What is the treatment for symptomatic bradycardia?

Treatment of Symptomatic Bradycardia

For symptomatic bradycardia, the first-line treatment is atropine 0.5 mg IV every 3-5 minutes (maximum 3 mg), followed by β-adrenergic agonists (dopamine 2-10 μg/kg/min or epinephrine 2-10 μg/min) if unresponsive, and temporary pacing for refractory cases. 1

Initial Assessment and Management

1. Assess for hemodynamic compromise:

   • Altered mental status
   • Hypotension
   • Chest pain
   • Acute heart failure
   • Shortness of breath
   • Syncope or pre-syncope 1

2. Immediate interventions:

   • Maintain patent airway
   • Assist breathing if necessary
   • Provide oxygen if hypoxemic
   • Establish cardiac monitoring
   • Monitor blood pressure and pulse oximetry
   • Secure IV access
   • Obtain 12-lead ECG (don't delay therapy) 1

3. Laboratory studies:

   • Cardiac biomarkers (troponin)
   • Electrolytes
   • Complete blood count
   • Renal function tests 1

Medication Management Algorithm

First-Line Treatment

• Atropine 0.5 mg IV every 3-5 minutes (maximum 3 mg) 1, 2
  • Most effective for sinus bradycardia and AV block at the nodal level (Mobitz I)
  • Less effective for infranodal blocks (usually associated with anterior MI with wide-complex escape rhythm)
  • Caution: Paradoxical worsening can occur with infranodal blocks 3

Second-Line Treatment (if unresponsive to atropine)

• β-adrenergic agonists:
  • Dopamine 2-10 μg/kg/min IV infusion, OR
  • Epinephrine 2-10 μg/min IV infusion 1

Special Situations

• For beta-blocker or calcium channel blocker overdose:

  • Glucagon
  • High-dose insulin therapy
  • IV calcium 1

• For atropine-resistant bradycardia:

  • Consider aminophylline (bolus followed by continuous infusion) 4, 5

Temporary Pacing

Indicated for:

• Persistent hemodynamically unstable bradycardia refractory to medical therapy
• Symptomatic bradycardia unresponsive to drug therapy
• Sinus bradycardia with hypotension unresponsive to atropine
• Mobitz type II second-degree AV block
• New bifascicular block with first-degree AV block 1

Options include:

1. Transcutaneous pacing (immediate but uncomfortable)
2. Transvenous pacing (more stable but requires more time and expertise) 1

Permanent Pacing Indications

Permanent pacemaker implantation is indicated for:

• 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
• Transient advanced second-degree AV block with associated bundle branch block
• Persistent and symptomatic second- or third-degree AV block
• Mobitz type II second-degree AV block (even if asymptomatic) 1

Important Considerations and Pitfalls

1. Medication-induced bradycardia:

   • Identify and discontinue/reduce causative medications (beta-blockers, non-dihydropyridine calcium channel blockers)
   • Administer beta-blockers and ACE inhibitors at different times to minimize hypotension 1

2. Location of heart block matters:

   • Atropine is effective for sinus bradycardia and nodal blocks
   • Atropine is contraindicated in asymptomatic sinus bradycardia and may worsen infranodal AV blocks 1, 3
   • Approximately 50% of patients with hemodynamically unstable bradycardia respond to atropine, with better response rates in sinus bradycardia than AV block 6

3. Monitoring response:

   • If initial treatment is effective in the pre-hospital setting, patients are more likely to maintain normal sinus rhythm 6
   • Patients with AV block are more likely to require additional interventions and have higher rates of acute myocardial infarction than those with sinus bradycardia 6

4. Avoid worsening bradycardia:

   • Use opioids with caution as they may worsen bradycardia
   • Have atropine and naloxone readily available when opioids are administered 1

5. Consider underlying causes:

   • Correct electrolyte abnormalities
   • Discontinue medications that may cause AV block before proceeding to permanent pacing 1