Bradycardia: Causes, Symptoms, and Management

Definition

Sinus bradycardia: heart rate <60 bpm (or <50 bpm per some guidelines) with normal sinus rhythm.

Causes

Category	Examples
Physiologic	Athletes, sleep, vagal tone
Cardiac	Ischemia (inferior MI), conduction disease, post-cardiac surgery
Medications	β-blockers, CCBs (non-DHP), digoxin, clonidine, amiodarone, opioids
Metabolic/Endocrine	Hypothyroidism, hyperkalemia, hypercalcemia, hypothermia
Neurologic	Increased ICP, stroke, vasovagal
Infiltrative	Sarcoidosis, amyloidosis, Lyme disease

Clinical Assessment

• Symptoms? (syncope, fatigue, exercise intolerance, confusion, dyspnea)
• Hemodynamic stability?
• Medication review (often reversible)
• ECG, labs (TSH, electrolytes, troponin, digoxin level)

Management

• Asymptomatic, physiologic: observe
• Symptomatic/unstable: Atropine 0.5 mg IV (repeat to 3 mg), transcutaneous pacing, dopamine/epinephrine infusion
• Medication-induced: adjust or hold offending agent
• Conduction disease: permanent pacemaker if symptomatic/irreversible

Key Point

Treat the patient, not the number. Asymptomatic bradycardia in a fit elder may be normal; the same rate in sepsis is ominous.