Impulses from SA node to the left atrium and AV node passes through:

There are three bundles of atrial fibers that contain Purkinje-type fibers and connect the SA node to the AV node: the anterior, middle (tract of Wenckebach), and posterior (tract of Thorel) tracts. Bachmann bundle is sometimes used to identify a branch of the anterior internodal tract that connects the right and left atria.    Key Concept 3 INTERNODAL TRACTS: Connects SA node to AV node: Anterior – Bachman’s bundle Middle – Wenckebach’s bundle Posterior – Thorel’s bundle Reference: Ganong’s Review of Medical Physiology T W E N T Y - F I F T H   E D I T I O N page no 519