Gastric pacing improves emptying and symptoms in patients with gastroparesis

Anal electrical stimulation with long pulses increases anal sphincter pressure in conscious dogs

PURPOSE

This study was designed to investigate the effects and mechanisms of anal electric stimulation with long pulses on anal sphincter pressure in conscious dogs.

METHODS

The study was performed after enema in nine healthy female hound dogs and composed of four randomized sessions ("dose"-response, anal electric stimulation only, or with atropine or phentolamine). The anal sphincter pressure was measured by using manometry and quantified by using the area under the contractile curve (mmHg/sec). Anal electric stimulation was performed via a pair of ring electrodes attached to a manometric catheter. The stimulation parameters in all but dose-response sessions included a frequency of 20 ppm, pulse width of 200 ms, and amplitude of 3 mA.

RESULTS

The anal sphincter pressure was 55.7 +/- 6 at baseline and increased by 37 percent to 76.4 +/- 6.5 during electric stimulation (P = 0.009). The increase of anal pressure during stimulation was positively correlated with the stimulation energy (r = 0.395; P < 0.01). The excitatory effect of electric stimulation was sustained for at least 20 minutes. Atropine did not alter anal pressure and did not abolish the excitatory effect of anal electric stimulation on the sphincter. Phentolamine reduced anal pressure from the baseline value of 50.5 +/- 4.7 to 33.1 +/- 5.4 (P = 0.019). The electric stimulation induced increase in anal pressure was dropped from 19 +/- 2.6 to 9.9 +/- 2.8 (P = 0.029) at the presence of phentolamine.

CONCLUSIONS

Anal electric stimulation with long pulses increases anal sphincter pressure in an energy-dependent manner. The alpha-adrenergic but not the cholinergic pathway at least partially mediates the excitatory effect of anal electric stimulation.

Colonic electrical stimulation regulates colonic transit via the nitrergic pathway in rats

Gastrointestinal electrical stimulation has been proposed for the treatment of gastrointestinal motor disorders. However, little is known about potential roles of colonic electrical stimulation (CES). The aim of this study was to evaluate the effect and mechanism of CES on colonic transit in conscious rats. Male rats (N = 14) were equipped with a pair of colonic serosal electrodes for stimulation and a catheter in the colon. Colonic transit was assessed in four randomized sessions with or without CES and with or without nitric oxide synthesis blocker, L-NNA, by calculating the output of phenol red from the anus every 10 min for 90 min. Results were as follows. (1) CES with trains of short pulses significantly enhanced colonic transit. Colonic emptying was 57.3 +/- 6.1% in the control session and 81.9 +/- 4.6% with CES at 90 min, reflecting a 43% increase. (2) L-NNA delayed colonic transit compared with saline and prevented the accelerative effect of CES on colonic transit. We conclude that CES has an excitatory effect on colonic transit and this excitatory effect may be mediated via the nitrergic pathway.

Gastric electrical stimulation in gastroparesis: where do we stand?

Gastroparesis is a chronic disabling condition of impaired gastric motility that results in decreased quality of life. Currently available medical therapy consists of prokinetic and/or antiemetic therapy, dietary modifications, and nutritional supplementation. For patients with medication-resistant gastroparesis a non-pharmacological therapy, gastric electric stimulation, has evolved over the last decade. Based on the frequency of the electrical stimulus, gastric electric stimulation can be classified into low- and high-frequency gastric electric stimulation. The first method aims to normalize gastric dysrhythmia and entrain gastric slow waves and accelerates gastric emptying, whereas high-frequency gastric electric stimulation is unable to restore normal gastric emptying, but nevertheless stunningly reduces symptoms, such as nausea and vomiting, re-establishes quality of life, nutritional state in all patients, and metabolic control in patients with diabetic gastroparesis. Gastric electric stimulation presents a new possibility in the treatment of gastroparesis.

Neural mechanisms involved in the inhibition of intestinal motility induced by intestinal electrical stimulation in conscious dogs

The effects and mechanisms of intestinal electrical stimulation (IES) with long pulses on intestinal motility were investigated in conscious dogs. Eighteen dogs were equipped with serosal electrodes and an intestinal cannula in the small bowel. The first experiment was designed to study the effect of one-channel IES on intestinal motility and the extent of this effect. The second experiment was conducted to study the effect of IES on intestinal motility and the involvement of neural pathway. The IES with long pulses significantly inhibited intestinal motility. Intestinal motility of the entire measured segment (40-220 cm distal to the stimulation electrodes) was inhibited by 60-74% with the single-channel IES with long pulses. Hexamethonium, guanethidine, phentolamine, propranolol partially, but not N(omega)-nitro-L-arginine (L-NNA), ondansetron and naloxone prevented the inhibitory effect of IES on intestinal motility. We conclude that single-channel IES inhibits intestinal motility within a distance of at least 2 m. This inhibitory effect induced by IES with long pulses is mediated via sympathetic but not nitrergic, serotoninergic 5-HT(3) and opiate pathway.

Reverse gastric pacing reduces food intake without inducing symptoms in dogs

OBJECTIVE

To investigate the therapeutic potential of reverse gastric pacing (RGP) for obesity by studying the effects of RGP on food intake and symptoms in dogs.

MATERIAL AND METHODS

The study was performed in 9 dogs in 3 sessions (control, strong RGP and moderate RGP). Gastric myoelectrical activity and food intake were measured in each session. RGP was performed using serosal electrodes implanted in the distal stomach at the physiological frequency of the intrinsic gastric myoelectrical activity with a pulse width of 550-950 ms. The amplitude of the stimulus was set at a level maximally tolerable by the animals in the strong RGP session and 50% of the maximum level in the moderate session.

RESULTS

1) Compared with the control, strong RGP (p<0.001) and moderate RGP (p<0.01) significantly reduced the amount of food intake by 62.9% and 31.7%, respectively (p<0.05, ANOVA). 2) Whereas strong RGP induced significant symptoms, moderate RGP did not induce any significant symptoms in comparison with the control session. 3) The regularity and coupling of gastric myoelectrical activity were significantly impaired with both strong RGP and moderate RGP in the fasting state.

CONCLUSIONS

RGP impairs intrinsic gastric myoelectrical activity and substantially and acutely reduces food intake. The reduced food intake and freedom from symptoms resulting from moderate RGP are indicative of the therapeutic potential of RGP in obesity.

Electrical stimulation for gastroparesis

BACKGROUND

Gastroparesis is a disabling, and sometimes fatal, disease that often does not respond to medical treatment. This single-surgeon prospective study examines the safety and 6-month efficacy of electrical stimulation for the treatment of gastroparesis.

METHODS

Sixteen patients with medically refractory gastroparesis underwent laparoscopic implantation of an electrical stimulator device (Enterra Therapy, Medtronic, Minneapolis, MN, USA) consisting of a subcutaneous stimulator and two gastric wall leads. Gastric emptying scans (GES) confirmed the diagnosis of gastroparesis. Patients were evaluated preoperatively using a self-administered GI symptomatology questionnaire and RAND 36 Health Survey. Once patients were >6-months from implantation, a repeat GES was obtained and patients completed a postoperative GI symptomatology questionnaire and RAND 36 Health Survey. Ten of 16 patients in this case series were >6-months from implantation. One was lost to follow-up. An F-test was used to establish equality of standard deviations between the 16 patients evaluated preoperatively and the subset of 10 patients evaluated postoperatively. A Student's t-test was used to evaluate the significance of differences in pre- and postoperative results.

RESULTS

Average operating time was 117 min with no intraoperative complications. The majority of patients were discharged on postoperative day 1. There were two complications in the postoperative period. Patients experienced a significant decrease in nausea and vomiting as measured by the GI symptomatology questionnaire. Half of all patients no longer required gastric prokinetic medications and there was a subjective reduction of pyrosis, early satiety, and epigastric pain. A significant increase in quality of life as measured by the RAND 36 Health Survey was seen, and six of eight patients no longer demonstrated gastroparesis on GES.

