Jiande Chen

Gastric pacing improves emptying and symptoms in patients with gastroparesis.

BACKGROUND & AIMS No effective treatment is available for patients with gastroparesis refractory to standard medical therapy. The aim of this study was to investigate the effects of gastric pacing on gastric electrical activity, gastric emptying, and symptoms in patients with gastroparesis. METHODS Nine patients with gastroparesis participated in this study. Four pairs of cardiac pacing wires were implanted on the serosa of the stomach. The protocol consisted of two portions: a temporary inpatient study period and an outpatient study for a period of 1 month or more. RESULTS Gastric pacing entrained the gastric slow wave in all subjects and converted tachygastria in 2 patients into regular 3-cpm slow waves. Gastric emptying was significantly improved after the outpatient treatment with gastric pacing. The gastric retention at 2 hours was reduced from 77.0% +/- 3.3% to 56.6% +/- 8.6% (P < 0.05). Symptoms of gastroparesis were substantially reduced at the end of the outpatient treatment (1.51 +/- 0.46 vs. 2.84 +/- 0.61; P < 0.04). Eight of 9 patients no longer relied on jejunostomy tube feeding, and no adverse events were noted related to the pacing unit. CONCLUSIONS Gastric pacing seems to be able to improve symptoms of gastroparesis and to accelerate gastric emptying in patients with gastroparesis. More controlled studies are necessary to further investigate the role of gastric pacing in clinical practice.

Abnormal gastric myoelectrical activity and delayed gastric emptying in patients with symptoms suggestive of gastroparesis

Gastric myoelectrical activity modulates gastric motor activity. Abnormalities in gastric myoelectrical activity may be associated with gastric motility disorders. The aim of this study was to investigate the correlation of gastric myoelectrical activity with gastric emptying in symptomatic patients with and without gastroparesis. Ninety-seven patients with symptoms suggestive of gastroparesis participated in the study. Gastric myoelectrical activity was recorded using surface electrogastrography. The electrogastrogram (EGG) was recorded for 30 min in the fasting state and for 120 min after a solid test meal. Gastric emptying of the solid meal was simultaneously monitored for 120 min. Patients with delayed gastric emptying showed a significantly lower percentage of normal gastric slow waves (P<0.03) and a significantly reduced increase of the dominant power in the postprandial EGG (P<0.02). Postprandial EGG parameters were found to be able to predict delayed emptying of the stomach. Postprandial gastric dysrhythmia predicts delayed gastric emptying with an accuracy of 78%, while the abnormality in postprandial EGG power predicts delayed gastric emptying with an accuracy of 75%. All patients with abnormalities in both the rhythmicity and the power had delayed gastric emptying. Patients with delayed gastric emptying have a lower percentage of normal gastric slow waves in the EGG and a lower postprandial increase in the dominant power. Abnormalities in the postprandial EGG seem to be able to predict delayed emptying of the stomach. However, a normal EGG does not seem to guarantee normal emptying of the stomach.

Effects of pacing parameters on entrainment of gastric slow waves in patients with gastroparesis

The aim of this study was to investigate the effect of pacing parameters on the entrainment of gastric slow waves in patients with gastroparesis. Four pairs of cardiac pacing wires were placed on the serosal surface of the stomach in 13 patients with gastroparesis. After a baseline recording for 30 min, gastric pacing was performed in a number of sessions with different effective parameters, each lasting for 30 min. The following parameters were found to be effective for the entrainment of the gastric slow wave: a pacing frequency 10% higher than the intrinsic gastric slow wave frequency (IGF), 300 ms pulse width, and 4 mA pacing amplitude. A reduction of pacing amplitude from 4 to 2 mA and 1 mA reduced the percentage of entrainment of the gastric slow wave to 79 ± 10% and 50 ± 11%, respectively. Pacing with a pulse width of 30 or 3 ms was not able to entrain the gastric slow wave in any of the patients. An ectopic pacemaker of tachygastria found in three patients was reversed with gastric pacing. It was concluded that gastric pacing at a frequency up to 10% higher than the IGF and with an amplitude of 4 mA and a pulse width of 300 ms is able to completely entrain the gastric slow wave and normalize gastric dysrhythmias in patients with gastroparesis.The aim of this study was to investigate the effect of pacing parameters on the entrainment of gastric slow waves in patients with gastroparesis. Four pairs of cardiac pacing wires were placed on the serosal surface of the stomach in 13 patients with gastroparesis. After a baseline recording for 30 min, gastric pacing was performed in a number of sessions with different effective parameters, each lasting for 30 min. The following parameters were found to be effective for the entrainment of the gastric slow wave: a pacing frequency 10% higher than the intrinsic gastric slow wave frequency (IGF), 300 ms pulse width, and 4 mA pacing amplitude. A reduction of pacing amplitude from 4 to 2 mA and 1 mA reduced the percentage of entrainment of the gastric slow wave to 79 +/- 10% and 50 +/- 11%, respectively. Pacing with a pulse width of 30 or 3 ms was not able to entrain the gastric slow wave in any of the patients. An ectopic pacemaker of tachygastria found in three patients was reversed with gastric pacing. It was concluded that gastric pacing at a frequency up to 10% higher than the IGF and with an amplitude of 4 mA and a pulse width of 300 ms is able to completely entrain the gastric slow wave and normalize gastric dysrhythmias in patients with gastroparesis.

