Peroral endoscopic myotomy (POEM) for the treatment of achalasia: a narrative review of recent advances

Introduction

Peroral endoscopic myotomy (POEM) was first introduced in 2010 by Inoue et al. as a treatment for achalasia (1), and since then more than 7,000 procedures have been performed worldwide (2). Before the advent of POEM, achalasia patients were traditionally treated with laparoscopic Heller myotomy (LHM), pneumatic dilation (PD) or botulinum toxin injection of the lower esophageal sphincter (LES). However, the introduction of POEM opened a new window in the treatment of achalasia with the hope of offering patients an endoscopic treatment alternative to the conventional laparoscopic myotomy. Similar to any other novel treatment, POEM has gone through an extensive examination in terms of safety and efficacy and has faced challenges such as increasing the risk of postprocedural gastroesophageal reflux disease (GERD) with several procedural modifications, and adjunct treatments so far have been proposed to mitigate the risk. In this article, we aim to provide an updated review of the data on the outcomes of POEM in the treatment of achalasia and focus on recent advances in this field. We present this article in accordance with the Narrative Review reporting checklist (available at https://ales.amegroups.com/article/view/10.21037/ales-24-2/rc).

Methods

A literature review was done using PubMed to find relevant articles regarding POEM in the treatment of achalasia through January 2024. Only English articles were included. The search terms included achalasia, peroral endoscopic myotomy, POEM, outcome, safety and efficacy. All study designs were considered. Data not exclusive to the diagnosis of achalasia were excluded. Two authors (O.S. and I.B.) reviewed and verified the relevance of the selected papers. A strong focus was given to the randomized clinical trials (RCTs) and meta-analyses in the selection process. The UptoDate was also reviewed and referenced as an adjunct source in this work (Table 1).

Initial assessment and patient selection

First, clinicians must confirm the diagnosis of achalasia. This is accomplished by taking a thorough clinical history, physical examination and data obtained from supportive paraclinical tests such as high-resolution esophageal manometry (classified based on Chicago classification version 4.0) and barium esophagram (3,4). Of note, functional lumen imaging probe (FLIP) can be used as another adjunct diagnostic tool. In fact, by measuring the cross-sectional area (CSA) of the esophagogastric junction (EGJ) and dividing it by FLIP bag pressure, the machine can calculate the EGJ distensibility index (EGJ-DI) which is abnormally low in patients with achalasia (5). This tool becomes specially more useful in establishing the diagnosis of achalasia when there is an inconclusive diagnosis in patients presenting with dysphagia or when there is a question whether the patient is suffering from EGJ outflow obstruction (EGJOO) or achalasia (4,6).

Patients with severe erosive esophagitis, liver cirrhosis with portal hypertension, significant coagulation disorders and those with prior treatments leading to submucosal fibrosis or disruption of esophageal mucosal integrity (e.g., receivers of radiation, radiofrequency ablation or endoscopic mucosal resection) will not be a candidate for POEM (3).

Preoperatively, we place patients on full liquid diet 48 hours prior and clear liquid diet for 24 hours and eventually fasting overnight to ensure appropriate clearance of the esophagus. In patients with sigmoid or dilated esophagus, longer fasting periods might be required to minimize the aspiration risk during the procedure. The procedure is generally performed under general anesthesia and patients will have endotracheal tube during the procedure (7).

Procedural site, equipment and electrosurgical generator (ESG)

POEM can be performed in an endoscopy suite or in an operating room. We perform our POEM procedures in an endoscopy suite. The equipment we use includes standard or therapeutic upper endoscope, regular or tapered tip transparent cap, carbon dioxide (CO₂) insufflator with flow regulation settings, electrosurgical knife (ideally with a dual function of injection and cutting/coagulation) with sufficient length to perform myotomy, ESG, injection needle, coagulation grasper for bleeding prophylaxis and control, hemostatic clips or endoscopic suturing device for incision closure, and a 14-gauge angiocath, a Veress needle or an equivalent to prevent or treat tension capnoperitoneum (8,9).

