What is the initial workup for a patient presenting with bradycardia (abnormally slow heart rate)?

Initial Workup for Bradycardia

The initial workup for a patient presenting with bradycardia should include a comprehensive history and physical examination, 12-lead ECG, and targeted laboratory testing based on suspected underlying causes, with cardiac monitoring to establish correlation between symptoms and bradycardia. 1

History and Physical Examination

• Obtain detailed information about symptoms including frequency, timing, duration, severity, circumstances, triggers, and alleviating factors 1
• Document relationship of symptoms to medications, meals, medical interventions, emotional distress, physical exertion, and positional changes 1
• Review all prescription and over-the-counter medications thoroughly, as many commonly prescribed medications can elicit or exacerbate bradyarrhythmias 1
• Assess for specific triggers such as urination, defecation, cough, prolonged standing, shaving, tight collars, and head turning 1
• Perform cardiovascular risk assessment, family history, travel history, and complete review of systems 1
• Physical examination should evaluate for signs of bradycardia and underlying structural heart disease 1

Diagnostic Testing

Immediate Testing

• 12-lead ECG to document rhythm, rate, conduction abnormalities, and screen for structural heart disease or systemic illness 1
• The ECG can confirm rhythm and rate, nature and extent of conduction disturbance, and document other abnormalities suggesting structural heart or systemic disease (e.g., left ventricular hypertrophy, diagnostic Q waves, prolonged QT interval, hyperkalemia) 1
• Initial vital signs including blood pressure and oxygen saturation 1
• Establish IV access for potential medication administration 1
• Provide supplementary oxygen if patient is hypoxemic or shows signs of increased work of breathing 1

Additional Testing Based on Clinical Presentation

• Cardiac rhythm monitoring to establish correlation between heart rate/conduction abnormalities and symptoms, with the specific type of monitor chosen based on frequency and nature of symptoms 1
• Laboratory testing directed toward suspected specific diagnoses 1:
  • Thyroid function tests if hypothyroidism is suspected 1
  • Lyme titer in young patients developing AV block in endemic areas 1
  • Electrolyte panel, particularly potassium levels, to rule out hyperkalemia 2, 3
  • Renal function tests (BUN, creatinine) to assess for renal failure, especially in patients taking AV nodal blockers 2, 3

Special Considerations

• Exercise electrocardiographic testing is reasonable for patients with:

  • Suspected chronotropic incompetence 1
  • Exercise-related symptoms suspicious for bradycardia or conduction disorders 1
  • 2:1 atrioventricular block of unknown level 1

• Genetic testing should be considered in:

  • Patients with family history of inherited conduction disease 1
  • First-degree relatives of patients in whom a conduction disorder-causative mutation has been identified 1

Monitoring and Evaluation Algorithm

1. Assess if bradycardia is appropriate for clinical condition (heart rate typically <50/min if pathological) 1
2. Determine if patient is symptomatic (syncope, presyncope, dizziness, fatigue, dyspnea, chest pain) 4, 5
3. Evaluate for signs of poor perfusion or shock (hypotension, altered mental status, signs of heart failure) 1
4. Identify and treat potentially reversible causes:
   • Medication effects (beta-blockers, calcium channel blockers, digoxin) 5, 6
   • Electrolyte abnormalities, particularly hyperkalemia 2, 3
   • Acute myocardial infarction 5
   • Increased vagal tone 6
   • Hypothyroidism 1
   • Infectious causes (e.g., Lyme disease) 1

Important Pitfalls to Avoid

• Do not rely solely on the initial ECG for diagnosis, as it provides a rhythm correlation with symptoms in only approximately 5% of patients with syncope 1
• Be aware that BRASH syndrome (Bradycardia, Renal failure, AV nodal blockers, Shock, and Hyperkalemia) requires specific management beyond standard bradycardia protocols 2, 3
• Avoid treating asymptomatic or minimally symptomatic patients unless there is suspicion that the rhythm is likely to progress or become life-threatening (e.g., Mobitz type II second-degree AV block in acute myocardial infarction) 1
• Remember that bradycardia may be physiologically normal in some patients (e.g., athletes), while a heart rate >50 beats per minute may be inadequate for others 1, 6