Gastric pacing improves emptying and symptoms in patients with gastroparesis

Idiopathic and Diabetic Gastroparesis

The management of both diabetic and idiopathic gastroparesis often represents a substantial clinical challenge. In formulating recommendations for therapy, it should be recognized that these are based on less than optimal evidence; in particular, there are substantial deficiencies in current knowledge relating to the pathophysiology of gastroparesis, as well as the natural history of gastrointestinal symptoms, and the majority of pharmacologic trials have been short term and associated with methodologic limitations. Although the etiologic factors differ, the overall management principles are similar in the two conditions. Maintenance of adequate nutrition is pivotal, and parenteral nutrition may be required in severe cases associated with malnutrition. In patients with diabetes, rigorous attempts should be made to optimize glycemic control--hyperglycemia slows gastric emptying and may exacerbate symptoms and attenuate the effects of prokinetic drugs. Despite the relatively poor predictive value of symptoms, it is reasonable to suggest a trial of prokinetic therapy for about 4 weeks, rather than initially establishing the diagnosis by measurement of gastric emptying. However, it should be recognized that there is a substantial placebo response, a lack of evidence to support the cost effectiveness of such an approach, and that most patients will require prolonged therapy. In type 1 diabetic patients, prokinetic therapy may potentially benefit glycemic control, and this forms an additional rationale (albeit not established) for therapy. Some patients with diabetes and idiopathic gastroparesis with severe vomiting are unable to tolerate oral medication; in such cases subcutaneous metoclopramide may prove useful. Patients with intractable symptoms should be hospitalized and given intravenous erythromycin. The repertoire of prokinetic agents available in the United States is limited and includes metoclopramide, erythromycin, and cisapride (available by special program from its manufacturer); all of these drugs are associated with side effects. The use of metoclopramide may represent the first choice for chronic oral therapy, although it has been studied less comprehensively than cisapride. Combination therapy may be potentially more efficacious than the use of single agents. Dehydration and metabolic derangements should be corrected. The choice of chronic medical therapy should be individualized, taking factors such as age, presence of diabetes, concurrent medications, and comorbidities into account. In a small number of patients in whom medical treatment fails, surgery should be considered, and, if performed, done in a specialized center. A number of novel therapies, including gastric electrical stimulation, are currently being evaluated.

Diagnosis and treatment of neuromuscular disorders of the stomach

Gastric neuromuscular disorders encompass a spectrum of dysfunction in nerve and smooth muscle that includes gastric visceral hypersensitivity, gastric dysrhythmias, fundic dysfunction, antral hypomotility, and gastroparesis. Patients with each disorder may present with such vague dyspepsia symptoms as early satiety, upper abdominal discomfort, bloating, or nausea with or without vomiting. A careful history and physical examination may suggest a gastric neuromuscular disorder, but symptoms are nonspecific. Gastroparesis is the most severe form of neuromuscular dysfunction. Such reversible causes of gastroparesis as mechanical obstruction of the stomach and chronic mesenteric ischemia must be excluded. Gastroparesis, gastric dysrhythmias, and hypersensitivity may follow viral infection or be due to degenerative processes that affect the gastric enteric neurons, smooth muscle, or interstitial cells of Cajal. Commonly, the cause of these gastric neuromuscular disorders is unknown. An approach to the diagnosis and treatment of gastric neuromuscular disorders is reviewed, including dietary counseling, drugs, and medical devices.

The effect of gastric electrical stimulation on canine gastric slow waves

This study determined the most efficient parameters of low-frequency/long-pulse gastric electrical stimulation (GES) required to entrain gastric slow waves and also evaluated the effect of entrainment and high-frequency, short-pulse GES on gastric electrical activity (GEA). Nine dogs were fitted with stimulation wires along the greater curvature. Entrainment was observed in six or seven animals, with long-pulse GES at six cycles per minute (cpm), at various combinations of current and pulse width and was directly related to the energy delivered. Entrainment was observed in four to seven animals, with GES at 12 cpm, and the maximal driven frequency was 6 cpm. Entrainment did not significantly increase the dominant power of GEA. High-frequency, short-pulse GES, using pulse trains of 14 Hz, 5 mA, and 330 micros, with 0.1 s on and 5 s off, and pulse trains of 40 Hz, 10 mA, and 330 micros, with 2 s on 3 s off, did not affect variables of GEA. We conclude that acute low-frequency GES but not high-frequency, short-pulse GES can entrain slow waves; the power of slow waves is not affected by either type of stimulation.

Gastrointestinal disturbances in diabetes

Gastrointestinal disorders are common in patients with diabetes mellitus. As many as 75% of patients visiting diabetes clinics will report significant gastrointestinal (GI) symptoms. The symptom complex experienced may vary widely. Many patients go undiagnosed and undertreated. Patients with a history of retinopathy, nephropathy, or neuropathy should be presumed to have GI abnormalities until proven otherwise. The workup should start with a thorough patient history and appropriate laboratory, radiographic, and GI testing. In addition to pharmacologic therapy, glycemic control and dietary manipulation play an important role in managing GI disorders in people with diabetes.

Gastric electrical stimulation at proximal stomach induces gastric relaxation in dogs

Gastric electrical stimulation (GES) improves symptoms in patients with gastroparesis. However, the underlying mechanisms remain unclear. To determine if GES at proximal and distal stomach could affect the biomechanical properties of the stomach, thus contributing to the beneficial effect of GES. Four pairs of electrodes were implanted along the greater curvature of the stomach in seven dogs. Gastric tone and compliance was assessed with a barostat. Measurements were obtained randomly during control and proximal and distal stimulation (4 mA, 375 ms and 6/18 cpm). Data as mean or median (25-75th percentiles). Gastric compliance was not affected by proximal and distal GES. Gastric tone was significantly reduced during proximal GES: 82.0 (66.8, 89.1) mL vs control 49.7 (39.6,75.9) mL at 6 cpm (P = 0.016), and 90.6 (54.5, 117.9) mL vs control 62.8 (39.6, 75.9) mL at 18 cpm (P = 0.031). Tone was not affected by distal GES at 6 cpm: 95.8 (46.3, 106.7) mL vs control 75.2 (49.7, 86.1) mL (P = 0.47) and at 18 cpm: 80.4 (38.1, 170.3) mL vs control 62.8 (44.6, 156.3) mL (P = 0.44). Proximal GES induces gastric relaxation. This effect, if seen also in humans, may explain, in part, the symptomatic improvement associated with GES therapy in patients with gastroparesis.

