Sinus bradycardia
Also calledsinus brady · SB · sinus bradycardia
Definition
A sinus rhythm at a rate below 60 bpm by the traditional definition; the 2018 ACC/AHA/HRS bradycardia guideline uses below 50 bpm. Impulses arise normally from the sinoatrial node (a P wave with a normal axis, upright in lead II, before every QRS complex, with a PR interval of at least 120 ms), but the sinus discharge rate is slow.
Clinical noteCommon in healthy people during sleep and in those with high vagal tone, such as athletes; asymptomatic sinus bradycardia has not been associated with adverse outcomes, so a slow sinus rate on its own does not mean disease.
Sources
- Kusumoto FM, Schoenfeld MH, Barrett C, et al. 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay. Circulation. 2019;140(8):e382-e482. doi.org/10.1161/CIR.0000000000000628
- Da Costa D, Brady WJ, Edhouse J. ABC of clinical electrocardiography: bradycardias and atrioventricular conduction block. BMJ. 2002;324(7336):535-538. doi.org/10.1136/bmj.324.7336.535
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.