Gastroparesis is defined as a complex syndrome of symptoms including early satiety, post-prandial fullness, nausea, vomiting, bloating, and upper abdominal pain with a corresponding objective delay in gastric emptying in the absence of mechanical obstruction. Recent epidemiologic data has shown a substantial increase of 158% in hospitalizations related to gastroparesis in recent years. The pathogenesis underlying gastroparesis is complex with multiple potential underlying mechanisms including impaired gastric accommodation, autonomic neuropathy, vagal nerve injury, uncoordinated gastric contractility, and pyloric dysfunction.
Effective and durable medical treatment of gastroparesis has remained clinically challenging. Currently metoclopramide is the only medication approved by the U.S. Food and Drug Administration (FDA) for diabetic gastroparesis, and treatment courses are recommended to be limited to a maximum of 12 weeks due to the risk of the irreversible side effect of tardive dyskinesia. Surgical treatments for gastroparesis also remain limited, with sparse existing data to support the use of implanted gastric electrical stimulation for treatment of refractory gastroparesis, which is currently approved by the FDA only for compassionate use. More recently, surgical pyloroplasty has been examined in treatment of gastroparesis, which has long been recognized as a technique to improve gastric drainage for mechanical obstructions and during elective vagotomy after gastric surgery. A recent study examined surgical pyloroplasty in 28 patients with post-surgical gastroparesis with 83% patients reporting significant clinical improvement at one-month follow-up but current surgical literature remains limited in this area and has focused primarily on post-surgical gastroparesis.
Given the lack of effective treatment options, endoscopic therapies for gastroparesis have recently been investigated as adjunctive or alternative methods to treat gastroparesis. Pyloric dysfunction characterized by pyloric restriction or pylorospasm with prolonged periods of increased pyloric tone and contractions has been brought to attention as an area of targetable therapy for a subset of patients with gastroparesis. Pyloric botulinum toxin injections initially demonstrated improvement in gastric emptying after treatment, but subsequent results from double-blinded placebo-control studies failed to demonstrate a difference in symptoms compared to placebo.
Transpyloric stenting was initially reported in 2013 in three cases of refractory gastroparesis with placement of a double layered, fully-covered, Niti-S self-expandable metal stent (TaeWoong Medical) across the pylorus with improvement in gastric emptying and symptoms in all three patients. A subsequent study of 30 patients with refractory gastroparesis who underwent transpyloric stenting demonstrated high technical success of stent placement (98%) with improvement of clinical symptoms in 75% of patients and 4-hour gastric emptying studies in 69% of patients. Stent migration was found to occur in 59% of patients without any associated adverse events. Current focus on transpyloric stenting in gastroparesis centers around determining optimal stent type and method of stent anchorage as well as the role of transpyloric stenting in treatment given lack of long-term durability.
With advancements in endoscopic submucosal dissection, G-POEM has recently come in to light as a minimally invasive technique to treat refractory gastroparesis. Esophageal endoscopic myotomy has previously been well-described as a procedure for treatment of achalasia, and this technique was adopted by in 2013 with the first G-POEM for refractory gastroparesis. A subsequent multicenter study in 2017 reported on 30 patients with refractory gastroparesis who underwent G-POEM with a technical success rate of 100%. At 5.5-month follow-up, 86% of patients were found to have clinical response. Repeat gastric emptying studies after G-POEM also normalized or improved in 47% and 37% of patients respectively. G-POEM has now gained both national and international recognition in succeeding studies as a feasible and safe technique to effectively treat refractory gastroparesis in a subset of patients.
Identifying predictors of success of G-POEM for treatment of gastroparesis is essential in further recognizing appropriate patients who would benefit from this therapy. As transpyloric stenting and G-POEM share underlying mechanisms of disruption of the pylorus, the investigators propose that improvement with transpyloric stenting in patients with refractory gastroparesis can be a predictor of subsequent response with G-POEM.