Gastric electrical-stimulation effects on canine gastric emptying, food intake, and body weight

OBJECTIVE

It has been reported that electrical stimulation at the distal stomach can disrupt intrinsic gastric electrical activity and delay gastric emptying. Gastric dysrhythmia and impaired gastric emptying are associated with upper gastrointestinal symptoms and weight loss. The purpose of this study was to evaluate the effect of low-frequency/long-pulse gastric electrical stimulation (GES), at proximal and distal stomach, on canine gastric emptying, food intake, and body weight.

RESEARCH METHODS AND PROCEDURES

Eight dogs were surgically implanted with four pairs of electrodes along the greater curvature and a gastric tube at the dependent part of the stomach. Liquid gastric emptying at baseline, during proximal and distal GES at 6 cycles per minute, was assessed first by a dye dilution technique. Proximal and distal GES were then randomly delivered during feeding for 10 consecutive days, and food intake and body weight were recorded daily.

RESULTS

There was no significant difference in gastric emptying parameters among the various sessions. The mean daily food consumption was significantly reduced during both sessions of GES, resulting in significant immediate weight loss. Percentage weight loss was comparable between both sessions of GES.

DISCUSSION

Short-term GES significantly reduced canine food intake and weight. This effect may not be related to changes in gastric emptying. GES may have a potential role in the treatment of obesity.

Three-dimensional object-oriented modeling of the stomach for the purpose of microprocessor-controlled functional stimulation

Three-dimensional (3-D) object-oriented models are needed for optimizing gastric electrical stimulation by performing virtual computer experiments. The aim of the study was to create a 3-D object-oriented electromechanical model of the stomach in vivo for the purpose of microprocessor controlled functional stimulation. The stomach was modeled using coaxial truncated conoids as objects. The strength of an external stimulating electric field generated by circumferentially implanted wire electrodes is related to artificial neurogenic and myogenic control of smooth muscle depolarization and contraction. Variation of the field strength modulates the frequency and concentration of acetylcholine release, as well as the transmembrane voltage of the muscle cells. Mechanical response of the stimulated tissue was quantified by two parametric functions of the electric field strength representing the relative contractile force and geometrical displacement of the gastric surface. Data from previously conducted canine experiments were used to test the validity of the model. The model was applied to simulate contractions with different positions, orientation and number of the circumferentially implanted stimulating electrodes. The model combined most of the existing theoretical and experimental findings concerning functional gastric stimulation and can be utilized as a flexible tool for virtual medical tests involving external high-frequency (50 Hz) neural stimulation.

Gastric electrical stimulation as therapy of morbid obesity: preliminary results from the French study

BACKGROUND

Gastric electrical stimulation to treat morbid obesity, using the Transcend Implantable Gastric Stimulator (IGS), is being evaluated. We present our preliminary results from the French segment of the worldwide study to evaluate this therapy.

METHODS

Institutionally-approved informed consent was obtained from all patients. The IGS is placed laparoscopically. The system has two implantable components: 1) a lead with two electrodes that is implanted in a gastric lesser curvature muscle tunnel; 2) the lead is connected to an electrical pulse generator positioned subcutaneously on the abdominal wall. Two electrode positions were used; half (6/12, 50%) were "low" near the pes anserinus, and the other 50% "high" nearer the esophagogastric junction. Intraoperative gastroscopy is used to diagnose inadvertent gastric perforation. 12 patients (5 M, 7 F) had the IGS implanted between July 2000 and February 2001. Mean age was 40.6 years (31-51). Mean weight was 122.2 kg (93-146), mean BMI was 42.7 kg/m2 (39.1-48.6), and mean excess weight was 60 kg (42-74). Electrical stimulation commenced 1 month after implantation.

RESULTS

All devices were successfully placed laparoscopically. There were no deaths or major operative complications. Postoperative course was uneventful in all cases. In 25% (3/12), postoperative lead dislodgement occurred; 2 of the 3 had their leads replaced. By 9 months, mean excess BMI lost was 30 +/- 24% or 16 +/- 12 kg.

CONCLUSION

Implanting the IGS to treat morbid obesity is technically feasible and safe. Lead dislodgement has been simply and satisfactorily corrected. Satisfactory short-term weight loss has been achieved in a subset of patients. Long-term efficacy must now be determined.

The "electrical way" to cure gastroparesis

The treatment of gastroparesis recently received a heavy blow from the restrictions on the use of the prokinetic drug cisapride, but, fortunately, at the same time, a nonpharmacological approach, such as gastric electrical stimulation, came up again with new techniques. After an ultra-decennial experimentation with a large variety of electrical stimuli delivered to the gastric wall of animals and patients with gastroparesis, three principal methods are available at the moment: gastric electrical pacing, high-frequency gastric electrical stimulation, and sequential neural electrical stimulation. The first method aims to reset a regular slow-wave rhythm, but is unable to re-establish efficient contractions and a normal gastric emptying. High-frequency gastric electrical stimulation, although inadequate to restore a normal gastric emptying, nevertheless strikingly improves the dyspeptic symptoms, such as nausea and vomiting, giving the patients a better quality of life and a more satisfactory nutritional status. The last method, neural electrical gastric stimulation, consists of a microprocessor-controlled sequential activation of a series of annular electrodes which encircle the distal two thirds of the stomach and induce propagated contractions causing a forceful emptying of the gastric content. The latter method is the most promising, but it has so far only been tested in animals and would need to be tested in patients with gastroparesis before it can be used as a solution for this disease. All the aforementioned clinical studies, however, are not controlled and nearly all were published in abstract form. Therefore, further controlled trials are needed to establish which of these techniques is more useful for the treatment of gastroparesis.

