Prospective Evaluation of Per-Oral Endoscopic Myotomy (POEM) of the Lower Esophageal Sphincter for the Treatment of Esophageal Swallowing Disorders

Currently the most commonly performed definitive treatment for symptomatic esophago-gastric junction outflow obstruction is a laparoscopic esophageal myotomy (LEM). In this procedure the outer longitudinal and inner circular muscle fibers of the distal esophagus and proximal stomach are divided, releasing the spasm and resulting in an open lumen. Although this procedure is effective in relieving troubles swallowing and in improving esophageal emptying, it is often accompanied by the development of GERD (as the muscle division results in incompetence of the antireflux barrier, the lower esophageal sphincter). For this reason a laparoscopic esophageal myotomy is most often accompanied by a fundoplication, in which part of the fundus of the stomach is folded around the distal esophagus and sutured in place, recreating a flap-valve mechanism. (It is best to perform this at the time of the laparoscopic myotomy as reoperation in that area is difficult). The fundoplication however may be imperfect, and may result in some degree of outflow obstruction itself or fail to control reflux. LEM results in 80% to 90% global patient satisfaction; but 10-20% continue to experience moderate dysphagia and 10-35% will have GERD by esophageal pH testing.

Others have evaluated the possibility of surgically dividing the muscle fibers from within the esophagus, using an endoscope rather than a laparoscope, in an animal model. The first human experience was reported in Japan using a per-oral endoscope to (a) incise the mucosa in the proximal esophagus as an entry point, (b) create a submucosal tunnel downwards, (c) perform an esophageal myotomy of the distal esophageal circular muscle, and (d) close the mucosal entry site with clips. The creation of the submucosal tunnel for some distance before the myotomy is a safety measure, so that should the mucosal closure fail, native tissues will appose and help seal any leak (rather like the Z-entry for a thoracentesis). Subsequent to this initial report, multiple single-arm studies have reported that the technique is safe and is associated with excellent medium-term relief of dysphagia..

In the POEM technique no fundoplication is performed. By the endoscopic creation of an esophageal submucosal tunnel the inner circular muscle layer could be easily visualized and in contrast to conventional laparoscopic esophageal myotomy, the authors described the division of only this inner circular esophageal muscle layer leaving the outer longitudinal muscle layer intact. The distal esophagus is exposed in LEM, hence disrupting the attachments to the diaphragm. These attachments contribute to the overall antireflux mechanism. It is hypothesized that by only dividing the inner circular muscle, and not disrupting the contribution of the outer longitudinal muscle or the diaphragmatic attachments to the antireflux mechanism, POEM may not have the same potential for reflux as a LEM. If this is the case then an antireflux procedure may not be needed after the POEM procedure.