Use of Endoscopic Functional Lumen Imaging Probe (EndoFLIP) and Antroduodenal Manometry (ADM) in Predicting Clinical Response to Gastric Peroral Endoscopic Myotomy (G-POEM): A Pilot Study

Gastroparesis is defined as an objective delay in gastric emptying in the absence of mechanical obstruction with corresponding cardinal symptoms of postprandial fullness, early satiety, nausea, vomiting, bloating, and abdominal pain. Gastroparesis-related hospitalizations have increased by 158% in recent years as healthcare costs associated with gastroparesis have similarly risen exponentially by 1026% from 1997 to 2013.

Medical management of gastroparesis, primarily comprised of dietary and prokinetic therapy, is limited in effectiveness, tolerability, and durability, in part because the pathophysiologic mechanisms underlying gastroparesis are varied and multifactorial, including pyloric dysfunction, impaired fundic accommodation, vagal injury or neuropathy, gastric pacemaker dysrhythmias, hypocontractility, and aberrant gastric feedback. Pyloric dysfunction in particular, characterized by increased tone or pylorospasm, offers the potential for targeted endoscopic therapy in a subset of patients.

Gastric peroral endoscopic myotomy (G-POEM) has recently emerged as a feasible and safe treatment for severe refractory gastroparesis. Initially described in 2013, G-POEM is a minimally invasive technique that consists of creating a submucosal tunnel extending to the pylorus, dissecting circular and oblique muscle layers, and closing the tunnel with endoscopic clips. The first systematic review of early outcomes of G-POEM across 10 studies and 292 patients revealed 100% technical success, symptomatic improvement in 84%, and an adverse event rate of 6.8%.

However, a nuanced approach to appropriate patient selection for G-POEM, based on individual physiologic characteristics, is still lacking. The endoscopic functional lumen imaging probe (EndoFLIP; Crospon Inc., Galway, Ireland), previously well-described in assessing the lower esophageal sphincter in esophageal motility disorders, has been recently proposed as an adjunctive technology for evaluating pyloric sphincter compliance and distensibility. Few studies have investigated the efficacy of pyloric EndoFLIP in gastroparesis. Gourcerol et al. reported that gastroparesis patients have lower pyloric compliance compared to healthy volunteers, which also correlated with longer gastric emptying half times and reduced quality of life scores. A second pilot study of 20 gastroparesis patients who underwent pre- and post-myotomy EndoFLIP revealed that a distensibility index of <9.2 mm2/mmHg was associated with G-POEM clinical efficacy, however the study was limited by a short follow-up time of three months.

Antroduodenal manometry (ADM) has been the gold standard of assessing pyloric function and early studies revealed elevated pyloric pressures in greater than 50% of diabetics with gastroparesis. Recent data also shows a significant correlation between manometric and EndoFLIP pressures, though to date, no studies have utilized ADM in evaluating the efficacy of G-POEM. While conventional ADM was previously felt to be technically challenging and limited in availability, the advancement of high resolution manometry presents a unique opportunity for complementary assessment of not only pyloric pressures, but also antroduodenal pressure gradients.