Gastric stimulation: influence of electrical parameters on gastric emptying in control and diabetic rats

BACKGROUND

The aim of this study was to test the effect of different pulse frequencies and amplitudes during gastric stimulation (GS) on gastric emptying in the rat.

METHODS

GS was performed in 2 groups of laparotomized rats: healthy control animals, and rats with acute diabetes. The effects of four pulse frequencies (0.5, 1, 10, 20 Hz) and three pulse amplitudes (5, 20, 40 mA) were tested. The volumes emptied from the stomach after the oro-gastric instillation of a nutrient solution were compared to those obtained in animals without GS. Intragastric pH values were assessed under basal conditions and after GS.

RESULTS

In both groups, GS increased emptied volumes compared to conditions without stimulation (p < 0.05) for pulse frequencies above 0.5 Hz. Increases in pulse frequencies accelerated gastric emptying (p < 0.01) with a plateau at around 10 Hz. The increase in pulse amplitudes resulted in larger emptied volumes only when the pulse frequency was 1 Hz (p < 0.04) while the opposite effect was observed at 20 Hz (p < 0.04). The most effective combinations to enhance gastric emptying compared to baseline conditions were 10 Hz with 5 or 20 mA. The overall effect of GS on gastric emptying compared to baseline conditions without stimulation, was greater in diabetic than in controls rats (p < 0.05). During stimulation, intragastric pH values were not different from basal conditions during fasting or after a meal in control and diabetic rats.

CONCLUSIONS

Although both pulse frequency and amplitude should be considered during GS, frequency appears to be the most critical point. The possibility of increasing gastric emptying by electrical stimulation in diabetic rats suggests potential clinical applications for this method.

Physiology and pathophysiology of the interstitial cells of Cajal: from bench to bedside. VI. Pathogenesis and therapeutic approaches to human gastric dysrhythmias

This review describes recent advances in our knowledge about the pathogenesis and therapeutic approaches to human gastric dysrhythmias. A number of clinical conditions has been found to be associated with gastric slow-wave rhythm disturbances that may relate to the induction of nausea and vomiting. Human and animal studies indicate that multiple neurohumoral factors are involved in the generation of gastric dysrhythmias. Antral distension and increased intestinal delivery of lipids may cause slow-wave disruption and development of nausea. This may be mediated by cholinergic and serotonergic pathways. Similarly, progesterone and estrogen may also disrupt gastric slow-wave rhythm in susceptible individuals. Prostaglandin overproduction in gastric smooth muscle appears to mediate slow-wave disruption in diabetes and with tobacco smoking. On the other hand, central cholinergic pathways play an important role in the genesis of gastric dysrhythmias associated with motion sickness. This may be mediated by vasopressin released from the pituitary. Although it is difficult to ascribe with certainty a causative role of slow-wave rhythm disturbances in the genesis of nausea and vomiting, the search has begun for novel antiemetic therapies based on their abilities to ablate or prevent gastric dysrhythmia formation. This includes the use of prostaglandin synthesis inhibitors, central muscarinic receptor antagonists, and dopamine receptor antagonists. Finally direct gastric electrical stimulation using a surgically implanted neurostimulator has shown promise in reducing emesis in patients with gastroparesis and gastric dysrhythmias.

Stimulus artifact cancellation in the serosal recordings of gastric myoelectric activity using wavelet transform

Previous studies have shown that electrical stimulation of the stomach (i.e., gastric pacing) with appropriate parameters is a promising method for treatment of gastroparetic patients. The recording of gastric myoelectric activity (GMA) by serosal electrodes is often used to evaluate the effect of stimulation. However, the major problem with the measurement of GMA during gastric pacing is the stimulus artifacts which are often superimposed on the serosal recording and make analysis difficult. The frequency-domain adaptive filter has been used to reduce the stimulus artifacts but only with limited success. This paper describes a wavelet transform-based method for the reduction of stimulus artifacts in the serosal recordings of GMA. The key of this method lies in the use of the fuzzy set theory to select the stimulus artifact-related modulus maxima in the wavelet domain. Both quantitative and qualitative measures show that significant stimulus artifact cancellation was achieved through a series of computer simulations. Results from both single- and multichannel serosally recorded myoelectric signals during gastric pacing are presented to demonstrate the efficiency of the proposed method for the cancellation of stimulus artifacts.

Statistical processing for gastric slow-wave identification

Successful identification of gastric slow waves in canine gastric electrical activity (GEA) data was achieved using a statistical data-processing procedure based on the multiple linear regression (MLR) curve fitting technique. Both distal and proximal waveforms were identified, first by construction of separate orthonormal bases from pre-selected sets of representative distal and proximal gastric slow waves (GSWs). Respective basis matrices were used to fit proximal and distal data to an MLR data model. Residual waveforms were computed from the original and 'fitted' waveforms and used in identifying GSWs in the data. Canine GEA data were split into 1,800-point blocks, and each 245-point data segment in a block was processed to identify the GSWs. Gastric slow waves were located in the data using a residual mean-squared error (MSE) threshold and, for distal GEA data, the minimum value of the main distal waveform peak. All threshold values were determined empirically and were set to detect GSWs while limiting false matches. Identification rates of 95% and 99% for proximal and distal GSWs, respectively, represent a significant improvement over those obtained in a previous study in which the same data were analysed using linear signal-processing methods. The use of the method presented in this paper for real-time identification of GSWs in conjunction with an implantable gastric pacer unit appears promising. Because the technique is inherently customisable, results obtained in this study should also be applicable to human subjects.

Functional magnetic stimulation facilitates gastric emptying

OBJECTIVE

To evaluate the effect of functional magnetic stimulation (FMS) on gastric emptying in able-bodied and spinal cord injury (SCI) subjects.

DESIGN

A prospective, nonrandomized clinical experiment.

SETTING

SCI and disorder center in a Veterans Affairs medical facility.

PARTICIPANTS

Five healthy, able-bodied subjects and 4 subjects with SCI.

