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A new, reversible surgical procedure that uses a pacemaker-like device to stimulate the stomach and produce the sensation of satiety may prove more effective than conventional bariatric surgeries in treating obese patients with diabetes and other comorbidities.
Originally developed in Italy, implantable gastric stimulation (IGS), or gastric pacing, is currently being studied by a team of researchers at Tufts-New England Medical Center, in Boston.
"I am optimistic that ultimately this will be a major breakthrough in the treatment of obesity," says lead researcher Scott Shikora, MD, surgical director of the Obesity Consultation Center at Tufts.
MINIMALLY INVASIVE
The laparoscopic procedure to implant the device takes about an hour and is performed on an outpatient basis. During the surgery, a thin wire with two leads is implanted in the stomach. The leads are then connected to an electronic generator similar to a cardiac pacemaker that is placed in a pocket beneath the skin on the right side of the abdomen. The device is activated two weeks after the surgery, with each device set individually, based on the level of stimulation need to control the particular patient's appetite.
Already shown safe and effective in European trials,1 the procedure has been performed on 450 subjects worldwide. Research suggests that 80% of those individuals who underwent the surgery lost weight following implantation of the device, and 60% of the subjects lost more than 10% of their body weight over a 29-month follow-up period.
Once approved by the Food and Drug Administration (FDA), within an estimated 12 to 18 months, IGS may prove just as successful in treating obesity as gastric bypass surgery, but without gastric bypass's potential complications or long-term side effects.
The exact mechanism by which gastric pacing works on the body is unknown. Research shows that the device reduces circulating levels of cholecystokinin, somatostatin, GLP-1, and leptin2— peptides involved in appetite and satiety.
Patients given the IGS device on an experimental basis were followed for operative complications, postoperative untoward events, and weight loss. There were no significant differences between those in whom the device was activated and non-activated groups at 7 months from implant.
After 29 months of follow-up, weight loss approached 20% of excess. The devices were eventually activated in all patients. However, in one series of 103 patients, the devices were found to have dislodged or broken leads in 20 cases. For one, a lost needle required a second laparoscopic surgery to retrieve it.
Unlike gastric bypass, vertical banded gastroplasty, and other forms of bariatric surgery, gastric pacing is minimally invasive and does not alter the gastrointestinal anatomy. As such, it provides what ultimately could prove to be an extraordinarily attractive alternative for severely obese patients who are eligible for gastric bypass but avoid the surgery because of fear of its potential operative complications and long-term consequences.
"Currently, less than 1 percent of patients who are eligible for bariatric surgery agree to undergo the surgery," Shikora says.
"Some [patients] don't like the idea of having their plumbing rerouted; others don't want their stomach stapled or are unwilling to run the risk of sustaining vitamin deficiencies" and other long-term problems associated with gastric bypass, he says.
Although with IGS the weight loss is admittedly more gradual, test results indicate that the weight may be more likely to stay off than with either gastric bypass or the adjustable band, according to Shikora. And then there are the risks of gastric bypass surgery, which—in cases involving younger people especially—cannot be minimized.
"With any surgery performed on young people that is hard to reverse, you have to consider what the impact will be, not just 20 years from now, but 50 years from now," says Milton Owens, MD, medical director for the Coastal Obesity Center in Los Angeles, and a member of the IGS investigational team.
Although gastric pacing yields less dramatic results than other bariatric surgeries, the procedure itself is far safer than any other, says Owens. "In the hierarchy of effectiveness [of bariatric surgeries], the pacer probably would be tertiary. Even though you basically have the same risks that you would encounter with any surgery performed on the abdominal cavity, with IGS those risks are markedly less," he says.
Although a few patients have complained of some discomfort as a result of the stimulation of the muscles surrounding the trocar site, most people experience minimal side effects, according to Owens.
FDA APPROVAL AND MARKET USE
The IGS device, marketed under the name Transcend, is developed by Transneuronix, Inc., of Mt. Arlington, N.J. FDA approval for the gastric pacer could be granted within a year. Under FDA rules, devices may be approved if they are "substantially equivalent" to a product already on the market.
One other gastric pacing device is on the U.S. market. In 2000, the FDA cleared the Enterra Therapy System, which is produced by Minneapolis-based Medtronic, under a humanitarian device exemption. The designation recognizes that a condition is so unusual that it would be difficult for a company to scientifically demonstrate effectiveness in large numbers of patients. The Medtronic device is approved for the treatment of intractable nausea and vomiting secondary to gastroparesis.
IntraPace, a Menlo Park, Calif., start-up that has received investment from Oxford Bioscience Partners, Guidant Corp., and Johnson & Johnson, is developing a gastric pacing device that can be implanted in the stomach endoscopically, without the need for an incision. There are no indications that the IntraPace device has been used in any clinical trials.
For more information, visit
www.transneuronix.com.
References
2. Cigaina V, Hirschberg AL: Gastric pacing for morbid obesity: plasma levels of gastrointestinal peptides and leptin. Obesity Res 11:1456–1462, 2004.
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