Clinical significance of gastric myoelectrical dysrhythmias.

Normal rhythmic myoelectrical activity of the human stomach is 3 cpm, regulating gastric contractile activity. Dysrhythmia in gastric myoelectrical activity is found to be associated with functional disorders of the stomach. Gastric dysrhythmias are classified into tachygastria (frequency higher than normal), bradygastria (frequency lower than normal) and arrhythmia (no rhythmic activity). Clinical significance of gastric dysrhythmias is discussed in this paper, outlined as follows: (a) What is normal gastric myoelectrical activity and what is dysrhythmia? (b) How to detect gastric dysrhythmias? (c) Gastric dysrhythmias in clinical settings. (d) What may cause gastric dysrhythmias? (e) How to normalize gastric dysrhythmias?

Spectral analysis of episodic rhythmic variations in the cutaneous electrogastrogram

The cutaneous recording of gastric electrical activity is called the electrogastrogram (EGG). Gastric electrical dysrhythmic events associated with abnormal conditions of the stomach may be detected from the EGG. An adaptive spectral analysis method based on autoregressive moving average (ARMA) modeling has previously been developed. The ability of the previous method to detect gastric dysrhythmic events from the EGG is studied. A series of bench tests simulating typical problems with the analysis of nonstationary electric potentials was conducted. The application of the adaptive spectral analysis method to dysrhythmic events and rhythmic variations of the gastric slow wave is presented. The adaptive spectral analysis approach provides several advantages: narrow frequency peaks permitting more precise frequency identification, determination of changes in frequency components at any time point, and enhanced interpretation of cutaneous EGG recordings.<<ETX>>

A computerized data analysis system for electrogastrogram

A comprehensive computerized data analysis system for the electrogastrogram is presented in this paper. The electrogastrogram (EGG) is a cutaneous measurement of electrical activity of the stomach by positioning electrodes on the abdominal skin. Since the signal-to-noise ratio of the EGG is very low, visual analysis is impossible. The data analysis system presented in this paper contains a series of PC programs to perform: (a) data acquisition and real-time A/D conversion; (b) digital filter design and digital filtering; (c) adaptive cancellation of respiratory artifact; (d) smoothed power spectral analysis; (e) adaptive running spectral analysis; (f) two- or three-dimensional display of the EGG and analysis results. The basic principles of the system and sample results are presented.

What can be measured from surface electrogastrography: Computer simulations

The aims of this study were to investigate thedetectability of the propagation of the gastric slowwave from the cutaneous electrogastrogram (EGG) and thepatterns of the EGG when the gastric slow waves are uncoupled. A mathematical model wasestablished based on the volume conductor theory tosimulate the transfer of the serosal gastric slow wavefrom the stomach to the abdominal surface. A number of computer simulations were conducted using themodel, and the periodic cross-correlation function wasused to estimate the phase shift between the fourchannels. It was found that the propagation of the gastric slow wave was detectable from themultichannel EGG signals. The detectability of thepropagation was, however, associated with a number offactors, such as the thickness of the abdominal wall and the propagation velocity of the serosal slowwave. The amplitude of the EGG was found to beassociated with the coupling/uncoupling and propagationvelocity of the gastric slow wave. The amplitude of the EGG increased when the propagation velocity ofthe gastric slow wave increased. The amplitude of theEGG was substantially decreased when the gastric slowwaves were uncoupled. The uncoupling of the gastric slow wave at a frequency of 3 cpm produceddysrhythmias in the EGG, including tachygastria,bradygastria, and arrhythmia. The power spectra ofsimulated different positional EGG signals showedsimilar patterns when the gastric slow wave was coupled anddifferent and unpredictable patterns when the gastricslow wave was uncoupled. In conclusion, multichannel EGGrecordings may be necessary to obtain more information on gastric slow waves from the abdominalelectrodes. The propagation and coupling or uncouplingof the gastric slow wave may be detected frommultichannel EGG recordings.

