Per-oral endoscopic myotomy (POEM) represents the prototype for successful natural orifice surgery; an incisionless, endoscopic approach combined with the precision of a surgical myotomy. Since the initial description by Haru Inoue of the procedure in 2008 and publication of his initial results in 2010, POEM has been adopted at high-volume esophageal centers around the world [1]. The procedure is being performed by both surgical endoscopists and interventional gastroenterologists. This chapter reviews the characteristics and initial experience of early POEM operators, the existing literature regarding the learning curve for POEM, and initial outcomes in published series.

The early global POEM experience was summarized in the International POEM Survey (IPOEMS) [2] and formed the basis for a white paper published by the American Society for Gastrointestinal Endoscopy and the Society of American Gastrointestinal and Endoscopic Surgeons. The survey included initial results from the 16 centers around the world that had performed >30 procedures as of July 2012, when the survey was conducted. IPOEMS confirmed the high success and low complication rates initially reported by Inoue, in addition to outlining the training and techniques of the 25 POEM operators (14 surgeons and 11 gastroenterologists). The majority of the respondents reported having experience with either endoscopic submucosal dissection (ESD) or natural orifice translumenal endoscopic surgery (NOTES) prior to introducing POEM at their institutions. Overall, the operative technique described by the participating centers was similar to that initially described by Inoue [1]: submucosal access through a longitudinal mucosotomy ~10 cm above the squamocolumnar junction, creation of a submucosal tunnel extending 4–5 cm onto the stomach, performance of a selective myotomy of the inner, circular muscle fibers, and finally closure of the mucosotomy with hemostatic clips. Minor variations were reported in instrumentation choice and position on the esophageal wall for the creation of the mucosotomy and entry into the submucosal space. Most centers perform POEM with the patient supine and create the submucosal tunnel and subsequent myotomy in the anterior or right-anterior aspect of the esophageal lumen (the 12–2 o’clock position), with two centers reporting the use of a right-posterior approach (the 5 o’clock position). Ten of the 16 centers included in the survey contributed initial outcomes data for treatment efficacy, in terms of symptomatic relief as assessed by the Eckardt score and objectively in terms of decrease in lower esophageal sphincter (LES) pressure and improved bolus clearance on timed barium esophagram (TBE), and the safety of the procedure. All of the centers reported symptomatic relief in at least 80% of patients, with all but two centers reporting >93% efficacy. Significant decreases were also seen in LES pressure and column height at 5 min on TBE. Adverse events were rare in the combined early experience of the survey participants with rates of postoperative leak and bleeding of 0.2% and 1%, respectively [2].

Retrospective studies of the POEM learning curve at single centers have evaluated a variety of different components of the procedure [3–6]. Aspects that have been studied include: overall procedure duration, duration of procedure per centimeter of myotomy, time to complete the four main steps of submucosal access, tunnel creation, myotomy and mucosotomy closure as well as the rate of inadvertent mucosotomy creation and number of clips required to close the mucosotomy.

Kurian and colleagues reported the intraoperative learning curve observed during the first 40 cases performed by a surgeon with extensive endoscopic experience and by minimally invasive surgery fellows [3]. The senior author (Swanström) performed the first 16 cases and then transitioned to increasing participation by two fellows. Based on decreases in total procedure length, reduced variability in minutes/cm of myotomy, and reduction in the rate of inadvertent mucosotomies, the authors reported a learning curve of approximately 20 cases; their presented data, however, indicate that the last inadvertent mucosotomy during the cases performed by the senior surgeon occurred during case 14, with no additional events over the next seven cases.

Patel and associates at Winthrop University Hospital, in the largest series to date [4], reported the learning curve for a gastroenterologist with expertise in advanced endoscopy including endoscopic submucosal dissection (ESD) (Stavropoulos). In their study, the authors used cumulative sum (CUSUM) analysis and found efficiency to be achieved after 40 cases and mastery after 60 cases.