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. Key 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 & Inferences 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.

A theoretical study of the initiation, maintenance and termination of gastric slow wave re-entry

“…A relationship between longitudinal wave separation and slow wave frequency was measured in accordance to a previous intestinal functional re-entry (Angeli, O'Grady et al 2013), i.e., depolarization to depolarization distance between two successive wavefronts. Similarly, circumference separation distance was also measured.…”

“…Re-entry types were defined based on a previous HR mapping studies conducted by Lammers et al (Lammers, Ver Donck et al 2008) and Angeli et al (Angeli, O'Grady et al 2013). Specifically, a rotor re-entry was defined as a rotating wavefront emerging from an ectopic site and propagating in a circuit in a single-direction around a ‘core’ region in the center of the re-entrant activity (Fig.…”

“…Accurate spatiotemporal descriptions of GI slow waves have been reported relatively recently through the adoption of high-resolution (HR) electrical mapping (up to 256 electrodes; 1-8 mm inter-electrode pacing) (Lammers, Ver Donck et al 2009; Egbuji, O'Grady et al 2010; O'Grady, Du et al 2010). In a significant recent advance, GI slow wave dysrhythmias have recently been mapped in both the stomach and intestine in animals and humans (Lammers, Ver Donck et al 2008; O'Grady, Egbuji et al 2011; Lammers, Stephen et al 2012; O'Grady, Angeli et al 2012; Angeli, O'Grady et al 2013). In two separate studies, investigators have now specifically reported occurrences of functional rotor re-entry as one of the key mechanisms associated with gastric dysrhythmia (Lammers, Ver Donck et al 2008; O'Grady, Egbuji et al 2011).…”

“…In both studies, the functional re-entry events were perpetuated by tachygastria compared to the baseline recordings (tachygastria vs baseline in cycles-per-minute (cpm); canine: 11.8 vs 4.9 cpm; porcine: 4.1 vs 3.2 cpm) (Lammers, Ver Donck et al 2008; O'Grady, Egbuji et al 2011). Furthermore, a relationship of wave separation, which relates to the excitation gap between the successive activities in intestinal re-entrant pathway, as a function of velocity and frequency, was also defined (Angeli, O'Grady et al 2013). …”

A System and Method for Online High-Resolution Mapping of Gastric Slow-Wave Activity

“…As the primary function small intestine involves mixing of the digesta, its slow-wave activity is also more complex and dynamic making construction of isochronal activation maps more complex [34]. However, the animation-based analysis (as shown in Fig.…”