What is the management of symptomatic bradycardia with normal blood pressure (BP)?

Management of Symptomatic Bradycardia with Normal Blood Pressure

For symptomatic bradycardia with normal blood pressure, atropine 0.5-1 mg IV is the first-line treatment, which can be repeated every 3-5 minutes up to a maximum total dose of 3 mg, followed by transcutaneous pacing if atropine is ineffective. 1

Initial Assessment

• Evaluate if bradycardia (heart rate <50 bpm) is causing symptoms such as altered mental status, ischemic chest discomfort, acute heart failure, or other signs of shock 1
• Maintain patent airway, assist breathing as necessary, and provide supplemental oxygen if the patient is hypoxemic 2
• Establish cardiac monitoring, monitor blood pressure, and measure oxygen saturation 2
• Establish IV access and obtain a 12-lead ECG if available 2
• Identify and treat underlying causes of bradycardia 2

Treatment Algorithm

First-Line Treatment: Atropine

• Administer atropine 0.5-1 mg IV for symptomatic bradycardia 1
• Repeat every 3-5 minutes as needed up to a maximum total dose of 3 mg 1
• Avoid doses <0.5 mg as they may paradoxically worsen bradycardia due to parasympathomimetic response 2
• Atropine is most effective for sinus bradycardia occurring within 6 hours of onset of symptoms of acute MI 2

If Bradycardia Persists Despite Atropine

• Initiate IV infusion of β-adrenergic agonists (dopamine, epinephrine, or isoproterenol) 1
• Consider transcutaneous pacing for unstable patients who do not respond to atropine 2, 1
• Prepare for transvenous pacing if the patient does not respond to medications or transcutaneous pacing 2, 1

Special Considerations Based on Type of Bradycardia

Effective Use of Atropine

• Atropine is most effective for:
  • Sinus bradycardia 1
  • AV block at the nodal level 1
  • Sinus arrest 1

Limited Effectiveness of Atropine

• Atropine may be ineffective in:
  • Type II second-degree AV block 1
  • Third-degree AV block with new wide-QRS complex (infranodal block) 1, 3
  • Patients with heart transplants without evidence of autonomic reinnervation 1

Alternative Treatments for Atropine-Resistant Bradycardia

• Aminophylline has been used successfully in cases of severe symptomatic bradycardia resistant to atropine, potentially by increasing cyclic adenosine monophosphate (cAMP) and activating the sympathoadrenal system 4
• Enteral albuterol has shown promise in reducing the frequency of symptomatic bradycardia in cervical spinal cord injury patients, resulting in less need for rescue therapy with chronotropic agents 5

Potential Complications and Pitfalls

• Atropine administration should not delay implementation of external pacing for patients with poor perfusion 1
• Excessive doses of atropine (>3 mg) may cause central anticholinergic syndrome, including confusion, agitation, and hallucinations 1
• Paradoxical worsening of bradycardia can occur with atropine administration in patients with infranodal heart blocks 3
• Serious adverse effects of atropine include ventricular tachycardia or fibrillation, sustained sinus tachycardia, increased premature ventricular contractions, and toxic psychosis 6
• These adverse effects are more common with higher initial doses (≥1.0 mg) or cumulative doses exceeding 2.5 mg over 2.5 hours 6

Monitoring and Follow-up

• Continue cardiac monitoring during and after treatment 1
• Evaluate response to therapy by monitoring heart rate, blood pressure, and resolution of symptoms 1
• In patients with acute MI, atropine should be used with caution due to the protective effect of parasympathetic tone against ventricular fibrillation and myocardial infarct extension 2

Efficacy of Atropine in Pre-hospital Setting

• Approximately half of patients who receive atropine in the pre-hospital setting for compromising rhythms have either a partial or complete response to therapy 7
• Patients with bradycardia tend to respond better to a single dose and lower total dose of atropine compared to those with AV block 7