Electrogastrographic study of the effect of transcatheter arterial chemoembolization on gastric myoelectric activity

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.

Mediation of transcatheter arterial chemoembolization induced gastric slow-wave dysrhythmia by endogenous prostaglandin

BACKGROUND AND AIMS

In recent years, gastric slow-wave dysrhythmias induced by transcatheter arterial chemoembolization (TACE) have been observed. Enhanced endogenous prostaglandin may be a possible mechanism for the myoelectrical changes. The aim of this study was to evaluate whether the gastric slow-wave dysrhythmias induced by TACE may be mediated by ketoprofen, a prostaglandin synthesis inhibitor.

METHODS

Twenty-three patients with hepatocellular carcinoma (HCC) admitted for TACE were enrolled. A follow-up TACE was scheduled to take place 2 months later. During the next admission for TACE, 50 mg of ketoprofen was given intramuscularly 12 h for 3 days, beginning 48 h before TACE, as premedication. Cutaneous electrogastrography (EGG) was performed before and within 24 h after TACE.

RESULTS

The results showed that the change in the fasting EGG parameters after TACE without premedication was not statistically significant. However, the postprandial EGG parameters, including the dominant frequency (DF); the percentages of DF in the normal, bradygastric and tachygastric range; along with the dominant frequency instability coefficient, deteriorated significantly after the procedure (P < 0.01). After the follow-up TACE with ketoprofen premedication, neither the fasting nor postprandial EGG parameters in the control group changed significantly.

CONCLUSIONS

Gastric slow-wave dysrhythmias induced by TACE may be mediated by ketoprofen, a prostaglandin synthesis inhibitor, in HCC patients. However, the improvement in the gastric myoelectrical activity does not eliminate the degree of nausea/vomiting after TACE.

Cytotoxic chemotherapy has minimal direct effect on gastric myoelectric activity in children with 5HT(3) antagonist prophylaxis

BACKGROUND

Cancer patients receiving cytotoxic chemotherapy frequently develop nausea and vomiting. The direct effect of chemotherapy on gastric pacemaker is not clear. The objective of this study was to assess the direct interference of gastric electrical activity by chemotherapeutic agents as a possible cause of vomiting using electrogastrography (EGG).

PROCEDURE

Fasting surface EGGs were recorded in 24 children with malignancy and 24 age-matched controls. All oncology patients received the intravenous prophylatic ondansetron. According to the known emetic potential of the medications they received, the children were divided into mild, moderate, and severe groups. The EGG recordings of oncology patients were segmented into prechemotherapy period, chemotherapy period, and emetic period. The EGG data from each period were collected and analyzed (paired t-test and Mann-Whitney U test).

RESULTS

There were 24 children (M:F ratio: 14:10), with a mean age of 9.6 years. Eight children vomited during the course of recording (0/3 from the mild group, 2/6 from the moderate group, and 6/15 from the severe group). The average duration of intravenous medication infusion was 7.8 hr (range 2 min to 24 hr). There was no difference between the EGG of normal control and the prechemotherapy EGG of the oncology patients. No difference was detected between the EGG data from the prechemotherapy period and the chemotherapy period. A statistically significant increase in tachygastria was detected in emetic periods (28 episodes, mean duration 5 min; P = 0.01).

CONCLUSIONS

Insignificant EGG changes during chemotherapy suggest that chemotherapy has a minimal direct effect on gastric pacemaker. Tachygastria seemed to be a secondary effect of vomiting rather than the cause of it. These preliminary findings suggest that efforts to modify gastric electrical rhythm as a means of management of chemotherapy-induced vomiting may be futile. Further studies to identify factors responsible for vomiting are warranted.

Gastroduodenal motility

Several major themes emerged over the past year in the area of gastroduodenal motility. Mostly, these themes represented extensions of research areas discussed in prior reviews in this series rather than the emergence of completely new concepts. Thus, for example, considerable emphasis has again been placed on regional gastric motor function in dyspepsia and on the role of fundic relaxation and accommodation, in particular. Not surprisingly, basic physiologic research has also shown a keen interest in the regulation of fundic relaxation. One new and exciting development is the recognition of the stomach's role in satiety. The spectrum of gastric motor dysfunction in diabetes mellitus continues to be explored, and the important role of hyperglycemia in regulating gastric function has been further emphasized. More data have been provided on noninvasive alternatives to gastric motor function testing, and several studies have looked at factors that may influence variability in these various tests. There have been few innovations over the past year in the therapeutic arena; rather, the indications and limitations of current therapies have been further developed.