Some experts recommend using a high-definition therapeutic gastroscope for the procedure given the availability of large suction channel and a separate water jet channel (10). Nonetheless, its universal use is still debatable given the fact the high-definition therapeutic gastroscope is bulkier and may not have any significant advantage in retroflexion at cardia when examining the extent of dissection. A transparent distal cap is used for better visualization and CO₂ is used for insufflation (10).

ESG settings

We use ERBE VIO 300 as our preferred generator. For mucosal incision and myotomy, most endoscopists will prefer the use of Endocut I (effect 2–3, duration 1–2, cut interval 1–2) mode if using ERBE VIO 300 or ERBE VIO 3 ESG unit (ERBE, USA) or G2 35 W4 if using ConMed Beamer (ConMed, USA) for achieving a clean cut without any significant bleeding. For submucosal tunneling and to prevent any significant bleeding, spray coagulation (30 to 40 W) in both ERBE or ConMed ESG, Dry Cut mode or preciseSECT mode (5.5 to 6.7) using VIO 3, ERBE ESG are the most used coagulation settings. For hemostasis, soft coagulation (effect 5–8, 50 to 80 W) using ERBE ESG or gentle coagulation (40–60 W) using ConMed beamer ESG are the standard for hemostasis using coagulation grasper (9,11).

Technique

Mucosal incision

The first step of the POEM procedure is creating a submucosal bleb which is done using a mixture of 0.01% epinephrine and 2.25% indigo carmine in 0.9% saline (3). Once the esophageal mucosa is properly lifted, a 1.5–2 cm mucosal incision is made using an electrocautery knife. Subsequently the endoscope is steered to enter the submucosal space (Figure 1) (3).

Figure 1 Peroral endoscopic myotomy steps. (A) Clinical image showing injection; (B) clinical image showing mucosal incision; (C) clinical image showing submucosal tunneling; (D) clinical image showing myotomy; (E) clinical image showing closure.

Submucosal tunneling

Using the electrocautery knife and repeated water jet injections, the endoscopist tries to expand the submucosal space as they cut through the submucosal fibers and this process is continued until the target end of tunnel is reached. Typically, the submucosal tunnel is extended distally beyond the gastroesophageal junction (GEJ) into the gastric cardia by 2–3 cm (3) although studies have demonstrated that extending the gastric myotomy beyond 2.5 cm may increase the risk of esophagitis without improving the clinical efficacy (12). Extreme care should be taken to avoid injury to the overlying esophageal mucosa while creating the tunnel as with myotomy being performed in full thickness fashion (at least at the GEJ), an unsealed mucosotomy would be equivalent to esophageal perforation (Figure 1).

Myotomy

Starting about 2 cm distal to the mucosal incision site, the endoscopist initiates myotomy by dissecting the inner circular muscular layer of the esophageal wall. Once they reach the GEJ level the myotomy will be extended to the deeper longitudinal muscular layer (i.e., full thickness myotomy). However, it is important to mention that selective inner circular myotomy may be challenging given the possibility of longitudinal muscle layer separation especially at the LES level where the inner circular muscle layer becomes thinner (13). Myotomy can be done in an anterior (1–2 o’clock) or posterior (5–6 o’clock) position (14). With patient in the supine position, pooling of intraluminally-injected water will help the endoscopist to find the posterior esophageal wall properly and differentiate it from the anterior wall (Figure 1) (3).

Intraoperative impedance planimetry

An increasing number of centers are using intraoperative impedance planimetry to gauge the adequacy of myotomy. Using the available FLIP, the LES DI, CSA and compliance (C) can be measured after myotomy. With the intraoperative postmyotomy DI of both <2.9 mm²/mmHg and < double the premyotomy DI used as the criteria to extend myotomy, Holmstrom et al. found that the intraoperative use of FLIP can be associated with a significantly higher rate of clinical success (defined as Eckardt score ≤3) at 12-month follow-up (15). In another study, postmyotomy compliance ≥125 mm³/mmHg at 40 mL fill performed better than DI and CSA in predicting postoperative short-term clinical success (defined as Eckardt score <3), respectively at a median follow-up duration of 22 and 65 days (16). In all, despite these promising findings, further studies are warranted to find the optimal measurement variable(s)/target(s) associated with the best predictability value.

