What is the initial management for a patient presenting with bradyarrhythmia (abnormally slow heart rate)?

Initial Management of Bradyarrhythmia

Atropine 0.5 mg IV bolus, repeated every 3-5 minutes to a maximum total dose of 3 mg, is the first-line treatment for acute symptomatic bradycardia, while simultaneously identifying and treating reversible causes. 1, 2, 3

Immediate Assessment and Stabilization

The priority is determining whether bradycardia is causing hemodynamic compromise. Look specifically for: 1, 2

• Altered mental status (confusion, decreased responsiveness) 1, 2
• Ischemic chest discomfort or angina 1, 4
• Acute heart failure signs (pulmonary edema, dyspnea, jugular venous distension) 1, 4
• Hypotension (systolic BP <90 mmHg, cool extremities, delayed capillary refill) 1, 2
• Shock with end-organ hypoperfusion 1, 4

While assessing, immediately: 1, 2

• Maintain patent airway and assist breathing if needed 1
• Provide supplementary oxygen if hypoxemic (hypoxemia itself causes bradycardia) 1
• Attach cardiac monitor and measure oxygen saturation 1
• Establish IV access 1
• Obtain 12-lead ECG to document rhythm and identify conduction abnormalities, but do not delay treatment 1, 2

Identify and Treat Reversible Causes

Before or concurrent with pharmacologic treatment, rapidly screen for: 1, 2

• Medications: beta blockers, calcium channel blockers, digoxin, antiarrhythmic drugs 1
• Electrolyte abnormalities: hyperkalemia, hypokalemia 1
• Acute myocardial ischemia or infarction (especially inferior MI) 1, 2
• Hypothyroidism 1
• Increased intracranial pressure 1
• Hypothermia 1
• Infections 1

First-Line Pharmacologic Management: Atropine

Administer atropine 0.5-1 mg IV bolus, repeated every 3-5 minutes to a maximum total dose of 3 mg. 1, 2, 4, 3 Doses less than 0.5 mg may paradoxically slow heart rate. 4 Atropine is most effective for sinus bradycardia and AV nodal blocks but less effective for infranodal blocks. 4

Critical Atropine Contraindications and Limitations:

• Do NOT use atropine in cardiac transplant patients without evidence of autonomic reinnervation—it causes paradoxical effects due to denervation. 1, 2 Consider theophylline or aminophylline instead. 2
• Atropine is ineffective in spinal cord injury patients due to unopposed parasympathetic stimulation. 2
• Consider atropine a temporizing measure while awaiting pacemaker placement if needed. 1

Second-Line Pharmacologic Options (When Atropine Fails or Is Contraindicated)

If bradycardia is unresponsive to atropine or atropine is contraindicated, use IV beta-adrenergic agonists: 1, 2

• Epinephrine infusion: 2-10 μg/min IV 1, 2
• Dopamine infusion: 2-10 μg/kg/min IV (particularly if hypotension is present) 1, 2
• Isoproterenol (alternative option) 5

Special Situations for Drug Overdose:

• Beta-blocker or calcium channel blocker overdose: Glucagon 3-10 mg IV with infusion of 3-5 mg/h 1
• Calcium channel blocker overdose: 10% calcium chloride or 10% calcium gluconate 1

Transcutaneous Pacing

Initiate transcutaneous pacing in unstable patients who do not respond to atropine. 1, 2, 4 This serves as a bridge to transvenous pacing if needed. 2, 4 Transcutaneous pacing is reasonable for symptomatic bradycardia unresponsive to atropine (Class IIa, LOE B). 1, 4

Progression to Advanced Management

• Consider expert consultation for complex cases 1
• Prepare for transvenous pacing if temporary measures are ineffective and bradycardia persists 1, 2
• Permanent pacemaker evaluation is appropriate if bradycardia is documented, symptomatic, and reversible causes have been excluded 1, 4

Critical Pitfalls to Avoid

• Do not treat asymptomatic bradycardia: Heart rates of 40-50 bpm or lower are physiologic in well-conditioned athletes, during sleep, and in young healthy individuals with elevated parasympathetic tone. 2, 4 There is no established minimum heart rate requiring treatment—only symptom-bradycardia correlation matters. 4
• Do not pace asymptomatic nocturnal bradycardia or pauses—these are physiologic and common across all age ranges. 2
• Avoid temporary transvenous pacing in mildly symptomatic patients when episodes are intermittent without hemodynamic compromise—risks outweigh benefits. 2
• Limit total atropine dose to 0.03-0.04 mg/kg in patients with coronary artery disease to avoid excessive tachycardia and increased myocardial oxygen demand. 3