CONCLUSION

Laparoscopic implantation of an electrical stimulation device is a safe and effective treatment by subjective and objective standards for the management of medically refractory gastroparesis.

Efficiency and efficacy of multi-channel gastric electrical stimulation

Gastric electrical stimulation (GES) using single channel has been under investigation for its therapeutic potential for gastroparesis. The aim of this study was to study the efficacy and efficiency of multi-channel GES in accelerating gastric emptying in dogs. The study was performed in eight dogs, and gastric emptying of liquid was assessed in three randomized sessions of control, one-channel GES and four-channel GES. It was found that (i) GES of both one-channel and four-channel was able to completely entrain the slow waves in the entire stomach. However, the stimulation energy required by four-channel GES was only 1% of that required by one-channel GES. (ii) Four-channel, but not one-channel, GES significantly and substantially accelerated gastric emptying. An increase of 121.0 and 93.9% was noted with four-channel GES at 30 and 60 min after the meal, respectively. It was concluded that four-channel GES is substantially more efficient and effective than conventional single-channel GES in improving gastric emptying. It is worthy to explore its therapeutic potential for gastroparesis in clinical settings.

Tachygastria induced by gastric electrical stimulation is mediated via alpha- and beta-adrenergic pathway and inhibits antral motility in dogs

BACKGROUND

It is known that tachygastria is associated with gastric hypomotility and retrograde gastric electrical stimulation (RGES) delays gastric emptying and is proposed for treating obesity. The aim was to investigate the effects and mechanisms of RGES on postprandial antral contraction in dogs.

METHODS

Seven dogs were implanted with a gastric cannula and three pairs of gastric serosal electrodes. Antral contractions and gastric myoelectrical activity were recorded immediately after a solid meal, with or without RGES, or with GES on the corpus, or with RGES under administration of propranolol. The stimulus was composed of long pulses with a tachygastrial frequency.

RESULTS

(i) GES at the tachygastrial frequency impaired gastric myoelectrical activity and induced tachygastria (anovaP<0.05). (ii) GES at the tachygastrial frequency suppressed antral contractions (anovaP<0.01) and the effect was stronger with retrograde stimulation than forward stimulation (P<0.05). (iii) GES-induced tachygastria was correlated with antral hypomotility (r=-0.60, P=0.01). (iv) Propranolol and phentolamine abolished GES-induced tachygastria and antral hypomotility.

CONCLUSIONS

Long-pulse RGES at a tachygastrial frequency suppresses postprandial antral contractions, which is attributed to an induction of tachygastria via the alpha- and beta-adrenergic pathway.

Gastric electrical stimulation inhibits postprandial antral tone partially via nitrergic pathway in conscious dogs

Gastric electrical stimulation (GES) has recently been explored as a therapeutic option for gastrointestinal motility disorders or obesity. The mechanism behind it is not fully elucidated. The aims of this study were to assess the effects of GES with different parameters on antral tone and to explore the involvement of the nitrergic pathway. Eight dogs equipped with a gastric cannula and one pair of serosal electrodes in the greater curvature 4 cm above the pylorus were studied on separate days. The study was composed of seven randomized sessions in the fed state [control, GES with different parameters, and GES plus neuronal nitric oxide synthase (nNOS) inhibitor]. Each session included three consecutive 30-min periods (baseline, GES, and recovery). GES was performed with long pulses or pulse trains. The antral volume was measured using an intragastric balloon connected with a barostat device. Behaviors of the dogs during each stimulation period were also noted. We found that 1) postprandial antral tone was reduced with GES with all tested parameter settings, reflected as a significant and substantial increase in antral volume ranging from 179 to 309%; 2) the inhibitory effect of GES on antral tone was partially blocked (decreased by 39.5%) with an nNOS inhibitor; and 3) mild symptoms were induced with GES and found to be correlated with the GES-induced increase in antral volume. We conclude that retrograde GES with long pulses or pulse trains inhibits antral tone, and this inhibitory effect is partially mediated via the nitrergic pathway. These results suggest that retrograde GES may have a therapeutic potential for obesity.

An unusual electrocardiogram artifact: what is its source?

A diabetic female presented with nausea and vomiting. Her electrocardiogram showed sinus rhythm with two artifactual spikes, not synchronized with the cardiac rhythm. The patient had an implanted gastric electrical stimulation system for treating her diabetic gastroparesis. Recent DC shock for ventricular fibrillation during coronary angiography caused malfunction of the gastric pacemaker.

Gastric Motility, Gastroparesis, and Gastric Stimulation

Gastroparesis is the most common disorder of gastric motility. It is frequently overlooked in clinical practice because the symptoms of gastroparesis are nonspecific. This article reviews normal and abnormal gastric motility, discusses the etiology and pathogenesis of gastroparesis, and provides an overview on new treatment options for gastroparesis, including gastric stimulation.

New management approaches for gastroparesis

Management of patients with gastroparesis is challenging. Although the syndrome has multiple causes and knowledge of the pathophysiology and natural history is far from complete, a number of common management principles can be applied. The relatively poor correlation between upper-gastrointestinal symptoms and disordered gastric emptying represents a major difficulty in the therapeutic approach, and evidence to support the efficacy of current management strategies is often suboptimal, especially in relation to long-term therapy. In this review, the common causes and pathophysiology of gastroparesis are summarized, the diagnostic approach considered, and the evidence to support medical and surgical therapies reviewed. These therapies include currently available prokinetic drugs, novel medical therapies, and the promising technique of gastric electrical stimulation.

Gastric motor dysfunction: is eosinophilic mural gastritis a causative factor?

Delayed gastric emptying caused either by gastric motor dysfunction or by gastroparesis is a profoundly debilitating disorder. When unresponsive to medical therapy, patients may undergo radical surgery including near-total gastro-oesophageal, with varied symptomatic improvement. We describe two patients who presented with symptoms consistent with gastro-oesophageal reflux, unresponsive to medical management. After fundoplication both developed symptoms of profound gastric motor dysfunction and subsequently proceeded to near-total gastro-oesophageal with symptomatic improvement. Histological examination of both excised gastric specimens revealed eosinophilic mural gastritis. To our knowledge, these are the first cases to demonstrate the association of mural eosinophilia and symptomatic gastric motor dysfunction. We propose that patients with gastric motor dysfunction, refractory to medical management, progress to laparoscopy and mural biopsy before gastrectomy. This would allow histological analysis of the gastric wall, and in the event of a positive finding of mural eosinophilic gastritis would allow a trial of medical therapy that could include an eosinophilic stabilizer such as the leukotriene D4 receptor antagonist montelukast or intravenous corticosteroid therapy, which may alleviate the symptoms.

Visceral response to acute retrograde gastric electrical stimulation in healthy human

AIM: To investigate the visceral response to acute retrograde gastric electrical stimulation (RGES) in healthy humans and to derive optimal parameters for treatment of patients with obesity.

METHODS: RGES with a series of effective parameters were performed via a bipolar mucosal electrode implanted along the great curvature 5 cm above pylorus of stomach in 12 healthy human subjects. Symptoms associated with dyspepsia and other discomfort were observed and graded during RGES at different settings, including long pulse and pulse train. Gastric myoelectrical activity at baseline and during different settings of stimulation was recorded by a multi-channel electrogastrography.

RESULTS: The gastric slow wave was entrained in all the subjects at the pacing parameter of 9 cpm in frequency, 500 ms in pulse width, and 5 mA in amplitude. The frequently appeared symptoms during stimulation were satiety, bloating, discomfort, pain, sting, and nausea. The total symptom score for each subject significantly increased as the amplitude or pulse width was adjusted to a higher scale in both long pulse and pulse train. There was a wide diversity of visceral responses to RGES among individuals.

CONCLUSION: Acute RGES can result in a series of symptoms associated with dyspepsia, which is beneficial to the treatment of obesity. Optimal parameter should be determined according to the individual sensitivity to electrical stimulation.