INTERVENTION

A commercially available magnetic stimulator was used; a round magnetic coil was placed along the T9 spinous process. The intensity of the magnetic stimulation was 60%, with a frequency of 20 Hz, and a burst length of 2 seconds for the gastric emptying protocol. Man Outcome Measures: Rate of gastric emptying and time required to reach gastric emptying half-time (GE(t1/2)) with and without FMS. Data fit into linear regression curve.

RESULTS

Accelerated gastric emptying was achieved in both able-bodied and SCI subjects. The mean +/- standard error of mean of the GE(t1/2) at baseline and with FMS was 36+/-2.9 minutes and 33+/-3.1 minutes, respectively, for able-bodied subjects, and 84+/-11.1 minutes and 59+/-12.7 minutes, respectively, for SCI subjects.

CONCLUSION

Gastric emptying was enhanced by FMS in able-bodied subjects and was greatly enhanced in SCI subjects. FMS can be a useful noninvasive therapeutic tool to facilitate gastric emptying in humans.

Pyloric injection of botulinum toxin for treatment of diabetic gastroparesis

BACKGROUND

Diabetic gastroparesis is a common clinical problem. The pathophysiology includes prolonged pyloric contractions that may cause functional resistance to gastric outflow. Botulinum toxin was injected into the pyloric sphincter in an attempt to decrease pyloric resistance and improve gastric emptying.

METHODS

Six patients with diabetic gastroparesis and an abnormal solid phase gastric emptying study underwent upper endoscopy during which 100 units of botulinum toxin were injected into the pyloric sphincter. Gastric emptying studies were obtained at 48 hours and 6 weeks after injection. Patients were questioned about symptoms of gastroparesis, and a symptom score was obtained at baseline and at 2 weeks and 6 weeks after injection.

OBSERVATIONS

There was a mean improvement in the subjective symptom score at 2 weeks of 55% (range 14% to 80%). This improvement was maintained at 6 weeks. There was a 52% improvement in gastric emptying at 2 and 6 weeks.

CONCLUSION

Pyloric injection of botulinum toxin can improve symptoms and gastric emptying in patients with diabetic gastroparesis. Further evaluation of pyloric injection of botulinum toxin as a treatment for diabetic gastroparesis is warranted.

Predictors of response to a behavioral treatment in patients with chronic gastric motility disorders

Chronic gastric motility disorders have proven intractable to most traditional therapies. Twenty-six patients with chronic nausea and vomiting were treated with a behavioral technique, autonomic training (AT) with directed imagery (verbal instructions), to help facilitate physiological control. After treatment, gastrointestinal symptoms decreased by >30% in 58% of the treated patients. We compared those improved patients to the 43% who did not improve significantly. No significant differences existed in baseline symptoms and autonomic measures between both groups. However, baseline measures of gastric emptying and autonomic function predicted treatment outcome. Patients who improved manifested mild to moderate delay in baseline gastric emptying measures. The percent of liquid gastric emptying at 60 mins and the sympathetic adrenergic measure of percent of change in the foot cutaneous blood flow in response to cold stress test predicted improvement in AT outcome, with clinical diagnostic values of 77% and 71%, respectively. We conclude that AT treatment can be efficacious in some patients with impaired gastric emptying and adrenergic dysfunction. More work is warranted to compare biofeedback therapy with gastric motility patients and controls in population-based studies.

Nausea and vomiting of pregnancy: an obstetric syndrome

Although the cause of nausea and vomiting of pregnancy is not known, there is strong evidence linking human chorionic gonadoptropin or estrogens. Evidence is presented to show that the incidence and severity of nausea and vomiting of pregnancy is linked to temporal and pathologic alterations in these hormones during pregnancy. The way in which the pregnant woman responds to the primary stimulus to nausea and vomiting of pregnancy appears to depend on her susceptibility mediated by vestibular, gastrointestinal, olfactory, and behavioral pathways. Conceiving of nausea and vomiting of pregnancy as a syndrome suggests new pathways of investigation and possible therapies.

EUS guidance in gastric pacemaker implantation

BACKGROUND

EUS provides excellent imaging of the gastric wall. The utility of EUS imaging in guiding the placement of a gastric pacemaker was investigated.

METHODS

Fourteen patients underwent gastric pacemaker implantation for refractory gastroparesis at laparotomy. Placement of the lead into the muscle layer of the antrum of the stomach was imaged by intraoperative surface ultrasonography in the first 8 patients and by EUS in the subsequent 6 patients.

RESULTS

Surface US examination of the lead placement revealed reverberation artifacts. The images were uniformly unsatisfactory and the position of the lead in the gastric wall could not be visualized in any patient. In contrast, the lead was clearly and easily identified by EUS as a bright linear echo in the gastric wall. This was observed uniformly in all of the patients evaluated by EUS. Compared with surface US, EUS provided better images of the gastric lead placement as well as less abdominal distension and thus easier closure of the incision.

CONCLUSIONS

EUS is useful in confirming the accurate placement of pacemaker leads within the muscular coat of the stomach.

Gastric emptying in diabetes: clinical significance and treatment

The outcome of recent studies has led to redefinition of concepts relating to the prevalence, pathogenesis and clinical significance of disordered gastric emptying in patients with diabetes mellitus. The use of scintigraphic techniques has established that gastric emptying is abnormally slow in approx. 30-50% of outpatients with long-standing Type 1 or Type 2 diabetes, although the magnitude of this delay is modest in many cases. Upper gastrointestinal symptoms occur frequently and affect quality of life adversely in patients with diabetes, although the relationship between symptoms and the rate of gastric emptying is weak. Acute changes in blood glucose concentration affect both gastric motor function and upper gastrointestinal symptoms. Gastric emptying is slower during hyperglycaemia when compared with euglycaemia and accelerated during hypoglycaemia. The blood glucose concentration may influence the response to prokinetic drugs. Conversely, the rate of gastric emptying is a major determinant of post-prandial glycaemic excursions in healthy subjects, as well as in Type 1 and Type 2 patients. A number of therapies currently in development are designed to improve post-prandial glycaemic control by modulating the rate of delivery of nutrients to the small intestine.

