The Effect of Incremental Distal Gastric Myotomy Lengths On Intraoperative EGJ Distensibility During POEM for Achalasia

Ezra N Teitelbaum, MD, MEd, Joel M Sternbach, MD, Rym El Khoury, MD, Nathaniel J Soper, MD, John E Pandolfino, MD, Peter J Kahrilas, MD, Zhiyue Lin, MS, Eric S Hungness, MD. Northwestern University

Introduction: Limited data exist regarding the optimal distal gastric myotomy length in operations for treatment of achalasia. The functional lumen imaging probe (FLIP) is a novel diagnostic tool that measures esophagogastric junction (EGJ) distensibility, a metric that has been shown to be predictive of postoperative symptomatic outcomes after surgical myotomy. In this study, we used intraoperative FLIP to measure distensibility changes resulting from variable distal gastric myotomy lengths during peroral esophageal myotomy (POEM), a novel endoscopic operation for the treatment of achalasia.

Methods: EGJ distensibility (defined as the minimum cross-sectional area at the EGJ divided by intra-balloon pressure) was measured with FLIP (at a distension volume of 40ml) in patients undergoing POEM for the treatment of type I and type II achalasia, confirmed by high-resolution manometry. FLIP measurements were taken at baseline (after induction of anesthesia) and after each operative step. Additionally, each patient’s myotomy was performed in four incremental stages, advancing from proximal to distal: 1) An esophageal component, from 6cm proximal to the squamocolumnar junction (SCJ) to 1cm proximal to the SCJ, 2) across the EGJ complex, from 1cm proximal to the SCJ to 1cm distal to it, 3) an initial gastric extension from 1cm to 2cm distal to the SCJ, and 4) a final gastric extension from 2cm to 3cm distal to the SCJ. FLIP measurements were taken after completion of each myotomy segment. Myotomy distances were measured using the endoscope shaft markings in relation to the SCJ. Distensibility before and after each step was compared using a paired t-test.

Results: FLIP measurements were performed in 13 patients undergoing POEM with incremental distal myotomy extension. Overall, EGJ distensibility increased as a result of POEM (baseline 1.2 ±0.8 vs. final 7.6 ±2.8 mm2/mmHg, p<.001). The initial step of submucosal tunnel creation (prior to myotomy) increased distensibility (before 1.2 ±0.8 vs. after 3.9 ±1.8 mm2/mmHg, p<0.001). Creation of an esophageal myotomy (from 6cm proximal to 1cm proximal to the SCJ) did not affect distensibility (before 3.9 ±1.8 vs. after 4.1 ±2.1 mm2/mmHg, p=ns). Creation of a myotomy across the EGJ complex (from 1cm proximal to 1cm distal to the SCJ) increased distensibility (before 4.1 ±2.1 vs. after 6.4 ±2.4 mm2/mmHg, p<0.001), as did the initial gastric myotomy extension (from 1cm to 2cm distal to the SCJ) (before 6.4 ±2.4 vs. after 7.3 ±2.4 mm2/mmHg, p<0.01). The final gastric myotomy extension (from 2cm to 3cm distal to the SCJ) did not result in a significant change in distensibility (before 7.3 ±2.4 vs. after 7.6 ±2.8 mm2/mmHg, p=ns).

Conclusions: During POEM for treatment of non-spastic achalasia, EGJ distensibility was increased by submucosal tunnel creation alone. An initial esophageal myotomy did not affect distensibility, whereas subsequent myotomy extension across the EGJ complex and a gastric myotomy extension to 2cm distal to the SCJ both increased distensibility. Extension of the distal gastric myotomy from 2cm to 3cm distal to the SCJ did not further increase distensibility. A more limited distal gastric myotomy during POEM may be sufficient to normalize EGJ distensibility.

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