This was a 12-month prospective, multi-center study conducted in Germany. The protocol was approved by a central ethics committee (FECI 010/1049) and reviewed by each center’s ethics committee. The study was conducted in accordance with Good Clinical Practice and consistent with the Declaration of Helsinki, Informed consent was obtained from all enrolled participants.
The main participant inclusion and exclusion criteria are listed in Table 1. Prior to enrollment, the participants were prescreened using the Three-Factor Eating Questionnaire (TFEQ), which explores the three dimensions of eating behavior: cognitive restraint of eating, disinhibition, and hunger . The test was scored using a proprietary algorithm that characterizes the profile of the highest responders to GES therapy. The participant’s ability to respond to the gastric electrical therapy was assessed with an endoscopic electrical stimulation-based sensitivity screening. The participant was asked to describe their symptoms and to score them on a visual analogue scale (VAS).
abiliti® is an implantable system that delivers stimulation therapy triggered by a transgastric intake sensor. The stimulation targets the area of the anterior vagal branches at the lesser curve of the stomach (“crow’s foot”).
Using a programmer and a wand which provides telemetry-based communication with the device, the physician is trained to titrate the stimulation parameters based on the participant’s response and design a participant’s personalized therapy. The parameters of the pulse-train stimulation (4–30 mA, 100–2000 μs pulse duration, 40–120 Hz) are adjusted to obtain the desired symptoms of fullness and satiety, by asking the participant to report their symptom level using a visual scale. The daily therapy is individualized by creating “allowed” periods, where therapy is designed to produce satiety, and “disallowed” periods, where therapy is designed to cause discomfort and stop consumption. The allowed periods are tailored to the participant’s life schedule, to encourage a consistent meal schedule that is preferable for weight loss. Stimulation adjustment is done at initial programming when the stimulation is turned on, and at each subsequent follow-up visit as necessary.
The stimulator stores the meal and activity data derived from the intake sensor and three-axis accelerometer as a daily log, which is uploaded to the programmer and viewed at each follow-up visit. A custom model translates the output of the accelerometer to a daily exercise level and duration.
The implantation of the device is performed under general anesthesia similar to other laparoscopic gastric interventions. Three trocars are used for the standardized procedure. The transgastric food sensor is implanted in the anterior wall, body-fundus region, about 3 cm from the greater curvature. The stimulation electrode is implanted in the anterior wall, approximately 4 cm from the gastroesophageal junction and 1.5 cm from the lesser curvature of the stomach, at the point where the Laterjet nerve is divided into three branches (“crow’s foot”). The distance between electrodes should be 3 to 4 cm. Upon inflation of the stomach, a dilating needle is inserted through the trocar which is nearest and perpendicular to the implantation site, to pierce the gastric wall and then place the food sensor electrode with a silicon wafer which is fixed by a seromuscular suture. An upper endoscopy is performed to confirm the intragastric probe extension. A subcutaneous pocket is created in the left upper abdominal quadrant, the lead is exteriorized and connected to the stimulator, which is placed in the pocket. Figure 1 illustrates the placement of the transgastric food sensor, stimulation electrode, and stimulator. The mean duration of the implant surgery was 52.3 min (range 35–110).
Two weeks following the implant, the therapy was started, and the meal schedule and therapy parameters were consequently adjusted for each patient. Monthly follow-up was conducted that included weight measurement, dietary counseling and review of food sensor and activity data provided by the device, and if necessary therapy adjustment based on a stimulation sensitivity test.
The primary endpoint was safety of the transgastric implant evaluated by endoscopy examination 3 months after implant. The secondary outcomes were: the frequency and seriousness of all adverse events; the percentage excess weight loss (%EWL) measured at each follow-up visit up to 27 month, assessment of eating behavior with the TFEQ and quality of life with the Moorehead-Ardelt II at baseline and 12 months, and measurement of trends in exercise with the implanted 3D accelerometer during the first 12 months.
Data were pooled across the study sites and are presented as mean ± SD unless otherwise indicated, comparisons were evaluated using a paired student’s t test, and physical activity trends with linear regression. Means, total counts, standard deviations, medians, ranges, and 95 % confidence intervals for the means were calculated for continuous measures. Analyses were performed using Excel version 12 (Microsoft Corp., Mountain View, California, USA) and SAS Version 9.2 software (SAS, Cary, NC, USA).