Gastric electrical stimulation significantly increases canine lower esophageal sphincter pressure

This study determined the effect of low-frequency and high-frequency gastric electrical stimulation (GES) on canine lower esophageal sphincter (LES) pressure and also evaluated the effect of such stimulation on neurohumoral factors that modulate LES pressure. Eight dogs were fitted with stimulation wires along the greater curvature of the stomach. A sleeve device measured LES pressure before, during, and after GES, and regulatory peptides were measured during fasting and after a meal. A consistent and significant rise in LES pressure was observed during GES, and it was sustained after GES was discontinued. Plasma concentration and area under the curve of pancreatic polypeptide, motilin, gastrin and neurotensin were not affected by GES. We conclude that acute low- and high-frequency GES significantly increases LES pressure. This effect may not be modulated by efferent vagal activity or release of regulatory peptides.

Gastric electrical stimulation modulates neuronal activity in nucleus tractus solitarii in rats

Implantable gastric electric stimulation (GES) has been under investigation for the treatment of gastric motor disorders and obesity. However, possible central mechanisms involving the effects of GES on gastric function are unclear. The purpose of this study was to examine the effects of GES with different parameters on neuronal activity in the nucleus tractus solitarii (NTS) of the medulla. Extracellular potentials of single neurons in NTS were recorded in pentobarbital anesthetized, paralyzed, ventilated male rats. GES with four sets of parameters was applied for one minute: GES-A (6 mA, 0.3 ms, 40 Hz, 2 s-on and 3 s-off), GES-B (20 mA, 0.3 ms, 40 Hz, 2 s-on and 3 s-off), GES-C (6 mA, 6 ms, 40 Hz, 2 s-on and 3 s-off), and GES-D (6 mA, 200 ms, 12 imps/min). 35/118 (30%) neurons in NTS were responsive to gastric distension (GD, 20 mmHg, 20 s). Forty-one percent, 67%, 76% and 42% of all the responsive NTS neurons were affected by GES-A, -B, -C and -D, respectively. More NTS neurons with gastric inputs were affected with GES-C (19/25) than with GES-A (11/27, P<0.05) and GES-D (10/24, P<0.05). Maximal excitatory responses (17.9+/-2.6 imp/s) of NTS neurons to GES-C were significantly greater than GES-D (9.7+/-4.8 imp/s, P<0.05), whereas average duration of excitatory response (74.8+/-4.3 s) of NTS neurons to GES-B was significant longer than GES-A (60.3+/-3.3 s). Gastric electrical stimulation primarily has an excitatory effect on NTS neurons receiving input from the stomach; the central neuronal response to GES is enhanced with stimulation using an increased pulse width and/or amplitude. This modulatory effect of GES on the central neurons receiving vagal inputs may contribute to the neural mechanisms of GES therapy for the treatment of patients with obesity and gastric motility disorders.

Driving gastric electrical activity with electrical stimulation

Gastric electrical stimulation (GES) therapy is generating a lot of interest, but it is still investigational. Its efficacy in driving gastric electrical activity and improving motility, and the ideal frequency for bringing this about are still controversial. In this study, a rule-based computer model of tissue electrical response to stimulation was developed to examine the interaction between tissue electrical refractoriness and the onset of tissue activation. The results were compared to response to GES in 8 dogs implanted with electrodes and strain gauges and stimulated at frequencies ranging from 3 to 30 cycles/min. Simulated electrical control activity at an intrinsic frequency of 5/min was entrained from 2.0 cycles/min to 7.92 cycles/min. The regularity of the ECA elicited by stimulation depended on the number of pulses injected. Electrical stimulation in canine stomach entrained the native electrical control activity from a baseline average of 5.14 +/- 0.32 cycles/min up to 9.2 cycles/min. Contractile response to stimulation at 20-30 cycles/min were significantly higher (p < 0.05). Computer simulation of GES may be a useful tool to complement and reduce some of the costs associated with empirical studies of gastric electrical stimulation in establishing its possible use in treating drug refractory gastroparesis.

Cross-talk along gastrointestinal tract during electrical stimulation: effects and mechanisms of gastric/colonic stimulation on rectal tone in dogs

Gastric electrical stimulation (GES) has been shown to alter motor and sensory functions of the stomach. However, its effects on other organs of the gut have rarely been investigated. The study was performed in 12 dogs implanted with two pairs of electrodes, one on the serosa of the stomach and the other on the colon. The study was composed of two experiments. Experiment 1 was designed to study the effects of GES on rectal tone and compliance in nine dogs compared with colonic electrical stimulation (CES). Rectal tone and compliance were assessed before and after GES or CES. Experiment 2 was performed to study the involvement of sympathetic pathway in 8 of the 12 dogs. The rectal tone was recorded for 30-40 min at baseline and 20 min after intravenous guanethidine. GES or CES was given for 20 min 20 min after the initiation of the infusion. It was found that both GES and CES reduced rectal tone with comparable potency. Rectal compliance was altered neither with GES, nor with CES. The inhibitory effect of GES but not CES on rectal tone was abolished by an adrenergic blockade, guanethidine. GES inhibited rectal tone with a comparable potency with CES but did not alter rectal compliance. The inhibitory effect of GES on rectal tone is mediated by the sympathetic pathway. It should be noted that electrical stimulation of one organ of the gut may have a beneficial or adverse effect on another organ of the gut.

Nausea, gastroparesis, and aerophagia

Nausea, gastroparesis, and aerophagia are gastrointestinal phenomena that have variable impact on affected patients. The causes of nausea are varied; treatment of these conditions relates to the underlying etiology. Antiemetic agents acting on several distinct receptor subtypes produce benefits in distinct patient subsets. Gastroparesis is characterized by delays in gastric emptying, usually defined scintigraphically. Standard care of gastroparesis relies on dietary modification, antiemetic drug therapy, and initiation of medications that stimulate gastric motor activity. Recent advances include pyloric injection of botulinum toxin and surgical implantation of an electrical neurostimulator. Other surgical therapies are reserved for refractory cases. Aerophagia presents in individuals of normal and impaired cognitive function, most commonly with symptoms of overdistension or eructation. There are no pharmaceutical remedies for this condition; thus, therapy relies on behavioral treatments.

Electrogastrography: basic knowledge, recording, processing and its clinical applications

The slow wave (SW) of the gastrointestinal (GI) tract mainly functions to trigger the onset of spike to elicit smooth muscle contraction, which provides the essential power of motility. Smooth muscle myogenic control activity or SW is believed to originate in the interstitial cells of Cajal (ICC). The electrical coupling promotes interaction between muscle cells, and ICC additionally contribute to SW rhythmicity. Stomach SW originates in the proximal body showing the continuous rhythmic change in the membrane potential and propagates normally to the distal antrum with a regular rhythm of approximately 3 c.p.m. A technique using electrodes positioned on the abdominal skin to pick up stomach rhythmic SW refers to electrogastrography (EGG). The stomach SW amplitude is very weak, while many visceral organs also produce rhythmic electricities, for example heartbeat, respiration, other organs of the GI tract and even body movements. Thus noise other than SW should be filtered out during the recording, while motion artifacts are visually examined and deleted. Finally, the best signal among all recordings is selected to compute EGG parameters based on spectral analysis. The latter is done not only to tranform frequency domain to time domain but also to provide information of time variability in frequency. Obtained EGG parameters include dominant frequency/power, % normal rhythm, % bradygastria, % tachygastria, instability coefficient and power ratio. Clinical experience in EGG has been markedly accumulated since its rapid evolution. In contrast, lack of standardized methodology in terms of electrode positions, recording periods, test meals, analytic software and normal reference values makes the significance of EGG recording controversial. Unlike imaging or manometrical studies, stomach motility disorders are not diagnosed based only on abnormal EGG parameters. Limitations of EGG recording, processing, computation, acceptable normal parameters, technique and reading should be known to conduct subjective assessments when EGG is used to resolve stomach dysfunction. Understanding basic SW physiology, recording methodology and indications may open EGG as a new domain to approach the stomach motor dysfunction.

