Rechargeable Vagal Blocking System (Maestro) for Treating Obesity

May 25, 2017 | Emerging Technology Reports


Proprietary names: VBLOC Neurometabolic Therapy; Maestro® Rechargeable System; Maestro Neuroregulator, Model 2002; Maestro Lead System, Model 2200-47E; Maestro Mobile Charger, Model 2402; Maestro AC Adaptor, Model 1620; Maestro Transmit Coil, Models 2403-300, -60 and 60A; Maestro Clinician Programmer, Model 2501.

Generic names: Vagus nerve blocking therapy, vagus nerve stimulation (VNS), implanted VNS device.

Obesity is defined as an excessive accumulation of body fat, resulting from a positive imbalance between caloric intake and expenditure.1-3 Body fat content is usually estimated using the body mass index (BMI). Adults are considered obese if their BMI is greater than 30 kg/m2 and morbidly or severely obese if BMI is greater than 40 kg/m2.1,3,4 Behavioral, environmental, and genetic factors contribute to the development of obesity.2,5,6 Increased caloric consumption and low levels of physical activity promote weight gain and result from lifestyle choices, but also from socioeconomic status, psychological disorders, or physical disability.5 Certain types of medications used to treat mood disorders, seizures, migraines, cardiovascular disease, hypertension, and diabetes also promote weight gain.5 Clinicians estimate obesity is 40% to 70% inheritable, and results from a genome-wide association study suggest that common genetic variants may account for up to 21% of BMI variation.2,6

Patients with obesity are at an increased risk of morbidity and mortality. Obesity is a major risk factor for cardiovascular disease and is also associated with dyslipidemia, hypertension, and type 2 diabetes mellitus, which are also major cardiovascular risk factors. In addition, obese patients have a greater chance of fatty liver disease, gallbladder disease, osteoarthritis, stroke, sleep apnea, and certain forms of cancer.7,8 A meta-analysis of 57 prospective studies that enrolled nearly 900,000 adults suggests that overall mortality rises by 30% for every 5 kg/m2 above the ideal BMI of 25 kg/m2.9

Obesity treatments attempt to reduce obesity-related comorbidities and risks by reducing body weight. Total weight loss (TWL) as modest as 5% to 10% can significantly reduce comorbidity risks in obese patients.10 First-line therapies combine lifestyle modification (i.e., dietary and exercise education, counseling, clinically supervised regimen) and treatment of underlying medical conditions to reverse the caloric imbalance and induce weight loss.11-13 While some patients may achieve and maintain a healthy weight through these interventions, their overall efficacy may be limited.14,15 On average, patients enrolled in clinical weight loss programs lose 7% to 10% of their weight during the first year but frequently discontinue the interventions and regain most of the lost weight within the subsequent five years.16-18 Medication can complement lifestyle modification. Available drugs induce weight loss by suppressing hunger (phentermine, phentermine/topiramate, lorcaserin, liraglutide, and naltrexone/bupropion) or inhibiting lipid absorption (orlistat), typically achieving 3% to 9% TWL.2,19

The limited impact of conservative therapies has prompted investigators to explore several minimally invasive approaches to weight loss.20-22 Most of these involve endoscopic procedures and devices, such as intragastric balloons, to restrict food intake and/or delay gastric emptying to induce satiety. Most of these devices can remain in place only temporarily, usually between 6 and 12 months. A second type of approach aims to modulate the release of gastrointestinal neuroendocrine signals that control appetite. Gastric "pacing" with implanted neurostimulators is an example of this approach.21,23,24 Because of their novelty, these technologies have yet to be fully incorporated in the recommended clinical obesity treatment pathway.25,26

Clinical guidelines recommend offering bariatric surgery to patients with BMI greater than 40 kg/m2, or greater than 35 kg/m2 in the presence of 1 or more obesity-related comorbidities, whose condition has not responded to conservative treatments such as lifestyle modification and pharmacotherapy.12,13,22,27,28 Physicians also may offer the same procedures to patients with type 2 diabetes mellitus (T2DM) with BMI below 35 kg/m2 to improve glycemic control; this approach is referred to as metabolic surgery.5,11-13,19,22,28 Bariatric surgery generally involves reducing the functional volume of the stomach, the small intestine, or both. These changes produce weight loss by limiting nutrient absorption and altering the production of gastrointestinal hormones that regulate satiety and metabolism. The most frequently practiced procedures are Roux-en-Y gastric bypass, vertical sleeve gastrectomy, and laparoscopic gastric banding.29-32

Bariatric surgery is effective in achieving durable weight loss; clinical studies suggest that patients lose on average 50% to 70% of their excess weight (10% to 40% of their total weight) after one year, depending on the bariatric procedure used.33-36 Moreover, patients typically regain no more than 10% of the lost weight in the following 5 to 10 years.33-36 Mortality rates associated with bariatric surgery procedures range from 0.1% to 1.0%, while morbidity rates range between 7% and 20%.30 Potential adverse effects include nausea, vomiting, and nutrient deficiencies. Complications include gastrointestinal suture leakage, bleeding, and infection; for adjustable gastric banding (Lap-Band) procedures, complications could include implant slippage and stomach erosion.30-32 Despite bariatric surgery's effectiveness, only 1% to 2% of eligible patients choose to undergo this procedure, largely because patients and physicians are wary of complication risks and may not perceive surgery as warranted by the patient's condition.37,38 Therefore, physicians are interested in developing minimally invasive treatments that offer benefits comparable to those of bariatric surgery but are more acceptable to patients and physicians.

United States

Based on results of the 2011–2014 National Health and Nutrition Examination Survey, the U.S. Centers for Disease Control and Prevention estimates that 36% of U.S. adults have a BMI greater than 30 kg/m2. Obesity's prevalence in the United States has...

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