Atrioventricular (AV) junctional rhythm is an arrhythmia that originates from the AV node or bundle of His, or His bundle. In sinus rhythm, the heart rate originates in the sinoatrial (SA) node, traveling to the AV node and the bundle of His toward the ventricles. In AV junctional rhythm, the AV node or His bundle takes over, and/or the electrical activity of the SA node is less than the automaticity of the AV node. A junctional rhythm is normally slow, less than 60 beats per minute. If it is faster, it is referred to as an accelerated junctional rhythm. Because electrical activity still follows the normal conduction system (through His-Purkinje), the QRS complex is usually narrow, except in patients with a bundle branch block at baseline. P waves are often seen, although they may be inverted and can be before, after, or buried within the QRS complex due to retrograde conduction through the atria.
Terminology of the types of junctional rhythms depends on the rate. All rhythms will be regular and narrow-complex unless there is baseline intraventricular conduction delay.
- Junctional bradycardia: < 40 beats per minute
- Junctional escape rhythm: 40-60 beats per minute
- Accelerated junctional rhythm: 60-100 beats per minute
- Junctional tachycardia: > 100 beats per minute
Etiologies include sick sinus syndrome
, collagen vascular diseases, neuromuscular disorders, amyloidosis, Lyme carditis
, rheumatic fever
, ischemic heart disease, acute myocardial infarction
, coronary artery disease
, inherited channelopathy, sleep apnea
, and pericarditis
. Iatrogenic and medication-related causes include beta blockers, calcium channel blockers, digoxin, hyperkalemia, cannabinoids, chest trauma, radiation therapy, and vasovagal stimulation such as endotracheal suctioning.
Junctional rhythms are more common among those with sinus node dysfunction. Athletes and young children may also exhibit a junctional rhythm during sleep. Congenital ectopic junctional tachycardia is a rare disorder that is often refractory to medical therapy.