Heart Rate 145 in a 6-Year-Old Child
A heart rate of 145 bpm in a 6-year-old is at the borderline threshold and requires immediate assessment for hemodynamic stability and underlying causes, but does not automatically mandate emergency intervention if the child appears well.
Initial Assessment Priority
Immediately evaluate for signs of hemodynamic instability including acute altered mental status, respiratory distress, signs of shock, or hypotension 1, 2. If any of these are present, proceed directly to emergency management regardless of the heart rate 3, 1.
Key Clinical Context
- The upper normal limit for heart rate in children after 6 months of age is approximately 160 bpm (98th percentile) 3
- Heart rates ≥150 bpm typically indicate a true tachyarrhythmia requiring immediate evaluation and workup, according to the American College of Cardiology 1
- At 145 bpm, this child sits just below the critical 150 bpm threshold, making the clinical presentation the determining factor 1
Immediate Actions (Stable Patient)
If the child appears well-perfused with normal mental status:
- Attach cardiac monitor and obtain full vital signs including oxygen saturation, blood pressure, and respiratory rate 1, 2
- Establish IV access while simultaneously performing other assessments 2
- Obtain a 12-lead ECG to differentiate sinus tachycardia from supraventricular tachycardia (SVT) 3, 2
- Check for hypoxemia or respiratory distress (tachypnea, retractions), as hypoxemia commonly drives tachycardia 1, 2
Rhythm Differentiation
Distinguishing Sinus Tachycardia from SVT
The 12-lead ECG and clinical presentation are essential to differentiate these rhythms 3:
- Sinus tachycardia: Heart rate typically <180 bpm in children, with normal P waves preceding each QRS, rate varies with activity/stimulation 3, 4
- SVT: Heart rate generally exceeds 180 bpm in children (>220 bpm in infants), with a rapid and regular rate that does not vary 4
If Sinus Tachycardia
Search for and treat reversible causes 3:
- Fever, infection, dehydration (hypovolemia), pain, anxiety 3
- Anemia, hyperthyroidism, myocarditis 3
- Medications transmitted through breast milk or given directly 3
No emergency arrhythmia treatment is necessary if this is physiologic sinus tachycardia 3. Address the underlying condition and monitor for persistence 3.
If SVT (Narrow-Complex Tachycardia)
For a stable patient with confirmed SVT 3:
Attempt vagal stimulation first unless it will unduly delay other interventions 3
Adenosine is the drug of choice if IV access is readily available (Class I recommendation) 3
- Very effective with minimal and transient side effects 3
Monitor rhythm continuously during all therapeutic interventions 3
If Wide-Complex Tachycardia (QRS >0.09 seconds)
This is ventricular tachycardia until proven otherwise 2, 5:
- Most wide-complex tachycardias are ventricular in origin 2
- Urgent cardiology consultation is required even if self-terminated 1, 2
- Obtain echocardiography to evaluate for structural heart disease 2
Critical Pitfall
Do not assume all tachycardia at this rate is benign sinus tachycardia. The American Heart Association specifically identifies ≥150 bpm as the threshold where primary arrhythmia becomes more likely than physiologic response 1. At 145 bpm, you are at the edge of this threshold and must actively rule out SVT with a 12-lead ECG 3, 1.
When to Consult Cardiology
- Any suspected or confirmed SVT episode, even if self-terminated 1
- Wide-complex tachycardia of any kind 2
- Recurrent episodes requiring event monitoring 1
- Known ventricular dysfunction with tachycardia (lower threshold for concern) 1
- Consultation with a pediatric arrhythmia expert is strongly recommended before treating any hemodynamically stable child, as all arrhythmia therapies carry potential for serious adverse effects 3