What is the management approach for a patient with bradicardia (abnormally slow heart rate), considering symptoms and severity?

Management of Bradycardia

For patients with bradycardia, treatment is indicated ONLY if symptoms (syncope, presyncope, hypotension, altered mental status, chest pain, heart failure, or shock) are directly attributable to the slow heart rate—asymptomatic bradycardia, even with rates as low as 40-45 bpm, requires no intervention. 1, 2

Initial Assessment: Symptomatic vs. Asymptomatic

The critical first step is determining whether bradycardia is causing symptoms:

Symptoms requiring immediate intervention: 1, 2

• Syncope or presyncope (particularly concerning if causing trauma)
• Altered mental status (confusion, decreased responsiveness)
• Hypotension (systolic BP <90 mmHg, cool extremities, delayed capillary refill)
• Ischemic chest pain/angina
• Acute heart failure signs (pulmonary edema, dyspnea on exertion)
• Shock (end-organ hypoperfusion)

Asymptomatic bradycardia does NOT require treatment: 1, 3

• Common in athletes, during sleep, and young healthy individuals
• No minimum heart rate threshold exists—symptom correlation is the sole determinant for therapy
• A heart rate of 55 bpm or even lower requires no monitoring if asymptomatic

Immediate Management of Symptomatic Bradycardia

Step 1: Stabilization and Reversible Causes 4, 2

Immediate actions:

• Obtain 12-lead ECG (but don't delay treatment) 2
• Maintain airway, provide oxygen if hypoxemic 2
• Establish IV access 2
• Monitor rhythm, blood pressure, oxygen saturation 2

Identify and treat reversible causes: 4, 2

• Medications: Beta blockers, calcium channel blockers, digoxin, antiarrhythmics, lithium
• Electrolyte abnormalities: Hyperkalemia, hypokalemia, hypoglycemia
• Cardiac: Acute MI (especially inferior), cardiac surgery
• Metabolic: Hypothyroidism, hypothermia, hypoxemia
• Infections: Lyme disease, Legionella, viral illnesses
• Other: Sleep apnea, increased intracranial pressure, drug overdose

Step 2: Pharmacologic Management

First-line: Atropine 4, 2, 5

• Dose: 0.5-1 mg IV bolus, repeat every 3-5 minutes
• Maximum total dose: 3 mg
• Mechanism: Blocks muscarinic receptors, increases sinus rate and AV conduction 5
• Most effective for: Sinus bradycardia and AV nodal blocks 1
• Less effective for: Infranodal blocks (wide-complex escape rhythms) 1

Critical contraindication: Do NOT use atropine in heart transplant patients without autonomic reinnervation—it can cause paradoxical effects 4, 2

Second-line: Beta-adrenergic agonists (if atropine fails or contraindicated) 4, 2

• Dopamine: 5-20 mcg/kg/min IV, start at 5 mcg/kg/min, increase by 5 mcg/kg/min every 2 minutes (monitor for vasoconstriction/arrhythmias at >20 mcg/kg/min) 4
• Isoproterenol: 20-60 mcg IV bolus or 1-20 mcg/min infusion (monitor for ischemic chest pain) 4
• Epinephrine: 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV 4

Step 3: Transcutaneous Pacing 4, 2

Indications:

• Symptomatic bradycardia unresponsive to atropine 2
• Bridge to transvenous or permanent pacing 4
• Hemodynamically unstable patients 4

Do NOT pace: Patients with minimal/infrequent symptoms without hemodynamic compromise 4

Special Situations: Drug Overdose Management 4

Beta-blocker or calcium channel blocker overdose:

• Glucagon: 3-10 mg IV bolus, then 3-5 mg/h infusion 4
• High-dose insulin: 1 unit/kg IV bolus, then 0.5 units/kg/h infusion (monitor glucose and potassium) 4
• Calcium chloride 10%: 1-2 g IV every 10-20 minutes or 0.2-0.4 mL/kg/h infusion 4
• Calcium gluconate 10%: 3-6 g IV every 10-20 minutes or 0.6-1.2 mL/kg/h infusion 4

Digoxin toxicity:

• Digoxin Fab antibody fragment: Dose based on amount ingested or digoxin level (one vial binds ~0.5 mg digoxin) 4
• Administer over ≥30 minutes, may repeat 4
• Do NOT use dialysis for digoxin removal 4

Post-heart transplant or spinal cord injury:

• Aminophylline: 6 mg/kg in 100-200 mL IV over 20-30 minutes 4
• Theophylline: 300 mg IV, then 5-10 mg/kg/day oral (therapeutic level 10-20 mcg/mL) 4

Definitive Management: Permanent Pacemaker

Class I indications (permanent pacing recommended): 4, 1

• Symptomatic bradycardia directly attributable to sinus node dysfunction
• Symptomatic bradycardia from necessary guideline-directed medications with no alternative treatment
• High-grade AV block (second-degree type II or third-degree) with symptoms

Key principles: 1, 3

• Permanent pacing is indicated ONLY after excluding reversible causes
• Symptoms must be documented to correlate with bradycardia episodes
• Age alone is NOT a contraindication, but consider frailty, comorbidities, functional status, and goals of care
• Most patients with documented symptomatic bradycardia on standard ECG don't need prolonged monitoring before pacemaker decision

Common Pitfalls to Avoid

1. Don't treat asymptomatic bradycardia: Even rates of 40-45 bpm are physiologic in many patients 1, 3

2. Don't use atropine doses <0.5 mg: May paradoxically slow heart rate 1, 5

3. Don't use atropine in heart transplant patients: Can worsen bradycardia 4, 2

4. Don't implant permanent pacemakers for reversible causes: If metabolic/ischemic conditions or drug effects can be corrected, temporary pacing may suffice 6

5. Don't assume symptoms are from bradycardia: Correlation between documented bradycardia and symptoms is essential—symptoms may represent underlying cardiac dysfunction 1

6. Monitor for complications with dopamine: Doses >20 mcg/kg/min risk vasoconstriction and arrhythmias 4

7. Follow glucose/potassium with high-dose insulin therapy: Essential for safe administration 4