Two-channel gastric electrical stimulation accelerates delayed gastric emptying induced by vasopressin

The aim of this study was to investigate the effects of two-channel gastric electrical stimulation (GES) on delayed gastric emptying, gastric dysrhythmias, and motion sickness-like symptoms induced by vasopressin. Seven dogs implanted with four pairs of gastric electrodes and a duodenal cannula were studied in four randomized sessions (saline, vasopressin, single-channel GES, and two-channel GES). The experiment in each session was conducted sequentially as follows: 30-min baseline, ingestion of a liquid meal, 30-min iv infusion of vasopressin or saline, and two 30-min postprandial recordings. In the GES sessions, GES was applied via the first pair of electrodes for single-channel GES or the first and third pairs of electrodes for two-channel GES. Gastric emptying was collected every 15 min via the cannula for a period of 90 min. Results were as follows. (1) Vasopressin induced gastric dysrhythmias, motion sickness-like symptoms, and delayed gastric emptying (P < 0.01, ANOVA). (2) GES normalized gastric dysrhythmias (P < 0.01) but showed no effects on vasopressin-induced emetic response. (3) Two-channel GES improved delayed gastric emptying induced by vasopressin. In comparison with the vasopressin session, two-channel GES, but not single-channel GES, significantly increased gastric emptying at 30 min (43.9+/-12.6 vs. 27.5+/-7.7%; P < 0.03), 60 min (75.3+/-15.1 vs. 54.0+/-17.8%; P < 0.05), and 90 min (91.6+/-9.8 vs. 80.3+/-9.0%; P < 0.05). GES with long pulses is able to normalize gastric dysrhythmias. Two-channel GES improves delayed gastric emptying induced by vasopressin.

Therapeutic potential of duodenal electrical stimulation for obesity: acute effects on gastric emptying and water intake

OBJECTIVES

No satisfactory treatment is available for obesity. Previous animal studies suggested the therapeutic potential of intestinal electrical stimulation for obesity. The aim of this study was to investigate the effects of duodenal electrical stimulation (DES) on gastric emptying and water intake in healthy humans.

METHODS

The study was performed in 12 healthy volunteers intubated with a feeding tube in the duodenum under endoscopy. There were three ring electrodes at the end tip of the tube and the two distal electrodes were used for recording and electrical stimulation. On two separate days, each subject underwent a session of DES with various stimulation parameters, a water-intake test with DES or with sham-DES, and a gastric-emptying test with DES or with sham-DES.

RESULTS

DES did not induce any noticeable dyspeptic symptoms. The amount of water drunk by the subjects was significantly reduced from 897 +/- 88 ml with sham-DES to 673 +/- 63 ml with DES (p < 0.002). The mean T(50) of gastric emptying was significantly increased from 113.1 +/- 10.0 min with sham-DES to 176.5 +/- 20.8 min with DES state (p < 0.005). The gastric retention at 2 h was increased with DES (42.8 +/- 4.5% vs 61.4 +/- 4.7%; p < 0.02).

CONCLUSIONS

DES delays gastric emptying and reduces water intake. It may have a potential application for the treatment of obesity.

Effects of vasopressin and long pulse-low frequency gastric electrical stimulation on gastric emptying, gastric and intestinal myoelectrical activity and symptoms in dogs

The aim of this study was to investigate the effect of vasopressin and long pulse-low frequency gastric electrical stimulation (GES) on gastric emptying, gastric and intestinal myoelectrical activity and symptoms in dogs. The study was performed in eight healthy female dogs implanted with four pairs of gastric serosal electrodes and two pairs of small bowel serosal electrodes, and a duodenal fistula for the assessment of gastric emptying. Each dog was studied in three sessions on three separate days in a randomized order with recordings of gastric and small bowel slow waves. Each study session consisted of 30-min baseline, 30-min stimulation and 30-min recovery period. In sessions 1 and 2, infusion of either saline or vasopressin (0.75 U kg(-1) in 30 mL saline instilled in 30 min) was given during the second 30-min period. The protocol of session 3 was the same as session 2 except long pulse-low frequency GES was performed during the second 30-min period. It was found that: (i) Vasopressin significantly delayed gastric emptying 30 and 45 min after meal and GES did not improve the vasopressin induced delayed gastric emptying; (ii) Vasopressin induced gastric dysrhythmias and GES significantly improved vasopressin induced gastric dysrhythmia; (iii) Vasopressin also induced intestinal slow wave abnormalities but GES had no effect on vasopressin induced small bowel dysrhythmia; (iv) Vasopressin induced symptoms and behaviours suggestive of nausea that were not improved by GES. We conclude that: (i) Vasopressin delays gastric emptying and induces gastric and small bowel dysrhythmias and symptoms in the fed state, and (ii) long pulse-low frequency GES normalizes vasopressin induced gastric dysrhythmia with no improvement in gastric emptying or symptoms.

Alterations of gastrointestinal motility in obesity

All nutrients are absorbed in the gastrointestinal (GI) system, and GI motility plays a very critical role in the consumption of foods, digestion, and absorption of nutrients. Various segments of the GI tract (esophagus, stomach, and intestines) coordinate in a complex yet precise way to control the process of food consumption, digestion, and absorption of nutrients. GI motility not only regulates the rates at which nutrients are processed and absorbed in the gut but also participates in the control of appetite and satiety. Altered GI motility has been associated with various disease conditions (gastroparesis, etc.) and has been frequently observed in obese patients. The significance of these GI motility alterations in obesity is not fully understood, but they have been considered as potential contributing factors in the development and maintenance of obesity and changed eating behavior. Therapies aimed at regulating GI motility are being actively explored and applied clinically for the management of obese patients. To better understand the pathophysiology of obesity, we systematically reviewed GI motility changes observed in obese conditions. The relationship and pathological significance of these findings, as well as the potential therapies by modification of GI motility, are also discussed.

Temporary gastric electrical stimulation with orally or PEG-placed electrodes in patients with drug refractory gastroparesis

BACKGROUND

Gastric electrical stimulation (GES) has been shown to be efficacious for drug refractory gastroparesis, but GES requires surgery. Placement of temporary GES electrodes endoscopically (ENDOstim) or via a PEG (PEGstim) is feasible, thereby allowing rapid assessment and comparison of temporary use (TEMP) with permanent (PERM) implantation.

METHODS

Twenty consecutive patients with gastroparesis had TEMP electrodes placed (6 ENDOstim, 14 PEGstim). TEMP alone and TEMP vs. PERM placement of GES devices in 13 of 20 patients were compared via the following: average vomiting frequency score (VFS), total symptom score, days to symptom improvement, electrode impedance, and gastric emptying test.

RESULTS

For patients receiving TEMP, GES demonstrated a rapid, significant, and sustained improvement in VFS, results similar to those for PERM.

CONCLUSIONS

Both ENDO and PEG placement of GES electrodes are safe and effective in patients with gastroparesis, with outcomes that correspond to those achieved with permanent GES implantation.

Intercellular coupling of interstitial cells of cajal in the digestive tract

Interstitial cells of Cajal (ICC) are essential for the normal function of the digestive tract, both as pacemakers and as intermediates between nerves and smooth muscle cells. To perform their functions ICC must be electrically coupled both among themselves and to the muscle layers. This review focuses on the role gap junctions play in coupling ICC to ICC, providing a summary of the published literature as well as a critical appraisal of the data. Most of the experimental evidence for gap junction coupling of ICC networks is indirect, and consists of the ultrastructural observation of gap junctions. Dye coupling studies provide consistent support for the role of gap junctions among ICC of certain types. Physiological evidence in support of this role is scarce. The nature of ICC to smooth muscle coupling is even less certain.