Motility disorders. Diagnosis and treatment for the pediatric patient

Motility disorders are common in children and may affect any area of the GI tract. The past decade has brought significant advances in the understanding of motility disorders in pediatrics. More sophisticated testing techniques have helped to differentiate normal from abnormal motility in children of different ages. Manometry now may be used to clarify the pathophysiologic defect underlying chest pain, dysphagia, rumination, gastroparesis, chronic intestinal pseudo-obstruction, and colonic neuromuscular disorders. Motility testing also may be used to identify the motor defect responsible for persistence of symptoms after surgery for GER or HD. New investigational techniques and prokinetic agents likely to be available in the future also were discussed.

Gastric pacing is a new surgical treatment for gastroparesis

BACKGROUND

Gastroparesis is a chronic gastric motility disorder affecting mostly young and middle-aged women who present with nausea, abdominal pain, early satiety, vomiting, fullness, and bloating.

METHODS

From April 1998 to September 2000, 25 patients underwent gastric pacemaker placement. All had documented delayed gastric emptying by a radionucleotide study. Nineteen patients had diabetic gastroparesis, 3 had developed postsurgical gastroparesis, and 3 had idiopathic gastroparesis. Baseline and postoperative follow-ups were done by a self-administered questionnaire on which the patients rated the severity and frequency of nausea and vomiting. Gastric emptying times were also followed up using a radionucleotide technique.

RESULTS

Both the severity and frequency of nausea and vomiting improved significantly at 3 months and was sustained for 12 months. Gastric emptying time was also numerically faster over the 12-month period. Three of the devices have been removed. One patient died of causes unrelated to the pacemaker 10 months postoperatively.

CONCLUSIONS

After placement of the gastric pacemaker, patients rated significantly fewer symptoms and had a modest acceleration of gastric emptying.

A review of diabetic gastropathy

Diabetes mellitus affects various organs, including the gastrointestinal tract. The stomach is commonly affected, and symptoms related to the upper GI tract are frequently reported. Management of diabetic gastropathy involves dietary modifications, pharmacological agents, and occasionally, alternative feeding methods.

Interstitial cells of Cajal--their role in pacing and signal transmission in the digestive system

Interstitial cells of Cajal (ICC) are located in most parts of the digestive system. Although they were discovered over 100 years ago, their function began to be unravelled only recently. Morphological observations have led to a number of hypotheses on the possible physiological roles of ICC: (1) these cells may be the source of slow electrical waves recorded in gastrointestinal (GI) muscles; (2) they participate in the conduction of electrical currents, and (3) mediate neural signals between enteric nerves and muscles. These hypotheses were supported by experiments in which the ICC-containing layer was removed surgically, or when ICC were ablated chemically, and as a consequence the slow waves were absent. Electrophysiological experiments on isolated cells confirmed that ICC can generate rhythmic electrical activity and can also respond to messenger molecules known to be released from enteric nerves. In mice mutants deficient in ICC, or in mice treated with antibody against the protein c-Kit, slow wave activity was impaired. These results support the role of ICC as pacemaker cells. Physiological studies have shown that ICC in certain GI regions are important for signal transmission between nerves and smooth muscle. There is evidence that pathological changes in ICC may be associated with GI motility disorders. The full interpretation of the role of ICC in disease conditions will require much further study on the physiology and pharmacology of these cells.

Electrogastrography: a non-invasive measurement of gastric function

BACKGROUND

Electrogastrography (EGG) is the non-invasive measurement of gastric electrical activity. With the development of modern technology, improved recording and automated analysis, it is a reliable and accurate technique for the measurement of gastric myoelectrical activity providing information about the frequency and regularity of the gastric slow wave.

AIM

The aim of this report is to evaluate its role in clinical practice.

METHODS

The literature is reviewed and its role investigated.

RESULTS

EGG has been successfully used in the investigation of gastroparesis, non-ulcer dyspepsia (NUD), gastric emptying (GE) disorders and diabetes mellitus (DM). EGG also provides an insight into the effect of medications on gastric function, e.g. edrophonium, cisapride, erythromycin and proton-pump inhibitors (PPI).

CONCLUSIONS

EGG has a developing role in the assessment of gastric dysfunction and on the effect of medical treatment. The effect of surgery and anaesthesia on gastric myoelectric activity is less clear.

Gastric Dysmotility and Gastroparesis

Nutrition support in gastroparesis begins with encouraging smaller volume, low-fat, low-fiber meals and, if necessary, liquid caloric supplements. There should be a low threshold for placing a jejunal feeding tube either by laparoscopy or mini-laparotomy. Parenteral nutrition should be used only briefly during hospitalization and not encouraged or sustained as an outpatient. Metoclopramide is now the prokinetic of choice for patients who can tolerate this agent; subcutaneous administration is an important method that allows for continued guaranteed absorption. Low-dosage erythromycin also has a prokinetic role alone or in combination with metoclopramide. Domperidone, a centrally acting antiemetic and prokinetic, is only be available to US citizens who can access sources in Canada or Mexico. Antiemetics should be used extensively because nausea is a very severe debilitating symptom, which is under-appreciated and under-treated by physicians. We recommend scopolamine patches to gain maximal absorption, in spite of vomiting and unpredictable oral intakes. The 5-hydroxytryptamine-3 (5-HT3) antagonists ondansetron and granisetron are the most powerful agents. Relief bands using the P6 acupuncture point are useful adjunct. Special vigilance should be paid to situations that can undermine medical therapy or result in breakthrough symptoms, such as hyperglycemic events in patients with diabetes, migraine headaches, cyclic nausea and vomiting, menstrual cycles, rumination syndrome (psychogenic vomiting), and elevated herpes simplex titers. Most excitingly, the era of gastric electrical stimulation has arrived for patients not responding to standard medical therapy. The dramatic improvement in nausea and vomiting, as well as a sustained evidence of improved quality of life, gastric emptying, nutritional status, and decreased hospitalizations by this device are documented by long-term follow-up of more than a year for patients in this country and world-wide.

