How to manage symptomatic bradycardia?

Management of Symptomatic Bradycardia

For symptomatic bradycardia, immediate intervention with atropine 0.5 mg IV every 3-5 minutes (maximum 3 mg) is recommended as first-line therapy, followed by dopamine or epinephrine infusions if unresponsive, and temporary pacing for refractory cases. 1

Initial Assessment and Stabilization

1. Assess for hemodynamic compromise:

   • Altered mental status
   • Hypotension (systolic BP <90 mmHg)
   • Chest pain
   • Acute heart failure
   • Shortness of breath
   • Syncope or pre-syncope 1

2. Immediate interventions:

   • Maintain patent airway
   • Assist breathing if necessary
   • Provide oxygen if hypoxemic
   • Establish cardiac monitoring
   • Monitor blood pressure and pulse oximetry
   • Secure IV access
   • Obtain 12-lead ECG (don't delay therapy) 1

3. Laboratory studies:

   • Cardiac biomarkers (troponin)
   • Electrolytes
   • Complete blood count
   • Renal function tests 1

Medication Management Algorithm

Step 1: Identify and address reversible causes

• Discontinue or reduce causative medications:
  • Beta-blockers
  • Non-dihydropyridine calcium channel blockers (verapamil, diltiazem)
  • Digoxin
  • Tricyclic antidepressants 1
• Correct electrolyte abnormalities 1
• Consider timing of medications: Administer beta-blockers and ACE inhibitors at different times of day to minimize hypotension 1

Step 2: Pharmacological intervention for symptomatic bradycardia

1. Atropine (first-line):

   • Dosage: 0.5 mg IV every 3-5 minutes
   • Maximum total dose: 3 mg
   • Most effective for sinus bradycardia and AV block at nodal level (Mobitz I)
   • Less effective for infranodal blocks (wide-complex escape rhythm) 1, 2

   Caution: Atropine is contraindicated in asymptomatic sinus bradycardia and infranodal AV block. Low doses (<0.5 mg) may paradoxically worsen bradycardia due to central vagal effects 2, 3

2. If unresponsive to atropine:

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

3. For beta-blocker or calcium channel blocker overdose:

   • Glucagon
   • High-dose insulin therapy
   • IV calcium 1
   • Aminophylline may be considered for resistant cases 1, 4

Step 3: Temporary pacing for refractory bradycardia

• Transcutaneous pacing for symptomatic bradycardia unresponsive to drug therapy, particularly in:

  • Sinus bradycardia with hypotension unresponsive to atropine
  • Mobitz type II second-degree AV block
  • New bifascicular block with first-degree AV block 1

• Temporary transvenous pacing for persistent hemodynamically unstable bradycardia refractory to medical therapy 1

Specific Clinical Scenarios

Acute Myocardial Infarction with Bradycardia

• Obtain immediate ECG to look for ST-segment elevation/depression and AV block patterns
• Atropine has been shown to improve AV conduction in 85% of patients with acute inferior MI associated with high-degree AV block 1, 5
• Atropine decreased or abolished premature ventricular contractions in 87% of patients with MI and sinus bradycardia 5
• Caution: Higher initial doses (>0.5 mg) or cumulative doses exceeding 2.5 mg over 2.5 hours may increase risk of adverse effects including ventricular tachyarrhythmias 5

Bradycardia-Tachycardia Syndrome

• May present as part of sick sinus syndrome
• Can lead to bradycardia-related cardiomyopathy and heart failure
• Pacing at rates of 80-110 bpm can prevent bradycardia-related triggers of atrial fibrillation 6

Indications for Permanent Pacing

Consider permanent pacemaker implantation for:

1. Class I indications:

   • Symptomatic second-degree AV block
   • Asymptomatic Type II second-degree AV block
   • Third-degree AV block with symptoms
   • Persistent second-degree AV block in the His-Purkinje system with bilateral bundle branch block
   • Transient advanced second-degree AV block with associated bundle branch block
   • Persistent and symptomatic second- or third-degree AV block
   • Mobitz type II second-degree AV block (even if asymptomatic) 1

2. Additional indications:

   • Asymptomatic persistent third-degree AV block with average awake ventricular rates ≥40 bpm if cardiomegaly or LV dysfunction is present 1
   • Consider cardiac resynchronization therapy (CRT) for patients with LVEF ≤35% who require significant (>40%) ventricular pacing 1

Monitoring and Follow-up

• Ambulatory electrocardiographic monitoring to establish correlation between symptoms and rhythm abnormalities 1
• Exercise treadmill test for patients with exertional symptoms to determine whether they may benefit from permanent pacing 1
• Electrophysiological study (EPS) may be considered in selected patients to determine the level of block (nodal vs. infranodal) 1

Common Pitfalls and Caveats

• Low-dose atropine paradox: Doses <0.5 mg may worsen bradycardia due to central vagal effects 3
• Infranodal blocks: Atropine is less effective for infranodal blocks with wide-complex escape rhythms 1
• Medication interactions: Opioids should be used with caution as they may worsen bradycardia 1
• Special populations: Elimination half-life of atropine is more than doubled in children under two years and the elderly (>65 years) 2
• Pregnancy considerations: Life-sustaining therapy for pregnant women with symptomatic bradycardia should not be withheld due to concerns about fetal effects 2