Intraoperative Assessment of Esophagogastric Junction Distensibility During Per Oral Endoscopic Myotomy

Erwin Rieder, MD, Silvana Perretta, MD, Christy M Dunst, MD, Lee L Swanstrom, MD. Gastrointestinal and Minimally Invasive Surgery, The Orgeon Clinic, Portland, Oregon; Institute de Recherche contra les Cancers de l’Appareil Digestif (IRCAD), Strasbourg Cedex, France

Introduction: Per oral endoscopic myotomy (POEM) is a new treatment for esophageal motility disorders. Using endoscopic techniques derived from NOTES and ESD, this targeted therapy aims to only divide the inner muscular layers at the esophagogastric junction (EGJ), while leaving the outer longitudinal layer intact. The extent of this selective myotomy has been determined intraoperatively purely based on the subjective assessment of the endoscopist and the endoscopic image, making more accurate analyses difficult. We hypothesized that the real-time measurement of EGJ-distensibility would be a better method to objectively evaluate the completeness of this novel approach as well as being a useful tool for long-term follow-up.
Methods and procedures: Patients diagnosed with achalasia were enrolled in an institutional review board approved study and electively underwent POEM under general anesthesia. A sub-mucosal tunnel from the mid-esophagus onto the gastric cardia was created with subsequent selective division of the circular and sling fibers at the lower esophageal sphincter using endoscopic needle-knife cautery.
Using impedance planimetry with a transorally inserted functional lumen-imaging probe (EndoFLIP®), cross sectional areas (CSA) as well as distensiblities at the EGJ were intraoperatively measured immediately before and immediately after the selective myotomy (n=4). Measurement profiles of the EGJ were obtained with a 40ml-fill mode and recorded when a plateau of the cross sectional area was reached. Two patients had completed their with EndoFlip measurements, as well as EGD, manometry and pH testing at the 6-month postoperative follow-up.
Results: POEM was successfully performed in all patients (4/4). Pre-myotomy distensibility measurements (40ml) showed a median diameter of only 6.6 mm (range: 5.9 to 7.9 mm) at the narrowest location of the EGJ. Intraoperative post-myotomy assessment observed an increased median diameter of 10.1 mm (7.3 to 13.4 mm). CSA increased from 41.5 mm2 (28 to 49 mmHg) to a median of 86 mm2 (41 to 140 mm2, p=0.07) at a similar median intra-balloon pressure (pre: 36.6 mmHg vs. post: 38.6 mmHg), which also indicates increased EGJ distensibility/compliance. Two achalasia patients have had EndoFLIP measurements repeated after 6 months. Using the same balloon distension (40 ml) the observed median EGJ diameters was 12.7 mm (13.7 mm and 11.7 mm). CSA was found to be 128 mm2 (147 mm2 and 108 mm2) with a median balloon pressure of 35 mmHg, indicating persistence in EGJ compliance. Both patients indicated no dysphagia (symptom score: 0) and had normal LES resting pressures, and their DeMeester scores were found to be 3.4 and 37.8.
Discussion: Early results indicate that POEM provides an immediate correction of the non-relaxing LES and that this result appears to persist at long-term follow-up. Intraoperative EGJ profiling, performed with a functional lumen-imaging probe, may be an important tool to objectively evaluate the needed extent and completeness of myotomy during POEM. Additionally, it may also be an effective way to follow myotomized patients long-term.

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