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Approach to Bradycardia



  • Bradycardia may generally be caused by sinus node dysfunction, atrioventricular block or escape rhythms in the setting of either of the above.
    • Bradyarrhythmias

    • Regular

    • Sinus bradycardia
    • Sinus arrest with escape rhythm
    • Complete heart block with escape rhythm
    • Irregular

    • Sinus arrhythmia
    • Sinus arrest
    • Second or third degree sinoatrial exit block
    • Atrial fibrillation with slow ventricular rate
    • Atrial flutter with variable block
    • Second or third degree AV block
    • Causes of Bradycardia

    • Intrinsic (SA or AV Nodal)

    • Idiopathic degeneration
    • Myocardial infarction
    • Congenital - congenital heart disease, neonatal lupus
    • Infiltrative disease - sarcoidosis, amyloidosis, haemochromatosis
    • Connective tissue disease - SLE, scleroderma, RA
    • Cardiac procedures - valvular surgery, correction of congenital heart disease, catheter ablation
    • Infections - Lyme disease, endocarditis, viral myocarditis
    • Extrinsic

    • Physiologic - sleep, athletes
    • Autonomic - neurocardiogenic syncope, carotid sinus massage, carotid sinus hypersensitivity
    • Drugs - beta blockers, calcium channel blockers, digoxin, adenosine, amiodarone, ivabradine, clonidine, acetylcholinesterase inhibitors
    • Hypothyroidism
    • Hypothermia
    • Hyperkalaemia
    • Obstructive sleep apnoea
    • Raised intracranial pressure
    • Pearls

    • Sinoatrial exit block and sinus arrest present as pauses without P waves or QRS complexes.
    • Escape rhythms are likle to be present if there are pauses or non-conducted P waves followed by bradycardia with junctional or ventricular complexes.
    • Atrial fibrillation with slow ventricular rate produces fibrillation waves without P waves and with irregular QRS complexes.
    • Atrial flutter with variable block manifests as a sawtooth wave at ~300bpm with irregular QRS complexes.
    • Second degree heart block presents with intermittently non-conducted P waves (without a subsequent QRS complex); the pattern of PR interval prolongation determines the type.
    • Complete AV block produces complete dissociation between P waves and QRS complexes.
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Adan V, Crown LA. Diagnosis and treatment of sick sinus syndrome. American family physician. 2003 Apr;67(8):1725-32.
 Mangrum JM, DiMarco JP. The evaluation and management of bradycardia. New England Journal of Medicine. 2000 Mar 9;342(10):703-9.