Closure

The last step in POEM procedure is closure of the mucosal incision. This is usually done using endoscopic clips to prevent leakage of luminal content into the mediastinum via submucosal tunnel. Endoscopic suturing versus tack closure are alternative closure options although at the cost of increasing the duration of procedure (Figure 1) (17).

Post procedure

Postprocedural care is different in different centers. In some centers, patients are kept nil per os (NPO) overnight, followed by obtaining a next day gastrographin esophagram, which if shows no leak, it will allow the patient to be started on a soft diet. Alternatively, if the procedure is uneventful, some centers have recently adopted a new approach of discharging patients after a 2-hour postprocedural observation in the endoscopy unit with recommendation to start clear liquid diet the same day and advance it to a soft diet the day after. Patients will usually remain on a soft diet for about 7–10 days before returning to a regular diet (3).

POEM clinical outcomes

The efficacy of POEM has been studied in meta-analyses reporting a clinical success rate (Eckardt score ≤3) of up to 98% for the procedure (18). In terms of complications, minor procedural adverse events such as capnoperitoneum/pneumoperitoneum, or subcutaneous emphysema can be seen in as high as around 31% of procedures. However, the rates of major adverse events including mediastinal leak, postoperative bleeding or mortality are as low as 0.3%, 1.1% and 0.09%, respectively (19).

Despite being considered effective and safe, similar to any other novel procedure, it is important to discuss the performance of POEM against its established surgical counterpart, i.e., LHM. Multiple studies have shown comparable efficacy of the two procedures. A systematic review and meta-analysis of 15 studies including a total of 1,213 patients found a lower Eckardt score in patients undergoing POEM as compared with Heller myotomy [pooled standardized mean difference: −0.58; 95% confidence interval (CI): −1.03 to −0.13] (20). Similar comparison was later performed in a non-inferiority trial by Werner et al. where 221 idiopathic achalasia patients with Eckardt score >3 without prior surgical treatment (those with endoscopic treatments were kept in the study) were randomized in a 1:1 fashion to receive either POEM or LHM + Dor’s fundoplication. Clinical success, defined as an Eckardt of ≤3 without the use of additional treatments at 2-year follow-up, were 83% and 81.7% (P=0.007 for noninferiority) for POEM and LHM, respectively. Serious adverse events occurred in 3 (2.7%) and 8 (7.3%) patients in POEM and LHM groups, respectively (absolute between-group difference: 4.6%; 95% CI: −1.1% to 10.4%) (21).

POEM achieved another important milestone as a salvage treatment for patients who experienced persistent or recurrent symptoms after undergoing LHM. In a RCT comparing POEM with PD, POEM was able to achieve a significantly higher clinical success rate (defined as Eckardt score of ≤3 and without any unscheduled re-treatment) at 1-year follow-up [62.2% versus 26.7%; relative risk (RR) for success, 2.33; 95% CI: 1.37–3.99]. Similarly, POEM was associated with a significantly better (lower) basal LES pressure, integrated relaxation pressure and barium column height after 2 and 5 minutes (P=0.034; P=0.002; P=0.005; P=0.015, respectively) (22).

Given the novelty of POEM procedure, decade-long data on the efficacy and safety of the POEM is scarce and has yet to be reported. However, a recent Japanese single-center retrospective cohort of 15 achalasia patients reported the reduction of Eckardt score in as high as 93.3% after at least 10 years of follow-up post-POEM. Of note, 4 patients (26.7%) required pneumatic balloon dilatation during the follow-up period. The median preprocedural Eckardt score was 8 (range, 3–12) and Eckardt scores 10 years after POEM ranged between 0–4. Postprocedural reflux was assessed using GERD questionnaire (GERDQ) and positive result (defined as GERDQ score of 8 or higher) was only seen in 1 (6.7%) patient. No adverse events were reported in this study (23).

