Achalasia is the most common esophageal motility disorder worldwide, with an annual incidence of 1.6 per 100'000 individual and prevalence of 10 per 100'000 population. The incidence of achalasia has been dramatically rising over the past decade. A study conducted in Chicago suggested that over the 10 years from 2004 to 2014, the incidence and prevalence of achalasia were two- to threefold greater than estimates would have predicted. The likely explanation to the rise in incidence is an increased awareness of this condition and widespread availability of accurate diagnostic test with high resolution manometry. The cardinal features of achalasia include failed relaxation of lower esophageal sphincter and absent esophageal peristalsis. Owing to the benign nature of the disease, patients suffering from it would experience longstanding debilitating symptoms of dysphagia, chest pain, regurgitation, resulting in poor quality of life. In the past, laparoscopic Heller's cardiomyotomy with partial fundoplication and endoscopic pneumatic dilatation were considered as treatment options for achalasia.

In the past 10 years, per-oral endoscopic myotomy (POEM) has emerged as the incisionless minimally invasive endoscopic treatment of choice for achalasia. This Natural Orifice Transluminal Endoscopic Surgical (NOTES) technique involves mucosal incision and creation of a submucosal tunnel in the distal esophagus down to gastric cardia, followed by esophageal and gastric myotomy. Since the procedure was first reported by Inoue H, et al in 2010, it has seen worldwide acceptance as first-line therapy. POEM has been associated with excellent relief of dysphagia and achalasia-related symptoms with a low and acceptable adverse event rate of 0.5%. In a previous randomised controlled trial, POEM had a higher treatment success rate than pneumatic dilatation. When compared with laparoscopic Heller's cardiomyotomy, POEM was associated with at least similar treatment efficacy and a trend towards reduced short term adverse event. POEM could perform even better than surgical myotomy in patients with type III achalasia.

The main limitation of POEM is the incidence of gastroesophageal reflux disease (GERD) post-POEM. Kumbhari et al. looked at rates of GERD after POEM on patients who underwent subsequent objective pH testing. A total of 282 patients were included in this analysis from multiple centers in America, Asia, and Europe. About 58% of patients had objective evidence of abnormal acid exposure, with 23% showing evidence of esophagitis. More concerning, however, was that 60% of the patients with GERD were completely asymptomatic. This highlights an important issue at hand that many patients, either related to the propensity of GERD to be silent or the nature of achalasia to develop and insensate esophagus, do not report symptoms while showing high rates of GERD. POEM has been found to be consistently associated with higher rate of GERD than conventional Heller's cardiomyotomy or pneumatic dilatation across multiple studies.

Supported by evidence demonstrating the efficacy of partial fundoplication during Heller's operation, there has been a significant interest in performing fundoplication after POEM during the same session to prevent the development of post-POEM GERD. Inoue et al. pioneered the technique of POEM-F that mimics the surgical Dor (anterior partial fundoplication) procedure. In the pilot study, technical success was achieved in all 21 patients, and all but one had an intact fundoplication wrap on upper endoscopy at a 1-month follow-up. Four more studies conducted in Japan and India have reported good early outcomes with POEM-F (Technical success of 85-100%) for achalasia. No severe adverse event has been reported in these studies which reiterates the safety of this procedure. In the longest follow-up study on POEM-F, GERD diagnosed by an abnormal esophageal acid exposure was seen in 11.1% of the 21 cases at one-year follow-up: comparable (8.8%) to a large meta-analysis of 4871 Heller's cardiomyotomy with fundoplication procedures.

To date, no prospective multicenter randomised study has been conducted to compare the efficacy of POEM-F with conventional POEM in reducing post-procedure GERD. Therefore, in this study, the investigators aim to evaluate the of POEM-F in patients with achalasia through an international multicenter randomized controlled trial.