Clinical Course of Blown‐Out Myotomy After Peroral Endoscopic Myotomy in Patients With Achalasia‐Related Esophageal Motility Disorders

Objectives Blown‐out myotomy (BOM) is a diverticular‐like change that develops at the myotomy site after surgical or peroral endoscopic myotomy (POEM). This study aimed to elucidate BOM's incidence, clinical course, and risk factors after POEM. Patients and Methods This retrospective, single‐center study evaluated patients who underwent POEM for achalasia or non‐achalasia motility disorders at our institution between April 2015 and March 2023. Endoscopic grade at surveillance was classified as Grade 0, no diverticular‐like changes; Grade 1, mild diverticular‐like changes; Grade 2, obvious diverticular‐like changes with a septum; and Grade 3, obvious diverticular‐like changes with food retention. Grades 2 and 3 were defined as endoscopic BOM. The incidence and clinical course of BOM were evaluated using the Kaplan–Meier method, and factors associated with BOM were assessed using univariate analysis. Results Of 598 patients, 28 (4.7%) developed BOM during the study period. The 1‐, 2‐, and 5‐year incidence rates of endoscopic BOM were 3.1%, 6.6%, and 8.1%, respectively. Progression of BOM grade mainly occurred between 1 and 3 years after POEM and then plateaued in the Kaplan–Meier curve. Male sex (71.4% vs. 48.1%, p = 0.019), a thin esophageal muscle layer during myotomy (67.9% vs. 40.4%, p = 0.005), and clinical reflux after POEM (78.6% vs. 36.8%, p < 0.001) were significantly associated with BOM. Conclusions The incidence of BOM after POEM is low. BOM grade progression occurred within 3 years after POEM. Male sex, a thin esophageal muscle layer, and clinical reflux were associated with BOM.