Post-POEM GERD

One of the concerns following POEM procedure is the increased risk of GERD which is contrasted theoretically with LHM + fundoplication. Werner et al. RCT gives us objective evidence on the dynamics of postprocedural GER after POEM and LHM. In their RCT, the rate of post-procedure reflux esophagitis (any grade; graded based on Los Angeles Classification) was higher in POEM group (57%) as compared to LHM group (20%) at 3-month follow-up. However, the corresponding gap narrowed at 24-month follow-up with rates changing to 44% for POEM and 29% for LHM. In a similar way, the rate of high-grade esophagitis (defined as Los Angeles Classification of C or D) was 6% (6/100) versus 3% (3/96) at 3-month follow-up in POEM versus LHM groups, respectively. However, the corresponding gap narrowed at 24-month follow-up with rates changing to 5% (4/87) versus 6% (5/78), respectively (21). Such an opposite trend (decreasing the rate of reflux esophagitis with POEM as compared to increasing with LHM over time) could be explained to some extent by post-POEM GEJ healing, scar contraction, and remodeling as compared with post-LHM progressive loss of fundoplication efficacy (24). Importantly, esophageal pH monitoring showed similar rates of abnormal reflux at 3- and 24-month follow-up. The rates of low-dose proton pump inhibitor (PPI) use, however, was higher in POEM group as compared with LHM group at both 3- and 24-month follow-up points [30.6% (33/108) versus 27.6% (29/105) at 3 months, and 52.8% (56/106) versus 27.2% (28/103) at 24-month follow-up, respectively] (21).

Despite the substantial rate of post-POEM GERD, patients are generally managed medically with acid suppression using PPIs and the long-term GERD sequelae are rare and can be seen usually in patients with PPI noncompliance (24). Modayil et al. published a large prospective cohort study of 610 POEM patients with at least 66.6% having post-POEM pH study and 71.4% having upper gastrointestinal endoscopy done at a median of 4 months post-procedure. In that study, only five patients were found to have nondysplastic short-segment Barrett’s and five had peptic strictures (0.8%) at 3–6-year follow-up after POEM, all responded to serial dilations (mean 2.2; range, 1–4) and retreatment with PPI (25).

To reduce the risk of post-procedure GERD multiple POEM modifications have been proposed and studied which we will review here.

Myotomy position

As mentioned earlier, esophageal myotomy can be performed in anterior (1–2 o’clock) or posterior (5–6 o’clock) fashion. Given the heterogenous anatomical conformation of the LES, the major question will be which technique is better in terms of safety and efficacy.

Studies have shown that LES has an asymmetric structure with multiple components contributing to the creation of a high-pressure zone. Specifically, manometric three-dimensional images of LES high-pressure zone have shown the highest radial pressure generated toward the left posterior direction compatible with the area where the stronger and thicker sling fibers (more at the greater curve of the stomach) as compared to thinner and weaker semicircular clasp fibers (more at the lesser curve of the stomach) are located (26,27). Therefore, initially it was hypothesized that cutting the sling fibers, hence posterolateral POEM would be more effective in the treatment of dysphagia notably at the cost of an increase in the risk of postprocedural GERD (24). However, multiple studies including randomized controlled trials comparing anterior and posterior POEM approaches did not support this hypothesis. In a recent meta-analysis on a total of 19 studies (3 RCTs and 16 cohorts) including 1,261 patients, Jing et al. concluded that except for shorter procedure time with posterior approach, there was no significant differences between the anterior and posterior approaches in terms of clinical success (at 12 months or longer), adverse events, length of hospital stay, post-procedure GERD, length of total myotomy, and pooled difference of LES pressure, and Eckardt scores before and after the procedure (28).

