What causes supraventricular bradycardia?

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Causes of Supraventricular Bradycardia

Supraventricular bradycardia is most commonly caused by sinus node dysfunction, medications, electrolyte abnormalities, increased vagal tone, or atrioventricular block occurring at or above the level of the AV node. 1

Primary Causes

Sinus Node Dysfunction

  • Sick sinus syndrome (includes sinus bradycardia, sinus arrest, sinoatrial block)
  • Chronotropic incompetence (blunted heart rate response with exercise)
  • Bradycardia-tachycardia syndrome (alternating bradycardia with episodes of supraventricular tachycardia) 2

Atrioventricular Conduction Abnormalities

  • AV nodal block (first degree, second degree Mobitz type I/Wenckebach)
  • High-grade AV block occurring at the AV node level
  • Vagally-mediated AV block 1

Extrinsic/Reversible Causes

Medications

  • Beta-blockers - most common medication cause
  • Non-dihydropyridine calcium channel blockers (verapamil, diltiazem)
  • Cardiac glycosides (digoxin)
  • Antiarrhythmic drugs (especially sotalol and amiodarone)
  • Other sympatholytic agents used for hypertension 1

Electrolyte and Metabolic Disturbances

  • Hyperkalemia - can cause progressive bradycardia and conduction blocks 3
  • Hypokalemia
  • Hypoglycemia
  • Hypothyroidism
  • Acidosis 1

Increased Vagal Tone

  • Vasovagal reactions
  • Carotid sinus hypersensitivity
  • Vomiting or other vagal stimulation
  • Sleep (especially in patients with sleep apnea)
  • Pain (can heighten vagal tone leading to sinus bradycardia or heart block) 1

Ischemia and Structural Heart Disease

  • Acute myocardial infarction (especially inferior MI affecting the sinus node)
  • Left ventricular hypertrophy (LVH) - associated with bradyarrhythmias 1
  • Post-cardiac surgery (especially valve replacement, maze procedure, coronary bypass) 1

Other Conditions

  • Hypothermia (therapeutic or environmental)
  • Increased intracranial pressure
  • Obstructive sleep apnea (can manifest as nocturnal bradycardia) 1
  • Infections (Lyme disease, legionella, viral infections) 1
  • Athletic training (physiologic bradycardia) 1

Special Considerations

Heart Transplant Patients

  • Denervated transplanted hearts do not respond to atropine for bradycardia treatment 1

Elderly Patients

  • Higher susceptibility to bradycardia due to age-related changes in the conduction system
  • Elimination half-life of atropine is more than doubled in the elderly (>65 years) 4

Clinical Pearls

  • Always check medication list in patients presenting with bradycardia, as drug-induced bradycardia is common and potentially reversible
  • In patients with bradycardia-tachycardia syndrome, treatment with antiarrhythmic drugs alone may worsen bradycardia episodes, and pacing is often required 2
  • Non-dipping blood pressure profile (nocturnal BP reduction <10%) is associated with higher risk of bradyarrhythmias 1
  • When combining antihypertensive medications, caution should be exercised when using non-dihydropyridine CCBs with beta-blockers due to increased risk of bradycardia 1
  • In patients with chronic kidney disease, accumulation of beta-blockers or active metabolites can exacerbate bradyarrhythmias 1

Understanding the specific cause of supraventricular bradycardia is essential for appropriate management, particularly distinguishing between reversible and irreversible causes.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

3
Research

Syncope caused by iatrogenic hyperkalemia.

Journal of cardiovascular medicine (Hagerstown, Md.), 2009

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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