Junctional Bradycardia on ECG

Introduction

Junctional bradycardia is a type of abnormal heart rhythm (arrhythmia) where the heart's natural pacemaker (the sinoatrial or SA node) does not control the heartbeat. Instead, the atrioventricular (AV) junction takes over the function of pacing the heart, leading to a slower-than-normal heart rate (typically below 60 beats per minute).

ECG Characteristics of Junctional Bradycardia

To diagnose junctional bradycardia, doctors analyze an electrocardiogram (ECG). Key features include: - Heart Rate : Usually below 60 beats per minute. - P Waves : Either absent, inverted (negative) in leads II, III, and aVF, or appearing after the QRS complex. - QRS Complex : Usually normal in duration (<120 ms) if no underlying conduction delay exists. - Regular Rhythm : Typically a regular, slow rhythm.

Causes of Junctional Bradycardia

Several conditions can cause junctional bradycardia, including: - Sinus node dysfunction (e.g., sick sinus syndrome). - Increased vagal tone , which can occur in athletes or during sleep. - Myocardial infarction , particularly involving the inferior wall. - Drug effects , such as beta-blockers, calcium channel blockers, or digoxin. - Electrolyte imbalances , including hyperkalemia.

Symptoms of Junctional Bradycardia

Mild cases may not cause symptoms, but significant bradycardia can lead to: - Dizziness or lightheadedness. - Fatigue or weakness. - Shortness of breath. - Syncope (fainting).

Treatment Approach

The treatment depends on symptoms and underlying causes: - Asymptomatic patients : Usually do not require treatment. - Symptomatic cases : - Address underlying causes (e.g., drug adjustments, correcting electrolyte levels). - Medications like atropine may be used to increase heart rate in acute settings. - Pacemaker implantation may be considered in severe cases with persistent symptoms.

Conclusion

Junctional bradycardia is a condition where the AV junction controls the heart rhythm at a slow rate. Diagnosing it requires careful ECG interpretation. Treatment options depend on symptoms and underlying causes, with severe cases possibly necessitating pacemaker placement.

Source recommendations

1. American Heart Association Guidelines on Bradycardia

  1. https://cpr.heart.org/-/media/cpr-files/cpr-guidelines-files/algorithms/algorithmacls_bradycardia_200612.pdf
  2. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/bradycardia--slow-heart-rate
  3. https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines/algorithms
  4. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000628
  5. https://pubmed.ncbi.nlm.nih.gov/30586772/

2. European Society of Cardiology Guidelines on Arrhythmias

  1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Ventricular-Arrhythmias-and-the-Prevention-of-Sudden-Cardiac-Death
  2. https://academic.oup.com/eurheartj/article/43/40/3997/6675633
  3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Supraventricular-Tachycardia
  4. https://pubmed.ncbi.nlm.nih.gov/36017572/
  5. https://www.ahajournals.org/doi/10.1161/01.cir.0000091380.04100.84

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