Sinus node dysfunction and bradycardia
Separating physiological from pathological bradycardia, reversible causes, acute treatment of unstable bradycardia, and when sick sinus syndrome needs a pacemaker.
Tier 1Condition
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Bradycardia is a heart rate below 50/min (ESC 2021 and ACC/AHA 2018). It's often normal: athletes, sleep, young people.
- Sinus node dysfunction (SND, sick sinus syndrome) is a failure of impulse generation or exit from the sinus node, usually degenerative fibrosis in older people.
- Exclude reversible causes first, especially drugs, hyperkalaemia, hypothyroidism and ischaemia.
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Sources
- 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapyEuropean Society of Cardiology (European Heart Journal, doi:10.1093/eurheartj/ehab364), 2021
- ESC clinical consensus statement on indications for conduction system pacingEuropean Society of Cardiology and European Heart Rhythm Association (EP Europace), 2025
- 2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction DelayAmerican College of Cardiology, American Heart Association and Heart Rhythm Society (Circulation), 2018
- Cardiac Society of Australia and New Zealand (CSANZ) Position Statement on the Follow-Up of Cardiovascular Implantable Electronic Devices 2022AU/NZCardiac Society of Australia and New Zealand (Heart, Lung and Circulation 2022;31(8):1054-63, doi:10.1016/j.hlc.2022.05.001), 2022
- Brubaker PH, Kitzman DW. Chronotropic incompetence: causes, consequences, and management. Circulation 2011;123(9):1010-20Circulation (PMC3065291), 2011
- Assessing Fitness to Drive for commercial and private vehicle driversAU/NZAustroads and the National Transport Commission, 2022
- Last updated
- 14 November 2026
What changed
- 14 November 2026 Personal emails, About story and Australian-style copy