<unk>  occurs when a reentry circuit forms within or just next to the atrioventricular node.  The circuit usually involves two anatomical pathways: the fast pathway and the slow pathway, which are both in the right atrium. The slow pathway (which is usually targeted for ablation) is located inferiorly and slightly posterior to the AV node, often following the anterior margin of the coronary sinus. The fast pathway is usually located just superior and posterior to the AV node.  These pathways are formed from tissue that behaves very much like the AV node, and some authors regard them as part of the AV node.  In the usual form of<unk> , the conduction from the atrium to the ventricle is down the slow pathway, and the retrograde conduction from the ventricle to the atrium is up the fast pathway.
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AVNRT laboratory findings
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