Gastric Electrical Stimulation For Gastroparesis Research Articles

Gastric Electrical Stimulation: Role and Clinical Impact on Chronic Nausea and Vomiting.

Gastric electrical stimulation (GES) is currently used as an alternative treatment for medically refractory gastroparesis. GES has been initially developed to accelerate gastric motility, in order to relieve the symptoms of the patients. Subsequent studies, unfortunately, failed to demonstrate the acceleration of gastric emptying using high-frequency stimulation – low energy stimulation although the technique has shown a clinical impact with a reduction of nausea and vomiting for patients with gastroparesis. The present review details the clinical efficacy of GES in gastroparesis as well as its putative mechanisms of action.

O-BN08 Quality of Life 21 Years Following Gastric Pacing/ Gastric Electrical Stimulation for Gastroparesis – A real life data

Abstract Background Gastroparesis is defined as delayed emptying of the stomach in the absence of mechanical obstruction. Gastroparesis symptoms ranging from nausea, vomiting, bloating and abdominal pain with significant impact on overall quality of life (QALY). Gastric electrical stimulation (GES) for gastroparesis has been used in clinical practice since 1998 and was initially licensed as a “humanitarian” treatment when all else had failed. In the last two decades, it has been increasingly used in the treatment of refractory gastroparesis. We have been performing GES for refractory Gastroparesis since 2000 and we present our data on symptoms, quality of life and resource utilization Methods A prospective consecutive cohort study at a single center from December 2000 to July 2021 has been conducted. Data on patient demographics (gender and age), comorbidities, aetiology, the method of surgery, pre and post hospital stay, pre and post-operative SF-36 questionnaire (QALY) and symptom score (Likert Score), adjunct intervention, feeding regimen, mortality and morbidity were collated and subjected to student t-test for parametric data, the Wilcoxon test for non-parametric data, and McNemar’s test for binomial data Results A total of 162 patients underwent GES. There were 118 females. The median age was 36.5 years (range 6-80). Ninety-two patients were Idiopathic, 63 were Diabetic and 7 Post-Surgical. Overall QALY improved from a mean of 190/500 to 415/500(p = <0.001) with significant improvement in nausea (p = <0.001), abdominal pain (p = 0.005) and bloating (p = 0.001) severity score prior and following surgery. Number of hospital admissions (median) reduced post GES insertion from six to zero per year (p = 0.002). The median length of stay was 3 days (range 1-45) and follow up was up to 129 months (6-252). There was no mortality from the procedure. Conclusions This is one of a few long-term studies looking at the outcome following GES for Gastroparesis. Our data shows that GES is a safe procedure with very little morbidity and no mortality. It improves symptoms and quality of life. It also reduces the health care utilization for these patients. The effects of GES are also very durable and hence should be considered as a mainstream treatment for patients with refractory gastroparesis.

A Systematic Review of the Therapeutic Role of Gastric Pacemakers in Adults With Gastroparesis.

Gastroparesis or gastric stasis is the delayed transit of the ingested contents through the stomach in the absence of mechanical obstruction. It can have multiple etiologies, most commonly idiopathic (ID) and diabetic (DM). Gastroparesis can cause significant distress to patients as it leads to symptoms like intractable nausea and vomiting, weight loss, abdominal bloating, early satiety, etc. The pathogenesis is mainly thought to be due to the dysfunction of the gastric pacemaker cells, i.e., interstitial cells of Cajal (ICC), and their interaction with the other gastric motor function regulatory components. There are several proposed treatment options for gastroparesis. Despite that, most patients remain refractory to medical treatment and require additional interventions for symptomatic relief. One such intervention is gastric electrical stimulation or gastric pacemaker, which aids in improving gastric motility. We have searched PubMed, PubMed Central (PMC), Medline, Science Direct, and Google Scholar for articles pertaining to the use of gastric electrical stimulation in gastroparesis published in the last 10 years. The keywords used include "gastroparesis", "gastric stasis", "gastric pacemaker'', "gastric electrical stimulation", "nausea", "vomiting", "abdominal bloating", "gastric neuromodulation". We have finally included twelve studies that were the most relevant to our research question and met the quality assessment criteria. Exclusion criteria consisted of pediatric population studies, studies conducted on animals, books, and grey literature. Overall, these twelve studies helped evaluate the impact of gastric pacemakers on symptoms of gastroparesis like nausea, vomiting, weight loss, abdominal bloating, and quality of life. We found that most studies favored gastric pacemakers, improving the incidence of nausea and vomiting in patients with gastroparesis. There was a marked improvement in the BMI as well. On the other hand, most open-labeled studies showed improved quality of life and Gastroparesis Cardinal Symptom Index (GCSI) scores, while randomized controlled trials and meta-analyses did not reflect the same result. In addition, some other parameters improved with gastric pacemakers, Inflammatory markers, insulin levels (especially in diabetics), and the number of hospitalizations. In conclusion, gastric pacemaker is a potential treatment option for patients with medically refractory gastroparesis. As noted from the results of our study, nausea/vomiting, weight loss, and overall GCSI scores have shown marked improvement with gastric electrical stimulation (GES). Nevertheless, more extensive research is needed to understand better the full extent of this device’s use as a viable treatment option for patients suffering from gastroparesis.

