Visual Guide to AV Nodal Reentrant Tachycardia (AVNRT) - Pathophysiology

 - Dual AV nodal physiology is the underlying substrate for AVNRT.

 - Normal conduction takes place via fast pathway which blocks the incoming current from the slow pathway.

 - Premature atrial beats usually trigger the typical AVNRT. The setup is created if the beat is conducted through the slow pathway.

 - Once the PAC reaches the end of slow pathway, it can conduct retrograde via fast pathway back up to atrium as by that time the fast pathway is out of its refractory zone.

 - With the echo beat, the current stays inside the AV node and a reentrant circuit is formed. This reentrant circuit depolarizes the atria and ventricles simultaneously resulting in what known as AVNRT.

 - In most case P wave is hidden in the QRS complex. It can, however, sometimes be seen after the QRS. Can be seen as 'pseudo-s' wave in lead II, Ill or aVF and 'pseudo-r' wave in lead V1. ECG usually shows: regular narrow complex tachycardia at rates of 120 to 240.



By Usama Nasir MD @usamanasirmd via @Visualmedapp



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