Gastric electrical stimulation reduces gastric tone energy dependently

OBJECTIVE

Impaired gastric accommodation is one of the major pathophysiological factors in functional dyspepsia (FD). Gastrointestinal electric stimulation (GES) as a potential therapy for treating patients with motility disorders has been applied in animal models and clinical practice. However, the response of proximal gastric tone to different GES has not been fully understood. Therefore, the aims of this study were to investigate the effects of GES with different parameters on gastric tone and to estimate the relationship between gastric volume, stimulation energy, and symptoms.

MATERIAL AND METHODS

Seven dogs equipped with a gastric cannula and two pairs of serosal electrodes in the greater curvature were studied with different GES via a pair of electrodes located 10-14 cm above the pylorus. The gastric volume under constant pressure was measured using a barostat device.

RESULTS

The results showed that 1) GES increased the gastric volume in a dose-dependent manner with the increase of stimulation frequency or pulse amplitude. 2) The increase in gastric volume with GES was significantly correlated to stimulation energy. 3) Mild symptoms were noted with stimulation and the score of the induced symptoms was linearly and significantly correlated with gastric volume.

CONCLUSIONS

GES decreases the proximal gastric tone in an energy-dependent manner. These data suggest that GES could be used to treat patients with impaired gastric accommodation.

Progress in implantable gastric stimulation: summary of results of the European multi-center study

BACKGROUND

The Implantable Gastric Stimulator (IGS(R)), a pacemaker-like device, has been found to be safe and effective to induce and maintain weight loss. The LOSS (Laparoscopic Obesity Stimulation Survey) is a prospective non-randomized trial which enrolled 69 patients involving 11 investigator centers in 5 European Countries. In 19 patients, ghrelin was analyzed.

METHODS

Between January 2002 and December 2003, 69 patients (F/M 49/20), mean age 41 years (18-65) underwent IGS implantation. Mean BMI was 41 (35-57), mean weight 115.0 kg (65-160) and mean excess weight (EW) 52 kg (13-89). The IGS was actived 30 days after implantation. In a subset of 19 patients studied further, 0, 6, and 12 months appetite and satiety score were evaluated and 0 and 6 months ghrelin profile was analyzed.

RESULTS

The mean +/- standard error %EWL was: 8.6+/-1.8 at 1 month, 15.8+/-2.3 at 3 months, 17.8+/-2.6 at 6 months, 21.0+/-3.5 at 10 months, and 21.0+/-5.0 at 15 months. There were no intraoperative surgical or long-term complications. 7 intra-operative gastric penetrations occurred, observed by gastroscopy, without sequelae. 1 patient required a reoperation to remove a retained lead needle. In the subset of 19 patients, appetite was reduced and post-prandial and inter-prandial satiety was increased after IGS implantation. In the 19 patients, despite weight reduction, ghrelin did not increase.

CONCLUSION

IGS can be implanted laparoscopically with minimal perioperative complications. Appetite is reduced and satiety is increased after the implantation. Ghrelin levels could be one of the mechanisms explaining weight loss and weight maintenance in IGS patients. If weight loss is maintained, IGS could be considered a good option for selected patients.

Pyloric electrical stimulation reduces food intake by inhibiting gastric motility in dogs

BACKGROUND & AIMS

The pylorus plays an important role in regulating gastric emptying. The aim of this study was to investigate the therapeutic potential of pyloric electrical stimulation (PES) for obesity in dogs.

METHODS

The study was composed of 3 separate experiments. The first experiment was designed to study the effects of PES with various parameters on gastric emptying and gastric slow waves in 5 sessions. The second experiment was used to test the effects of PES on antral contractions. The acute effect of PES on food intake was studied in the third experiment.

RESULTS

(1) Pyloric myoelectrical recording showed dual frequencies. The lower frequency was identical to the frequency of the gastric slow waves, and the higher frequency was similar to that of the intestinal slow waves. (2) Gastric emptying was significantly delayed with PES, and the delay in gastric emptying was significantly and negatively correlated with stimulation energy ( r = -.673; P < .001). (3) PES significantly impaired the regularity and coupling of the intrinsic gastric myoelectrical activity in an energy-dependent manner. The delayed gastric emptying was significantly correlated with the impairment of the coupling of gastric myoelectrical activity ( r = .441; P < .02). (4) Antral contractions on the fed state were significantly and substantially inhibited with PES. (5) Acute PES significantly reduced food intake.

CONCLUSIONS

PES reduces food intake that may be attributed to its inhibitory effects on intrinsic gastric myoelectrical activity, antral contractions, and gastric emptying.

Clinical response to gastric electrical stimulation in patients with postsurgical gastroparesis

BACKGROUND & AIMS

The aim of this study was to report the long-term clinical response to high-frequency gastric electrical stimulation (GES) in 16 patients with postsurgical gastroparesis who failed standard medical therapy.

METHODS

Clinical data collected at baseline and after 6 and 12 months of GES included (1) severity and frequency of 6 upper gastrointestinal (GI) symptoms by using a 5-point symptom interview questionnaire and total symptom score, (2) health-related quality of life including physical composite score and mental composite score, (3) 4-hour standardized gastric emptying of a solid meal by scintigraphy, and (4) nutritional status.

RESULTS

The severity and frequency of all 6 upper GI symptoms, total symptom score, physical composite score, and mental composite score were significantly improved after 6 months and sustained at 12 months ( P < .05). All patients had delayed gastric emptying at baseline. Gastric emptying was not significantly faster at 12 months, although 3 normalized. At implantation, 7 of 16 patients required nutritional support with a feeding jejunostomy tube; after GES, 4 were able to discontinue jejunal feeding. The mean number of hospitalization days was significantly reduced by a mean 25 days compared with the prior year. One patient had the device removed after 12 months because of infection around the pulse generator.

CONCLUSIONS

Long-term GES significantly improved upper GI symptoms, quality of life, the nutritional status, and hospitalization requirements of patients with postsurgical gastroparesis. Although vagal nerve damage or disruption was part of the underlying pathophysiology, GES therapy was still effective and is a potential treatment option for the long-term management of postsurgical gastroparesis. A controlled clinical trial of GES for PSG patients (who are refractory to medical therapy) is indicated given these encouraging results.

American Gastroenterological Association technical review on the diagnosis and treatment of gastroparesis

This literature review and the recommendations herein were prepared for the American Gastroenterological Association Clinical Practice Committee. The paper was approved by the Committee on May 16, 2004, and by the AGA Governing Board on September 23, 2004.

Intestinal electric stimulation decreases fat absorption in rats: therapeutic potential for obesity

OBJECTIVE

Effective treatment of obesity is based on the restriction of food intake or reduction of absorption or both. The aim of this study was to study whether intestinal electric stimulation (IES) would reduce fat absorption and, thus, would be a potential therapy for obesity.

RESEARCH METHODS AND PROCEDURES

Forty rats implanted with serosal electrodes and two jejunal cannulas were divided into 4 groups of 10 each: control (no stimulation), IES with long pulses, IES with trains of short pulses, and IES with trains of short pulses plus treatment with lidocaine. Jejunal transit and fat absorption of a 20-cm jejunal segment (between two cannulas) were investigated during a 45-minute period with or without IES.

RESULTS

It was found that both methods of IES accelerated intestinal transit measured by recovery of phenol red and increased the percentage of triglycerides recovered from the distal cannula in comparison with the control group. IES with trains of short pulses was more effective than IES with long pulses in accelerating jejunal transit and reducing fat absorption. Neither of the two IES methods altered the output of fatty acids from the distal cannula. The effects of IES with trains of short pulses on the transit and fat absorption were partially abolished with the treatment of lidocaine.

DISCUSSION

It was concluded that IES accelerates intestinal transit and reduces fat absorption, suggesting a therapeutic potential for obesity. IES with trains of short pulses is more effective than IES with long pulses, and its effects are partially mediated by enteric nerves, jejunum.

