title: Extension of the inferior vena cava into the posteroinferior right atrium.
abstract: BACKGROUND
  The inferior vena cava (IVC) is obliquely connected to the right atrium (RA), and often a low-voltage area is observed in the posteroinferior RA.
  
  
  OBJECTIVE
  The purpose of this study was investigate the size of the IVC extension into RA and its anatomic background.
  
  
  METHODS
  We investigated 30 human hearts [11 men and 19 women; mean age 79 +/- 10 years; 7 cardiac deaths (group A) and 23 noncardiac deaths (group B)]. After obtaining macroscopic measurements around the RA-IVC junction, serial sections were cut and examined histologically. We defined a horizontal baseline at the level of the cavotricuspid isthmus and measured (1) the length of IVC extension, which was defined as the distance from the baseline to the top of the RA-IVC junction, and (2) the width of the RA-IVC junction at the baseline level.
  
  
  RESULTS
  The top of the RA-IVC junction was always located in the posteroinferior RA. The mean length of the IVC extension was 17.6 +/- 6.6 mm, and the mean width was 29.6 +/- 7.5 mm. The IVC extension was wider in group A than in group B (35.8 +/- 9.0 mm vs 27.5 +/- 5.9 mm; P = .0277). The right and left borders of the RA-IVC junction corresponded to the reflection of the pericardium. Histologic examination showed no myocardium in the IVC extension.
  
  
  CONCLUSIONS
  The IVC extension into the posteroinferior RA always exists and varies in size. Because this area lacks myocardium, it is important to consider when analyzing catheter mapping from this area.
authors.affiliation: Department of Cardiovascular Medicine, Faculty of Medicine, Tottori University, Yonago, Japan. oigawa@grape.med.tottori-u.ac.jp <oigawa@grape.med.tottori-u.ac.jp>
authors.forename: Osamu
authors.initials: O
authors.lastname: Igawa
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Adachi
authors.forename: Akio
authors.initials: A
authors.lastname: Yano
authors.forename: Junichiro
authors.initials: J
authors.lastname: Miake
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Inoue
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Ogura
authors.forename: Masaru
authors.initials: M
authors.lastname: Kato
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tanaka
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Iitsuka
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hisatome
authors.forename: Takao
authors.initials: T
authors.lastname: Inoue
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003643:Death; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000033:anatomy & histology*; D006325:Heart Atria / Q000033:anatomy & histology / Q000166:cytology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000166:cytology*; D012016:Reference Values; D014682:Vena Cava, Inferior / Q000033:anatomy & histology*