title: Circumferential and functional re-entry of in vivo slow-wave activity in the porcine small intestine.
abstract: BACKGROUND
  Slow-waves modulate the pattern of small intestine contractions. However, the large-scale spatial organization of intestinal slow-wave pacesetting remains uncertain because most previous studies have had limited resolution. This study applied high-resolution (HR) mapping to evaluate intestinal pacesetting mechanisms and propagation patterns in vivo.
  
  
  METHODS
  HR serosal mapping was performed in anesthetized pigs using flexible arrays (256 electrodes; 32 × 8; 4 mm spacing), applied along the jejunum. Slow-wave propagation patterns, frequencies, and velocities were calculated. Slow-wave initiation sources were identified and analyzed by animation and isochronal activation mapping.
  
  
  RESULTS
  Analysis comprised 32 recordings from nine pigs (mean duration 5.1 ± 3.9 min). Slow-wave propagation was analyzed, and a total of 26 sources of slow-wave initiation were observed and classified as focal pacemakers (31%), sites of functional re-entry (23%) and circumferential re-entry (35%), or indeterminate sources (11%). The mean frequencies of circumferential and functional re-entry were similar (17.0 ± 0.3 vs 17.2 ± 0.4 cycle min(-1) ; P = 0.5), and greater than that of focal pacemakers (12.7 ± 0.8 cycle min(-1) ; P < 0.001). Velocity was anisotropic (12.9 ± 0.7 mm s(-1) circumferential vs 9.0 ± 0.7 mm s(-1) longitudinal; P < 0.05), contributing to the onset and maintenance of re-entry.
  
  
  CONCLUSIONS
  This study has shown multiple patterns of slow-wave initiation in the jejunum of anesthetized pigs. These results constitute the first description and analysis of circumferential re-entry in the gastrointestinal tract and functional re-entry in the in vivo small intestine. Re-entry can control the direction, pattern, and frequency of slow-wave propagation, and its occurrence and functional significance merit further investigation.
authors.affiliation: Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
authors.forename: T R
authors.initials: TR
authors.lastname: Angeli
authors.forename: G
authors.initials: G
authors.lastname: O'Grady
authors.forename: P
authors.initials: P
authors.lastname: Du
authors.forename: N
authors.initials: N
authors.lastname: Paskaranandavadivel
authors.forename: A J
authors.initials: AJ
authors.lastname: Pullan
authors.forename: I P
authors.initials: IP
authors.lastname: Bissett
authors.forename: L K
authors.initials: LK
authors.lastname: Cheng
mesh_terms: D000818:Animals; D004594:Electrophysiology / Q000379:methods; D056885:Interstitial Cells of Cajal / Q000502:physiology*; D007421:Intestine, Small / Q000502:physiology*; D016065:Myoelectric Complex, Migrating / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D013552:Swine