Management of the patient with gastroparesis

Gastroparesis may be related to a variety of underlying disorders, but management options are fairly universal. Dietary measures and pharmacologic agents, primarily in the form of prokinetic medications, form the foundation of standard management. Some patients will have refractory symptoms and alternative dosing schemes or drug combinations may be used. An occasional patient will still require venting gastrostomy and/or jejunal feeding. This review addresses the standard dietary and pharmacologic approaches to gastroparesis, as well as issues pertaining to gastrostomy/jejunostomy tubes and to surgical options for refractory cases. Finally, experimental agents and techniques, such as gastric pacing, will be discussed.

Misinterpretation of human electrogastrograms related to inappropriate data conditioning and acquisition using digital computers

Despite the fact that digital techniques for data acquisition and processing were widely used in electrogastrographic (EGG) research during the last decade, inappropriate signal conditioning and digitization are still potential pitfalls threatening the reliability of the experiments. The aim of this paper was to review: (1) the importance of the antialiasing low-pass filtering for reducing recording artifacts and interferences, (2) the advantages brought by the proper choice of filter cutoff frequency and the slope for the decrement of the minimal required sampling frequency, (3) the impact of incorrectly selected sampling frequency on data interpretations, with particular attention to the percent distribution ranges, and (4) the "leakage effect" related to the finite number of samples processed simultaneously in frequency domain representation of the recordings. A model of electrogastrographic (EGG) recording was mixed with a model of electrocardiographic (ECG) artifact. The resulting finite-duration signal was low-pass filtered and then digitized with a sampling frequency of 1 Hz. The cutoff frequency of the first-order low-pass filter was altered from 0.5 to 0.1 Hz. Amplitude frequency spectra of the digitized recordings were investigated. An example with a real human electrogastrogram in which an ECG artifact was present confirmed the simulation results. When a first-order anti-aliasing filter is utilized at least a fivefold difference between the filter cutoff frequency and the sampling frequency is recommended for compliance with the Nyquist theorem of digitization. Leakage effects associated with the finite-time duration of the recordings and the use of the discrete Fourier transform should be considered when frequency domain analysis is performed. Misinterpretation of the "bradygastric" and "tachygastric" ranges in the percent distribution of EGG frequency components is possible if inappropriate signal conditioning and digitization are employed.

Small bowel motility: ready for prime time?

The primary function of the small bowel is the absorption of nutrients, and the motor patterns of the healthy bowel are intended to promote that function. The motor patterns of the small bowel are the result of close interaction between the enteric nervous system, extrinsic nerves, regulatory peptides, and the intestinal smooth muscle. The basic electrical rhythm governing intestinal contractions is determined by specialized pacemaker cells called the interstitial cells of Cajal. Diseases affecting any of these components may result in intestinal dysmotility and its associated symptoms. Although transit studies and intestinal manometry are helpful in the diagnosis of dysmotility, our understanding of pathophysiology is hampered by the difficulties involved in obtaining and analyzing intestinal tissue. Treatment of intestinal dysmotility relies on dietary manipulations and nutritional support (enteral or parenteral) because there is no drug therapy that can effectively enhance the propulsive function of the small bowel. Small bowel transplantation remains a life-saving intervention for patients who fail to respond to other therapies.

Quantitative analysis of intestinal motor patterns: spatiotemporal organization of nonneural pacemaker sites in the rat ileum

BACKGROUND & AIMS

Intestinal contractions are triggered by electric activity of pacemaker cells within the smooth muscle. However, the precise spatial organization of the pacemaker system is unknown. We directly assessed the spatiotemporal organization of pacemakers by video image analysis combined with manometry and electromyography.

METHODS

Isolated segments of rat ileum were perfused arterially with oxygenated fluorocarbon solution and luminally with saline. Luminal end pressures, extracellular electric activity, and images of the intestine were recorded simultaneously. Tetrodotoxin, N(G)-nitro-L-arginine methyl ester (L-NAME), L-arginine, and eserine were administered arterially.

RESULTS

Myogenic contractions originated in discrete areas (dominant pacemakers) and propagated faster in aboral than in oral direction. Dominant pacemakers were distributed along the intestine at regular intervals. The preparations were mostly driven by 1 pacemaker at the time, but 2 or 3 pacemakers with different frequencies could be active simultaneously. Tetrodotoxin decreased aboral propagation velocity and revealed multiple regularly spaced pacemaker areas. Eserine increased, whereas L-arginine decreased, their frequency. After L-NAME, pacemaker activity increased and isolated pacemakers with higher frequency appeared.

CONCLUSIONS

Nonneural pacemakers in rat ileum are functionally organized not as a continuous system but show a segmental arrangement, spatially and temporally modulated by neural activity.

Pharmacotherapy of gastroparesis

The evaluation and management of gastric motor dysfunction continues to represent a significant clinical challenge. The very definition of what constitutes a clinically relevant disturbance of gastric motility remains unclear. The spectrum of gastroparesis extends from those with classical symptoms and severe delay of gastric emptying to those with dyspepsia and a mild delay in emptying rate. Indeed, for many patients with dyspepsia, the role of gastric emptying delay in the pathogenesis of symptoms, remains unclear. Any assessment of the efficacy of any therapeutic class in gastroparesis must be mindful, therefore, of these variations in definition. For those individuals with severe established gastroparesis, therapeutic success often remains elusive and i.v. erythromycin and oral dopamine antagonists, or substituted benzamides, remain the best options for acute severe exacerbations and chronic maintenance therapy, respectively. Alternatives, currently under investigation, include a number of 5-HT4 agonists, macrolides devoid of antibiotic activity, CCK antagonists and gastric electrical stimulation. Other novel approaches include strategies to address some of the regional abnormalities in gastric motor function that have been identified in some patients with dyspepsia.

Microprocessor-controlled movement of solid gastric content using sequential neural electrical stimulation

BACKGROUND & AIMS

Gastric electrical stimulation has been attempted for years without much success. The aim of this study was to determine if movement of solid gastric content could be achieved using microprocessor-controlled sequential electrical stimulation.

