What is the management approach for symptomatic bradycardia (abnormally slow heart rate) in the Emergency Room (ER)?

Management of Symptomatic Bradycardia in the Emergency Room

For symptomatic bradycardia in the ER, first-line treatment is atropine 0.5-1 mg IV every 3-5 minutes (maximum 3 mg total), followed by transcutaneous pacing if unresponsive to medication, and consideration of second-line pharmacologic agents such as epinephrine or dopamine. 1, 2

Initial Assessment and Stabilization

1. Rapid evaluation of hemodynamic stability:

   • Assess for symptoms of inadequate perfusion: hypotension, altered mental status, chest pain, dyspnea, syncope
   • Obtain vital signs including blood pressure and oxygen saturation
   • Apply cardiac monitoring and secure IV access
   • Administer supplemental oxygen if hypoxemic

2. Identify the type and location of bradycardia:

   • Determine if sinus bradycardia or AV block
   • For AV block, determine if nodal (Mobitz type I) or infranodal (Mobitz type II)
   • QRS width helps determine location: narrow complex suggests nodal block, wide complex suggests infranodal block 2

Pharmacologic Management

First-line Treatment

• Atropine sulfate: 0.5-1 mg IV every 3-5 minutes to maximum total dose of 3 mg 1, 2
  • Most effective for sinus bradycardia and AV block at nodal level
  • Caution: Doses <0.5 mg may paradoxically worsen bradycardia 1
  • Effectiveness: Approximately 50% of patients show partial or complete response to atropine 3

Important Precautions with Atropine

• Use cautiously in acute coronary ischemia as increased heart rate may worsen ischemia 1, 2
• Likely ineffective in type II second-degree or third-degree AV block with new wide-QRS complex (infranodal block) 1, 4
• Contraindicated in heart transplant patients (may cause paradoxical high-degree AV block) 1, 2, 5

Second-line Pharmacologic Options

If atropine is ineffective:

• Epinephrine: 2-10 μg/min IV infusion 1, 2
• Dopamine: 2-10 μg/kg/min IV infusion 1, 2
• Specific clinical scenarios:
  • For bradycardia after inferior MI, cardiac transplant, or spinal cord injury: consider theophylline 100-200 mg slow IV injection (maximum 250 mg) 1, 6
  • For beta-blocker or calcium channel blocker overdose: consider glucagon 7

Pacing Interventions

Transcutaneous Pacing (TCP)

• Indicated for unstable patients not responding to atropine 1, 2
• Should not be delayed in patients with poor perfusion 2
• Initial settings: rate 50-60 bpm, increased as needed for hemodynamic stability
• Note: TCP is painful in conscious patients and should be considered a temporizing measure 1

Transvenous Pacing

• Indicated for patients who don't respond to medications or TCP 1, 2
• Reasonable for patients with symptomatic block refractory to medical therapy 2
• More reliable capture than TCP but requires more time and expertise to place

Algorithm Based on Type of Bradycardia

Sinus Bradycardia

1. If asymptomatic: observation only
2. If symptomatic: atropine 0.5-1 mg IV
3. If no response: TCP and/or second-line medications (epinephrine/dopamine)

AV Block

1. Mobitz Type I (Wenckebach):

   • If asymptomatic: observation
   • If symptomatic: atropine 0.5-1 mg IV (usually effective)
   • If no response: TCP and/or second-line medications

2. Mobitz Type II or Third-Degree AV Block:

   • Prepare for temporary pacing immediately, even if currently stable 2
   • Atropine may be tried but is often ineffective 1, 4
   • Proceed quickly to TCP if no immediate response
   • Arrange for transvenous pacing

Special Considerations

1. Acute MI setting:

   • Bradycardia in inferior MI is often transient and responds to atropine 8
   • In anterior MI with new bundle branch block and AV block, prepare for immediate pacing 2
   • Consider revascularization for patients with AV block who haven't received reperfusion therapy 2

2. Medication-induced bradycardia:

   • Identify and discontinue offending agents (beta-blockers, calcium channel blockers, digoxin)
   • For beta-blocker or calcium channel blocker toxicity, consider glucagon 7

3. Post-cardiac arrest:

   • Bradycardia may be protective in post-cardiac arrest setting
   • Avoid unnecessary pacing unless hemodynamically compromised

Monitoring and Disposition

• Continuous cardiac monitoring during treatment
• Serial ECGs to assess response to therapy and progression of conduction disease
• Cardiology consultation for patients requiring temporary pacing or with high-grade AV block
• ICU admission for patients requiring continuous infusions or temporary pacing

By following this structured approach to bradycardia management in the ER, clinicians can rapidly identify and treat symptomatic bradycardia while preparing for escalation of care when necessary.