Causes of Junctional Rhythm
Junctional rhythm is primarily caused by enhanced automaticity from an ectopic focus in the AV junction (including the His bundle), often resulting from underlying conditions such as digoxin toxicity or myocardial infarction. 1
Types of Junctional Rhythm
Focal Junctional Tachycardia: Characterized by heart rates of 120-220 bpm, narrow QRS complexes, and often AV dissociation. It's uncommon in adults and more typically seen in infants after cardiac surgery for congenital heart disease 1
Nonparoxysmal Junctional Tachycardia (Accelerated AV Junctional Rhythm): More common in adults, with heart rates of 70-130 bpm, showing typical "warm-up" and "cool-down" patterns that cannot be terminated by pacing maneuvers 1
Common Causes of Junctional Rhythm
Nonparoxysmal Junctional Tachycardia (70-130 bpm)
- Digoxin toxicity - A major cause of nonparoxysmal junctional tachycardia 1, 2
- Myocardial infarction/ischemia - Common cause of junctional rhythm due to altered automaticity 1
- Electrolyte abnormalities - Particularly hypokalemia 1, 3
- Post-cardiac surgery - Especially following valve replacement (33% incidence vs 13% after coronary artery bypass) 4
- Chronic obstructive lung disease with hypoxia - Can trigger junctional rhythm 1
- Inflammatory myocarditis - May lead to junctional rhythm due to inflammation near the conduction system 1
Focal Junctional Tachycardia (120-220 bpm)
- Congenital abnormalities - Such as atrial or ventricular septal defects 1
- Exercise or stress-related triggers - Common precipitating factors 1, 3
- Structurally normal hearts - Can occur even without structural abnormalities 1
Other Causes
- Sinus node dysfunction - When junctional automaticity exceeds sinus rate 1, 3
- Post-ablation - Transient junctional rhythm may occur after slow-pathway ablation for AVNRT 1
- Heart transplantation - Junctional arrhythmias can occur post-transplant 5
- Heterotaxy syndromes - Associated with disturbances in sinus node function leading to junctional rhythm 6
Clinical Significance and Complications
- In adults, junctional tachycardia typically has a relatively benign course, whereas in infants and children it can lead to heart failure or uncontrollable tachyarrhythmia 1
- Junctional rhythm can lead to hemodynamic impairment due to loss of synchronized atrial contraction 4
- Prolonged junctional rhythm may increase intensive care stay and mortality in post-surgical patients 7
- In Fontan patients, sinus node dysfunction with concomitant junctional rhythm has been recognized as a contributor to heart failure 8
Management Considerations
- The primary approach is to identify and correct the underlying cause (e.g., withholding digoxin if toxicity is suspected, correcting electrolyte abnormalities) 1, 3, 2
- For symptomatic cases, beta blockers are reasonable for both acute treatment and ongoing management 1
- Intravenous diltiazem, procainamide, or verapamil may be reasonable for acute treatment when beta blockers are ineffective 1
- Catheter ablation may be considered when medical therapy is ineffective but carries a 5-10% risk of AV block 1