Sinus tachycardia


Sinus rhythm with resting heart rate (HR) > 100 bpm in adults, or above the normal range for age in children

Normal heart rates in children
  • Newborn: 110 – 150 bpm
  • 2 years: 85 – 125 bpm
  • 4 years: 75 – 115 bpm
  • 6 years+: 60 – 100 bpm


Sinus tachycardia is usually a secondary condition. Inappropriate sinus tachycardia is a primary condition diagnosed in patients with symptomatic persisting sinus tachycardia in which the below causes have been excluded.

  • Beta-agonists: adrenaline, isoprenaline, salbutamol, dobutamine
  • Sympathomimetics: amphetamines, cocaine, methylphenidate
  • Antimuscarinics:  antihistamines, TCAs, carbamazepine, atropine
  • Others: caffeine, theophylline, marijuana

Example ECG
ECG Sinus Tachycardia

Sinus tachycardia:

  • Heart rate 150 bpm.
  • P waves are hidden within each preceding T wave.

Handy Tip

ECG Camel hump hidden p waves

With very fast heart rates the P waves may be hidden in the preceding T wave, producing a ‘camel hump’ appearance.

Advanced Reading



LITFL Further Reading


Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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