- Newborn: 110 – 150 bpm
- 2 years: 85 – 125 bpm
- 4 years: 75 – 115 bpm
- 6 years+: 60 – 100 bpm
- Normal during sleep
- Increased vagal tone (e.g. athletes)
- Vagal stimulation (e.g. pain)
- Inferior myocardial infarction
- Sinus node disease
- Anorexia nervosa
- Electrolyte abnormalities – hyperkalaemia, hypermagnesaemia
- Brainstem herniation (the Cushing reflex)
- Sinus bradycardia may be indistinguishable from type II sino-atrial block.
Sinus bradycardia secondary to anorexia nervosa
- Sinus bradycardia (35 bpm) in a 15-year old girl with anorexia nervosa.
- Note the prominent U waves in the precordial leads, a common finding in sinus bradycardia.
- Hampton, JR. The ECG In Practice, 6e
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric, 6e
- Wagner, GS. Marriott’s Practical Electrocardiography 12e
- Chan, TC. ECG in Emergency Medicine and Acute Care
- Mattu, A. ECG’s for the Emergency Physician
LITFL Further Reading
- ECG BASICS — Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis –alphabetical diagnostic approach to the ECG
- ECG CLINICAL CASES — ECG’s placed in clinical context with a challenging Q&A approach
- 100 ECG Quiz — Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS — the best of the rest
- LITFL ECG IMAGE Database — Searchable database of LITFL ECG’s
- ECG and Cardiology Eponymous Syndromes — Cheats guide to eponymous emancipation
- ECG Exam Template — a framework for answering ECG exam questions.