Sinus tachycardia

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Background

  • A cardiac abnormality characterized by the presence of a sinus rhythm at a rate that is above the upper limit of normal.
    • In adults, usually defined as a heart rate >100. In pediatric patients it varies by age. See pediatric vital signs.
  • Usually a secondary response to another medical condition.

Evaluation

  • History and physical exam, focusing on any evidence of intoxication, infection, dehydration, or a psychiatric/emotional state that may contribute to an elevated heart rate. Orthostatic vital signs should be measured.
  • EKG should be ordered to rule out other arrhythmias that may present with an elevated heart rate.
  • If history and physical are unable to explain the tachycardia, limited labs and imaging studies may be indicated.
    • CBC, BMP, UTox, UA, TSH, troponin, and CXR are often indicated.
    • If suspected, a CT of the pulmonary arteries may be able to diagnose a PE.

Differential Diagnosis

  • Emotional or psychiatric causes such as pain, anger, or anxiety
  • Appropriate response to fever (about 10 bpm per degree C > 37.0)
  • SIRS (from infection or other causes)
  • Dehydration
  • 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

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.