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Answer
I am afraid the 4th response is closer to truth .Readers may share their thoughts. If there are three distinct pathways spreading widely connecting the two spacious chambers and converging again with precision at the compact AV node , it is a marvel .
Further , If these pathways are real , we must experience different types of inter nodal re-entrant tachycardias.Of-course ,we do come across few macro re-entrant tachycardia in the form of atypical atrial flutters They need a close watch .Tracking these arrhythmia may throw light on existence of these pathways.
However, the presence of nodal approaches with preferential inputs to AV node from different parts of atria would indeed suggest existence of such pathways !
Further study
What does sophisticated carto and other electro anatomic mapping say about these inter nodal pathways ?
Dr.S.Venkatesan MD 
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