Design and Application of an Inflatable Cuff to Aid High-Resolution Intestinal Slow Wave Recordings. Annu Int Conf IEEE Eng Med Biol Soc 2020;2020:3953-3956. [PMID: 33018865 DOI: 10.1109/embc44109.2020.9175219]

The bioelectrical conduction system around the ileocecal junction defined through in vivo high-resolution mapping in rabbits

Coordinated contractions across the small and large intestines via the ileocecal junction (ICJ) are critical to healthy gastrointestinal function and are in part governed by myoelectrical activity. In this study, the spatiotemporal characteristics of the bioelectrical conduction across the ICJ and its adjacent regions were quantified in anesthetized rabbits. High-resolution mapping was applied from the terminal ileum (TI) to the sacculus rotundus (SR), across the ICJ and into the beginning of the large intestine at the cecum ampulla coli (AC). Orally propagating slow wave patterns in the SR did not entrain the TI. However, aborally propagating patterns from the TI were able to entrain the SR. Bioelectrical activity was recorded within the ICJ and AC, revealing complex interactions of slow waves, spike bursts, and bioelectrical quiescence. This suggests the involvement of myogenic coordination when regulating motility between the small and large intestines. Mean slow wave frequency between regions did not vary significantly (13.74-17.16 cycles/min). Slow waves in the SR propagated with significantly faster speeds (18.51 ± 1.57 mm/s) compared with the TI (14.05 ± 2.53 mm/s, P = 0.0113) and AC (9.56 ± 1.56 mm/s, P = 0.0001). Significantly higher amplitudes were observed in both the TI (0.28 ± 0.13 mV, P = 0.0167) and SR (0.24 ± 0.08 mV, P = 0.0159) within the small intestine compared with the large intestine AC (0.03 ± 0.01 mV). We hypothesize that orally propagating slow waves facilitate a motor-brake pattern in the SR to limit outflow into the ICJ, similar to those previously observed in other gastrointestinal regions.NEW & NOTEWORTHY Competing slow wave pacemakers were observed in the terminal ileum and sacculus rotundus. Prevalent oral propagation in the sacculus rotundus toward the terminal ileum potentially acts as a brake mechanism limiting outflow. Slow waves and periods of quiescence at the ileocecal junction suggest that activation may depend on the coregulatory flow and distention pathways. Slow waves and spike bursts in the cecum impart a role in the coordination of motility.

Anatomically-Specific, 3D-Printed Cradles Enable In Vivo Mapping of the Bioelectrical Activation across the Gastroduodenal Junction

Rhythmic bioelectrical 'slow waves' are a key regulatory mechanism underpinning digestion. The pyloric sphincter separates the independent slow wave and contractile behavior of the stomach and small intestine, while also regulating gastric emptying. In this study, we develop and validate anatomically-specific electrode cradles and analysis techniques in pigs, to map in vivo slow wave activation across this critical pylorus region for the first time. 3D printed electrode cradles were developed from reconstructions of magnetic resonance images, to accurately capture anatomical geometry. A low-pass Savitzky-Golay filter with an equivalent cut-off frequency of ~2 Hz was chosen as the optimal filter for analysis of both gastric and intestinal slow waves. Slow waves in the terminal antrum occurred with a frequency of (2.81±0.55) cycles per minute (cpm), velocity of (5.04 ± 0.29) mm s-1, and amplitude of (1.38±0.37) mV, before terminating at a zone of quiescence at the pylorus that was (41.22±7.4)nm wide. The proximal duodenal pacemaker initiated slow waves at a frequency of (18.1±0.80) cpm, velocity of (11.3±2.4) mm s-1, and amplitude of (0.376±0.027) mV. This work enables quantitative definitions of numerous physiological features of the in vivo pylorus region, including the electrically quiescent zone and duodenal pacemaker location. Clinical Relevance- This work establishes a novel method for in vivo measurement of bioelectrical slow wave activity of the pyloric region, which is a key target for physiological investigation and clinical intervention. In the future, the methods developed here may inform diagnosis and/or treatment of functional gastrointestinal disorders.