Long versus short myotomy

Initially, POEM was performed with a 7–10 cm esophageal myotomy with an additional 2–3 cm gastric myotomy. However, the introduction of shorter esophageal myotomy raised the question of whether there is any clinical benefit in favor of long or short myotomy approach (29). A systematic review of 474 esophageal achalasia patients looked at this question and concluded that both approaches had similar efficacy and safety. However, as expected, the operation time was shorter with the short myotomy approach. Of note, the study found similar rates of reflux symptoms. However, the short myotomy approach was associated with a lower risk of reflux esophagitis on endoscopy (RR =0.61, 95% CI: 0.39–0.98), as well as a lower rate of pathologic esophageal acid exposure on pH study (RR =0.58, 95% CI: 0.36–0.94) (30). Recently, a single-center, single-blinded, non-inferiority RCT was done by Familiari et al. in which 200 patients with achalasia were randomized to receive short-POEM (8 cm total myotomy length) or long-POEM (13 cm total myotomy length) and followed up for 24 months. Clinical success (defined as Eckardt score of ≤3 at 24-month follow-up) was 98.0% versus 89.1% in short-POEM versus long-POEM group with the conclusion of non-inferiority of short-POEM as compared to long-POEM approach. Only one severe adverse event was reported in each group. The two study arms were similar in terms of postoperative GERD with the esophageal acid exposure >6% at 6-month follow-up being observed in 34.3% and 31.1% of patients in long- and short-POEM group, respectively. Therefore, the reduction of cutting length did not reduce the rate of postoperative GERD. As expected, however, the procedure time was significantly shorter with short-POEM approach (40 versus 50 minutes, for short- versus long-POEM, respectively; P<0.0001) (31). Finally, it is important to mention the benefit of short myotomy in reducing the risk of blown out myotomy (BOM). BOM is a potential complication of myotomy and is essentially a pseudodiverticulum that develops in the distal esophagus and can gradually enlarge to a level that impairs the esophageal emptying. In the in silico study of esophageal contractions, it has been suggested that short myotomy would be less likely to be associated with deformation at myotomy site, hence would portend a lower risk of BOM development (32). On the same basis, it has been suggested to consider short myotomy for type I and II as compared to type III where the myotomy would need to span the length of the spastic segment (33). However, further studies are needed to provide more objective evidence to support this hypothesis.

Oblique muscle fibers preservation

The possibility of injury to oblique muscles during posterior approach which may theoretically lead to an increased rate of postprocedural GER was the basis for the Tanaka et al. study in which the authors studied post-POEM GER at 3 months after POEM with oblique muscle preservation (procedure was done in 5 o’clock position) (34). The oblique muscle preservation procedure was designed using the concept of “two penetrating vessels” (TPVs) which penetrate through the circular muscle along the edge of the oblique muscle in the cardia and can be considered as an endoscopic landmark for the distal end of submucosal tunnel on the gastric side (35). In this study, the rate of post-POEM grade B or higher reflux esophagitis was significantly lower in patients who underwent oblique muscle preserving procedure using TPVs exposure during tunneling as compared to the other group in whom myotomy was done without TPVs exposure [31.3% (26/83) versus 58.1% (18/31), respectively; P=0.017] (34). Despite this promising result, a recent RCT done by Nabi et al. did not support the oblique (sling) muscle preservation hypothesis. In a study on 115 patients randomized in a 1:1 fashion to conventional myotomy (CM) versus oblique fiber-sparing (OFS) myotomy, the rate of grade B esophagitis or higher at 3 months post-procedure (primary outcome) was similar between the two groups (25.9% versus 31.6% for CM versus OFS, respectively; P=0.541). The rates of increased esophageal acid exposure >6%, high DeMeester scores, and the mean number of reflux episodes were also comparable between the two groups. The investigators did not find any significant differences between the two groups in terms of symptomatic reflux (defined as GERDQ score >7) or PPI use rate at 1-year follow-up (36).

Adjunct anti-reflux procedures

Several adjunct anti-reflux procedures performed either endoscopically or surgically have been proposed to reduce the rate of post-POEM reflux. For instance, transoral incisionless fundoplication (TIF) is an endoscopic anti-reflux procedure which can be done in the same session after POEM is completed. Currently, data regarding the TIF performance is scarce. In a retrospective study of 12 patients, the procedure was reported as technically successful in 100% of patients, and in seven patients in whom pH study was done, a significant reduction in the mean DeMeester score (P=0.05) and mean percentage acid exposure time (P=0.04) were observed (37).

