What is the treatment for symptomatic bradycardia?

Management of Symptomatic Bradycardia

Atropine is the first-line pharmacological treatment for symptomatic bradycardia, administered at a dose of 0.5-1 mg IV, repeated every 3-5 minutes as needed up to a total of 3 mg. 1

Initial Management Algorithm

1. First-Line Treatment:

   • Administer atropine 0.5-1 mg IV
   • Onset of action: 1-2 minutes
   • Peak effect: 2-4 minutes
   • May repeat every 3-5 minutes up to a total dose of 3 mg 1, 2

2. Second-Line Treatments (if unresponsive to atropine):

   • Pharmacological options:

     • Dopamine: 2-10 μg/kg/min IV infusion
     • Epinephrine: 2-10 μg/min IV infusion 1

   • Pacing options:

     • Initiate transcutaneous pacing (TCP) while preparing for transvenous pacing if needed 1
     • Proceed to transvenous temporary pacing if symptoms or hemodynamic compromise persist 1

Special Considerations

Atropine Cautions

• May paradoxically worsen bradycardia in patients with cardiac transplantation 1
• Can cause tachycardia at higher doses (>0.8 mg) 1
• May worsen bradycardia in patients with infranodal heart blocks (His-Purkinje level) 3
• Higher initial doses (1.0 mg vs. 0.5-0.6 mg) or cumulative doses exceeding 2.5 mg over 2.5 hours are associated with increased adverse effects including ventricular tachycardia/fibrillation 4

Alternative Agents for Specific Scenarios

• Theophylline/Aminophylline: Consider for bradycardia unresponsive to atropine after:

  • Inferior myocardial infarction
  • Cardiac transplantation
  • Spinal cord injury
  • Dosage: 100-200 mg slow IV injection (maximum 250 mg) 1, 5

• Glucagon: May be effective for drug-induced bradycardia, particularly:

  • Beta-blocker overdose
  • Calcium channel blocker overdose
  • Digoxin toxicity 6

Permanent Pacemaker Indications

• Symptomatic second-degree AV block
• Asymptomatic Type II second-degree AV block
• Third-degree AV block with symptoms
• Persistent second-degree AV block in the His-Purkinje system with bilateral bundle branch block 1

Monitoring During Treatment

• Maintain continuous cardiac monitoring
• Obtain serial ECGs to assess response to therapy
• Monitor for adverse effects of atropine:
  • Tachycardia
  • Dry mouth
  • Blurred vision
  • Urinary retention 1

Important Caveats

• Not all bradycardia requires immediate intervention—assessment of symptoms and hemodynamic status is crucial 7
• Identify and treat potentially reversible causes:
  • Medication effects (beta-blockers, calcium channel blockers, digoxin)
  • Electrolyte abnormalities
  • Acute myocardial ischemia/infarction 1
• Atropine has been shown to improve AV conduction in 85% of patients with acute inferior myocardial infarction associated with 2° or 3° AV block 4
• Atropine can decrease or abolish premature ventricular contractions in most patients (87%) with sinus bradycardia following myocardial infarction 4

Pharmacodynamics of Atropine

• Competitive antagonism of muscarinic actions of acetylcholine
• Prevents or abolishes bradycardia produced by vagal stimulation
• May lessen the degree of partial heart block when vagal activity is a factor
• In some patients with complete heart block, may accelerate idioventricular rate 2

Remember that the management approach should be guided by the patient's clinical status, with immediate intervention required for symptomatic bradycardia causing hypotension, altered mental status, chest pain, or other signs of shock.