Beyond Metoclopramide for Gastroparesis

Beyond Metoclopramide for Gastroparesis

An Interactive System for Visualizing and Interpreting Propagating Vagal Nerve Activity to Improve the Efficacy of Gastric Electrical Stimulation for Gastroparesis

Gastroparesis is a stomach condition that results in abnormal processing of food and delayed gastric emptying without a mechanical obstruction. Nausea and vomiting are the most common symptoms. When pharmaceutical treatments and dietary changes fail to relieve symptoms, a gastric electrical stimulation (GES) device is implanted and used to electrically stimulate the stomach wall. Although the exact mechanism is unknown, there is evidence that GES stimulates the vagus nerve, which is the primary nerve that the stomach uses to communicate sensory information to the brain. We hypothesize that GES relieves nausea and vomiting by stimulating the vagus nerve. Vagal nerve recordings were obtained in human subjects receiving GES for gastroparesis using a novel, noninvasive method, consisting of placing a multi-electrode array (MEA) on the skin surface overlying the left and right cervical vagus nerves. The array allows for visualization of propagating nerve activity that is tied to the electrical stimulus delivered by the GES device. Since nerve signals propagate at specific speeds, the MEA can be used to learn properties of the vagal nerve pathways that transmit information to the brain in response to GES (Fig. 1A). Cervical measurements can also be collected from the subjects to determine optimal placement of the MEA. Due to the complex nature of the data sets collected, it is necessary to simplify the interpretation of the data to ensure that the importance of the signals is understood by a broad audience. A graphical user interface was created as an interactive tool to visualize and interpret vagal nerve activity using the data collected from the MEA. The interface includes a color-coded outline of the cervical measurements obtained on an image of the neck and a description of each measurement in terms of its anatomical position (Fig. 2A). It features an interactive component that allows users to view each measurement individually by selecting the identifying letter representative of each measurement (Fig. 2B). Users can select a subject from a drop-down menu, which results in automatic placement of the MEA on the image using the cervical anatomy measurements specific to that subject. To visualize nerve activity, a colormap is implemented where brighter colors denote activity (Fig. 1B). The data collected and analyzed from the MEA is the 70 millisecond window after each stimulus is applied. To maximize visualization, the rate of the activity is reduced and allows users to control the playback speed of the data using a slider. We are determining the limitations of detecting vagal nerve activity through the skin surface, including body mass index and the parameters of the GES device. Visualizing and analyzing the data traveling across the electrodes may provide insight into the typical anatomical course of the vagus nerve. We aim to use this display of vagal nerve activity to decode and analyze its involvements in GES and the treatment of gastroparesis.

S1324 Gastric Electrical Stimulation for Gastroparesis: Is it Effective and is the Effect Durable?

S1324 Gastric Electrical Stimulation for Gastroparesis: Is it Effective and is the Effect Durable?