Similarly, the single-session endoscopic fundoplication after POEM (POEM+F) has been proposed to prevent post-POEM GER. However, again, the data is still scarce regarding its performance and limited to a small prospective cohort of 25 patients showing 92% (23/25) technical success with abnormal esophageal acid exposure reported in 2/18 (11.1%) patients at 2 months (38). However, this combination is still in its infantile stages and not ready for prime time yet.

Strengths and limitations

This review focused on the most recent evidence regarding the clinical outcomes of POEM in the treatment of achalasia. The authors gave a strong focus to the high-quality studies including RCTs and meta-analyses. However, as a narrative review, there are inherent limitations to this work including but not limited to the authors’ subjective data extraction and lack of a predefined study selection criteria which may be grounds for potential biases.

Conclusions

After a decade of experience, POEM appears to have positioned itself as a safe and effective endoscopic treatment alternative to LHM. POEM is now regarded as first-line treatment for the management of achalasia and esophageal motility disorders in the appropriate clinical scenarios. However, there are always cons and pros to any procedure. One of the concerns around POEM has always been postprocedural GERD as compared to LHM + fundoplication. So far, procedural modifications of POEM have not been successful in tackling the post-POEM GERD problem. On the other hand, we have the emerging add-on procedures such as TIF or POEM+F which have yet to be examined in terms of safety and efficacy. The good news is that the post-POEM reflux is manageable medically with the long-term GERD sequelae being rare.

With the available data on favorable clinical success rate for POEM over around 4 years of follow-up, achalasia patients could be reassured about the procedure’s long-term efficacy. However, further studies are warranted before we can compare the efficacy and safety of POEM and LHM at the decade-long follow-up level.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://ales.amegroups.com/article/view/10.21037/ales-24-2/rc

