What is the treatment for symptomatic bradycardia?

Treatment for Symptomatic Bradycardia

For symptomatic bradycardia, atropine 0.5-1 mg IV is the first-line treatment, followed by beta-adrenergic agonists (dopamine or epinephrine) or transcutaneous pacing if atropine fails, with progression to transvenous pacing for refractory cases. 1

Initial Assessment and Management

Symptomatic bradycardia is defined as a heart rate less than 50 beats per minute with associated signs of hemodynamic compromise, including:

• Acutely altered mental status
• Ischemic chest discomfort
• Acute heart failure
• Hypotension
• Other signs of shock 1, 2

First-Line Treatment: Atropine

• Dosage: 0.5-1 mg IV, repeated every 3-5 minutes as needed 1
• Maximum total dose: 3 mg 1, 2
• Mechanism: Blocks parasympathetic (vagal) activity, increasing heart rate 3
• Class of recommendation: IIa, Level of Evidence B 1

Important caveat: Atropine should be used with caution in patients after heart transplantation as it may cause paradoxical AV block 1, 2

Second-Line Treatments (if bradycardia is unresponsive to atropine)

1. Beta-adrenergic agonists (Class IIa, LOE B) 1:

   • Dopamine: 2-10 μg/kg/min IV infusion 1, 2
   • Epinephrine: 2-10 μg/min IV infusion 1, 2

2. Transcutaneous pacing (TCP) (Class IIa, LOE B) 1:

   • Indicated when medications fail 1
   • May be considered as initial therapy in unstable patients with high-degree AV block when IV access is not available (Class IIb, LOE C) 1
   • Apply transcutaneous patches and activate the system promptly 1

3. Transvenous pacing (Class IIa, LOE C) 1:

   • Indicated if the patient does not respond to drugs or TCP 1
   • Consider early for patients likely to require ongoing pacing 1

Special Considerations Based on Etiology

Location of AV Block

• AV nodal block (Mobitz Type I or nodal third-degree block):

  • More likely to respond to atropine 2
  • Often transient 2
  • Common in inferior MI 2

• Infranodal block (Mobitz Type II or infranodal third-degree block):

  • Less responsive to atropine 2
  • May worsen with atropine in some cases 4
  • Associated with higher mortality risk 2
  • Common in anterior MI 2
  • May require immediate pacing 1, 2

Medication-Induced Bradycardia

• Identify and discontinue causative medications if possible 2:

  • Beta-blockers
  • Calcium channel blockers (especially non-dihydropyridines like verapamil and diltiazem)
  • Digitalis
  • Tricyclic antidepressants

• For beta-blocker or calcium channel blocker overdose:

  • Consider glucagon (Class IIa) 2, 5
  • High-dose insulin therapy (Class IIa) 2
  • IV calcium (Class IIa) 2

Alternative Agents for Specific Situations

• Theophylline/Aminophylline: May be effective for bradycardia after inferior MI, cardiac transplant, or spinal cord injury 1, 6
• Glucagon: Consider for drug-induced bradycardia, particularly with beta-blocker toxicity 5

Indications for Permanent Pacemaker

Consider permanent pacemaker implantation for:

• Persistent symptomatic bradycardia despite medical therapy 2
• Symptomatic second-degree AV block (Class I) 2
• Third-degree AV block with symptoms (Class I) 2
• Mobitz type II second-degree AV block, even if asymptomatic (Class I) 2
• Sick sinus syndrome with symptomatic bradycardia 7

Treatment Algorithm

1. Assess for signs of hemodynamic compromise
2. Ensure adequate airway and breathing
3. Administer atropine 0.5-1 mg IV
4. If no response after 3-5 minutes, repeat atropine (max 3 mg total)
5. If still no response, initiate one of the following:
   • Dopamine infusion (2-10 μg/kg/min)
   • Epinephrine infusion (2-10 μg/min)
   • Transcutaneous pacing
6. Prepare for transvenous pacing if the above measures fail
7. Consider permanent pacemaker for persistent symptomatic bradycardia

Remember that treatment should be guided by the patient's clinical condition, the suspected etiology of bradycardia, and the location of the conduction block.