Sinus tachycardia

Background

• Sinus rhythm at a rate above the upper limit of normal
  • In adults, usually >100 bpm
  • In pediatric patients it varies by age until age 8 or 9 (see pediatric vital signs)
• Usually seen as a secondary response to a primary medical condition

Differential Diagnosis

Algorithm for the Evaluation of Sinus Tachycardia

• Emotional or psychiatric causes
  • Pain, anger, or anxiety
• Response to fever (about 10 bpm per degree C > 37.0)
• SIRS (from infection or other causes)
• Dehydration/Hypovolemia
• Anemia
• Drug/alcohol intoxication (particularly sympathomimetic or anticholinergic drugs, but may also be seen in aspirin, theophylline, or other ingestions)
• Drug/alcohol withdrawal
• Anion gap acidosis
• Hyperthyroidism
• PE
• CHF
• Cardiac tamponade
• Myocardial contusion
• Cardiac valvular disease
• Hyper or hypoglycemia
• Myocardial infarction
• Pheochromocytoma

Evaluation

• History and physical exam
  • Look for intoxication/withdrawal, infection, dehydration, bleeding, or a psychiatric/emotional state
• Consider orthostatic vital signs
• ECG to rule out other arrhythmias that may present with an elevated heart rate
  • Look for regular rate and presence of p-waves to support diagnosis of sinus tachycardia
• If history and physical are unable to explain the tachycardia, limited labs and imaging studies may be indicated:
  • CBC
  • BMP
  • UTox
  • Urine pregnancy
• Consider:
  • Empiric treatment for anxiety or pain (e.g. benzodiazepine or NSAID)
  • Urinalysis
  • TSH
  • Troponin
  • CXR
  • Workup for PE (e.g. D-dimer or CTA)

Management

• Management should be tailored to the specific cause of sinus tachycardia. This may range from fluids for mild dehydration to admission to the ICU for severe sepsis.
• If no cause can be found, treatment is not usually indicated. Be extremely cautious if treating unexplained sinus tachycardia with beta blockers or other anti-arrhythmics, as the patient may require the elevated heart rate to maintain an appropriate cardiac output.
• Unexplained tachycardia should be thoroughly worked up. If no etiology can be found and no serious pathology is suspected, discharge can be considered with close follow up and strict return precautions.