Jessica L Reynolds, MD, Joerg Zehetner, MD, Nikolai Bildzukewicz, MD, Sharon Shiraga, MD, John C Lipham, MD. University of Southern California
Magnetic sphincter augmentation (MSA) is approved for the treatment for mild to moderate GERD with published results to date showing symptom resolution compareable to laparoscopic nissen fundoplication (LNF).
MSA involves placing a ring of magnetic titanium beads around the lower esophageal sphincter (LES) in order to augment the dysfunctional LES. It involves minimal dissection of the hiatus, preserving the native LES and just approximates the tissues so that it is noncompressive on the LES; except during bolus transport or other instances of LES dilation.
MSA is performed laparoscopically with minimal dissection at the left and right crura to make a space for the device. Anterior tissue on the esophagus is removed so the device approximates the esophagus. A sizing tool aids in choosing a device that is nether too loose or too tight. A device with the appropriate number of beads is placed around the esophagus and securely closed and the procedure is over. Most procedures take less than 30 min at our institution with experienced surgeons.
So, how does the device respond to gastric and esophageal distention? How does it augment the dysfunctional LES? First we see a patient just before undergoing MSA. The dysfunctional LES opens widely with gastric insufflation. Following placement of the LINX the LES appears endoscopically as a normal Hill grade 1 valve. With insufflation the LES remains closed and there is not enough pressure to cause actuation of the device beads and the LES remains closed.
We used a balloon catheter with impedence planimetry to further investigate how the MSA device reacts to changes in esophageal pressures in situ. The balloon is infinitly compliant with intra-balloon pressure transmitted evenly throughout the balloon. Electrodes on the catheter use changes in AC current to determine the diameter of the balloon at various points along the catheter. The balloon catheter can be seen in the upper right corner. With filling of the balloon and increased pressure on the LES, initially the device augements the sphincter and resists opening; however, as pressure on the LES increases, the beads on the device are actuated allowing the LES to open. As the balloon deflates and pressure decreases, the beads return to their closed position and the LES closes.