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Rhythm

Sinus tachycardia

Not medically reviewed · Content last updated · 1 min read ·

This is the date the draft was written, not a medical review date.

Sinus tachycardia is a sinus rhythm faster than 100 beats/min. It is usually a physiological response to a demand such as exercise, fever, pain, hypovolaemia or anxiety, and the cause should be sought rather than the rate treated.

ECG criteria

  • Rate above 100 beats/min, usually below about 150 to 160 in adults (the maximum falls with age).
  • Regular rhythm, with gradual rather than abrupt onset and offset.
  • Normal P wave before every QRS, upright in I, II and aVF.
  • Constant PR interval, which may shorten slightly at fast rates.
  • Narrow QRS; P wave may merge with the preceding T wave at higher rates.

Mechanism

Increased sympathetic activity or reduced vagal tone raises the firing rate of the sinoatrial node, often with circulating catecholamines or thyroid hormone contributing. The activation sequence is normal, so P, PR and QRS keep their usual relationship.

Common causes

  • Physiological: exercise, emotion, pain, caffeine.
  • Fever, infection and sepsis, anaemia, hypovolaemia or haemorrhage.
  • Hyperthyroidism, pulmonary embolism, heart failure, acute coronary syndrome.
  • Drugs and substances: sympathomimetics, stimulants, alcohol withdrawal.

Management principles

Treatment is directed at the underlying cause, not at the rate itself, because the tachycardia is usually compensatory. Reassess the patient for the trigger and follow local guidelines for the condition identified.

High-level principles for study. Treatment decisions follow local guidelines and the clinical situation.

Pitfalls and mimics

  • A fixed regular rate near 150 beats/min should raise suspicion of atrial flutter with 2:1 conduction; sinus tachycardia varies with the patient state.
  • At high rates the P wave hides in the T wave and a re-entrant supraventricular tachycardia may be mistaken for sinus tachycardia (abrupt onset and offset favour re-entry).
  • A wide-complex tachycardia is not sinus tachycardia unless a bundle branch block is already known.

Practise in the ECG trainer — Recognise this pattern on generated tracings.

References

  1. 2019 ESC Guidelines for the management of patients with supraventricular tachycardia. European Society of Cardiology (2019) — Tier 2 (guidelines / primary literature)
  2. Wagner GS, Strauss DG. Marriott's Practical Electrocardiography. Wolters Kluwer, 12th edition (2013) — Tier 3 (textbook)
  3. Loscalzo J, et al.. Harrison's Principles of Internal Medicine. McGraw-Hill, 21st edition (2022) — Tier 3 (textbook)

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