title: Could the peristaltic transition zone be caused by non-uniform esophageal muscle fiber architecture? A simulation study.
abstract: BACKGROUND
  Based on a fully coupled computational model of esophageal transport, we analyzed how varied esophageal muscle fiber architecture and/or dual contraction waves (CWs) affect bolus transport. Specifically, we studied the luminal pressure profile in those cases to better understand possible origins of the peristaltic transition zone.
  
  
  METHODS
  Two groups of studies were conducted using a computational model. The first studied esophageal transport with circumferential-longitudinal fiber architecture, helical fiber architecture and various combinations of the two. In the second group, cases with dual CWs and varied muscle fiber architecture were simulated. Overall transport characteristics were examined and the space-time profiles of luminal pressure were plotted and compared.
  
  
  RESULTS
  Helical muscle fiber architecture featured reduced circumferential wall stress, greater esophageal distensibility, and greater axial shortening. Non-uniform fiber architecture featured a peristaltic pressure trough between two high-pressure segments. The distal pressure segment showed greater amplitude than the proximal segment, consistent with experimental data. Dual CWs also featured a pressure trough between two high-pressure segments. However, the minimum pressure in the region of overlap was much lower, and the amplitudes of the two high-pressure segments were similar.
  
  
  CONCLUSIONS
  The efficacy of esophageal transport is greatly affected by muscle fiber architecture. The peristaltic transition zone may be attributable to non-uniform architecture of muscle fibers along the length of the esophagus and/or dual CWs. The difference in amplitude between the proximal and distal pressure segments may be attributable to non-uniform muscle fiber architecture.
authors.affiliation: Program of Theoretical and Applied Mechanics, Northwestern University, Evanston, IL, USA.
authors.forename: W
authors.initials: W
authors.lastname: Kou
authors.affiliation: Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Pandolfino
authors.affiliation: Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Kahrilas
authors.affiliation: Department of Mechanical Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: N A
authors.initials: NA
authors.lastname: Patankar
mesh_terms: D000818:Animals; D003198:Computer Simulation; D004947:Esophagus / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000033:anatomy & histology / Q000502:physiology*; D010528:Peristalsis
keywords: computer simulation; esophageal manometry; esophageal myoarchitecture; esophageal peristalsis; transition zone