Laparoscopic revision of gastric pacing wires

Currently, electrical stimulation is utilized to treat morbid obesity, gastroparesis, and diaphragmatic paralysis. Although this technology is in its infancy, numerous case reports and small series appear throughout the literature. Furthermore, electrical stimulation is not relegated to only academic centers and tertiary referral centers. As these technologies continue to evolve and alter the treatment of several different pathophysiologic processes, the general surgeon needs to understand the technical aspects of these devices and their potential complications. This paper presents the management of a gastroparetic patient with chronic abdominal pain following the successful placement of gastric pacing wires. A 45-year-old female with idiopathic gastroparesis underwent laparoscopic placement of gastric pacing wires without complications. Four months postoperatively, she presented with chronic left upper quadrant abdominal pain. Her nausea and vomiting had dissipated and she was tolerating a regular diet. Abdominal and pelvic computed tomography (CT) was normal except for the presence of a generator and pacing wires. Ultimately, she required a diagnostic laparoscopy and an upper endoscopy. The upper endoscopy was normal. The diagnostic laparoscopy showed a wide adhesive band from the seromuscular tunnel of the pacing wires to the abdominal wall in the left upper quadrant. The band was lysed and an omental patch was sutured over the insertion site of the wires. On postoperative day 1, the patient was pain-free and discharged home on a regular diet. This case presents an unusual complication of electrical pacing wires. This patient experienced somatic pain due to an adhesive band from her pacing wires to the abdominal wall. Based on the findings of this case, an omental patch was placed on top of the seromuscular electrode tunnel in order to prevent adhesions and potentially persistent abdominal wall pain.

Gastric pacing for severe gastroparesis in a heart-lung transplant recipient

Gastroparesis is a serious complication of lung and heart-lung transplantation that can lead to malnutrition, gastroesophageal reflux, aspiration pneumonia and deteriorating lung function. Some patients with severe gastroparesis have symptoms that are refractory to dietary modifications and gastric promotility agents and require surgery. We describe the successful use of gastric pacing for the management of intractable gastroparesis, malnutrition and recurrent aspiration in a heart-lung allograft recipient. Lung transplant recipients with severe gastroparesis may benefit from gastric pacing.

Implantable gastric stimulation for weight loss

With the epidemic of obesity worldwide, bariatric surgery has rapidly grown in popularity. Currently, a variety of surgical procedures are performed including Roux-en-Y gastric bypass, laparoscopic adjustable gastric banding, vertical banded gastroplasty, and biliopancreatic diversion. All of these procedures have been shown to succeed in achieving significant and sustainable weight loss for the majority of patients. However, these procedures also carry the potential for serious operative morbidity, altered gastrointestinal anatomy or function, or both. Electrical gastric stimulation via the implantable gastric stimulation (IGS) system is a relatively new and novel approach to treat obesity. The operative technique is relatively simple and the system does not alter gastrointestinal anatomy. Preliminary worldwide investigations have demonstrated safety and efficacy. This article will review the current experience with the IGS system.

Gastric myoelectrical activity post-chemoradiotherapy and esophagectomy: a prospective study using subscapular surface recording

The aims of this study were to prospectively evaluate gastric function in esophageal cancer patients after chemoradiotherapy and following surgery, using cutaneous electrogastrography (EGG). Twenty-three patients with esophageal adenocarcinoma were recruited to the study. A subset of patients (n = 11) underwent neoadjuvant chemoradiotherapy and were also studied at 14 days after treatment. All patients underwent EGG studies prior to and following surgery, at 3 months postoperatively. Ten of these patients were also studied at medians of 6 months and 12 months after surgery. Twenty normal volunteers were used as controls. Post-operative EGG studies were monitored with a modified technique; the electrodes being placed in the subscapular region in the area of the transposed stomach. Following neoadjuvant treatment there was a significant increase in abnormal gastric myoelectrical activity involving changes in tachygastrias and decreased motility as measured by power ratio. Post-operatively there was a significant increase in bradygastria which persisted at 6 months but not at 12 months. There was a corresponding decrease in normogastria which persisted at 6 months and to a lesser extent at 12 months. Dominant frequency remained significantly depressed at 3, 6 and 12 months. Gastric myoelectrical activity is normal in untreated esophageal cancer. Neoadjuvant chemoradiotherapy causes a disruption to normal myoelectrical activity involving reduced motility and tachygastrias. Surgery causes a depression in dominant frequency with a reduced incidence of normogastria at 3 months and 6 months but with a tendency towards normality at 12 months.

Treatment of diabetic gastroparesis by high-frequency gastric electrical stimulation

OBJECTIVE

To investigate the long-term efficacy of high-frequency gastric electrical stimulation (GES) for treating diabetic gastroparesis.

RESEARCH DESIGN AND METHODS

This is a retrospective review of 48 adult diabetic patients with refractory gastroparesis who had a GES system implanted surgically and had follow-up evaluations at 6 and 12 months. The outcome measures were total symptom score (TSS), derived from six upper gastrointestinal (GI) symptom subscores; health-related quality of life (HQOL), including physical composite score (PCS) and mental composite score (MCS) assessed by SF-36 questionnaire, radionuclide gastric emptying test, nutritional status, HbA1c, and adverse events.

RESULTS

In comparison with baseline, TSS, all six upper GI symptom subscores, PCS, and MCS were significantly improved at 6 months, with the improvement sustained at 12 months. Of 13 patients receiving nutritional support at baseline by tube feeding, only 5 required supplemental enteral feeding at 12 months, and none of the 9 on total parenteral nutrition continued this support. The mean number of hospitalization days during the year after GES was significantly reduced by 52 days compared with the prior year. HbA1c levels were significantly reduced at 12 months. Gastric emptying was only minimally and not significantly faster. Because of infections at the pulse generator pocket site, four patients had their GES systems removed 3-17 months postsurgery.

CONCLUSIONS

In diabetic patients with refractory gastroparesis, high-frequency GES by a permanently implanted system significantly improved upper GI symptoms, HQOL, nutritional status, glucose control, and hospitalizations with an acceptably low complication rate.

Effect of high-frequency gastric electrical stimulation on gastric myoelectric activity in gastroparetic patients

The aim of this study was to investigate the effect of gastric electrical stimulation (GES) on gastric myoelectric activity (GMA) and to identify possible mechanisms that could help explain how high-frequency GES is effective in treating nausea and vomiting associated with gastroparesis. Fifteen gastroparetic patients who received high-frequency GES were enrolled. Two pairs of temporary pacing wires were implanted on the serosa of the stomach along the greater curvature during surgery for placement of the permanent stimulation device. Two-channel serosal recordings of GMA before and during GES were measured. A gastric emptying test and severity of nausea and vomiting were assessed at baseline and at 3 months of GES. Power spectral and cross correlation analyses revealed that impaired propagation of slow waves (50%), tachygastria (30%) and abnormal myoelectric responses to a meal (50%) were the main abnormalities observed at baseline. GES with a high frequency significantly enhanced the slow wave amplitude and propagation velocity, and resulted in a significant improvement in nausea and vomiting but did not entrain the gastric slow wave or improve gastric emptying after 3 months of GES.

Effects of gastric pacing on gastric emptying and plasma motilin

AIM: To investigate the effects of gastric pacing on gastric emptying and plasma motilin level in a canine model of gastric motility disorders and the correlation between gastric emptying and plasma motilin level.

METHODS: Ten healthy Mongrel dogs were divided into: experimental group of six dogs and control group of four dogs. A model of gastric motility disorders was established in the experimental group undergone truncal vagotomy combined with injection of glucagon. Gastric half-emptying time (GEt_1/2) was monitored with single photon emission computerized tomography (SPECT), and the half-solid test meal was labeled with an isotope ^99mTc sulfur colloid. Plasma motilin concentration was measured with radioimmunoassay (RIA) kit. Surface gastric pacing at 1.1-1.2 times the intrinsic slow-wave frequency and a superimposed series of high frequency pulses (10-30 Hz) was performed for 45 min daily for a month in conscious dogs.

