What role does the submucosa play in the pathophysiology and treatment of achalasia? An analysis of impedance planimetry during POEM.

BACKGROUND: It is thought the therapeutic benefit of per-oral endoscopic myotomy (POEM) in the treatment of esophageal dysmotility disorders is from longitudinal myotomy creation, but it is unknown if the submucosa contributes to the pathophysiology. This study investigates if submucosal tunnel (SMT) dissection alone contributes to POEM's luminal changes as measured by EndoFLIP. METHODS: A single-center, retrospective review of consecutive POEM cases from June 1, 2011 to September 1, 2022 with intraoperative luminal diameter and distensibility index (DI) data as measured by EndoFLIP. Patients with diagnoses of achalasia or esophagogastric junction outflow obstruction were grouped by those with pre-SMT and post-myotomy measurements (Group 1) and those with a third measurement post-SMT dissection (Group 2). Outcomes and EndoFLIP data were analyzed using descriptive and univariate statistics. RESULTS: There were 66 patients identified, of whom 57 (86.4%) had achalasia, 32 (48.5%) were female, and median pre-POEM Eckardt score was 7 [IQR: 6-9]. There were 42 (64%) patients in Group 1, and 24 (36%) patients in Group 2, with no differences in baseline characteristics. In Group 2, SMT dissection changed luminal diameter by 2.15 [IQR: 1.75-3.28]cm, which comprised 38% of the median 5.6 [IQR: 4.25-6.3]cm diameter of complete POEM change. Similarly, the median post-SMT change in DI of 1 [IQR: 0.5-1.2]units comprised 30% of the median 3.35 [2.4-3.98]units overall change in DI. Post-SMT diameters and DI were both significantly lower than the full POEM. CONCLUSIONS: Esophageal diameter and DI are significantly affected by SMT dissection alone, though not equaling the magnitude of diameter or DI changes from full POEM. This suggests that the submucosa does play a role in achalasia, presenting a future target for refining POEM and developing alternative treatment strategies.