What is the management approach for a patient with symptomatic bradycardia (heart rate less than 60 beats per minute)?

Management of Bradycardia

Immediate Assessment and Stabilization

For symptomatic bradycardia (heart rate <50 bpm with hemodynamic compromise), immediately administer atropine 0.5-1 mg IV as first-line therapy, repeating every 3-5 minutes up to a maximum total dose of 3 mg. 1, 2

Initial Evaluation Steps

• Identify if bradycardia is causing the symptoms by assessing for signs of poor perfusion: altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or shock 3, 1
• Evaluate oxygenation immediately as hypoxemia is a common reversible cause—look for tachypnea, intercostal retractions, suprasternal retractions, and check pulse oximetry 3, 4
• Establish cardiac monitoring and obtain IV access while simultaneously obtaining a 12-lead ECG to document rhythm and identify conduction abnormalities 3, 1
• Search for reversible causes: medications (beta-blockers, calcium channel blockers, digoxin), electrolyte abnormalities (hyperkalemia), hypothyroidism, acute MI, increased intracranial pressure, hypothermia, Lyme disease, and infections 1, 4

Pharmacologic Management Algorithm

First-Line: Atropine

• Administer atropine 0.5-1 mg IV bolus, repeat every 3-5 minutes to maximum total dose of 3 mg 3, 1, 2
• Critical caveat: Doses <0.5 mg may paradoxically worsen bradycardia through increased vagal tone 5
• Use cautiously in acute coronary syndrome as increased heart rate may worsen ischemia 5
• Atropine will be ineffective in cardiac transplant patients due to denervation—consider theophylline or aminophylline instead 3, 5

Second-Line: Sympathomimetic Infusions

If atropine fails or is contraindicated:

• Epinephrine infusion: 2-10 μg/min IV 3, 1, 5
• Dopamine infusion: 2-10 μg/kg/min IV 3, 1, 5

Special Populations Requiring Alternative Agents

For post-cardiac transplant patients or spinal cord injury patients with refractory bradycardia:

• Theophylline 100-200 mg slow IV (maximum 250 mg) or aminophylline infusion targets adenosine receptor blockade and addresses unopposed parasympathetic stimulation 3, 5
• These agents are particularly effective when atropine fails due to the underlying pathophysiology 3, 4
• Treatment can typically be withdrawn after 4-6 weeks 3, 4

Temporary Pacing Indications

Transcutaneous Pacing

• Consider for severe symptoms or hemodynamic compromise when atropine is ineffective, as a bridge to transvenous pacing or until bradycardia resolves 3, 4
• This is a Class IIb recommendation (may be considered) 3

Transvenous Pacing

• Indicated for persistent hemodynamically unstable bradycardia refractory to medical therapy until permanent pacemaker placement or resolution of reversible cause 3, 4
• This is a Class IIa recommendation (reasonable to perform) 3
• Start CPR immediately if heart rate <60 bpm with poor perfusion despite adequate oxygenation and ventilation in pediatric patients 3

When NOT to Treat

Do not treat asymptomatic bradycardia, even if heart rate is significantly low, in the following situations:

• Well-conditioned athletes with physiologic bradycardia 1, 6
• Sleep-related bradycardia or nocturnal pauses 1
• Young healthy individuals with elevated parasympathetic tone 1
• Asymptomatic sinus node dysfunction without other pacing indications 1

Definitive Management

Permanent pacemaker implantation is indicated for:

• Chronic symptomatic bradycardia that persists after reversible causes are addressed 1, 6
• Symptomatic sick sinus syndrome 6, 7
• High-grade second-degree or third-degree AV block with symptoms 6, 7
• Symptomatic bradycardia caused by necessary medications with no alternatives 1

Approximately 50% of patients presenting with compromising bradycardia ultimately require permanent pacemaker implantation 8

Critical Pitfalls to Avoid

• Never use atropine in post-cardiac transplant patients as it may paradoxically cause high-degree AV block 3, 5, 2
• Avoid benzodiazepines and opioids if sedation is needed, as they worsen bradycardia through sympatholytic effects 5
• Do not place temporary transvenous pacing in mildly symptomatic patients with intermittent episodes—risks (venous thrombosis, pulmonary emboli, life-threatening arrhythmias, infection) outweigh benefits 4
• Recognize that approximately 39% of patients with compromising bradycardia respond to bed rest alone without requiring pharmacologic intervention 8
• In complete heart block, atropine may occasionally cause AV block and nodal rhythm rather than improvement 2