Safety and Feasibility of Per-Oral Pyloromyotomy as Augmentative Therapy after Prior Gastric Electrical Stimulation for Gastroparesis

For medically refractory diabetic or idiopathic gastroparesis, gastric electrical stimulation (GES) is an excellent option for symptom control; however, a small subset of patients may develop recurrent or persistent symptoms. Per-oral pyloromyotomy (POP, also described by some authors as gastric per-oral endoscopic myotomy or G-POEM) is an emerging therapy for medically refractory gastroparesis. This study investigated the safety and feasibility of POP after previous GES for recurrent or persistent gastroparesis. We retrospectively identified all patients undergoing POP between January 2016 and December 2017, with GES in situ. Patient characteristics, gastroparesis etiology, and procedural data were collected. Symptoms were assessed with the Gastroparesis Cardinal Symptom Index (GCSI) both before and 30 to 90 days after POP. Standard pre- and post-procedure 4-hour gastric emptying tests were obtained when available. There were 22 patients who met inclusion criteria (81.8% female, mean age 42.3 ± 12.4 years). Causes of gastroparesis were diabetes in 38.1%, and idiopathic in 61.9%. The average time since GES insertion was 3.45 years. Mean preoperative 4-hour gastric retention was 50.1%. Most POP procedures were performed in the operating room (90.9%), with mean operative time of 40 minutes and a 1.4-day length of stay. There were 4 readmissions within 30 days, but no POP-related complications. Overall, GCSI improved by an absolute reduction of 1.63 points (p= 0.002), with significant improvements in all sub-scores. Of 11 patients with post-procedural motility or emptying studies available, 7 were normal. Per-oral pyloromyotomy appears to be safe and feasible for patients with recurrent gastroparesis symptoms after GES. Both symptoms and motility significantly improved in the short-term. These data replicate similar data suggesting laparoscopic pyloroplasty as an effective augmentative therapy after GES, but may provide a less invasive option for patients.

Safety and Feasibility of Per-Oral Pyloromyotomy as an Augmentative Therapy after Prior Gastric Electrical Stimulation for Gastroparesis

Safety and Feasibility of Per-Oral Pyloromyotomy as an Augmentative Therapy after Prior Gastric Electrical Stimulation for Gastroparesis

Efficacy of Gastric Electrical Stimulation for Gastroparesis: US/European Comparison.

BackgroundGastric electrical stimulation (GES) is used in both the US and Europe, but little research has investigated the demographics of gastroparesis patients receiving GES by geographic location.MethodsWe compared data from 380 patients, 296 female and 84 males, mean age 42 years, 246 idiopathic (ID), 107 diabetic (DM), and 27 post-surgical (PS). The statistical significance was calculated by Chi-square test and a P-value obtained for ID, DM, and PS. The statistical significance was calculated by Fischer exact test and a P-value obtained comparing male vs. female.ResultsEuropean centers had 61 GES patients compared to 319 from the US. In Europe, 100% of patients had gastric emptying test (GET) values available; in the US, it was 75% of patients. European centers had more DM patients (59%) than the US (22%), and a smaller proportion of ID patients (25%) than the US (72%). There was a statistical difference between the causes of gastroparesis in the patients receiving GES (P-value < 0.00001). There was also significant difference in the gender of the patients receiving GES, with a greater proportion of women in the US (P value = 0.0023).ConclusionsComparing GES in US vs. Europe demonstrated significant differences in gastroparesis demographics and percentage of patients with GET data. After analyzing the previously discussed results and reviewing recent updates in evidence-based medicine guidelines, the discrepancy and variance in patient populations in the US and Europe emphasizes the need for a database that allows better analysis and treatment of gastroparesis patients worldwide including stimulation therapies.

296 Effectiveness of Gastric Electrical Stimulation in Gastroparesis: Results From a Large Prospectively Collected Database of a National Gastroparesis Registry

296 Effectiveness of Gastric Electrical Stimulation in Gastroparesis: Results From a Large Prospectively Collected Database of a National Gastroparesis Registry

