Gastric Per-Oral Endoscopic Myotomy

Gastroparetic patients present with a wide variety of symptoms that include nausea, vomiting, early satiety, and weight loss. Gastroparesis inflicts a significant burden on the patient and the healthcare system.¹,²,³ Hospitalizations related to gastroparesis as the primary diagnosis has increased by 158% between 1995 and 2004.¹ The pathogenesis of the disease is heterogeneous and not fully understood, which renders treatment challenging. The loss of myenteric interstitial cells of Cajal, myopathy, and neuropathy with secondary derangement in gastric motility and accommodation are thought to be part of the pathophysiology. Pylorospasm and loss of synchrony between the antrum and the duodenum further aggravate the problem.⁴

Treatment of gastroparesis can be challenging for both patients and physicians. Conservative management with dietary modification is recommended. Low-residue diet can alleviate the key symptoms of gastroparesis in patients with diabetes. ⁵Medical therapy is limited by considerable side effects, such as cardiac arrhythmias, extrapyramidal symptoms, and tachyphylaxis. Pylorus-directed therapies aim to decrease pyloric spasms. Botulinum toxin injection may be effective in certain subset of patients (females, younger ages, idiopathic gastroparesis)⁶ but lacks effectiveness in randomized controlled trials.⁷,⁸ Pylorus stenting, which is usually used as a palliative treatment for malignant gastric outlet obstruction, has been studied retrospectively in gastroparesis. Seventy-five percent of gastroparesis patients with pylorus stenting had positive clinical response, which is not long lived, as the stents are prone to migration.⁹ Surgical pyloroplasty aims at decreasing pylorospasm. It has been shown to be effective in reducing gastric emptying time in 86% of patients in a large study of 177 patients.¹⁰

Pylorus-directed therapies are promising and have been increasingly used for the treatment of refractory gastroparesis. In this chapter, we describe clinical indications, contraindications, complications, and technical aspects of gastric per-oral endoscopic myotomy (G-POEM), which was first described in 2013 by Khashab et al.¹¹

INDICATIONS AND PATIENT SELECTION

Patients with retention of >10% at 4 hours on gastric emptying scintigraphy (GES) regardless of the etiology are considered to have gastroparesis. Those who fail conservative treatment with dietary modification and/or medications including prokinetic agents are considered for G-POEM. Endoscopic functional luminal imaging probe (endoFLIP) may be used to measure the pressure, diameter, and distensibility of the pylorus¹² and is a promising modality which could help identify patients who would benefit from pyloric intervention such as G-POEM. Gastroparesis symptoms like postprandial fullness and early satiety have been shown to be inversely related to diameter and cross-sectional area of the pylorus.¹³ Also, pyloric pressure was found to be high in about 50% of patients with nausea and vomiting in the setting of delayed gastric emptying.¹⁴ However, the use of endoFLIP in triaging optimal candidates for G-POEM is still investigational.

PROCEDURE TEAM

G-POEM team involves an advanced endoscopist with experience in submucosal endoscopy, a trained endoscopy technician, and an anesthesia team. The procedure can be performed in the operating room or the endoscopy suite.

PREPARATION

Patients are placed on liquid diet for 1 to 2 days prior to the procedure. This ensures clear endoscopic views and reduces the risk of aspiration.

Antiplatelet and/or anticoagulant medications should be stopped prior to the procedure after consultation with the treating physician whenever needed.¹⁵ Patients with prior gastric surgery involving the pylorus or antrum and those on anticoagulation that cannot be stopped/held are contraindicated.

Periprocedural prophylactic intravenous antibiotics are used, usually a second-generation cephalosporin.

EQUIPMENT

A high-definition gastroscope with water jet is used. Disposable distal attachment is secured at the tip of the gastroscope using zinc oxide-based tape (HyTape). Carbon dioxide is used for insufflation to reduce the risk of pneumoperitoneum and gas-related adverse events. Either a triangle tip knife (Olympus, Tokyo, Japan) or HybridKnife (Erbe, Tubingen, Germany) can be used to create the tunnel and perform the myotomy. Some experts prefer using the insulated tip knife (Olympus) for pyloromyotomy as the ceramic tip protects against injury of the duodenal wall, which runs close and perpendicular to the pyloric ring.

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