Low Heart Rate (Bradycardia): Causes and Implications

Introduction

A low heart rate, also called bradycardia, occurs when the heart beats fewer than 60 times per minute. While it can be normal in healthy individuals, especially athletes, it can also indicate underlying health issues.

Causes of Bradycardia

1. Physiological Causes

  • Athletic Heart Syndrome: Well-trained athletes often have a naturally lower heart rate due to increased heart efficiency.
  • Sleep: Heart rate slows naturally during sleep.

2. Pathological Causes

  • Heart Conditions:
    • Sick sinus syndrome (malfunctioning natural pacemaker)
    • Heart block (disruptions in electrical signals of the heart)
    • Prior heart attack or heart disease causing structural damage
  • Metabolic Disorders:
    • Hypothyroidism (underactive thyroid)
    • Electrolyte imbalances (especially potassium and calcium disturbances)
  • Neurological Factors:
    • Increased vagal tone (e.g., due to vasovagal syncope)
    • Nervous system disorders like Parkinson’s disease
  • Infections and Inflammatory Diseases:
    • Myocarditis (inflammation of heart muscle)

3. Medications That Can Cause Bradycardia

  • Beta-blockers (e.g., metoprolol)
  • Calcium channel blockers (e.g., diltiazem, verapamil)
  • Digoxin
  • Some sedatives or opioids

4. Other Causes

  • Hypothermia (low body temperature)
  • Obstructive sleep apnea
  • Aging and degenerative changes in heart tissue

When to Seek Medical Attention?

  • Dizziness, fainting, or fatigue
  • Confusion or shortness of breath
  • Chest pain or heart palpitations
  • Sudden worsening of symptoms

Conclusion

While some cases of bradycardia are harmless, others require medical evaluation. Identifying the underlying cause is essential for determining the best treatment.

Source recommendations

1. American College of Cardiology/American Heart Association Guidelines for the Evaluation and Management of Bradycardia

  1. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000628
  2. https://www.acc.org/latest-in-cardiology/ten-points-to-remember/2018/11/05/15/12/2018-acc-aha-hrs-guideline-on-bradycardia
  3. https://www.jacc.org/guidelines/bradycardia
  4. https://pubmed.ncbi.nlm.nih.gov/30412710/
  5. https://www.hrsonline.org/guidance/clinical-resources/2018-accahahrs-guideline-evaluation-and-management-patients-bradycardia-and-cardiac-conduction

2. European Society of Cardiology Guidelines on Cardiac Pacing and Implantable Cardioverter Defibrillators

  1. https://academic.oup.com/eurheartj/article/34/29/2281/401445
  2. https://www.escardio.org/Journals/E-Journal-of-Cardiology-Practice/Volume-14/Overview-of-devices-in-advanced-heart-failure
  3. https://pmc.ncbi.nlm.nih.gov/articles/PMC11757831/
  4. https://www.escardio.org/Journals/E-Journal-of-Cardiology-Practice/Volume-12/The-subcutaneous-defibrillator-who-stands-to-benefit
  5. https://pubmed.ncbi.nlm.nih.gov/39836347/

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