The Rumination Syndrome (Clinical and Manometric Profile, Therapy, and Long-Term Outcome)

The aims of this study were to investigate thediagnostic studies necessary to identify ruminationsyndrome and the long-term therapeutic outcomes ofpatients with rumination syndrome. Sixteen patients with rumination were evaluated between 1989 and1995. Esophageal motility, gastric emptying, uppergastrointestinal motility, and electrogastrography ofall patients were reviewed; follow-up information about their current status was available from10 of the 16 patients. Duration of symptoms was 77.2months and the mean age was 28.5 years at the time ofdiagnosis. Esophageal and upper gastrointestinal motility, gastric emptying, andelectrogastrographic studies were all normal. Mean loweresophageal pressure was 12.7 mm Hg and three of the 16patients had a decreased pressure of less than 6 mm Hg.Ten patients were followed for a mean duration of31.2 months. Five of 10 patients used biofeedback andrelaxation techniques and reported subjectiveimprovement. Our results indicate that ruminationsyndrome is often confused with a gastric motilitydisorder and diagnosis is possible if one is aware ofthis condition. Although there is not a definitivemanagement protocol for this condition, reassurance and education of the patient and the family arecrucial first steps followed by behavioral andrelaxation programs.

Efficiency and efficacy of the electrogastrogram.

The efficiency and efficacy of theelectrogastrogram (EGG) involve a few practical factors,including recording length, sample size, and thecharacteristics of subjects. The aim of this study wasto investigate the effect of these factors on the accuracy ofEGG analysis. Gastric myoelectrical activity wasrecorded using electrogastrography in 24 subjects (ages22-91 years) for 1 hr in the fasting state and 2 hr after a test meal. Computerized spectralanalysis was performed to compute EGG parameters,including dominant frequency, dominant power, and thepercentage of 2-4 cycles per minute (cpm) slow waves. A parameter called misinterpretation was definedto investigate the effect of recording length. Theresults were as follows: (1) Using the recording lengthof 1 hr in each state as a gold standard, themisinterpretation for the recording length of 30 min was 27% forthe dominant frequency and 17% for the dominant power.When the recording length was reduced to 15 min, themisinterpretation increased to 61% for the dominant frequency and 38% for the dominant power. (2)With a sample size of 10 subjects and a recording lengthof 60 min, a statistically significant postprandialincrease was observed in the dominant frequency and power, and a trend in the postprandialincrease of the regularity of the EGG was noted. Whenthe sample size increased to 24 subjects, a significantpostprandial increase was found in all these parameters. (3) None of the EGG parameters exhibited anysignificant difference between the younger and oldersubjects or between men and women. In conclusion, arecording length of 30-60 min seems to be appropriate and produces reliable and predictable results.Age and gender do not affect any of the EGGparameters.

Impaired Gastric Myoelectrical Activity in Patients with Chronic Renal Failure

Dysmotility and delayed emptying of the stomachhave been reported in patients with chronic renalfailure (CRF). The aim of this study was to investigatewhether gastric myoelectrical activity was impaired in patients with CRF using electrogastrography.The electrogastrogram (EGG) was recorded in 24symptomatic patients with CRF (15 with diabetes) and 12normal subjects. Two 30-min EGG recordings before and after a test meal were analyzed using spectralanalysis methods. It was found that patients with CRFshowed a significantly lower percentage of normal 2-4cpm slow waves in both fasting and fed states in comparison with healthy controls (in fastingstate: 88.9 ± 2.5% vs 67.4 ± 6.6%/63.27.0%, P < 0.01; in fed state: 89.6 ± 1.8% vs64.6 ± 6.2%/62.0 ± 8.3%, P < 0.01;controls vs diabetic patients/nondiabetic patients). Both patient groups showed a significantlyhigher prevalence of the abnormal EGG, which was definedas the percentage of 2-4 cpm slow waves lower than 70%(fasting state: 8% vs 60%/56%, P < 0.01/0.05; fed state: 0% vs 53%/56%, P < 0.005/0.002;controls vs diabetic patients/nondiabetic patients). Nosignificant difference was observed in the regularity ofthe gastric slow waves between the two patient groups. The healthy controls showed a significantincrease in the dominant power and frequency of the EGGafter the test meal. However, this increase was absentin the two patient groups. It was concluded that patients with chronic renal failure haveabnormal gastric myoelectrical activity, includingimpaired regularity of the gastric slow wave and afailed increase in the power of the EGG at 3 cpm.Electrogastrography is an attractive noninvasive method for thestudy of gastric motility in patients with severechronic renal failure.