Sa1255 INCREMENTAL MYOTOMY LENGTH REVEALS ACHIEVEMENT OF MINIMUM AND NORMAL DISTENSIBILITY INDEX THRESHOLDS DURING POEM: A PATHWAY TO SHORTER MYOTOMY?

Abstract

The challenge of esophagogastric myotomy for the treatment of achalasia is to strike a balance between obstruction relief and the development of reflux. Despite its importance, the length of myotomy has varied significantly during per oral endoscopic myotomy (POEM) to treat achalasia I and II. Distensibility index (DI) is measured using an endoscopic functional luminal imaging probe (EndoFLIP) placed across the gastroesophageal junction. Healthy volunteers have exhibited a DI range of 4.9-6.7 mm2/mmHg, while a minimum DI of 2.8 mm2/mmHg has been shown to be a strong predictor of achieving a post-POEM Eckardt score <3. We hypothesized that performing POEM in incremental lengths could aid in determining a minimum myotomy length using the EndoFLIP to measure DI. Between 2017 and 2019, patients were treated for primary achalasia I and II using a standard length POEM completed in a stepwise fashion (3 stages). Using a balloon volume of 40 ml, the EndoFLIP was used to measure the DI (defined as the minimum cross-sectional area divided by the pressure) at 5 points: (1) prior to any intervention, (2) following creation of the submucosal tunnel, (3) following a 2 cm myotomy including the high pressure zone (HPZ) and gastroesophageal junction (GEJ), (4) following the 2 cm distal gastric myotomy, and (5) following completion of the 6 cm myotomy. A total of 14 patients underwent a stepwise myotomy. Ages ranged from 33-78 years, 8 were male, and 11 had type II achalasia. At baseline, the median DI was 2.7 mm2/mmHg. Following creation of the submucosal tunnel, the median DI was 2.65 mm2/mmHg. After performing a 2 cm myotomy involving the GEJ and proximal esophagus, the median DI was 3.6 mm2/mmHg. After completion of a 2 cm distal or gastric myotomy, the median DI was 3.5 mm2/mmHg. After completion of a 2 cm proximal esophageal myotomy for a total 6 cm myotomy length, the DI was 5.1 mm2/mmHg (p=0.05). During POEM, the minimal threshold DI of greater than 2.8 mm2/mmHg is achieved after completion of the submucosal tunnel and performing a 2 cm myotomy proximal to and including the GEJ (Figure 1). Comparatively, distal extension of the myotomy 2 cm on to the stomach did not yield a significant change in DI but completion of the 6 cm myotomy proximally resulted in a DI within the normal range. This raises the possibility that a 2 cm myotomy of the GEJ/HPZ may be all that is necessary to treat achalasia by POEM.