METHODS

The study was performed on 9 anesthetized dogs. The dogs underwent laparotomy, pyloroplasty, and implantation of 4-6 sets of bipolar stainless-steel wire electrodes. Each set consisted of 2-6 electrodes (10 x 0.25 mm, 3 cm apart) implanted circumferentially. The stomach was filled with solid food mixed with plastic pellets, and the process of gastric emptying was monitored. Artificial contractions were produced using microprocessor-controlled phase-locked bipolar trains of 50-Hz rectangular voltage with flexible amplitudes.

RESULTS

Using the above stimulating parameters, we were able to produce circumferential gastric contractions that were artificially propagated distally by embedding and phase-locking the stimulating voltage. The number of expelled pellets after the stimulation sessions was significantly higher than the number of pellets emptied during the nonstimulation sessions (P < 0.01).

CONCLUSIONS

Microprocessor-controlled electrical stimulation produced artificial peristalsis and markedly accelerated the movement of solid gastric content.

Prototype algorithm for automated determination of gastric slow wave characteristics

An algorithm for determining the frequency and propagation time of the gastric slow wave has been designed for integration into a demand gastric pacing system. The algorithm analyses the serosal activity in both the time and frequency domains, and the results are compared to produce a conclusion only when the values are within 5% of each other. Thus, the probability of inappropriate intervention is reduced, at the expense of unidentified segments. The system is verified by comparing the conclusions produced by the algorithm with conclusions from hand analysis of seven canine and one human serosal recordings. The algorithm correctly identifies the slow-wave frequency in the distal portion of the stomach for 90% of the segments, while producing no incorrect results. Slow-wave propagation times in the antrum are correctly identified for 84% of the segments, with no incorrect identifications.

Interstitial cells of cajal generate electrical slow waves in the murine stomach

1. The gastric corpus and antrum contain interstitial cells of Cajal (ICC) within the tunica muscularis. We tested the hypothesis that ICC are involved in the generation and regeneration of electrical slow waves. 2. Normal, postnatal development of slow wave activity was characterized in tissues freshly removed from animals between birth and day 50 (D50). Slow wave amplitude and frequency increased during this period. Networks of myenteric ICC (IC-MY) were present in gastric muscles at birth and did not change significantly in appearance during the period of study as imaged by confocal immunofluorescence microscopy. 3. IC-MY networks were maintained and electrical rhythmicity developed in organ culture in a manner similar to normal postnatal development. Electrical activity was maintained for at least 48 days in culture. 4. Addition of a neutralizing antibody (ACK2) for the receptor tyrosine kinase, Kit, to the culture media caused progressive loss of Kit-immunoreactive cells. Loss of Kit-immunoreactive cells was associated with loss of slow wave activity. Most muscles became electrically quiescent after 3-4 weeks of exposure to ACK2. 5. In some muscles small clusters of Kit-immunoreactive IC-MY remained after culturing with ACK2. These muscles displayed slow wave activity but only in the immediate regions in which Kit-positive IC-MY remained. These data suggest that regions without Kit-immunoreactive cells cannot generate or regenerate slow waves. 6. After loss of Kit-immunoreactive cells, the muscles could not be paced by direct electrical stimulation. Stimulation with acetylcholine also failed to elicit slow waves. The data suggest that the generation of slow waves is an exclusive property of IC-MY; smooth muscle cells may not express the ionic apparatus necessary for generation of these events. 7. We conclude that IC-MY are an essential element in the spontaneous rhythmic electrical and contractile activity of gastric muscles. This class of ICC appears to generate slow wave activity and may provide a means for regeneration of slow waves.

Gastric emptying in diabetes mellitus: relationship to blood-glucose control

The application of novel investigative techniques has established that disordered gastric motility is a frequent complication of diabetes mellitus. Thus, gastric emptying of solid or nutrient liquid meals is abnormal in 30% to 50% of randomly selected outpatients with long-standing type 1 or type 2 diabetes. Delayed gastric emptying occurs more frequently than rapid emptying. There is increasing evidence that disordered gastric motility has a major impact on the management of patients with diabetes mellitus by leading to gastrointestinal symptoms and poor glycemic control. Although both gastroparesis and upper gastrointestinal symptoms have been attributed to irreversible autonomic damage, it is now clear that acute changes in the blood-glucose concentration have a major effect on both gastrointestinal motor function and the perception of sensations arising in the gut. For example, there is an inverse relationship between the rate of gastric emptying and the blood-glucose concentration, so that gastric emptying is slower during hyperglycemia and accelerated during hypoglycemia. This article reviews some issues in the etiology, diagnosis, and management of problems associated with gastric emptying in elderly persons with diabetes mellitus.

Normalization of atropine-induced postprandial dysrhythmias with gastric pacing

Gastric pacing has received increasing attention recently. However, few studies have systematically assessed the effect of pacing on gastric dysrhythmias. The aims of this study were to investigate the effect of gastric pacing on gastric dysrhythmia and to explore whether the effect of gastric pacing was mediated via cholinergic nerves. Eight hound dogs implanted with three pairs of serosal electrodes were studied. Three study sessions were performed on each dog. The experiment was conducted sequentially as follows: a 30-min myoelectrical recording immediately after a meal, intravenous injection of atropine or saline, and three sequential 20-min myoelectrical recordings with or without gastric pacing during the second 20-min recording. The percentage of regular slow waves (3.5-7. 0 cycles/min) was calculated using spectral analysis. The percentage of the regular slow waves was progressively reduced from 96.7 +/- 1. 7% at baseline to 29.6 +/- 9.0 (P < 0.001), 23.1 +/- 7.1 (P < 0.001), and 27.3 +/- 4.3% (P < 0.001), respectively, during the first, second, and third 20 min after atropine injection. Normalization of the gastric slow wave was achieved with gastric pacing 2.3 +/- 1.0 min after the initiation of pacing. The percentage of regular slow waves was significantly increased both during pacing (93.6 +/- 2.4 vs. 23.1 +/- 7.1%, P < 0.002) and after pacing (70.9 +/- 6.8 vs. 27. 3 +/- 4.3%, P < 0.003) in comparison with the session without pacing. We conclude that 1) atropine induces gastric myoelectric dysrhythmia in the fed state, 2) gastric pacing is able to normalize gastric postprandial dysrhythmia induced by atropine, and 3) the effect of gastric pacing is not mediated by vagal cholinergic mechanism.

