Bradycardia is characterized by a heart rate of less than 60 bpm. It is a normal physiological finding in young adults, trained athletes, elderly individuals, and during sleep. Additionally, it may result from vagal stimulation such as coughing, vomiting, or straining. However, when bradycardia is associated with cardiovascular or metabolic disorders, it may reflect a potentially life-threatening condition.

Clinical significance

Bradycardia alone is a nonspecific sign. It becomes clinically significant when accompanied by symptoms such as:

• Chest pain

• Syncope

• Dizziness

• Dyspnea

• Fatigue

These signs may indicate critical pathologies, including myocardial infarction, hypothyroidism, or increased intracranial pressure.

Clinical Evaluation

History

• Ask about symptoms (syncope, fatigue, shortness of breath)

• Inquire about medical history (hypothyroidism, cardiac diseases)

• Review medications (e.g., beta-blockers, calcium channel blockers, digitalis)

• Check family history for inherited bradyarrhythmias

Physical examination

• Monitor vital signs: HR, BP, RR, O₂ saturation, and temperature

• Evaluate for signs of:

  • Cardiomyopathy (JVD, peripheral edema, orthopnea)

  • Hypothyroidism (facial puffiness, dry skin, brittle nails)

  • MI (chest pain, nausea, cold clammy skin)

Etiologies of bradycardia

Cardiac Causes

• Arrhythmias: May be benign or life-threatening (e.g., sick sinus syndrome)

• Cardiomyopathy: Can lead to conduction delays

• Myocardial infarction: Commonly causes sinus bradycardia

Metabolic and Endocrine

• Hypothyroidism: Results in decreased cardiac output and bradycardia

• Hypothermia: Bradycardia appears when core temperature < 32°C

Pharmacologic Agents

• Beta-blockers, calcium channel blockers, digitalis, antiarrhythmics

• Withdrawal of thyroid medication

• Topical agents (e.g., pilocarpine)

Procedural and Surgical

• Cardiac surgery

• Vagal stimulation during suctioning

• Cardiac catheterization

Emergency interventions

In symptomatic bradycardia (with hypotension, altered mentation, chest pain, or dyspnea):

1. Monitor cardiac rhythm continuously

2. Establish IV access

3. Administer:

   • Atropine (first-line pharmacologic treatment)

   • IV fluids (if hypotensive)

   • Thyroid hormone (if hypothyroidism is present)

4. Consider transcutaneous pacing if unresponsive to atropine

5. Intubate if respiratory depression is present

6. Treat underlying causes (e.g., MI, electrolyte abnormalities)

Investigations

• ECG (12-lead)

• CBC, electrolytes, glucose

• Thyroid function tests (TSH, free T4)

• Cardiac enzymes (if MI suspected)

• Arterial blood gases (ABG)

• Drug levels

• 24-hour Holter monitoring for intermittent symptoms

Population-Specific Considerations

Pediatric Patients

• Heart rates are higher; bradycardia is < 120 bpm in fetuses

• May occur due to:

  • Umbilical cord compression

  • Congenital heart defects

  • Apnea in premature infants

Geriatric Patients

• Common cause: Sick sinus syndrome

• Often drug-induced (beta-blockers, antihypertensives)

• Treatment: medication review and pacemaker if symptomatic

Patient Counseling

• Educate on pulse checking and symptom recognition

• Advise when to seek emergency care

• Explain pacemaker function and follow-up needs

Conclusion

Bradycardia is a multifactorial condition with both benign and life-threatening causes. A detailed history, physical exam, and targeted investigations are critical for diagnosis. Management should be guided by symptoms and etiology, with special considerations in pediatric and elderly patients. Prompt identification and treatment can prevent morbidity and mortality in at-risk populations.

References

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