Outcomes of Short-length vs Standard-length Myotomy Using Per-Oral Endoscopic Myotomy (POEM) for Achalasia: A Randomized Controlled Pilot Study

BACKGROUND:

Achalasia is a disorder of esophageal dysmotility characterized by dysfunctional peristalsis and increased lower esophageal sphincter (LES) tone. Achalasia is further divided into three subtypes using high-resolution manometry (HRM) following the Chicago Classification. Type I, or classic achalasia, and Type II achalasia are both characterized by aperistalsis and increased LES tone and are thought to be a spectrum of the same disease process with Type II evolving into Type I.

Per-oral Endoscopic Myotomy (POEM) was first developed in 2008 as a treatment for achalasia. The technique involves a trans-oral approach with a flexible endoscope. An endoscopic incision is made in the esophagus and a submucosal tract is created towards the LES and gastric cardia to expose the underlying muscle of the LES and distal esophagus. The inner circular muscle is then dissected to create a myotomy and the tract is then closed with endoscopic clips. By creating a myotomy, the increased LES tone is improved, allowing food to pass into the stomach in order to relieve the dysphagia caused by achalasia.

Unlike Type III achalasia, where POEM myotomy length is determined by HRM, the standard myotomy length in Type I/Type II achalasia is typically 8 cm. The rationale for the 8 cm myotomy is derived from the Heller myotomy procedure which is a laparoscopic surgery approach in which the teaching has been to perform at least a 5 cm myotomy in the esophagus and an additional 2-3 cm myotomy in the gastric cardia. However, the purpose of the myotomy in POEM, is to reduce the LES tone. The clinical efficacy of the procedure comes from the myotomy of the high pressure zone within the LES, which is only 2-3cm in length. This is much shorter than the current standard POEM myotomy length. There are a few potential pitfalls regarding longer myotomy lengths in the esophagus and in the gastric cardia. A longer esophageal myotomy may result in esophageal wall strain in the area weakened by esophageal myotomy resulting in a blown out myotomy which is identified by the presence of a pseudo-diverticulum endoscopically. Longer gastric cardia myotomy has been thought to lead to an increased rate of gastroesophageal reflux in patients undergoing POEM. There are no data looking at shorter myotomy lengths in POEM for Type I and Type II achalasia. Our anecdotal experience at Northwestern when performing short myotomy during POEM has not resulted in any difference in procedural efficacy.

STUDY ENDPOINTS: