Normal and abnormal electrical propagation in the small intestine

Abstract

As in other muscular organs, small intestinal motility is determined to a large degree by the electrical activities that occur in the smooth muscle layers of the small intestine. In recent decades, the interstitial cells of Cajal, located in the myenteric plexus, have been shown to be responsible for the generation and propagation of the electrical impulse: the slow wave. It was also known that the slow waves as such do not cause contraction, but that the action potentials ('spikes') that are generated by the slow waves are responsible for the contractions. Recording from large number of extracellular electrodes simultaneously is one method to determine origin and pattern of propagation of these electrical signals. This review reports the characteristics of slow wave propagation through the intestinal tube, the occurrence of propagation blocks along its length, which explains the well-known decrease in frequency, and the specific propagation pattern of the spikes that follow the slow waves. But the value of high-resolution mapping is highest in discovering and analysing mechanisms of arrhythmias in the gut. Most recently, circus movements (also called 're-entries') have been described in the small intestine in several species. Moreover, several types of re-entries have now been described, some similar to what may occur in the heart, such as functional re-entries, but others more unique to the small intestine, such as circumferential re-entry. These findings seem to suggest the possibilities of hitherto unknown pathologies that may be present in the small intestine.

Intra‐operative high‐resolution mapping of slow wave propagation in the human jejunum: Feasibility and initial results

“…Focal pacemaker patterns were also similar to previous descriptions in the canine and porcine intestine . Re‐entrant patterns were not observed in this study, unlike mapping studies in animal models, but the lack of re‐entry may have been due to the limited number of recordings and/or duration of mapping in the intra‐operative setting. Re‐entry is theoretically possible in the human small intestine and may prove a notable target for future investigations.…”

“…These historic studies developed a foundational understanding of human small intestinal slow wave activity, but were restricted to single or sparse electrode recordings that limited analyses to amplitude and/or frequency‐based approaches, precluding spatial analysis of slow wave propagation. There have since been very few detailed human studies of small intestine slow wave activity, and several important principles still await clarification, including the spatiotemporal quantification of human pacesetting, slow wave velocity profiles, and patterns of intestinal propagation dynamics …”

“…An important advance for investigating slow wave activity has been the translation of high‐resolution (HR; multi‐electrode) mapping to the gut, whereby spatially dense arrays of many electrodes enable slow wave activation to be accurately defined in spatiotemporal detail . High‐resolution mapping has already been productively applied in many studies investigating slow wave and spike activity in the small intestine of animal models, and in the human stomach, but the technique has not yet been applied to the human small intestine.…”

Dynamic slow‐wave interactions in the rabbit small intestine defined using high‐resolution mapping

“…Small intestinal motility is coordinated in part by rhythmic underlying bioelectric events known as slow waves . The interstitial cells of Cajal (ICC) are present as a syncytium within the smooth muscle and generate and mediate slow waves in the intestinal musculature .…”

“…To date, HR mapping has been applied to several studies investigating the slow‐wave characteristics in the small intestine of animals and humans . It has shown that multiple pacemakers (ie, sites of slow‐wave initiation) exist along the intestine and the location of these pacemakers can move over . Further studies have revealed the presence of dysrhythmic activity during the in vivo state and during diabetic states .…”