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.
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What this article covers
- Overview
Definition: bradycardia is a ventricular rate below 60 per minute; it becomes clinically significant when the rate is inadequate for physiologic needs and produces symptoms.
- Epidemiology
Common and often physiologic in young, fit, or sleeping people.
- Risk factors
Age-related conduction system degeneration.
- Pathophysiology
Reduced automaticity: slowed or absent sinoatrial node firing reduces the intrinsic rate.
- Clinical features
Symptoms of hypoperfusion: fatigue, lightheadedness, presyncope, syncope, and exertional intolerance.
- Differential diagnosis
Sinus bradycardia: normal P waves at a slow rate (sinus bradycardia).
- Diagnosis
Establish with an ECG documenting a rate below 60 and defining the mechanism: the diagnostic basis is a 12-lead ECG (and rhythm strip) showing the slow rate and classifying it as sinus bradycardia…
- Management
First-line, assess stability and treat instability: for a symptomatic unstable patient (hypotension, ischemia, altered mentation, or shock) give atropine 0.5 mg IV, repeated every 3 to 5 minutes up to 3 mg total.
- Complications
Syncope and falls with injury. Hemodynamic collapse and cardiac arrest from asystole or a failed escape rhythm.
- Prognosis
Excellent for physiologic or reversible bradycardia, which resolves with treatment of the cause.
- Prevention
Review and minimize nodal-blocking drugs, especially combinations, in older patients.
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Related articles
- 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.
- Atrioventricular blocks
Atrioventricular block is impaired conduction between atria and ventricles, graded first-degree, second-degree (Mobitz I and II), and third-degree (complete). The key distinction is nodal versus infranodal disease: Mobitz I is usually benign, whereas Mobitz II and complete block are infranodal, unstable, and require pacing.
- Syncope
Syncope is a transient loss of consciousness from global cerebral hypoperfusion with spontaneous complete recovery. The central task is separating benign reflex and orthostatic causes from dangerous cardiac syncope, using history, examination, and ECG, since cardiac syncope carries a risk of sudden death; treatment is directed by mechanism, from reassurance and hydration for reflex syncope to a pacemaker, ICD, or structural intervention for cardiac syncope.
- 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.
- Atrial fibrillation
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.