What are the treatment guidelines for inpatient symptomatic bradycardia?

Treatment Guidelines for Inpatient Symptomatic Bradycardia

For inpatient symptomatic bradycardia, initial treatment should be atropine 0.5-1 mg IV (may be repeated every 3-5 minutes to a maximum dose of 3 mg), followed by beta-agonists if atropine is ineffective, and temporary pacing for refractory cases. 1, 2, 3

Initial Assessment and Management

Definition and Recognition

• Bradycardia: Heart rate <50 beats per minute
• Symptomatic bradycardia presents with:
  • Altered mental status
  • Ischemic chest discomfort
  • Acute heart failure
  • Hypotension (systolic BP <80 mmHg)
  • Signs of shock
  • Lightheadedness or syncope
  • Increased work of breathing

Immediate Actions

1. Evaluate airway, breathing, and circulation
2. Establish IV access
3. Provide supplemental oxygen if hypoxemic
4. Obtain 12-lead ECG
5. Identify and treat reversible causes

Pharmacological Management

First-Line Therapy

• Atropine:
  • Dosage: 0.5-1 mg IV (may be repeated every 3-5 minutes)
  • Maximum total dose: 3 mg
  • Mechanism: Competitive antagonism of muscarinic acetylcholine receptors 3
  • Indications: Symptomatic sinus bradycardia, AV block at nodal level 1, 2
  • Caution: Doses <0.5 mg may cause paradoxical bradycardia 1

Second-Line Therapies (if atropine ineffective)

• Dopamine:

  • Dosage: 5-20 mcg/kg/min IV infusion
  • Start at 5 mcg/kg/min and increase by 5 mcg/kg/min every 2 minutes

• Isoproterenol:

  • Dosage: 2-10 mcg/min IV infusion
  • Alternative: 20-60 mcg IV bolus followed by 10-20 mcg doses

• Epinephrine:

  • Dosage: 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV

Special Situations

• Calcium channel blocker overdose:

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

• Beta-blocker or calcium channel blocker overdose:

  • Glucagon: 3-10 mg IV with infusion of 3-5 mg/h 4

• Heart transplant patients:

  • Avoid atropine (ineffective due to denervated heart) 2
  • Consider theophylline (100-200 mg slow IV) or aminophylline (6 mg/kg in 100-200 mL IV fluid over 20-30 minutes) 5

Temporary Pacing

Transcutaneous Pacing

• Indications:
  • Symptomatic bradycardia unresponsive to drug therapy
  • Hemodynamic compromise despite medical therapy
• Implementation:
  • Apply transcutaneous patches
  • Activate system promptly if needed
  • Note: Associated with significant pain; consider sedation if patient is conscious

Transvenous Pacing

• Indications:
  • Persistent hemodynamically unstable bradycardia refractory to medical therapy
  • Persistent second-degree AV block in His-Purkinje system with bilateral BBB
  • Complete heart block after acute MI
  • Transient advanced AV block with associated BBB
• Access routes:
  • Internal/external jugular vein
  • Subclavian vein
  • Femoral vein
  • Brachial vein (percutaneously or by cutdown)

Special Considerations

Type of Bradycardia

• Sinus bradycardia:

  • Responds well to atropine, especially within 6 hours of acute MI onset 1
  • May be related to ischemia, reperfusion, chest discomfort, or medication effects

• AV block:

  • Type I second-degree AV block at nodal level: Responds to atropine
  • Type II second-degree AV block or infranodal block: Atropine may be ineffective or worsen condition 6
  • Complete heart block: Consider immediate temporary pacing

Monitoring

• Continuous ECG monitoring is essential for all patients with bradycardia
• Regular assessment of vital signs and symptoms
• Monitor for potential adverse effects of medications:
  • Atropine: Ventricular tachycardia/fibrillation, sustained sinus tachycardia, increased PVCs, toxic psychosis 7
  • Beta-agonists: Tachyarrhythmias, myocardial ischemia

Common Pitfalls and Caveats

1. Paradoxical response to atropine:

   • May occur with doses <0.5 mg or in infranodal blocks
   • Can worsen bradycardia and AV conduction 6

2. Inappropriate use in specific conditions:

   • Avoid atropine in Type II second-degree AV block and third-degree AV block with new wide QRS complex 1
   • Use with caution in acute MI due to potential for increased ischemia 1

3. Overtreatment:

   • Excessive atropine (>2.5 mg over 2.5 hours) increases risk of adverse effects 7
   • Asymptomatic bradycardia >40 bpm without hypoperfusion generally doesn't require treatment 1

4. Failure to identify reversible causes:

   • Always check for medication effects (beta-blockers, calcium channel blockers, digoxin)
   • Evaluate for electrolyte disturbances, hypothyroidism, sleep apnea, and increased vagal tone