

• Measure vital signs including heart rate, blood pressure, and pulse oximetry to assess both the tachycardia severity and the effects of the current medications. 2

Medication-Specific Considerations

Clonidine Management

• Hold clonidine if heart rate is <50 bpm or systolic BP <90 mmHg, as clonidine causes bradycardia and hypotension through its central alpha-2 agonist mechanism. 1

• Never abruptly discontinue clonidine even if holding doses temporarily, as this can precipitate severe rebound hypertension and hypertensive crisis. Any discontinuation must be tapered gradually. 1

• The paradox: Clonidine typically causes bradycardia, not tachycardia. If this child has tachycardia while on clonidine, consider whether the tachycardia represents a compensatory response to hypotension from clonidine, or whether it's an independent arrhythmia. 1

Atomoxetine (Strattera) Considerations

• Atomoxetine increases heart rate and blood pressure in 5-15% of patients through its norepinephrine reuptake inhibition mechanism, which could be contributing to the tachycardia. 3

• Cardiovascular side effects of atomoxetine include tachycardia, orthostatic hypotension (paradoxically), and syncope in rare cases. 4

• Consider holding atomoxetine temporarily until the tachycardia mechanism is clarified, particularly if the ECG shows sinus tachycardia that may be medication-induced. 3

Diagnostic Workup Based on ECG Findings

If Sinus Tachycardia (P waves present, normal morphology, rate <220 minus age)

• Treat the underlying cause rather than the heart rate itself. 2 The upper limit of physiologic sinus tachycardia is approximately 220 minus the patient's age (212 bpm for an 8-year-old). 2

• Common causes to evaluate: Dehydration, fever, pain, anxiety, hypoxemia, anemia, or medication effect (atomoxetine). 2

• If medication-induced: Consider dose reduction or temporary discontinuation of atomoxetine after discussing with the prescribing physician. 3

If Supraventricular Tachycardia (SVT)

• For hemodynamically stable SVT, attempt vagal maneuvers first (ice to face, Valsalva if age-appropriate) unless this will delay definitive treatment. 3, 2

• Adenosine is the drug of choice (Class I recommendation): Give 0.1 mg/kg rapid IV/IO bolus (maximum first dose 6 mg), followed by rapid saline flush. If unsuccessful, give second dose of 0.2 mg/kg (maximum 12 mg). 2

• If adenosine fails or SVT recurs: Consider synchronized cardioversion at 0.5-1 J/kg, increasing to 2 J/kg if needed. 3, 2

• Do NOT use verapamil in this age group without expert consultation, as it can cause myocardial depression, hypotension, and cardiac arrest in children. 3

If Pre-excitation (Delta Waves) Present

• Immediate pediatric cardiology referral is mandatory as this indicates Wolff-Parkinson-White syndrome, which requires specialized management and carries risk of sudden death. 2

• Avoid AV nodal blocking agents (adenosine, beta-blockers, calcium channel blockers) if pre-excitation with atrial fibrillation is present, as these can precipitate ventricular fibrillation. 2

Mandatory Cardiology Referral Criteria

Refer immediately to pediatric cardiology for: 2

• Pre-excitation (Wolff-Parkinson-White syndrome) on ECG
• Syncope during tachycardia or with exercise
• Wide complex tachycardia of unknown origin
• Documented sustained SVT
• Any uncertainty about diagnosis or management

Monitoring and Follow-up

• Before each dose of clonidine, monitor heart rate and blood pressure, holding the dose if HR <50 bpm or systolic BP <90 mmHg. 1

• Obtain personal and family cardiac history including sudden death, cardiovascular symptoms, Wolff-Parkinson-White syndrome, hypertrophic cardiomyopathy, and long QT syndrome. If risk factors present, obtain ECG and consider cardiology referral before continuing ADHD medications. 3

• Monitor for tachycardia-mediated cardiomyopathy if tachycardia persists for weeks to months, as this is reversible but requires careful long-term follow-up. 2

Common Pitfalls to Avoid

• Do not assume the tachycardia is benign or medication-related without obtaining a 12-lead ECG to rule out pathologic arrhythmias. 2

• Do not abruptly stop clonidine even if concerned about medication interactions, as rebound hypertension can be life-threatening. 1

• Do not give verapamil to children without expert consultation, particularly in this age group. 3

• Do not delay cardioversion if the child shows any signs of hemodynamic instability while attempting vagal maneuvers or waiting for IV access. 2