Electrogastrographic impact of multi-site functional gastric electrical stimulation

Microprocessor-controlled multi-site functional gastric electrical stimulation using synchronized higher frequency (above 25 Hz) bipolar voltages has been suggested as a possible new avenue towards efficient artificial control of gastric motility. However, the effect of this sequential stimulation on gastric electrical activity is unknown. Because of the substantial strength of the invoked sequential contractions, using implanted electrodes to assess gastric electrical activity (GEA) in experimental animals is difficult, if not impossible. Electrogastrography (EGG), the non-invasively obtained recording of GEA, provides an excellent opportunity to study the changes associated with the multi-site functional stimulation. In this study, we investigated 4 unconscious dogs with 4 circumferential sets of subserosally-implanted stimulating electrodes and 4 force transducers attached close to each stimulating electrode set at operation. The abdominal cavity of each dog was closed after the electrode implantations and 3 standard neonatal electrocardiographic electrodes were attached overlying the abdominal projection of the gastric axis. Two-channel EGG recordings were obtained for 1/2 h before any electrical stimulation and during 1/2 h of intensive sequential stimulation. Significant changes were observed in the EGG pattern during stimulation. These changes were quantified and compared to the basal recordings. Our findings indicate that the interrelation between spectral changes in cutaneous EGG and mechanical activity of the stomach could be far more complex than previously speculated.

Diabetic and Nondiabetic Gastroparesis

Nutritional support is essential in treating patients with gastroparesis. Initially, dietary changes should be instituted to reduce extra fat and bulk, and patients should be encouraged to eat frequent small meals with liquid supplementation. Enteral feeding should be introduced in the event of weight loss or persistent vomiting. Medical therapy is usually necessary early in treatment. Cisapride is the initial agent of choice and may be combined with an antiemetic agent, such as promethazine or chlorpromazine or, if side effects occur, ondansetron and granesitron. If cisapride is ineffective or contraindicated, metoclopramide is a reasonable option, though limited by side effects. Erythromycin is useful in the acute treatment of postoperative ileus and hospitalized gastroparetic patients, but its role is limited based on concerns about poor long-term effectiveness and antimicrobial resistance. Once domperidone becomes available in the United States, it will be useful for its promotility and antiemetic qualities. Combination therapy should be considered if monotherapy with cisapride or metoclopramide alone is ineffective. While not yet well studied, combination therapy has the potential to offer dramatic benefit for patients with refractory gastroparesis. Metoclopramide may be added to cisapride for patients with breakthrough symptoms or refractory chronic symptoms. Other combinations include metoclopramide with erythromycin, domperidone with cisapride, and domperidone with erythromycin. In the future, gastric pacing may become an effective option for patients not responding to medical therapy. Total gastrectomy should be performed only for end-stage gastroparesis when all other therapy has failed. Both procedures should be reserved for centers that specialize in severe gastric motility disorders.

Gastric electrical stimulation in patients with gastroparesis

As in the heart, there is a pacemaker in the human stomach and it generates myoelectrical activity with a frequency of approximately three cycles per minute. Abnormalities in gastric myoelectrical activity may result in gastric motility disorders, such as gastroparesis. Electrical stimulation of the stomach is achieved by delivering electrical currents via electrodes attached to the smooth muscle of the stomach. Recently, a number of studies on electrical stimulation of the stomach in both humans and dogs have indicated that gastric electrical stimulation with appropriate parameters is able to entrain gastric slow waves and normalize gastric dysrhythmias. This has led some investigators to use gastric electrical stimulation to treat patients with gastroparesis. Previous studies and the current state of the field in gastric electrical stimulation in treatment of gastroparesis will be discussed and summarized.

Demography, clinical characteristics, psychological and abuse profiles, treatment, and long-term follow-up of patients with gastroparesis

Patients with gastroparesis frequently present challenging clinical, diagnostic, and therapeutic problems. Data from 146 gastroparesis patients seen over six years were analyzed. Patients were evaluated at the time of initial diagnosis and at the most recent follow-up in terms of gastric emptying and gastrointestinal symptomatology. The psychological status and physical and sexual abuse history in female idiopathic gastroparesis patients were ascertained and an association between those factors and gastrointestinal symptomatology was sought. Eighty-two percent of patients were females (mean age: 45 years old). The mean age for onset of gastroparesis was 33.7 years. The etiologies in 146 patients are: 36% idiopathic, 29% diabetic, 13% postgastric surgery, 7.5% Parkinson's disease, 4.8% collagen vascular disorders, 4.1% intestinal pseudoobstruction, and 6% miscellaneous causes. Subgroups were identified within the idiopathic group: 12 patients (23%) had a presentation consistent with a viral etiology, 48% had very prominent abdominal pain. Other subgroups were gastroesophageal reflux disease and nonulcer dyspepsia (19%), depression (23%), and onset of symptoms immediately after cholecystectomy (8%). Sixty-two percent of women with idiopathic gastroparesis reported a history of physical or sexual abuse, and physical abuse was significantly associated with abdominal pain, somatization, depression, and lifetime surgeries. At the end of the follow-up period, 74% required continuous prokinetic therapy, 22% were able to stop prokinetics, 5% had undergone gastrectomy, 6.2% went onto gastric electrical stimulation (pacing), and 7% had died. At some point 21% had required nutrition support with a feeding jejunostomy tube or periods of parenteral nutrition. A good response to pharmacological agents can be expected in the viral and dyspeptic subgroups of idiopathics, Parkinson's disease, and the majority of diabetics, whereas a poorer outcome to prokinetics can be expected in postgastrectomy patients, those with connective tissue disease, a subgroup of diabetics, and the subset of idiopathic gastroparesis dominated by abdominal pain and history of physical and sexual abuse. Appreciation of the different etiologies and psychological status of the patients may help predict response to prokinetic therapy.