RESULTS: After surgery, GEt_1/2 in dogs undergone truncal vagotomy was increased significantly from 56.35 ± 2.99 min to 79.42 ± 1.91 min (P < 0.001), but surface gastric pacing markedly accelerated gastric emptying and significantly decreased GEt_1/2 to 64.94 ± 1.75 min (P < 0.001) in animals undergone vagotomy. There was a significant increase of plasma level of motilin at the phase of IMCIII (interdigestive myoelectrical complex, IMCIII) in the dogs undergone bilateral truncal vagotomy (baseline vs vagotomy, 184.29 ± 9.81 pg/ml vs 242.09 ± 17.22 pg/ml; P < 0.01). But plasma motilin concentration (212.55 ± 11.20 pg/ml; P < 0.02) was decreased significantly after a long-term treatment with gastric pacing. Before gastric pacing, GEt_1/2 and plasma motilin concentration of the dogs undergone vagotomy showed a positive correlation (r = 0.867, P < 0.01), but after a long-term gastric pacing, GEt_1/2 and motilin level showed a negative correlation (r = -0.733, P < 0.04).

CONCLUSION: Surface gastric pacing with optimal pacing parameters can improve gastric emptying parameters and significantly accelerate gastric emptying and can resume or alter motor function in a canine model of motility disorders. Gastric emptying is correlated well with plasma motilin level before and after pacing, which suggests that motilin can modulate the mechanism of gastric pacing by altering gastric motility.

Effects of surface gastric pacing on gastric myoelectrical activity and plasma motilin in a canine model of gastric motility disorders

OBJECTIVE

To investigate the effects of surface gastric pacing on gastric myoelectrical activity and plasma motilin concentration in a canine model of gastric motility disorders.

METHODS

Ten healthy mongrel dogs were divided into two groups: an experimental group of six dogs and control group of four dogs. The model of gastric motility disorders was established in the experimental group with truncal vagotomy combined with injection of glucagon. Gastric serosal myoelectrical activity was recorded with a four-channel computer analysis device. Plasma motilin concentration was measured with a radioimmunoassay (RIA) kit. Surface gastric pacing at 1.1-1.2-fold the intrinsic slow-wave frequency superimposed with a series of high frequency pulses (10-30 Hz) was performed for 45 min daily for 1 month in the conscious dogs.

RESULTS

The basic electrical rhythm (BER) amplitude (2.32 +/- 0.35 mV) and propagation velocity (4.06 +/- 0.40 cm/s) of the dogs with bilateral truncal vagotomy in the fed state decreased more significantly than those of the controls (4.25 +/- 0.12 mV, 6.92 +/- 0.24 cm/s) (P < 0.03). After long-term surface gastric pacing, the BER amplitude (3.97 +/- 0.19 mV) and propagation velocity (5.57 +/- 0.48 cm/s) was increased significantly compared with before pacing (P < 0.05). Postprandial gastric dysrhythmias were provoked by large doses of glucagon; the percentage of regular slow waves of the dogs with vagotomy was markedly reduced from 67.4 +/- 6.2% at baseline to 10.0 +/- 6.7% (P < 0.001), and that of the control was also decreased from 87.1 +/- 6.9% to 35.0 +/- 11.0% (P < 0.01), but the entrainment of gastric slow waves was 100% by means of gastric pacing at optimal parameters. There was a significant increase in the plasma concentration of motilin at the phase III of the interdigestive myoelectrical complex (IMC III) in the dogs with bilateral truncal vagotomy (baseline vs vagotomy, 184.29 +/- 9.81 pg/mL vs 242.09 +/- 17.22 pg/mL; P< 0.01). However, the plasma motilin concentration (212.55 +/- 11.20 pg/mL; P < 0.02) was decreased significantly after long-term gastric pacing. Before gastric pacing the plasma motilin concentration showed an equally negative correlation with the BER amplitude, and propagation velocity in the dogs with vagotomy in the fed state (r = -0.473, r = -0.807, P < 0.04), but after long-term gastric pacing, the plasma motilin concentration showed an equally positive correlation with the BER amplitude and propagation velocity (r = 0.523, r = 0.896, P < 0.02).

CONCLUSIONS

Surface gastric pacing with optimal pacing parameters is able to entrain completely propagated slow waves, improve the parameters of gastric myoelectrical activity and normalize gastric dysrhythmias induced by a pharmacological agent. Surface gastric pacing might be useful in the treatment of gastric dysrhythmia. The gastric myoelectrical activity correlated well with the plasma motilin concentration before and after pacing, which suggests that motilin could modulate the effect of gastric pacing through alteration of the gastric myoelectrical parameters.

Current concepts in diabetic gastroparesis

Diabetic gastroparesis is a common and debilitating condition affecting millions of patients with diabetes mellitus worldwide. Although gastroparesis in diabetes has been known clinically for more than 50 years, treatment options remain very limited. Until recently, the scientific literature has offered few clues regarding the precise aetiology of gastric dysfunction in diabetes.Up to 50% of patients with diabetes may experience postprandial abdominal pain, nausea, vomiting and bloating secondary to gastric dysfunction. There is no clear association between length of disease and the onset of delayed gastric emptying. Gastroparesis affects both type 1 (insulin dependent) and type 2 (non- insulin dependent) forms of diabetes. Diagnosis requires identifying the proper symptom complex, while excluding other entities (peptic ulcer disease, rheumatological diseases, medication effects). The diagnosis of gastroparesis may be confirmed by demonstrating gastric emptying delay during a 4-hour scintigraphic study. Treatment options are limited and rely on dietary modifications, judicious use of available pharmacological agents, and occasionally surgical or endoscopic placement of gastrostomies or jejunostomies. Gastric pacing offers promise for patients with medically refractory gastroparesis but awaits further investigation. Current pharmacological agents for treating gastroparesis include metoclopramide, erythromycin, cisapride (only available via a company-sponsored programme) and domperidone (not US FDA approved). All of these drugs act as promotility agents that increase the number or the intensity of gastric contractions. These medications are not uniformly effective and all have adverse effects that limit their use. Cisapride has been removed from the open market as a result of over 200 reported cases of cardiac toxicity attributed to its use. Unfortunately, there is a paucity of clinical studies that clearly define the efficacy of these agents in diabetic gastroparesis and there are no studies that compare these drugs to each other. The molecular pathophysiology of diabetic gastroparesis is unknown, limiting the development of rational therapies. New studies, primarily in animals, point to a defect in the enteric nervous system as a major molecular cause of abnormal gastric motility in diabetes. This defect is characterised by a loss of nitric oxide signals from nerves to muscles in the gut resulting in delayed gastric emptying. Novel therapies designed to augment nitric oxide signalling are being studied.

Current concepts in diabetic gastroparesis

Diabetic gastroparesis is a common and debilitating condition affecting millions of patients with diabetes mellitus worldwide. Although gastroparesis in diabetes has been known clinically for more than 50 years, treatment options remain very limited. Until recently, the scientific literature has offered few clues regarding the precise aetiology of gastric dysfunction in diabetes.Up to 50% of patients with diabetes may experience postprandial abdominal pain, nausea, vomiting and bloating secondary to gastric dysfunction. There is no clear association between length of disease and the onset of delayed gastric emptying. Gastroparesis affects both type 1 (insulin dependent) and type 2 (non- insulin dependent) forms of diabetes. Diagnosis requires identifying the proper symptom complex, while excluding other entities (peptic ulcer disease, rheumatological diseases, medication effects). The diagnosis of gastroparesis may be confirmed by demonstrating gastric emptying delay during a 4-hour scintigraphic study. Treatment options are limited and rely on dietary modifications, judicious use of available pharmacological agents, and occasionally surgical or endoscopic placement of gastrostomies or jejunostomies. Gastric pacing offers promise for patients with medically refractory gastroparesis but awaits further investigation. Current pharmacological agents for treating gastroparesis include metoclopramide, erythromycin, cisapride (only available via a company-sponsored programme) and domperidone (not US FDA approved). All of these drugs act as promotility agents that increase the number or the intensity of gastric contractions. These medications are not uniformly effective and all have adverse effects that limit their use. Cisapride has been removed from the open market as a result of over 200 reported cases of cardiac toxicity attributed to its use. Unfortunately, there is a paucity of clinical studies that clearly define the efficacy of these agents in diabetic gastroparesis and there are no studies that compare these drugs to each other. The molecular pathophysiology of diabetic gastroparesis is unknown, limiting the development of rational therapies. New studies, primarily in animals, point to a defect in the enteric nervous system as a major molecular cause of abnormal gastric motility in diabetes. This defect is characterised by a loss of nitric oxide signals from nerves to muscles in the gut resulting in delayed gastric emptying. Novel therapies designed to augment nitric oxide signalling are being studied.

