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AV Nodal Reentrant Tachycardia AV Nodal Reentrant Tachycardia (Example) AV nodal reentrant tachycardia (AVNRT) is the most common form of PSVT in adults. AVNRT occurs when a reentrant circuit occurs within the AV node itself. In this situation, there are two separate conduction pathways within the AV node instead of just one (this occurs in about 5% of the general population). One pathway is slower and has a long refractory period while the other is faster and has a short refractory period. Normal conduction occurs through the faster pathway with the longer refractory period. If a premature atrial contraction (or PVC) occurs at the right time, the normal conduction pathway will still be refractory, so the action potential will conduct through the slower pathway with the shorter refractory period instead. After this action potential reaches the ventricules, it will conduct retrograde (backwards) up the normal AV nodal conduction pathway since it will no longer be refractory and a circuit will be created. Findings on EKG include: 1) Narrow complex tachycardia 2) A P wave that occurs after the QRS complex (a long RP interval). 3) This tachycardia will quickly terminate with AV blocking maneuvers (carotid massage or adenosine). |
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