We have known for a long time that the brain regulates hunger and fullness. The brain also regulates how we store energy. The brain receives signals from throughout the body, including the gut. The signals come through nerves and through circulating hormones. At any point in time, the brain knows when you last ate, if you are digesting food, and how full your stomach and intestines are. This knowledge led to research to manipulate the signals sent to the brain from the stomach and intestines. As it turns out, the vagus nerves, the two major nerves that carry signals to and from the brain, became a treatment target.
Vagus Nerve Blocking Therapy
VBLOC vagal blocking therapy delivered via the Maestro System (EnteroMedics Inc., Minneapolis, MN) is now approved to treat adults with obesity. The device was approved for patients ages 18 to 65 years, with a body mass index (BMI) of 40 to 45 kg/m2, or >35 kg/m2 with 1 or more obesity-related complications (such as diabetes, hypertension, and high cholesterol). The device should be used only in people who have first tried to lose weight in a supervised weight management program within the past 5 years.
The device blocks the vagus nerves that connect the brain and stomach. Blocking the vagus nerves helps control hunger between meals and promotes the feeling of fullness earlier after eating, according to the device’s manufacturer EnteroMedics Inc. Electrodes are placed on the vagus nerves and are attached via small wires to a rechargeable pulse generator that is placed just under the skin (Figure below). The generator sends small electric pulses to the electrodes to block the vagus nerve.
Figure (above). VBLOC vagal blocking therapy delivered via the Maestro System consists of electrodes that are implanted to the trunks of the abdominal vagus nerve and receive electrical pulses from a rechargeable pulse generator that is placed under the skin. As shown in the inset, a mobile charger is placed over the skin where the generator is implanted to recharge the battery.
Half of People Lose at Least 20% of Excess Weight With the Device
In a study that led to the approval of the Maestro System, 233 people with obesity received the device for 12 months, and 76 people received a placebo system (meaning that they received a nonworking pulse generator only). After 1 year, the people who received the system lost an average of 8.5% more excess weight than the placebo group. Approximately half (52.5%) of the people who received the system lost at least 20% of their excess weight, and 38.3% lost at least 25% of their excess weight compared with 32.5% and 23.4% in the placebo group, respectively.
In addition, approval was based on an FDA-sponsored survey showing that people would accept risks associated with this device given the amount of expected weight loss.
Side Effects of the Device
Serious adverse events reported with the system include nausea, pain where the pulse generator is placed under the skin, vomiting, and complication from surgery. Other adverse events included pain, heartburn, problems swallowing, belching, mild nausea, and chest pain. The device should not be used in people who have liver cirrhosis, portal hypertension, esophageal varices, clinically significant hiatal hernia, or implantable devices (eg, pacemakers, defibrillators, neurostimulators). The device should not be used in those who are at high risk for complications from surgery. In addition, people who may need magnetic resonance imaging, or shortwave, microwave, or therapeutic ultrasound diathermy in the future should not receive the device.
As part of the approval, EnteroMedics is following at least 100 people who received the device for 5 years to monitor the safety and efficacy of the system.
EnderoMedics. EnteroMedics announces FDA approval of VBLOC vagal blocking therapy for the treatment of obesity. January 14, 2015. http://www.prnewswire.com/news-releases/enteromedics-announces-fda-approval-of-vbloc-vagal-blocking-therapy-for-the-treatment-of-obesity-300020551.html. Accessed March 19, 2015.
U.S. Food and Drug Administration. EnteroMedics Maestro Rechargeable System - P130019. http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/DeviceApprovalsandClearances/Recently-ApprovedDevices/ucm430696.htm?source=govdelivery&utm_medium=email&utm_source=govdelivery. Accessed March 19, 2015.
U.S. Food and Drug Administration. FDA News Release: FDA approves first-of-kind device to treat obesity. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm430223.htm. Accessed March 19, 2015.