Management of Symptomatic Bradycardia
For patients with symptomatic bradycardia, treatment should begin with atropine 0.5 mg IV every 3-5 minutes (maximum 3 mg) as first-line therapy, followed by transcutaneous pacing if unresponsive, and then infusion of β-adrenergic agonists such as dopamine (2-10 μg/kg/min) or epinephrine (2-10 μg/min) if necessary. 1
Initial Assessment and Management
Assess appropriateness for clinical condition:
Initial interventions:
- Maintain patent airway; assist breathing as necessary
- Provide oxygen if hypoxemic (hypoxemia is a common cause of bradycardia)
- Establish cardiac monitoring, blood pressure monitoring, and pulse oximetry
- Secure IV access
- Obtain 12-lead ECG if available (don't delay therapy) 2
Identify and treat underlying causes:
- Evaluate for potentially reversible causes (medications, electrolyte disturbances, myocardial infarction)
- Determine type of bradycardia (sinus bradycardia, AV block, etc.)
Pharmacological Management
First-line: Atropine
- Dosing: 0.5 mg IV every 3-5 minutes, maximum total 3 mg 2, 1
- Caution: Doses <0.5 mg may paradoxically worsen bradycardia 2, 1
- Mechanism: Blocks vagal effects on the heart 3
- Ineffective in: Cardiac transplant patients (due to lack of vagal innervation) 1
- Potential adverse effects: May worsen bradycardia in patients with infranodal (His-Purkinje) heart blocks 4
Second-line (if atropine ineffective):
- β-adrenergic agonists:
- Dopamine: 2-10 μg/kg/min IV infusion
- Epinephrine: 2-10 μg/min IV infusion 1
Pacing Interventions
Transcutaneous Pacing (TCP)
- Indications: Hemodynamically unstable bradycardia unresponsive to atropine 1
- Implementation: Start with TCP while preparing for transvenous pacing if needed
Transvenous Temporary Pacing
- Indications: Persistent symptoms or hemodynamic compromise despite pharmacological therapy 1
Permanent Pacing
- 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
- Mobitz type II second-degree AV block (even if asymptomatic) 1
Special Considerations
Myocardial Infarction
- In inferior MI: AV block often transient and may respond to atropine 1, 5
- In anterior MI with new bundle branch block: High likelihood of developing complete AV block; preventive temporary pacing may be warranted 1
- Atropine can be effective for ventricular arrhythmias and conduction disturbances in patients with inferior MI 6
Heart Block Location
- Nodal blocks or bradycardia due to increased vagal tone typically respond well to atropine
- Infranodal blocks (His-Purkinje system) may worsen with atropine administration 4
Medication-Induced Bradycardia
- Consider glucagon for bradycardia induced by beta-blockers or calcium channel blockers that is unresponsive to atropine 7
- Discontinue or adjust medications that may be causing or exacerbating bradycardia (e.g., digoxin, beta-blockers) 1
Monitoring During Treatment
- Maintain continuous cardiac monitoring
- Obtain serial ECGs to assess response to therapy
- Monitor for adverse effects of medications
- Watch for progression of conduction disease 1
Treatment Algorithm
- Assess for signs of poor perfusion
- If symptomatic bradycardia confirmed:
- Administer atropine 0.5 mg IV
- Repeat every 3-5 minutes as needed (maximum 3 mg)
- If unresponsive to atropine:
- Initiate transcutaneous pacing
- Begin infusion of β-adrenergic agonist (dopamine or epinephrine)
- If continued instability:
- Arrange for transvenous temporary pacing
- Evaluate for permanent pacing based on type of block and clinical situation
Remember that asymptomatic or minimally symptomatic patients do not necessarily require treatment unless there is suspicion that the rhythm is likely to progress to symptoms or become life-threatening (e.g., Mobitz type II second-degree AV block in the setting of acute myocardial infarction) 2.