Initial Management of Symptomatic Bradycardia
The initial management for symptomatic bradycardia includes identifying and treating underlying causes, ensuring adequate oxygenation, establishing IV access, and administering atropine as first-line pharmacologic therapy. 1
Assessment and Initial Steps
- Evaluate appropriateness of heart rate for clinical condition (typically <50 beats/min when symptomatic) 1
- Identify signs and symptoms of poor perfusion (altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or shock) to determine if they are caused by bradycardia 1
- Maintain patent airway and assist breathing as necessary 1
- Provide supplementary oxygen if hypoxemic (hypoxemia is a common cause of bradycardia) 1
- Attach cardiac monitor to identify rhythm, monitor blood pressure, and measure oxygen saturation 1
- Establish IV access 1
- Obtain 12-lead ECG if available (but don't delay therapy) 1
Identify and Treat Reversible Causes
- Medications are frequent culprits (beta blockers, calcium channel blockers, digoxin, antiarrhythmic drugs) 1
- Electrolyte abnormalities (hyperkalemia, hypokalemia) 1
- Hypothyroidism 1
- Acute myocardial ischemia or infarction 1
- Increased intracranial pressure 1
- Hypothermia 1
- Infections (particularly Lyme disease) 1
- Sleep apnea 1
Pharmacologic Management
- Atropine remains the first-line drug for acute symptomatic bradycardia (Class IIa, LOE B) 1
- Recommended atropine dose: 0.5 mg IV every 3-5 minutes to maximum total dose of 3 mg 1
- Caution: Doses <0.5 mg may paradoxically worsen bradycardia 1
- Atropine works by reversing cholinergic-mediated decreases in heart rate 2
- Atropine should be considered a temporizing measure while awaiting pacemaker placement if needed 1
When Atropine Is Ineffective or Contraindicated
- If bradycardia is unresponsive to atropine, IV infusion of β-adrenergic agonists (dopamine, epinephrine) can be effective (Class IIa, LOE B) 1
- Dopamine infusion may be used particularly if bradycardia is associated with hypotension (Class IIb, LOE B) 1
- Transcutaneous pacing (TCP) is reasonable to initiate in unstable patients who don't respond to atropine (Class IIa, LOE B) 1
- Consider immediate pacing in unstable patients with high-degree AV block when IV access is not available (Class IIb, LOE C) 1
- If patient doesn't respond to drugs or TCP, transvenous pacing is probably indicated (Class IIa, LOE C) 1
Special Considerations
- Atropine may be ineffective in cardiac transplant patients due to lack of vagal innervation 1
- Avoid relying on atropine in type II second-degree or third-degree AV block with new wide-QRS complex 1
- For drug-induced bradycardia resistant to atropine, aminophylline/theophylline may be considered 3, 4
- Glucagon may be beneficial in beta-blocker or calcium channel blocker-induced bradycardia 5
- For chronic symptomatic bradycardia where pacemaker is refused or contraindicated, theophylline (400-600 mg/day) may be considered 3