Follow-Up after Gastric Electrical Stimulation for Gastroparesis

Gastric electrical stimulation (GES) is used to treat medically refractory gastroparesis. However, there are few large series with outcomes beyond 12 months. This study reports surgical outcomes of GES for patients up to 8 years receiving treatment from a single institution. A prospective database was reviewed from 2003 to 2013 for patients undergoing GES. Baseline patient characteristics were recorded, including age, sex, cause of gastroparesis, gastric emptying, and Hgb A1C. Outcomes variables included nutrition supplementation, additional operations, 30-day morbidity, and mortality. Pre- and postoperative pain and function scores are analyzed over time using generalized estimating equations. Patient outcomes in terms of reoperation rates and types of operations are also reviewed. Seventy-nine patients underwent GES with a mean ± SD age of 43 ± 11 years and a BMI of 27 ± 8 kg/m(2). Symptom scores were available for 60 patients: 60 patients at baseline, 52 patients at 1 year, 14 patients during years 2 to 3, and 18 patients during years 4 to 8. Symptom scores decreased considerably in all categories. At 1-year follow-up, 44% and 31% of patients had at least a 25% reduction in symptom distress for functional and pain symptoms, respectively. Preoperatively, 9 patients required nutrition supplementation. After implantation, 34 (43%) patients underwent additional operations, with a mean of 2.15 operations per patient. Generator-related causes were the most common indication for reoperation, including battery exchanges and relocation. Other operations included 8 gastrectomies and 7 median arcuate ligament releases. Postoperatively, 4 patients required supplemental nutrition. There were no 30-day mortalities, but 11 patients died during the study period. Gastric electrical stimulation was significantly associated with reductions in both functional and pain-related symptoms of gastroparesis. Patients who undergo GES have a high likelihood of additional surgery.

Treatment of high‐frequency gastric electrical stimulation for gastroparesis

The aim of this study was to assess the effects of gastric electrical stimulation (GES) on symptoms and gastric emptying in patients with gastroparesis, and the effects of GES on the three subgroups of gastroparesis. A literature search of clinical trials using high-frequency GES to treat patients with gastroparesis from January 1995 to January 2011 was performed. Data on the total symptom severity score (TSS), nausea severity score, vomiting severity score, and gastric emptying were extracted and analyzed. The statistic effect index was weighted mean differences. Ten studies (n = 601) were included in this study. In the comparison to baseline, there was significant improvement of symptoms and gastric emptying (P < 0.00001). It was noted that GES significantly improved both TSS (P < 0.00001) and gastric retention at 2 h (P = 0.003) and 4 h (P < 0.0001) in patients with diabetic gastroparesis (DG), while gastric retention at 2 h (P = 0.18) in idiopathic gastroparesis (IG) patients, and gastric retention at 4 h (P = 0.23) in postsurgical gastroparesis (PSG) patients, did not reach significance. Based on this meta-analysis, the substantial and significant improvement of symptoms and gastric emptying, and the good safety we observed, indicate that high-frequency GES is an effective and safe method for treating refractory gastroparesis. DG patients seem the most responsive to GES, both subjectively and objectively, while the IG and PSG subgroups are less responsive and need further research.

Sa1952 The Analysis of Different Electrical Energies Applied Intraoperatively May Help Understand the Mechanisms of Gastric Electrical Stimulation in Gastroparesis

Introduction: Gastric electrical stimulation (GES) appears to have a beneficial effect in disorders of foregut dysfunction but the mechanisms are unknown. We have previously reported that different electrical energies may cause differing responses when measured during surgical implantation of GES devices. We now report on a large series of consecutive patients who were given different magnitudes of electrical stimulation intraoperatively. We aimed to investigate the types of response to better understand the mechanisms of GES. Patients: We intraoperatively evaluated 87 consecutive patients with drug-refractory gastroparesis (68 female, 19 male; aged 13-76 years, mean 43.4 years; 37 diabetic, 50 idiopathic etiologies) who had elected treatment by permanent GES. Methods: Four energy settings were studied sequentially by using previously standardized parameters: low (pulse width, 330 μs; amplitude, 5 mA; frequency, 14 Hz; cycle ON, 0.1 s; cycle OFF, 5.0 s), medium (pulse width of 330 μs; amplitude, 10 mA; frequency, 28 Hz; cycle ON: 1.0 s; cycle OFF, 4.0 s), and high (pulse width of 450 μs; amplitude, 20 mA; frequency, 55 Hz; cycle ON: 4.0 s; cycle OFF, 1.0 s) energy settings, along with a ‘super high' setting (pulse width of 450 μs: amplitude 20mA; frequency, 130 Hz; cycle ON: 4.0 s; cycle OFF, 1.0 s). Surgical incision exposed the stomach. One pair of leads (‘Lead 1') was attached to the gastric serosa at the cardia-body junction, another pair (‘Lead 2') attached to the serosa at the antrum, and an initial 10-minute EGG recording was obtained simultaneously from each pair (‘Baseline Lead 1'; ‘Baseline Lead 2'). The cardia-body leads were then connected to the stimulator and used to deliver current for the remainder of the study. EGG frequency and amplitude were recorded through the antral leads. Results: Overall, mean frequency did not show much change with incremental GES energy settings. However many patients showed changes at low setting and a few showed irregular frequency changes throughout study session.(figure1, 2). Baseline mean (25%Q, 75%) frequency was 3.97[3.74, 4.21]cpm which changed to 4.01 (3.75, 4.27)cpm with low energy stimulation (p=0.942). Conclusions: Intraoperative delivery of differing energies to the stomach reveals diverse patterns of response in patients with the symptoms of gastroparesis. For the majority of patients, the greatest change seemed to occur at the first energy level applied without much further change with the application of increasing energy. This finding creates the question of whether the effect is caused by the mere application of energy or the amount applied. Further analysis of this data may help us better understand the mechanism of the beneficial effect of GES.

