Sinus bradycardia
Sinus bradycardia is a sinus rhythm below 60 per minute with normal P-wave morphology and a normal PR interval. It is most often a benign physiologic finding in fit or sleeping people, and treatment is needed only when it is symptomatic or reflects a reversible cause such as drugs, ischemia, or hypothyroidism.
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What this article covers
- Overview
Definition: sinus bradycardia is a sinus rhythm at a rate below 60 per minute, with a normal upright P wave preceding every QRS in the expected leads and a normal PR interval.
- Epidemiology
Very common and usually benign, especially in young, fit, or sleeping people.
- Risk factors
High vagal tone: athletic conditioning, sleep, and the Valsalva or vomiting reflex.
- Pathophysiology
Reduced sinoatrial firing: increased vagal tone or reduced sympathetic drive slows the pacemaker rate.
- Clinical features
Usually asymptomatic, an incidental finding.
- Differential diagnosis
Physiologic (athletic) bradycardia: a benign slow resting rate, distinguished from pathologic bradycardia by appropriate rate rise with exertion and the absence of symptoms.
- Diagnosis
Establish with an ECG showing a sinus rhythm below 60 with normal P-wave morphology and PR interval: the diagnostic basis is a 12-lead ECG demonstrating an upright sinus P wave before every QRS at a…
- Management
First-line, treat only if symptomatic or hemodynamically significant: asymptomatic physiologic sinus bradycardia needs no treatment, only reassurance.
- Complications
Presyncope, syncope, and falls when symptomatic.
- Prognosis
Excellent when physiologic, with a benign lifelong course.
- Prevention
Review nodal-blocking medications and adjust in symptomatic patients.
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Related articles
- Bradycardia
Bradycardia is a heart rate below 60 per minute, ranging from a benign physiologic finding to symptomatic sinus node dysfunction or high-grade atrioventricular block. Management is driven by symptoms and stability: unstable patients receive atropine and then transcutaneous pacing or a chronotropic infusion, and durable symptomatic conduction disease is treated with a permanent pacemaker.
- Sinus node dysfunction
Sinus node dysfunction (sick sinus syndrome) is failure of the sinoatrial node to generate or transmit impulses appropriately, causing sinus bradycardia, pauses, arrest, or the brady-tachy syndrome. Diagnosis rests on correlating symptoms with ECG or ambulatory monitoring, and symptomatic irreversible disease is treated with a permanent pacemaker.
- Sinus tachycardia
Sinus tachycardia is a sinus rhythm above 100 per minute, almost always a physiologic response to an underlying stressor such as fever, hypovolemia, pain, anemia, hypoxia, or hyperthyroidism. Management targets the cause rather than the rate, and rate-slowing drugs are usually harmful when tachycardia is compensatory.
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Atrial fibrillation is a supraventricular tachyarrhythmia with disorganized atrial activation and an irregularly irregular ventricular response, the most common sustained arrhythmia and a major cause of stroke. Diagnosis is by ECG showing no discrete P waves with irregular RR intervals, and management addresses rate or rhythm control, stroke prevention by CHA2DS2-VASc-guided anticoagulation, and the underlying cause.