sinus bradycardia

Introduction

Sinus bradycardia refers to a rhythm generated by a slowed pattern of initial depolarization in the sinus node.

Etiology

• physiologic
  • endurance-trained athletes
  • during sleep (pulse may be as low as 30/min)
• pathologic
  • increased vagal tone
  • antiarrhythmic agents
  • myocardial ischemia
    • acute inferior myocardial infarction
  • sick sinus syndrome
  • increased intracranial pressure
  • hypothermia
  • myxedema
  • recovery from infection
    • typhoid
    • influenza

Clinical manifestations

• patients may be asymptomatic
• lightheadedness
• breathlessness
• angina
• weakness
• syncope & near-syncope
• inability to increase heart rate with exercise

Diagnostic procedures

• electrocardiogram
• atrial rate <60/min
• p waves with normal configuration & axis
• normal or prolonged PR interval
• normal QRS pattern
• exercise stress test

Complications

• sinus bradycardia does not affect mortality
  • endurance athletes with physiologic sinus bradycardia are healthier than others their age thus risk of mortality is more likely than not diminished

Management

• asymptomatic patients require no therapy
• treatment of symptomatic patient is directed towards specific etiology
  • atropine 0.5-2.0 g IV
  • transcutaneous pacemaker vs permanent pacemaker
  • bradycardia refractory to atropine & transcutaneous pacemaker not available
    • dopamine 5-20 ug/kg/min
    • epinephrine 2-20 ug/min
    • isoproterenol 2-10 ug/min

More general terms

• supraventricular arrhythmia
• bradyarrhythmia (bradycardia)

More specific terms

• sinus arrest/pause

Additional terms

• sick sinus syndrome; atrial fibrillation with bradyarrhythmia; tachycardia-bradycardia syndrome
• sinoatrial exit block