What is the initial treatment for patients with severe bradycardia (abnormally slow heart rate)?

Management of Severe Bradycardia

For patients with severe bradycardia, atropine 0.5-1 mg IV is the first-line treatment, which can be repeated every 3-5 minutes up to a maximum dose of 3 mg. 1, 2, 3

Initial Assessment

• Evaluate if bradycardia is causing symptoms or hemodynamic compromise (altered mental status, chest discomfort, heart failure, hypotension, or shock) 2
• Maintain patent airway, assist breathing if necessary, and provide supplemental oxygen if hypoxemic 1
• Establish cardiac monitoring, IV access, and obtain 12-lead ECG if available 1, 2
• Identify and treat underlying causes of bradycardia 1

Treatment Algorithm

First-Line Treatment

• Administer atropine 0.5-1 mg IV for symptomatic bradycardia 1, 3
• Repeat every 3-5 minutes as needed up to a maximum total dose of 3 mg 1, 2
• Avoid doses <0.5 mg as they may paradoxically worsen bradycardia 1

If Bradycardia Persists Despite Atropine

• Initiate transcutaneous pacing (TCP) for unstable patients who do not respond to atropine 1
• Consider IV infusion of β-adrenergic agonists: 1, 2
  • Dopamine: 5-20 mcg/kg/min IV 1
  • Epinephrine: 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV 1
  • Isoproterenol: 1-20 mcg/min IV (use with caution in patients with coronary artery disease) 1, 2
• Prepare for transvenous pacing if the patient does not respond to drugs or TCP 1, 4

Special Considerations

Type of AV Block

• Atropine is effective for sinus bradycardia, AV nodal block, or sinus arrest 1, 2
• Atropine may be ineffective in type II second-degree or third-degree AV block with new wide-QRS complex (infranodal block) 1, 5
• In these cases, proceed directly to TCP or β-adrenergic agents 1, 2

Specific Clinical Scenarios

• Avoid atropine in heart transplant patients without evidence of autonomic reinnervation 1
• Use atropine cautiously in acute coronary ischemia or MI as increased heart rate may worsen ischemia 1, 2
• Consider aminophylline (250 mg IV bolus) for bradycardia resistant to atropine, particularly in inferior MI 1, 6

Potential Complications and Pitfalls

• Do not delay TCP for patients with poor perfusion while waiting for atropine to take effect 1, 2
• High doses of atropine (>2.5 mg over 2.5 hours) may cause ventricular tachycardia, increased PVCs, sustained sinus tachycardia, or toxic psychosis 7
• Paradoxical worsening of bradycardia can occur with atropine, especially in infranodal blocks 5
• Approximately 20% of patients with compromising bradycardia require temporary emergency pacing, and 50% may ultimately need permanent pacemakers 4, 8

Monitoring and Follow-up

• Continue cardiac monitoring during and after treatment 2
• Evaluate response to therapy by monitoring heart rate, blood pressure, and resolution of symptoms 2, 8
• Prepare for permanent pacing if bradycardia is due to irreversible causes 4, 8