Manometric Changes to the Lower Esophageal Sphincter Following Magnetic Sphincter Augmentation in Patients with Gastroesophageal Reflux Disease

Heather F Warren, MD, Brian E Louie, MD, MPH, Alexander S Farivar, MD, Candice Wilshire, MD, Ralph W Aye, MD. Swedish Cancer Institute and Medical Center

Background: Magnetic Sphincter Augmentation (MSA) has been shown to effectively control gastroesophageal reflux disease (GERD) in patients without Barrett’s esophagus, with normal motility, < 3 cm hiatal hernia, and BMI < 35 kg/m2. The underlying mechanism of the magnetic sphincter is based on the concept that a loose ligature increases the gastric pressure threshold required to open the lower esophageal sphincter (LES); however the exact mechanism of action is unknown. To date, no one has evaluated the physiologic effect of MSA on the LES or esophageal body function. We sought to compare the preoperative and postoperative manometric measurements for patients undergoing MSA.

Methods: A single institution retrospective case control study of manometric changes following MSA. High-resolution manometry (ManoScan, 36 channels of circumferential pressure sensors and 18 impedence channels) was performed prior to, and 6-12 months following MSA. Data included preoperative and postoperative changes in time pH<4, DeMeester scores, GERD Health Related Quality of Life (GERD HRQL) and high- resolution manometry measurements.

Results: Nineteen patients underwent pre and post-operative evaluation. Clinically, there were significant improvements in the preoperative versus postoperative GERD measurements of percentage of time pH<4 (11.3% versus 3.6%, p<0.01), DeMeester scores (38 versus 11.7, p<0.01) and GERD HRQL (21 versus 5, p<0.01) following MSA. Manometry findings demonstrated significant changes in the LES, including total and intra-abdominal length and integrated relaxation pressure (Table 1).

Preoperative and Postoperative Manometry Measurements Following Magnetic Sphincter Augmentation
Preoperative Postoperative P value
LES Length (cm) 2.4 3.2 P<0.01
Intra abdominal LES Length (cm) 1.0 2.1 P<0.01
LES Basal Pressure (mmHg) 19.3 25.4 P=0.06
LES Integrated Relaxation Pressure (mmHg) 6.9 16


Distal Wave Amplitude (mmHg) 74.2 103.4 P<0.07
Distal Contractile Integral (mmHg-cm-s) 2158 2666 P=0.27
Peristalsis (%) 92 100 P=0.16

Conclusions: Following magnetic sphincter implantation, the LES characteristics appear to be undergo improvement in all metrics. The manometric changes in the LES occur without significant change to the esophageal body. Understanding the physiologic manometric changes following MSA, and how these relate to changes in reflux and clinical outcomes, may further elucidate the pathophysiologic characteristics of GERD and illuminate ways to optimize disease treatment.

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