Strategies to Refine Gastric Stimulation and Pacing Protocols: Experimental and Modeling Approaches

Gastric pacing and stimulation strategies were first proposed in the 1960s to treat motility disorders. However, there has been relatively limited clinical translation of these techniques. Experimental investigations have been critical in advancing our understanding of the control mechanisms that innervate gut function. In this review, we will discuss the use of pacing to modulate the rhythmic slow wave conduction patterns generated by interstitial cells of Cajal in the gastric musculature. In addition, the use of gastric high-frequency stimulation methods that target nerves in the stomach to either inhibit or enhance stomach function will be discussed. Pacing and stimulation protocols to modulate gastric activity, effective parameters and limitations in the existing studies are summarized. Mathematical models are useful to understand complex and dynamic systems. A review of existing mathematical models and techniques that aim to help refine pacing and stimulation protocols are provided. Finally, some future directions and challenges that should be investigated are discussed.

P149 MINIMAL INVASIVE TEMPORARY GASTRIC ELECTRO STIMULATION - 1 YEAR FOLLOW

Aim To predict the outcome of the implantation of an electronic gastric stimulation device (Enterra®, Medtronic) we established a minimal invasive procedure to perform a temporary gastric test stimulation prior to a definite implantation (1). We achieved promising short time results. This study will demonstrate the long-term results after more than 1 year. Background & Methods Gastroparesis (GP) is a complex disorder of gastric motility. It is defined as a delayed gastric emptying without pyloric obstruction. Due to its etiology GP is divided into three groups: diabetic (GP), postoperative (PG) and idiopathic (IP). Although electronic stimulation of the stomach is a well-established and approved procedure since over 18 years for the therapy of symptomatic GP, the response to gastric stimulation remains unpredictable. 13 patients (11 female, 2 male) with a history of symptomatic gastroparesis (4 idiopathic, 7 postoperative, 2 diabetic) were included. Patients underwent laparoscopy and received 2 temporary electrodes (Medtronic Streamline 6492®) 10 cm proximal to the pylorus into the gastric wall. Threads were passed through the abdominal wall and connected to an external gastric stimulator (Enterra, Fa. Medtronic). The device was taped to the abdominal wall by a dressing. Symptom intensity was measured by a standardized questionnaire, Gastoparesis Cardinal Symptom Index (GCSI)(2). Therapeutic response was defined as a GCSI reduction of at least 50% under the preoperative score. Half time gastric emptying was also measure pre and postoperatively using a half-solid test meal. Results 10 of 13 patients reported a response to temporary gastric stimulation with an increase of the pre-therapeutic GCSI over 50 %. 10 patients received a permanent stimulation device. 7 patients reached the 1-year follow up. They all remained responders with a reduction of GCSI over more than 50 %. In comparison to results after 6 months gastric half time emptying continued to decrease. Conclusion Temporary gastric electronic stimulation can predict the long-term outcome of patients receiving a definite implantation of an electronic gastric stimulation device.

Gastric stimulation to treat the type 2 diabetes: Results on week 16

Background/Aim. Gastric contraction modulation (GCM) with the implanted DIAMOND device improves glycemic control and decreases weight. The main aim of this study was to evaluate the early efficacy of GCM using the DIAMOND (previously named TANTALUS) System in the improvement of glycemic control measured by changes in glycosylated hemoglobin (HbA1c). The effects of GCM on weight loss, body mass index (BMI), reduction of the waist circumference and metabolic parameters other than HbA1c were also evaluated. Methods. A total of 18 adult patients with type 2 diabetes were surgically treated at the Department for Minimally Invasive Upper Digestive Surgery, Clinic for Digestive Surgery in Belgrade, Serbia, using gastric pacemaker (DIAMOND System) from November 2014 to March 2016. Out of the total number of patients, 11 finished week 16 visit and were enroled in this prospective cohort study. Results. During the observed period, the average weight loss amounted to 8.05 kg (p < 0.05). The average difference between the baseline fasting glucose level and the level after 16 weeks period is 2.56 mmol/L. Similar findings were noted in fasting insulin levels, with an average decrease of 6.44 m/U/L after 16 weeks. The majority of patients experienced a decrease in HbA1c value: in 4 patients higher than 2%, and in 4 patients up to 2% (p < 0.05). Lower level of fasting insulin with simultaneous decrease in fasting glucose indicates improvement in insulin sensitivity on week 16 [homeostatic model assessment of insulin resistance (HOMA IR) average 5.25]. Conclusion. Gastric stimulation using the DIAMOND System for 16 weeks causes significant early improvement in glycemic control and insulin resistance. There is an additional positive effect on weight loss, body mass index (BMI) and reduction of the waist circumference as a main parameter of the metabolic syndrome.