An update on endoscopic treatment for achalasia: From per oral endoscopic myotomy to endolumenal functional lumen imaging probe

Abstract

Traditional endoscopic treatment of achalasia includes endoscopic local injection of botulinum toxin into the lower esophageal sphincter (LES) muscle, endoscopic balloon dilations. Injection of botulinum toxin is safe and only may be associated with minor complications but the main drawback is the short duration of maintaining successful treatment which lasts only for 9 months or less. It is therefore recommended for elderly patients with concomitant comorbid disease who are at high risks to receive other treatment modalities. On the other hand, conventional fluoroscopy-guided or endoscopeguided pneumatic dilations (PD)were reported to have unsatisfactory recurrences in large-scale long-term follow-up investigations although some may claim that long-term remission could be achieved by under the “on-demand” strategy with repeated PD based on symptom recurrence. In addition, although the incidence rate of perforation was approximately 0% to 2% but could be disaster if not properly handled. In the past, surgery is always an encouraging treatment of choice because of the reported higher long-term results with myotomy of the LES and a concomitant antireflux procedure in minimally invasive laparoscopic Heller myotomy (LHM) to reduce postoperative reflux. The utilization of per oral endoscopic myotomy (POEM) has changed the backdrop for the treatment of achalasia. The story changes with the emergence of POEM which was first reported by Pasricha et al in porcine models and was then promoted by Inoue et al for patient with achalasia in real world clinical practice. Basically, it was introduced as a natural orifice transluminal endoscopic surgery (NOTES) with incisionless with good efficacy with only minor morbidity. POEM can be proficient through a submucosal tunnel at the half of the esophageal circumference, with myotomy beginning 3 cm distal to entry and approximately 7 cm above the gastroesophageal junction by dissecting the inner circular muscle layer of the esophagus and divided via a small proximal opening of the esophageal mucosa. Once the myotomy is completed by POEM it opening is properly clipped. This is in contrast to LHM by most surgeons who generally choose a length of myotomy of 4-5 cm into the esophagus (shorter than the length dissected by POEM) and 2-3 cm into the stomach. One other advantage of POEM is that patients with advanced disease and severe fibrosis can also be successfully performed by this endoscopic skill. In this circumstance, it could be harder for the surgeons to extend the length of the myotomy to the thoracic esophagus by LHM. Up to now, reports on good short-term results were good without serious complications. The most recent mid to long term report published by McKay et al revealed that the long-term overall success was achieved in 79% of patients (80% of achalasia patients, 67% of diffuse esophageal spasm patients) during the mean follow-up duration was 75 months. Obviously, more evidences on long-term followup results and complications are still needed in order to validate of the long-term safety and durability, especially large scale prospective studies. The introduction of high-resolution manometry is very crucial gastrointestinal motility evolution. This device can diagnose achalasia and identify the clinical subtype of achalasia and predict the treatment outcome. There are currently three types of achalasia in real world clinical classification. Based on current evidence, POEM is a promising strategy and has been reportedly effective against all three subtypes of achalasia. Emerging evidences have shown that type I and II achalasia respond well to POEM, LHM, and PD while most studies have shown that type III achalasia, responds better to POEM than LHM, and PD. The reported clinical remission rates of POEM in achalasia patients are also cheering (81% to 100%)with onlyminor adverse events even among those who failed previous treatments. However, it is worthmentioning that POEM is a very technically demanding procedure even for an experienced endoscopist. There are important key factors to a successful procedure which includes the usage of operating devices such as a triangular tip knife, an electrosurgical current other than spray coagulation sigmoid-type esophagus and the endoscopist experience level of less than 20 cases tominimize the occurrence of adverse events. The most concerned complication of POEM is the occurrence of gastroesophageal reflux disease (GERD). Reports have showed that higher incidence of GERD were encountered after POEM when compared with laparoscopic Heller Received: 11 January 2021 Accepted: 31 January 2021