A double-masked, randomized, placebo-controlled trial of temporary endoscopic mucosal gastric electrical stimulation for gastroparesis

Endoscopically placed, temporary gastric electrical stimulation (tGES) may relieve symptoms of gastroparesis (Gp) and predict permanent gastric electrical stimulation (GES) outcomes. To measure effects of 72 hours of temporary GES on Gp symptoms. From 2005 to 2006, we conducted a hospital-based, randomized, placebo-controlled, crossover trial of two consecutive, 4-day sessions (session 1 and session 2), enrolling 58 patients (11 males, 47 females; mean age 46 years) with GP symptom histories of three etiologies (idiopathic, 38; diabetes mellitus, 13; postsurgical, 7). 72 continuous hours temporary GES was provided for group A during session 1, and for group B during session 2. Symptoms measured daily; gastric emptying, electrogastrography, and quality of life measured at baseline and session close. In session 1, vomiting decreased in both groups, but was greater with stimulation, resulting in a day 3 difference of -1.02 (95% CI, -1.62 to -0.42; P < .001). Scores did not return to baseline during washout; on day 4, the difference persisted at -1.08 (95% CI, -1.81 to -0.35; P = .005). In session 2, vomiting slightly decreased with stimulation and slightly increased without it; at day 8, the nonactivated group had nonsignificantly greater vomiting, 0.12 (-0.68 to 0.92; P = .762). An overall treatment effect of a slight, nonsignificant daily decrease in average vomiting scores, -0.12 (-0.26 to 0.03; P = .116), was observed by pooling stimulation effects across sessions. Missing data; potential physiological imbalances between groups. Although overall treatment effects were not significant, differences in favor of stimulation were suggested. Barriers to observing treatment effects included a decrease in vomiting for both groups during session 1, insufficient washout, and the absence of baseline vomiting for some patients. Future studies should better define inclusion criteria, use longer washout periods, randomize by etiology and baseline physiological findings, and pursue alternative designs. ( 00432835.).

Gastric electrical stimulation for gastroparesis: A goal greatly pursued, but not yet attained

The lack of an effective medical treatment for gastroparesis has pushed the research of new techniques of gastric electrical stimulation (GES) for nearly half a century of experimentation with a large variety of electrical stimuli delivered to the gastric wall of animals and patients with gastroparesis. Three principal methods are currently available: gastric low-frequency/high-energy GES with long pulse stimulation, high-frequency/low-energy GES with short pulse stimulation and neural sequential GES. The first method aims to reset a regular slow wave rhythm, but has variable effects on contractions and requires devices with large and heavy batteries unsuitable for implantation. High-frequency/low-energy GES, although inadequate to restore a normal gastric electro-mechanical activity, improves dyspeptic symptoms, such as nausea and vomiting, giving patients a better quality of life together with a more satisfactory nutritional status and is suitable for implantation. Unfortunately, the numerous clinical studies using this type of GES, with the exception of two, were not controlled and there is a need for definitive verification of the effectiveness of this technique to justify the cost and the risks of this procedure. The last method, which is neural sequential GES, consists of a microprocessor-controlled sequential activation of a series of annular electrodes along the distal two thirds of the stomach and is able to induce propagated contractions causing forceful emptying of the gastric content. The latter method is the most promising, but has been used only in animals and needs to be tested in patients with gastroparesis before it is regarded as a solution for this disease.