Peer Review File: Available at https://ales.amegroups.com/article/view/10.21037/ales-24-2/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://ales.amegroups.com/article/view/10.21037/ales-24-2/coif). O.S. was already a shareholder of Medtronic and Pfizer. However, no payment or reimbursement from Medtronic or Pfizer have been received by Omid Sanaei for his contribution to this work. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Given the fact that complete anonymity was maintained in clinical pictures included in this review, obtaining written consent for publication of pictures would reasonably not be necessary.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Inoue H, Minami H, Kobayashi Y, et al. Peroral endoscopic myotomy (POEM) for esophageal achalasia. Endoscopy 2010;42:265-71. [Crossref] [PubMed]
2. Kim WH, Cho JY, Ko WJ, et al. Comparison of the Outcomes of Peroral Endoscopic Myotomy for Achalasia According to Manometric Subtype. Gut Liver 2017;11:642-7. [Crossref] [PubMed]
3. Khashab MA. Peroral endoscopic myotomy (POEM). In: UpToDate; 2024. Available online: https://www.uptodate.com/contents/peroral-endoscopic-myotomy-poem?search=poem&source=search_result&selectedTitle=1%7E16&usage_type=default&display_rank=1 (accessed on January 04, 2024).
4. Yadlapati R, Kahrilas PJ, Fox MR, et al. Esophageal motility disorders on high-resolution manometry: Chicago classification version 4.0 Neurogastroenterol Motil 2021;33:e14058. [Crossref] [PubMed]
5. Triggs JR, Carlson DA, Beveridge C, et al. Functional Luminal Imaging Probe Panometry Identifies Achalasia-Type Esophagogastric Junction Outflow Obstruction. Clin Gastroenterol Hepatol 2020;18:2209-17. [Crossref] [PubMed]
6. Bredenoord AJ, Rancati F, Lin H, et al. Normative values for esophageal functional lumen imaging probe measurements: A meta-analysis. Neurogastroenterol Motil 2022;34:e14419. [Crossref] [PubMed]
7. Jawaid S, Draganov PV, Yang D. Esophageal POEM: the new standard of care. Transl Gastroenterol Hepatol 2020;5:47. [Crossref] [PubMed]
8. Inoue H, Ikeda H, Kudo SE. Peroral endoscopic myotomy for esophageal achalasia: Indication and technique. Techniques in Gastrointestinal Endoscopy 2013;15:131-4. [Crossref]
9. ASGE Technology Committee. Per-oral endoscopic myotomy (with video). Gastrointest Endosc 2016;83:1051-60. [Crossref] [PubMed]
10. Khashab MA, Messallam AA, Saxena P, et al. Jet injection of dyed saline facilitates efficient peroral endoscopic myotomy. Endoscopy 2014;46:298-301. [PubMed]
11. Jawaid S, Keihanian T, Khalaf M, et al. Settings of a novel electrosurgical generator to enable efficient and safe submucosal endoscopic procedures. Endosc Int Open 2023;11:E743-51. [Crossref] [PubMed]
12. Grimes KL, Bechara R, Shimamura Y, et al. Gastric myotomy length affects severity but not rate of post-procedure reflux: 3-year follow-up of a prospective randomized controlled trial of double-scope per-oral endoscopic myotomy (POEM) for esophageal achalasia. Surg Endosc 2020;34:2963-8. [Crossref] [PubMed]
13. Hasan A, Low EE, Fehmi SA, et al. Evolution and evidence-based adaptations in techniques for peroral endoscopic myotomy for achalasia. Gastrointest Endosc 2022;96:189-96. [Crossref] [PubMed]
14. Khashab MA, Sanaei O, Rivory J, et al. Peroral endoscopic myotomy: anterior versus posterior approach: a randomized single-blinded clinical trial. Gastrointest Endosc 2020;91:288-297.e7. [Crossref] [PubMed]
15. Holmstrom AL, Campagna RAJ, Cirera A, et al. Intraoperative use of FLIP is associated with clinical success following POEM for achalasia. Surg Endosc 2021;35:3090-6. [Crossref] [PubMed]
16. Amundson JR, Wu H, VanDruff V, et al. Esophagogastric junction compliance on impedance planimetry (EndoFLIP™) following peroral endoscopic myotomy (POEM) predicts improvement in postoperative eckardt score. Surg Endosc 2023;37:1493-500. [Crossref] [PubMed]
17. Pescarus R, Shlomovitz E, Sharata AM, et al. Endoscopic suturing versus endoscopic clip closure of the mucosotomy during a per-oral endoscopic myotomy (POEM): a case-control study. Surg Endosc 2016;30:2132-5. [Crossref] [PubMed]
18. Akintoye E, Kumar N, Obaitan I, et al. Peroral endoscopic myotomy: a meta-analysis. Endoscopy 2016;48:1059-68. [Crossref] [PubMed]
19. Patel K, Abbassi-Ghadi N, Markar S, et al. Peroral endoscopic myotomy for the treatment of esophageal achalasia: systematic review and pooled analysis. Dis Esophagus 2016;29:807-19. [Crossref] [PubMed]
