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Chapter 22: Atrioventricular Junctional Tachycardias

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Chapter 22: Atrioventricular Junctional Tachycardias

The most common junctional tachycardia is paroxysmal supraventricular tachycardia, also known as atrioventricular nodal reentrant tachycardia (AVNRT). WPW syndrome is also an atrioventricular reentry tachycardia.

Patients with AVNRT have an AV node with a dual pathway. A reentry circuit confined to the AV node and the atrial tissue around it causes a regular supraventricular tachycardia. The QRS complex in the common variant of AVNRT is narrow (< 0.12 seconds), indicating normal ventricular activation via the His-Purkinje system. 

The presence of aberrant conduction characterizes the rare variant of AVNRT. When aberrant conduction occurs, a wide QRS complex appears. The aberrant conduction may be a bundle-branch block. 

AVNRT is the most common form of regular paroxysmal supraventricular tachycardia and occurs in two-thirds of patients diagnosed with it. AVNRT is seen more frequently in women than men. AVNRT with an accessory pathway is more likely to appear in young adults, but it can manifest at any age. 

The dual-channel in AVNRT may be caused by an increase in atrial pressure, which leads to the electrophysiologic changes of the AV nodal inputs. There are also reports of AVNRT being a familial disease.

Reentry requires the conduction between these two pathways to have different velocities. One pathway must have a faster velocity relative to its long refractory period. The second pathway must conduct slowly with a shorter refractory period.


Related Video – ECG Rhythm Review – Accelerated Junctional