What are the treatment options for symptomatic bradycardia?

Treatment Options for Symptomatic Bradycardia

Atropine is the first-line drug for acute symptomatic bradycardia, followed by β-adrenergic agonists (dopamine or epinephrine) or transcutaneous pacing if atropine fails, with transvenous pacing indicated for persistent bradycardia unresponsive to initial measures. 1, 2

Initial Assessment and Management

• Evaluate if bradycardia is causing symptoms or hemodynamic compromise (altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or shock) 2
• Maintain patent airway, assist breathing as necessary, provide supplemental oxygen if hypoxemic 2
• Establish cardiac monitoring to identify rhythm, monitor blood pressure, and oxygen saturation 2
• Establish IV access for medication administration 2
• Obtain 12-lead ECG if available 2

Treatment Algorithm

First-Line Treatment: Atropine

• Administer atropine 0.5 mg IV every 3-5 minutes to a maximum total dose of 3 mg 1, 2
• Doses <0.5 mg may paradoxically result in further slowing of heart rate and should be avoided 1, 2
• Atropine works by reversing cholinergic-mediated decreases in heart rate 1, 3
• Atropine is most effective for sinus bradycardia, conduction block at the AV node level, or sinus arrest 1, 2

Second-Line Treatments (If Bradycardia Persists Despite Atropine)

• Initiate IV infusion of β-adrenergic agonists 1:
  • Dopamine infusion (2-10 μg/kg/min), particularly if associated with hypotension 1
  • Epinephrine infusion (2-10 μg/min) 1
• Initiate transcutaneous pacing (TCP) in unstable patients who do not respond to atropine 1
• Prepare for transvenous pacing if the patient does not respond to drugs or TCP 1

Special Considerations and Cautions

Type of AV Block

• Avoid relying on atropine in type II second-degree or third-degree AV block with new wide-QRS complex (block likely in non-nodal tissue) 1, 2
• These bradyarrhythmias are less likely to respond to atropine and are preferably treated with TCP or β-adrenergic support 1, 4
• Paradoxical worsening of bradycardia can occur with atropine in patients with infranodal (His-Purkinje) blocks 4

Specific Clinical Scenarios

• Use atropine cautiously in acute coronary ischemia or MI; increased heart rate may worsen ischemia or increase infarction size 1, 5
• Atropine will likely be ineffective in heart transplant patients due to lack of vagal innervation 1, 2
• In BRASH syndrome (Bradycardia, Renal failure, AV nodal blockers, Shock, Hyperkalemia), atropine may be ineffective and isoproterenol may be required 6

Efficacy and Outcomes

• In one study, approximately 39% of patients with compromising bradycardia improved with bed rest alone 7
• 61% required IV drugs to increase ventricular rate 7
• 20% required additional temporary transvenous/transcutaneous pacing 7
• 50% ultimately required permanent pacemaker implantation 7
• Atropine has been shown to improve heart rate, symptoms, and signs associated with bradycardia in clinical trials 1
• Atropine can also improve atrioventricular conduction in patients with acute inferior myocardial infarction associated with high-degree AV block 5

Potential Complications

• Atropine administration should not delay implementation of external pacing for patients with poor perfusion 1, 2
• Excessive doses of atropine (>3 mg) may cause central anticholinergic syndrome (confusion, agitation, hallucinations) 2, 5
• Serious adverse effects of atropine may include ventricular tachycardia/fibrillation, sustained sinus tachycardia, and increased premature ventricular contractions 5
• These adverse effects are more common with higher initial doses (≥1.0 mg) or cumulative doses exceeding 2.5 mg over 2.5 hours 5