title: Anatomy of the inferior interatrial route in humans.
abstract: OBJECTIVE
  To explore the morphology of the proximal coronary sinus (CS) and the surrounding tissues in order to identify possible routes for interatrial conduction.
  
  
  METHODS
  Specimens containing interatrial septum and proximal CS were taken from 21 necropsied hearts and sliced into 10-microm thick parallel histological sections in 1-mm steps starting from the valve plane, up to the atrial roof (40-80 sections per heart). The sections were stained with van Gieson's stain.
  
  
  RESULTS
  Media in the proximal CS consists of smooth muscle cells that do not form a continuous layer. CS was not surrounded by striated atrial myocardium in 10 specimens in which posterior CS wall was covered by epicardial fat only. In seven specimens, striated muscle bundles of up to 2-mm width connected the myocardium surrounding the CS with the left atrium. Regardless of their presence, variable posterior and/or anterior interatrial muscular connections were identified in all specimens.
  
  
  CONCLUSIONS
  Variability of the striated atrial myocardium surrounding proximal CS may affect interatrial conduction. Striated muscular fascicles connecting the proximal CS with the left atrium are not obligatory cardiac structures and may be considered as supplementary to the larger interatrial connections outside the CS.
authors.affiliation: Almazov Research Institute of Cardiology, Petersburg, Russia.
authors.forename: Lubov
authors.initials: L
authors.lastname: Mitrofanova
authors.forename: Vitaly
authors.initials: V
authors.lastname: Ivanov
authors.forename: Pyotr G
authors.initials: PG
authors.lastname: Platonov
mesh_terms: D000368:Aged; D002102:Cadaver; D005260:Female; D006325:Heart Atria / Q000033:anatomy & histology*; D006329:Heart Conduction System / Q000033:anatomy & histology*; D006346:Heart Septum / Q000033:anatomy & histology*; D006801:Humans; D008297:Male