S1817 Gastric Electrical Stimulation for Gastroparesis and Abdominal Pain

S1817 Gastric Electrical Stimulation for Gastroparesis and Abdominal Pain

Preoperative Predictors of Significant Symptomatic Response After 1 Year of Gastric Electrical Stimulation for Gastroparesis

In cases of gastroparesis where significant symptoms fail to respond to standard medical therapy, gastric electrical stimulation (GES) may be of benefit. Unfortunately, not all patients improve with this therapy. Reliable preoperative predictors of symptomatic response to GES may allow clinicians to offer this expensive and invasive treatment to only those patients most likely to benefit. Therapy was initiated in 15 patients more than 12 months prior to this retrospective review of our prospectively maintained data. All patients completed a Total Symptom Score (TSS) survey at every encounter as well as the SF-36 quality-of-life instrument prior to surgery. A failure of GES therapy was considered to have occurred when after 1 year of treatment, preoperative TSS had not decreased by at least 20%. Four patients (4 idiopathic) failed to improve more than 20% on multiple assessments after a year of therapy. All diabetic patients experienced a durable symptomatic improvement with GES. Review of individual items of the TSS revealed that nonresponders experienced less severe vomiting preoperatively. Diabetic gastroparesis patients respond best to GES. Responders tend to have more severe vomiting preoperatively. Patients with idiopathic gastroparesis who do not experience severe vomiting should be cautioned about a potentially higher rate of poor response to GES and may be better served with alternative treatments.

Review article: gastric electrical stimulation for gastroparesis – physiological foundations, technical aspects and clinical implications

Application of electrical stimulation to the gut, primarily the stomach, has rapidly advanced in the last two decades, from mostly animal studies to the clinical arena. Most studies focused on the use of electrical stimulation for gastroparesis, the only approved indication for such intervention. To review the physiological basis of gastric electrical activity and the technical aspects and clinical outcome of gastric electrical stimulation (GES) for gastroparesis. PubMed search from 1966 to 2009, using gastroparesis and GES as search terms. Areas in focus were systematically reviewed. The literature consists of open-label studies, mostly from single centres, published in the last decade. Improvement in symptoms, quality of life and nutritional status was reported by most studies. Physiologically, stimulation parameters approved in clinical practice do not regulate gastric slow wave activity and have inconsistent effect on gastric emptying. The mechanism of action of GES is not fully known, but data support modulation of gastric biomechanical activity and afferent neural mechanisms. Gastric electrical stimulation is a helpful intervention in recalcitrant gastroparesis. Controlled studies and better understanding of mechanisms of action of electrical stimulation are needed to evaluate further the clinical utility of this intervention and to exploit its therapeutic potential better.

Mechanisms of symptomatic improvement after gastric electrical stimulation in gastroparetic patients

The aims were to investigate the effects of gastric electrical stimulation (GES) on autonomic function, gastric distention and tone, and central control mechanisms in gastroparetic patients. Ten gastroparetic patients refractory to standard medical therapy participated in this study and data were collected at baseline, within two weeks before surgery for implantation of GES system, and at follow-up sessions between 6 and 12 weeks after GES therapy was initiated. In each session, electrocardiogram, electrogastrogram (EGG) and gastric barostat measurements were conducted before and after a caloric liquid meal. Positron Emission Tomography (PET) brain scans were performed on a separate day. During GES therapy there was a significant increase in the discomfort threshold for mean pressure from 21 mmHg at baseline to 25 mmHg at follow-up, and for mean volume from 561 mL to 713 mL. A significant increase in the postprandial EGG power (amplitude) was observed between baseline and follow up. The sympathovagal balance was significantly decreased after GES therapy, indicating a significant increase in vagal activity. The cumulative PET data showed an increase in quantitative radioactive counts relative to the standardized data base in both the thalamic and caudate nuclei after chronic GES therapy. We conclude that our data suggest that the symptomatic improvement achieved by GES in gastroparesis is best explained by activation of vagal afferent pathways to influence CNS control mechanisms for nausea and vomiting accompanied by enhanced vagal efferent autonomic function and decreased gastric sensitivity to volume distention which enhances postprandial gastric accommodation.

M1586 Preoperative Predictors of Significant Symptomatic Response After 1 Year of Gastric Electrical Stimulation for Gastroparesis

M1586 Preoperative Predictors of Significant Symptomatic Response After 1 Year of Gastric Electrical Stimulation for Gastroparesis