Approach to Pediatric Tachycardia

Click for pdf: Tachycardia

Background

General Presentation

Tachycardia is an abnormally rapid heart rate.  In adults, this is usually defined as >100 beats per minute (bpm).  In pediatrics, the normal heart rate varies with age (see Table 1).  Therefore, in children, the definition of tachycardia is age dependent.  Presentation varies with underlying cause, but most often the symptoms are vague and non-specific, such as “fussiness” or “difficulty feeding”.

Basic Anatomy and Physiology

Normal pediatric ranges for heart rate can be found in Table 1. The heart receives both sympathetic (sympathetic ganglion, increases heart rate) and parasympathetic (vagus nerve, decreases heart rate) innervation.  Tachycardia may result from physiologic processes that alter the sympathetic/parasympathetic tone, resulting in a sinus tachycardia.  Alternatively, tachycardia may be the result of an arrhythmia:  atrial fibrillation; atrial flutter; supraventricular tachycardia; or ventricular tachycardia. There are many medications that can cause tachycardia, either by leading to the release of catecholamines, or by inducing an arrhythmia.

Questions to Ask

• Does the child have a history of tachycardia, or a known cardiac condition?
• What is the onset and duration of the child’s current illness (if present)?
• Does the child have other symptoms, such as:
• Chest pain
• Palpitations
• Shortness of breath
• Colour change
• Syncope
• Neurologic symptoms (e.g., change in level of consciousness)
• Does the child take any medications?
• Does the child have any allergies?
• Is there a family history of cardiac problems?
• Arrythmias
• Does the tachycardia occur at certain times (e.g., with activity, following meals, under stress)?
• Does the child feel hot/have a fever?
• Has the child been vomiting or having diarrhea?
• Has the child been drinking?
• What is their urine output?

Differential Diagnosis

• Sinus Tachycardia secondary to dehydration/hypovolemia (most common), fever, hypoxia, anemia, shock, MI, pulmonary edema, hyperthyroidism, hypocalcemia, or medications
• Supraventricular Tachycardia (AV re-entry, junctional, or atrial ectopic)
• Ventricular Tachycardia
• Atrial flutter
• Atrial fibrillation

*See Table 3

Investigations

Physical exam

• Focus on general appearance, hydration status, vital signs, respiratory exam (retractions, increased work of breathing, crackles, wheezing), cardiac exam (dyspnea, liver size, peripheral perfusion, cyanosis, rate/rhythm, murmurs), level of consciousness.

Labs

• Electrolytes, CBC, glucose, Mg, Ca.  Consider toxicology screen, thyroid function studies, blood gas.
• Consider CXR, cardiac echo.
• 12 lead ECG

Appendix

Table 1:  Pediatrics HR ranges

Table 2: Tachycardia inducing medications

Table 3:  Differential diagnosis

References

Behrman RE, Kliegman RM. Nelson essentials of pediatrics. Philadelphia : W.B. Saunders, c2002

Cheng A, Williams BA, Sivaragan BV. The HSC Handbook of Pediatrics. Toronto : Elsevier Canada, c2003

Doniger SJ, Sharieff GQ. Pediatric Dysrhythmias. Pediatr Clin N Am 53 (2006) 85– 105

Farah M. Pediatrics, Tachycardia. http://www.emedicine.com/EMERG/topic408.htm

Acknowledgements

Written by: Justin Haba

Edited by: Anne Marie Jekyll