How to manage a patient with bradycardia?

Management of Bradycardia with Heart Rate of 36 BPM

For a patient with a heart rate of 36 BPM causing hemodynamic instability, immediate intervention with atropine 0.5 mg IV (up to 3 mg total) followed by temporary pacing if bradycardia persists is recommended. 1

Initial Assessment and Management

Immediate Interventions for Symptomatic Bradycardia

1. Assess for hemodynamic instability:

   • Look for symptoms: syncope, lightheadedness, dizziness, chest pain, dyspnea, altered mental status
   • Check blood pressure (systolic <90 mmHg indicates instability)

2. First-line pharmacologic therapy:

   • Administer atropine 0.5 mg IV every 3-5 minutes (maximum total dose 3 mg) 1, 2
   • Atropine works by blocking vagal effects on the heart, increasing heart rate and improving symptoms 2
   • Atropine is most effective for sinus bradycardia and AV nodal blocks, with approximately 50% of patients showing partial or complete response 3

3. If atropine is ineffective:

   • Initiate beta-adrenergic agonist infusion:
     • Epinephrine (2-10 μg/min) or
     • Dopamine (2-10 μg/kg/min) 1
     • Isoproterenol may be considered for second-degree or third-degree AV block with low likelihood of coronary ischemia 4

4. Temporary pacing options (if medications fail):

   • Transcutaneous pacing for immediate management 4, 1
   • Transvenous pacing for persistent symptomatic bradycardia refractory to medical therapy 4
   • For prolonged temporary pacing, an externalized permanent active fixation lead is preferable over standard passive fixation temporary pacing lead 4

Identifying and Treating Reversible Causes

Always identify and treat reversible causes of bradycardia before considering permanent interventions:

1. Medication-induced bradycardia:

   • Beta-blockers, calcium channel blockers, digoxin
   • Consider dose reduction or discontinuation if possible
   • For calcium channel blocker overdose: calcium (10% calcium chloride 1-2g IV)
   • For beta-blocker overdose: glucagon (3-10mg IV with infusion of 3-5mg/h) 1

2. Other reversible causes:

   • Electrolyte abnormalities (particularly hyperkalemia)
   • Hypothyroidism
   • Increased vagal tone
   • Sleep-related sinus bradycardia (physiologic)
   • Inferior myocardial infarction (consider aminophylline) 4, 1

Long-term Management Considerations

Indications for Permanent Pacing

Permanent pacing is indicated in the following scenarios:

1. Persistent symptomatic bradycardia not responding to medical therapy 1

2. High-grade or third-degree AV block not due to reversible causes 1

3. Symptomatic second-degree Mobitz type II AV block 1

4. Tachy-brady syndrome (alternating fast and slow heart rates, typically with atrial fibrillation) 4, 5

5. Chronotropic incompetence (inability to increase heart rate with physical activity) 4

Contraindications for Permanent Pacing

Permanent pacing should NOT be performed in:

1. Asymptomatic sinus bradycardia or pauses due to physiologically elevated parasympathetic tone 4, 1

2. Sleep-related sinus bradycardia or transient sinus pauses during sleep 4

3. Asymptomatic sinus node dysfunction 4

4. Cases where symptoms occur in the absence of bradycardia 4

5. Acute AV block attributable to a known reversible and non-recurrent cause that has resolved 4

Special Considerations

• Athletes and young individuals may have resting heart rates below 40 bpm without requiring intervention 1

• Elderly patients (>65 years) may have altered pharmacokinetics of medications like atropine, requiring careful dosing 2

• Bradycardia-induced ventricular arrhythmias can be life-threatening and may require pacing at rates of 80-110 bpm 5

• Combination therapy using beta-blockers with calcium channel blockers or digoxin significantly increases bradycardia risk 1

Remember that the management approach should prioritize treating the underlying cause when possible, while ensuring adequate cardiac output and tissue perfusion to prevent morbidity and mortality associated with severe bradycardia.