What is the initial management for acute stable and unstable bradycardia?

Physician Checklist for Acute Bradycardia Management

For acute bradycardia management, first determine if the patient is stable or unstable based on symptoms and hemodynamic parameters, then follow the appropriate treatment pathway. 1

Initial Assessment for All Bradycardia Patients

• Define bradycardia: Heart rate <60 bpm, but clinically significant typically <50 bpm 1
• Obtain vital signs: HR, BP, RR, O₂ saturation
• Assess for signs of hemodynamic compromise:
  • Hypotension (systolic BP <90 mmHg)
  • Altered mental status
  • Chest pain/acute heart failure
  • Signs of shock
  • Ischemic ECG changes
• Establish IV access
• Apply cardiac monitor
• Obtain 12-lead ECG (if available, but don't delay treatment)
• Identify rhythm: Sinus bradycardia, AV block (1st, 2nd, or 3rd degree), junctional rhythm
• Identify and treat reversible causes:
  • Hypoxemia (provide supplemental oxygen if SpO₂ <94%)
  • Medication effect (beta-blockers, calcium channel blockers, digoxin)
  • Electrolyte abnormalities (especially hyperkalemia)
  • Increased vagal tone
  • Acute myocardial infarction (especially inferior)

Acute Stable Bradycardia Management

Stable = No hypotension, no altered mental status, no signs of shock, no acute heart failure, no ischemic chest pain

1. Monitor and observe

   • Continuous cardiac monitoring
   • Serial vital signs
   • Prepare for possible deterioration

2. Identify and treat underlying causes

   • Review medication list for potential culprits
   • Check electrolytes, especially potassium and magnesium
   • Consider thyroid function tests if appropriate
   • Evaluate for sleep apnea if relevant 1

3. Consider cardiology consultation if:

   • New high-degree AV block (Mobitz type II or third-degree)
   • New bundle branch block
   • Symptomatic sinus node dysfunction

4. Specific scenarios requiring closer monitoring:

   • Mobitz type II second-degree AV block
   • New-onset third-degree heart block
   • Alternating bundle branch blocks
   • Bradycardia with frequent pauses >3 seconds

Acute Unstable Bradycardia Management

Unstable = Hypotension, altered mental status, signs of shock, acute heart failure, or ischemic chest pain attributed to bradycardia

1. First-line: Atropine

   • Dose: 0.5-1 mg IV 1
   • May repeat every 3-5 minutes
   • Maximum total dose: 3 mg
   • Caution: Doses <0.5 mg may paradoxically worsen bradycardia
   • Contraindication: Heart transplant patients without autonomic reinnervation 1
   • Ineffective for: Type II second-degree AV block and third-degree AV block with wide QRS 1

2. If atropine ineffective, proceed to:

   a) Transcutaneous pacing (TCP)

   • Set rate 60-80 bpm
   • Increase output until electrical capture achieved
   • Confirm mechanical capture (pulse with each paced beat)
   • Provide analgesia/sedation as needed for comfort 1

   b) Pharmacologic therapy (if TCP unavailable or while preparing):

   • Dopamine: 5-20 mcg/kg/min IV 1, 2
     • Start at 5 mcg/kg/min
     • Increase by 5 mcg/kg/min every 2 minutes until response
   • Epinephrine: 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV 1
   • Isoproterenol: 20-60 mcg IV bolus followed by 1-20 mcg/min infusion 1
     • Caution: Avoid in suspected ischemia or AMI

3. Prepare for transvenous pacing if:

   • Transcutaneous pacing ineffective
   • Prolonged pacing anticipated
   • Patient unstable despite above measures 1

4. Special scenarios:

   • Beta-blocker or calcium channel blocker overdose:

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

   • Calcium channel blocker overdose:

     • Calcium chloride 10%: 1-2 g IV every 10-20 min 1
     • Calcium gluconate 10%: 3-6 g IV every 10-20 min 1

   • Inferior MI with high-degree AV block:

     • Aminophylline: 250 mg IV bolus 1

Common Pitfalls to Avoid

1. Treating asymptomatic bradycardia - Heart rate <50 bpm without symptoms generally doesn't require intervention 1, 3

2. Using atropine for infranodal blocks - Atropine is ineffective and potentially harmful for Type II second-degree AV block and third-degree AV block with wide QRS 1

3. Delaying pacing in unstable patients - If pharmacologic therapy fails, rapidly initiate transcutaneous pacing 1

4. Overlooking reversible causes - Always identify and treat underlying causes (medications, electrolytes, hypoxia) 1

5. Missing signs of instability - Even mild symptoms may indicate need for intervention if caused by bradycardia 1

6. Failing to recognize bradycardia-induced ventricular arrhythmias - Severe bradycardia can trigger ventricular tachyarrhythmias 4

By following this structured approach, new residents can effectively manage both stable and unstable bradycardia while avoiding common pitfalls and optimizing patient outcomes.