What is the initial workup for a patient presenting with sinus bradycardia?

Initial Workup for Sinus Bradycardia

For patients presenting with sinus bradycardia, the initial workup should include a 12-lead ECG, thorough evaluation for reversible causes, and cardiac monitoring to establish symptom-rhythm correlation, with the specific type of monitoring determined by symptom frequency. 1

Definition and Initial Assessment

• Sinus bradycardia is defined as a sinus heart rate less than 60 beats per minute 2
• A comprehensive history and physical examination should focus on identifying potential underlying causes and assessing symptom severity 1
• A 12-lead ECG is essential to document rhythm, rate, and conduction, and to screen for structural heart disease or systemic illness 1

Evaluation for Reversible Causes

• Medications are frequent culprits of sinus bradycardia and should be thoroughly reviewed, particularly: 1

  • Beta blockers
  • Non-dihydropyridine calcium channel blockers
  • Digoxin
  • Sodium-channel and potassium-channel blocking antiarrhythmic drugs

• Laboratory tests should be considered based on clinical suspicion: 1

  • Thyroid function tests (hypothyroidism is a common reversible cause)
  • Electrolytes (particularly potassium)
  • pH (acidosis)
  • Lyme titer when clinically indicated

• Other potentially reversible causes to evaluate include: 1

  • Elevated intracranial pressure
  • Acute myocardial infarction
  • Severe hypothermia
  • Obstructive sleep apnea
  • Hypoxemia or hypercarbia

Cardiac Monitoring

• Cardiac rhythm monitoring is crucial to establish correlation between heart rate/conduction abnormalities and symptoms 1
• The type of monitor should be selected based on symptom frequency: 1
  • Holter monitor (24-72 hours) for frequent symptoms
  • Event recorder or mobile cardiac telemetry for less frequent symptoms
  • Implantable cardiac monitor for very infrequent symptoms (>30 days between episodes) 1

Additional Testing Based on Initial Findings

• If initial evaluation is nondiagnostic and symptoms persist, consider: 1

  • Extended monitoring with an implantable cardiac monitor for infrequent symptoms
  • Electrophysiology study (EPS) in selected patients when noninvasive evaluation remains inconclusive 1

• EPS should NOT be performed in asymptomatic patients with sinus bradycardia unless other indications for electrophysiological testing exist 1

Management Considerations

• Patients with symptomatic sinus bradycardia secondary to a reversible cause should first be managed by addressing the underlying condition 1
• Permanent pacing should be considered only after reversible causes have been excluded or when they cannot be adequately managed 1
• In acute settings with hemodynamic compromise, temporary interventions may be needed while completing the diagnostic workup 1

Common Pitfalls to Avoid

• Failing to distinguish physiologic sinus bradycardia (e.g., in athletes) from pathologic causes 3
• Initiating treatment based solely on heart rate without correlation to symptoms 3
• Overlooking medication-induced bradycardia, which is often reversible with dose adjustment or medication change 1
• Premature consideration of permanent pacing before adequate evaluation for reversible causes 1