Magnetic sphincter augmentation and high-resolution manometry: impact of biomechanical properties on esophageal motility and clinical significance for selection and outcomes

Magnetic sphincter augmentation (MSA)was introduced as an alternative to laparoscopic Nissen fundoplication (LNF). This reproducible, outpatient procedure addresses the etiology of gastroesophageal reflux disease by implanting a ring of magnetic beads across the esophagogastric junction (EGJ). MSA is designed to resist effacement of the lower esophageal sphincter (LES) and, similar to LNF, results in restoration of anti-reflux barrier competency by increasing overall length, intraabdominal length and resting pressure of the sphincter. However, the novel use of magnets to augment the physiology of the LES poses unique challenges to the physiology of the EGJ and esophagus. These impacts are best revealed through manometry. The degree of restrictive forces at the EGJ, as measured by intrabolus pressure and integrated relaxation pressure, is higher after MSA compared with LNF. In addition, contrary to the LNF, which retains neurohormonal relaxation capability during deglutition, the magnetic forces remain constant until forcibly opened. Therefore, the burden of overcoming EJG resistance is placed solely on the esophageal body contractile force, as measured by distal contractile integral and distal esophageal amplitude. The main utility of preoperative manometry is in determining whether a patient's esophagus has sufficient contractility or peristaltic reserve to adapt to the challenge of an MSA. Manometric thresholds predictive of MSA outcomes deviate from those used to define named Chicago Classification motility disorders. Therefore, individual preoperative manometric characteristics should be analyzed to aid in risk stratification and patient selection prior to MSA.