What is the management of symptomatic bradycardia?

Management of Symptomatic Bradycardia

For patients with symptomatic bradycardia, treatment should begin with atropine 0.5-1 mg IV (repeated every 3-5 minutes to a maximum of 3 mg), followed by inotropic agents if needed, and temporary pacing for refractory cases. 1

Initial Assessment and Reversible Causes

Before initiating treatment, evaluate for potentially reversible causes:

• Medications (beta-blockers, calcium channel blockers, digoxin)
• Electrolyte abnormalities (hyperkalemia)
• Hypothyroidism
• Increased vagal tone
• Acute myocardial ischemia/infarction
• Sleep apnea
• Hypothermia
• Infections (e.g., Lyme disease)

Treating the underlying cause should be the first priority when identified 1, 2.

Treatment Algorithm for Symptomatic Bradycardia

Step 1: Pharmacological Management

• Atropine: 0.5-1 mg IV, may repeat every 3-5 minutes to a maximum dose of 3 mg 1
  • Mechanism: Blocks muscarinic acetylcholine receptors, increasing sinus node automaticity 3
  • Caution: May paradoxically worsen bradycardia in infranodal AV blocks 4
  • Contraindication: Should not be used in heart transplant patients without evidence of autonomic reinnervation 1

Step 2: If Atropine Ineffective

Use one of the following:

• Dopamine: 5-20 mcg/kg/min IV, starting at 5 mcg/kg/min and increasing by 5 mcg/kg/min every 2 minutes 1
• Epinephrine: 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV titrated to desired effect 1
• Isoproterenol: 20-60 mcg IV bolus followed by doses of 10-20 mcg, or infusion of 1-20 mcg/min based on heart rate response 1
  • Note: Use only in patients with low likelihood of coronary ischemia 1

Step 3: Temporary Pacing

For bradycardia refractory to pharmacological management:

• Transcutaneous pacing: Reasonable for severe symptoms or hemodynamic compromise while preparing for transvenous pacing 1
• Transvenous pacing: Indicated for persistent hemodynamically unstable bradycardia not responding to medications 1

Special Situations

Calcium Channel Blocker Overdose

• 10% calcium chloride: 1-2 g IV every 10-20 min or infusion of 0.2-0.4 mL/kg/h 1
• 10% calcium gluconate: 3-6 g IV every 10-20 min or infusion at 0.6-1.2 mL/kg/h 1

Beta-Blocker Overdose

• Glucagon: 3-10 mg IV with infusion of 3-5 mg/h 1
• High-dose insulin therapy: IV bolus of 1 unit/kg followed by infusion of 0.5 units/kg/h 1

Post-Heart Transplant Bradycardia

• Aminophylline: 6 mg/kg in 100-200 mL IV fluid over 20-30 min 1
• Theophylline: 300 mg IV, followed by oral dose of 5-10 mg/kg/d 1, 5

Spinal Cord Injury-Related Bradycardia

• Aminophylline: 6 mg/kg in 100-200 mL IV fluid over 20-30 min 1, 6
• Theophylline: Oral dose of 5-10 mg/kg/d 1

Indications for Permanent Pacing

Consider permanent pacemaker for:

• Persistent symptomatic bradycardia not responding to medical therapy
• High-grade AV block or third-degree AV block
• Symptomatic Mobitz type II second-degree AV block 2

Monitoring During Treatment

• Continuously monitor heart rate, blood pressure, and ECG
• Target heart rate >50-60 bpm
• Assess for resolution of symptoms (dizziness, syncope, fatigue, altered mental status)
• Monitor for medication side effects (tachycardia, hypertension with inotropes)

Common Pitfalls to Avoid

1. Using atropine in infranodal AV blocks, which may worsen bradycardia 4
2. Administering atropine to heart transplant patients (ineffective due to denervation) 1
3. Delaying temporary pacing in hemodynamically unstable patients not responding to medications
4. Missing reversible causes of bradycardia
5. Using doses of atropine less than 0.5 mg, which may paradoxically worsen bradycardia 1

By following this structured approach, most cases of symptomatic bradycardia can be effectively managed while addressing the underlying cause.