Esophageal longitudinal muscle contraction: Another component of transient lower esophageal sphincter relaxation (tLESR)?

Abstract

Background. Longitudinal muscle contraction is an integral part of primary peristalsis (PP). This study aimed to characterize longitudinal muscle contraction during tLESR. Method. 8 healthy subjects (4 males, 26_+1 yrs) had metal clips endoscopically affixed at O, +3, and + 8 cm relative to the squamocolumnar junction (SCJ), defining two distal esophageal segments. Axial clip movement was assessed by concurrent manometry and fluoroscopy during LES relaxation with PP, secondary peristalsis (SP) induced by esophageal air injection, and tLESR induced by gastric distension with 800ml of air through the manometric catheter. Segment lengths were measured at 0.5 s intervals during relaxation and the percentage change relative to the initial length was calculated. If a tLESR ended with PP or SP, only the earlier period was used. Maximal SCJ upward movement was measured at end expiration. Results (Table). Although significant shortening was evident in both segments with all three types of LES relaxation, the magnitude of distal segment shortening was least with tLESR and greatest with PP. On the other hand, the maximal degree of overall esophageal shortening durin 0 tLESR, evident by the SCJ excursion, was similar to that during PP suggesting a global effect on the esophagus. In three instances, the moment of LES opening and gas reflux was optimally imaged and SCJ excursion was 0.3-+0.1 cm prior to LES opening and 1.4-+0.7 cm immediately after the occurrence of an esophageal common cavity. Conclusions. Although the segmental pattern appears to be distinct from that seen during PP or SP, esophageal shortening (likely attributable to longitudinal muscle contraction) occurs during tLESR. However, elevation of the LES did not precede LES opening during tLESR suggesting that this is nut part of the opening mechanism, but rather a consequence of the esophageal distension induced by gas reflux.