Circumferential and functional re-entry of in vivo slow-wave activity in the porcine small intestine

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; 32x8; 4mm 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 +/- 3.9min). 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 min1; P=0.5), and greater than that of focal pacemakers (12.7 +/- 0.8 cycle min1; P<0.001). Velocity was anisotropic (12.9 +/- 0.7mms1 circumferential vs 9.0 +/- 0.7mms1 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.