What is junctional ectopic tachycardia?

Junctional Ectopic Tachycardia: A Simple Explanation

Junctional ectopic tachycardia (JET) is an abnormal heart rhythm that originates from the area between the upper and lower chambers of the heart (AV junction), causing the heart to beat too fast with disrupted coordination between the heart's chambers.

What Is Junctional Ectopic Tachycardia?

Junctional ectopic tachycardia is characterized by:

• Origin: Arises from the atrioventricular (AV) node or His bundle (the junction between upper and lower heart chambers) 1
• Heart Rate: Typically ranges from 110-250 beats per minute in focal JET 1
• Mechanism: Caused by either abnormal automaticity (cells firing on their own) or triggered activity (cells being stimulated to fire) 1

Types of Junctional Tachycardias

There are several distinct types:

1. Focal Junctional Tachycardia:

   • Also known as automatic or paroxysmal junctional tachycardia
   • Heart rate: 110-250 bpm
   • More common in young adults
   • Often exercise or stress-related 1

2. Nonparoxysmal Junctional Tachycardia:

   • A benign, slower form (70-120 bpm)
   • Often indicates underlying problems like digitalis toxicity, post-surgery complications, low potassium, or heart damage
   • Shows a typical "warm-up" and "cool-down" pattern 1

3. Congenital JET:

   • Occurs in children without prior heart surgery
   • Can be difficult to treat and has higher risks 2

4. Postoperative JET:

   • Occurs within 72 hours after heart surgery
   • Caused by trauma, lack of oxygen, or stretching of heart tissues during surgery 2, 3

How to Recognize JET on an ECG

Key features include:

• Narrow QRS complexes (normal-looking heartbeats on ECG)
• Atrioventricular dissociation (upper and lower chambers beating independently)
• Absent P waves or retrograde P waves (upside down in certain ECG leads)
• Sometimes irregular rhythm that may be confused with atrial fibrillation 1, 4

Clinical Significance

JET is important because:

• In adults, focal JET is uncommon but can cause significant symptoms
• Patients may develop heart failure if left untreated, especially with incessant tachycardia 1
• In children, particularly infants, JET can be life-threatening with high mortality rates 2
• It may indicate underlying serious conditions like digitalis toxicity or heart damage 1

Treatment Approaches

Treatment depends on the type and severity:

• For Focal JET in Adults:

  • Beta-blockers are first-line therapy 1, 4
  • IV flecainide can slow or terminate the tachycardia 1
  • Catheter ablation may be considered for drug-resistant cases (carries 5-10% risk of AV block) 1

• For Nonparoxysmal JET:

  • Treat the underlying cause (e.g., stop digitalis if toxicity is present)
  • Beta-blockers or calcium channel blockers for persistent cases 1, 4

• Important Considerations:

  • Sometimes junctional rhythm is a protective response when the heart's main pacemaker fails and shouldn't always be suppressed 4
  • In some cases, the rhythm may cause symptoms similar to "pacemaker syndrome" due to poorly timed atrial contractions 1

Common Pitfalls in Diagnosis

• Misdiagnosing JET as other supraventricular tachycardias like AVNRT or AVRT
• Failing to recognize AV dissociation, which is a key distinguishing feature
• Confusing irregular junctional rhythm with atrial fibrillation
• Overlooking underlying causes like digitalis toxicity or electrolyte abnormalities 1, 4

JET requires careful evaluation and management, as it can significantly impact heart function and quality of life, particularly when it occurs at rapid rates or persists for extended periods.