A systematic review of surgical therapy for gastroparesis

Gastroparesis is characterized by delayed gastric emptying in the absence of obstruction. Common symptoms include nausea, vomiting, and abdominal pain. Severe gastroparesis might result in recurrent hospitalizations, malnutrition, and significant mortality. Patients failing medical therapy are often considered for a variety of surgical interventions, the efficacy of which is not well studied. This review summarizes available literature on surgical interventions in gastroparesis. A MEDLINE search for the period from 1966 to 2002 was performed to identify all English language literature regarding surgical interventions in gastroparesis. Therapies reviewed were gastrostomy, jejunostomy, gastric pacing/stimulation, and gastrectomy or surgical drainage procedures. Candidate studies involved human subjects and included surgical series or trials. The search was conducted independently by two authors and discrepancies resolved by consensus opinion. Seventeen articles met inclusion criteria. These included series reporting on gastrostomy (2), jejunostomy (3), gastric stimulation (2), and gastrectomy for postsurgical (6), diabetic (3), and idiopathic (1) gastroparesis. All trials were unblinded, uncontrolled case series or retrospective reviews. Methodologic differences did not allow for pooled analysis. Completion gastrectomy seems to provide symptom relief in postsurgical gastroparesis. Benefits of gastric surgery for other forms of gastroparesis are not adequately studied. Gastrostomy might provide symptom improvement, but only 26 subjects in two trials were evaluable. Jejunostomy improved symptoms and nutrition in 32 evaluable subjects in three trials but had significant complications. Gastric neurostimulation improves symptoms of nausea and vomiting, but therapeutic gain beyond placebo has not been demonstrated. Limited data exist concerning surgical therapies of gastroparesis. Completion gastrectomy seems effective for postsurgical gastroparesis, but a cautious approach is warranted before surgical therapies in diabetic or idiopathic gastroparesis are used.

Nutrition therapy for diabetic gastroparesis

The management of diabetic gastroparesis often represents a significant clinical challenge in which the maintenance of nutrition is pivotal. Gastric emptying is delayed in 30% to 50% of patients with longstanding type 1 or type 2 diabetes and upper gastrointestinal symptoms also occur frequently. However, there is only a weak association between the presence of symptoms and delayed gastric emptying. Acute changes in blood glucose concentrations affect gastric motility in diabetes; hyperglycemia slows gastric emptying whereas hypoglycemia may accelerate it; blood glucose concentrations may also influence symptoms. It is now recognized that gastric emptying is a major determinant of postprandial glycemia and, therefore, there is considerable interest in the concept of modulating gastric emptying, by dietary or pharmacologic means, to optimize glycemic control in diabetes.

Pacing of interstitial cells of Cajal in the murine gastric antrum: neurally mediated and direct stimulation

Phase advancement of electrical slow waves and regulation of pacemaker frequency was investigated in the circular muscle layer of the gastric antra of wild-type and W/W(V) mice. Slow waves in the murine antrum of wild-type animals had an intrinsic frequency of 4.4 cycles min(-1) and were phase advanced and entrained to a maximum of 6.3 cycles min(-1) using 0.1 ms pulses of electrical field stimulation (EFS) (three pulses delivered at 3-30 Hz). Pacing of slow waves was blocked by tetrodotoxin (TTX) and atropine, suggesting phase advancement was mediated via intrinsic cholinergic nerves. Phase advancement and entrainment of slow waves via this mechanism was absent in W/W(V) mutants which lack intramuscular interstitial cells of Cajal (ICC-IM). These data suggest that neural regulation of slow wave frequency and regulation of smooth muscle responses to slow waves are mediated via nerve-ICC-IM interactions. With longer stimulation parameters (1.0-2.0 ms), EFS phase advanced and entrained slow waves in wild-type and W/W(V) animals. Pacing with 1-2 ms pulses was not inhibited by TTX or atropine. These data suggest that stimulation with longer pulse duration is capable of directly activating the pacemaker mechanism in ICC-MY networks. In summary, intrinsic excitatory neurons can phase advance and increase the frequency of antral slow waves. This form of regulation is mediated via ICC-IM. Longer pulse stimulation can directly activate ICC-MY in the absence of ICC-IM.

Effects of gastric electrical field stimulation with long pulses on gastric emptying in dogs

The aim was to investigate the effects of electrical field stimulation (EFS) with long and short pulses on gastric emptying, gastric contractility and vagal activity in dogs. Sixteen dogs were equipped with a duodenal cannula, electrodes and strain gauges (10 dogs) in the stomach. Each dog was fed with Ensure and gastric effluent was collected from the cannula. Electrical stimulation was applied via two electrodes (about 12 cm apart, one in the corpus and the other in the antrum) with long pulses (a frequency of 6 cycles min-1, pulse amplitude of 6 mA and width of 100 ms) in 10 dogs and with short pulses (frequency of 30 Hz and pulse width of 300 micros) in six dogs. The electrocardiogram was also recorded and heart rate variability was derived to assess the vagal activity. It was found that: (i). EFS with long pulses did not alter gastric emptying during stimulation but increased gastric emptying during the 45 min immediately after stimulation; (ii). EFS with long pulses increased gastric contractility in both proximal and distal antrum during and after the stimulation; (iii). EFS with long pulses resulted in an increase in vagal tone during the 45 min immediately after stimulation. However, there is no difference during the 45 min period of stimulation; (iv). EFS with short pulses had no effect on gastric emptying. We concluded that long pulse gastric electrical field stimulation with one electrode in the corpus and the other electrode in the antrum has postponed effects on gastric emptying of liquid, gastric contractility and vagal activity.

Gastric electrical stimulation for medically refractory gastroparesis

BACKGROUND & AIMS

This study investigated the efficacy of gastric electrical stimulation for the treatment of symptomatic gastroparesis unresponsive to standard medical therapy.

METHODS

Thirty-three patients with chronic gastroparesis (17 diabetic and 16 idiopathic) received continuous high-frequency/low-energy gastric electrical stimulation via electrodes in the muscle wall of the antrum connected to a neurostimulator in an abdominal wall pocket. After implantation, patients were randomized in a double-blind crossover design to stimulation ON or OFF for 1-month periods. The blind was then broken, and all patients were programmed to stimulation ON and evaluated at 6 and 12 months. Outcome measures were vomiting frequency, preference for ON or OFF, upper gastrointestinal tract symptoms, quality of life, gastric emptying, and adverse events.

RESULTS

In the double-blind portion of the study, self-reported vomiting frequency was significantly reduced in the ON vs. OFF period (P < 0.05) and this symptomatic improvement was consistent with the significant patient preference (P < 0.05) for the ON vs. OFF period determined before breaking the blind. In the unblinded portion of the study, vomiting frequency decreased significantly (P < 0.05) at 6 and 12 months. Scores for symptom severity and quality of life significantly improved (P < 0.05) at 6 and 12 months, whereas gastric emptying was only modestly accelerated. Five patients had their gastric electrical stimulation system explanted or revised because of infection or other complications.

CONCLUSIONS

High-frequency/low-energy gastric electrical stimulation significantly decreased vomiting frequency and gastrointestinal symptoms and improved quality of life in patients with severe gastroparesis.