Bradyarrhythmias

Basics

Description

  • Ventricular heart rate <60 beats/min:
    • Sinus bradycardia can be a normal variant
    • All other rhythms are pathologic
  • Wide variation of presentations from asymptomatic to shock, hypotension, altered mental status, dyspnea, fatigue, nausea, syncope
  • Treatment and evaluation varies based on ECG findings, clinical status, and degree of symptoms

Etiology

  • Idiopathic:
    • Healthy athletes
  • Intrinsic cardiac disorders:
    • Sinus node dysfunction such as sick sinus syndrome (may alternate with tachycardia)
    • Atrioventricular block
    • Junctional or ventricular escape rhythm
    • Infiltrative disease:
      • Amyloidosis, sarcoidosis, hemochromatosis
    • Collagen vascular disease:
      • Systemic lupus erythematosus (SLE), scleroderma, rheumatoid arthritis
    • Anatomic abnormalities:
      • Congenital, postsurgical, posttransplant, postradiation
    • Muscular disorders:
      • Myotonic muscular dystrophy
    • Trauma with myocardial contusion
  • Extrinsic disorders:
    • Hypoxia
    • Cardiac injury and infarction:
      • RCA infarction can cause sinus bradycardia
      • LAD infarction can cause high-grade block
    • Toxic ingestion or overdose:
      • Opiates, β-blockers (BBs), calcium channel blockers (CCBs), digoxin, clonidine, antiarrhythmics, lithium, organophosphates
      • Certain chemotherapeutic agents and checkpoint inhibitors such as tyrosine kinase inhibitors, her2 inhibitors, and alkylating agents
    • Hypothermia
    • Electrolyte abnormalities:
      • Hypo-/hyperkalemia, hypoglycemia, hypo-/hypercalcemia, hypermagnesemia
  • Acidosis
  • Endocrine abnormalities:
    • Hypothyroidism
  • Infectious disease:
    • Lyme disease, Chagas disease, diphtheria, endocarditis, myocarditis
  • Neurologic disorders:
    • Hemorrhagic CVA, head injury, increased intracranial pressure, increased vagal tone, carotid sinus hypersensitivity, spinal cord injury
    • Can be triggered by micturition, defecation, coughing, vomiting, ocular pressure, or other Valsalva maneuvers

Pediatric Considerations

  • Hypoxia is the most common etiology in children. In an infant, start compressions for HR <60

Pregnancy Considerations

  • Physiologic tachycardia is expected in pregnancy. Fetal monitoring is warranted for all bradycardias in pregnancy
  • Maternal SLE can result in congenital complete heart block

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