20. Park CH, Jung DH, Kim DH, et al. Comparative efficacy of per-oral endoscopic myotomy and Heller myotomy in patients with achalasia: a meta-analysis. Gastrointest Endosc 2019;90:546-558.e3. [Crossref] [PubMed]
21. Werner YB, Hakanson B, Martinek J, et al. Endoscopic or Surgical Myotomy in Patients with Idiopathic Achalasia. N Engl J Med 2019;381:2219-29. [Crossref] [PubMed]
22. Saleh CMG, Familiari P, Bastiaansen BAJ, et al. The Efficacy of Peroral Endoscopic Myotomy vs Pneumatic Dilation as Treatment for Patients With Achalasia Suffering From Persistent or Recurrent Symptoms After Laparoscopic Heller Myotomy: A Randomized Clinical Trial. Gastroenterology 2023;164:1108-1118.e3. [Crossref] [PubMed]
23. Onimaru M, Inoue H, Fujiyoshi Y, et al. Long-term clinical results of per-oral endoscopic myotomy (POEM) for achalasia: First report of more than 10-year patient experience as assessed with a questionnaire-based survey. Endosc Int Open 2021;9:E409-16. [Crossref] [PubMed]
24. Sharma P, Stavropoulos SN. Is peroral endoscopic myotomy the new gold standard for achalasia therapy? Dig Endosc 2023;35:173-83. [Crossref] [PubMed]
25. Modayil RJ, Zhang X, Rothberg B, et al. Peroral endoscopic myotomy: 10-year outcomes from a large, single-center U.S. series with high follow-up completion and comprehensive analysis of long-term efficacy, safety, objective GERD, and endoscopic functional luminal assessment. Gastrointest Endosc 2021;94:930-42. [Crossref] [PubMed]
26. Stein HJ, Liebermann-Meffert D, DeMeester TR, et al. Three-dimensional pressure image and muscular structure of the human lower esophageal sphincter. Surgery 1995;117:692-8. [Crossref] [PubMed]
27. Friedel D, Modayil R, Iqbal S, et al. Per-oral endoscopic myotomy for achalasia: An American perspective. World J Gastrointest Endosc 2013;5:420-7. [Crossref] [PubMed]
28. Jing W, Luo X, Yang J, et al. An Updated Meta-analysis: Similar Clinical Efficacy of Anterior and Posterior Approaches in Peroral Endoscopic Myotomy (POEM) for Achalasia. Gastroenterol Res Pract 2022;2022:8357588. [Crossref] [PubMed]
29. Wang J, Tan N, Xiao Y, et al. Safety and efficacy of the modified peroral endoscopic myotomy with shorter myotomy for achalasia patients: a prospective study. Dis Esophagus 2015;28:720-7. [Crossref] [PubMed]
30. Ghazaleh S, Beran A, Khader Y, et al. Short versus standard peroral endoscopic myotomy for esophageal achalasia: a systematic review and meta-analysis. Ann Gastroenterol 2021;34:634-42. [PubMed]
31. Familiari P, Borrelli de Andreis F, Landi R, et al. Long versus short peroral endoscopic myotomy for the treatment of achalasia: results of a non-inferiority randomised controlled trial. Gut 2023;72:1442-50. [Crossref] [PubMed]
32. Halder S, Acharya S, Kou W, et al. Myotomy technique and esophageal contractility impact blown-out myotomy formation in achalasia: an in silico investigation. Am J Physiol Gastrointest Liver Physiol 2022;322:G500-12. [Crossref] [PubMed]
33. Triggs JR, Krause AJ, Carlson DA, et al. Blown-out myotomy: an adverse event of laparoscopic Heller myotomy and peroral endoscopic myotomy for achalasia. Gastrointest Endosc 2021;93:861-868.e1. [Crossref] [PubMed]
34. Tanaka S, Toyonaga T, Kawara F, et al. Novel per-oral endoscopic myotomy method preserving oblique muscle using two penetrating vessels as anatomic landmarks reduces postoperative gastroesophageal reflux. J Gastroenterol Hepatol 2019;34:2158-63. [Crossref] [PubMed]
35. Tanaka S, Kawara F, Toyonaga T, et al. Two penetrating vessels as a novel indicator of the appropriate distal end of peroral endoscopic myotomy. Dig Endosc 2018;30:206-11. [Crossref] [PubMed]
36. Nabi Z, Chandran V, Basha J, et al. Conventional versus oblique fiber-sparing endoscopic myotomy for achalasia cardia: a randomized controlled trial (with videos). Gastrointest Endosc 2024;99:1-9. [Crossref] [PubMed]
37. Brewer Gutierrez OI, Chang KJ, Benias PC, et al. Is transoral incisionless fundoplication (TIF) an answer to post-peroral endoscopic myotomy gastroesophageal reflux? A multicenter retrospective study. Endoscopy 2022;54:305-9. [Crossref] [PubMed]
38. Bapaye A, Dashatwar P, Dharamsi S, et al. Single-session endoscopic fundoplication after peroral endoscopic myotomy (POEM+F) for prevention of post gastroesophageal reflux - 1-year follow-up study. Endoscopy 2021;53:1114-21. [Crossref] [PubMed]