Isopower maps of the electrogastrogram (EGG) after total gastrectomy or total colectomy

Abstract

Isopower or topographic electrogastrograms (EGG) correspond to topographic electroencephalograms. Both project the topographic localizations of the spectral frequencies on the abdominal surface or scalp. This paper compares the pre-operative control isopower EGG maps with those of total gastrectomy or total colectomy. EGGs were recorded simultaneously at 27 locations on the epigastro-abdominal surface. Spectral analysis by the maximal entropy method (MEM) was performed and the ensemble means of pre-prandial and post-prandial spectra were calculated. The spectral frequencies were arbitrarily classified into five groups, 1 cycle per minute (cpm) (0-2.4 cpm), 3 cpm (2.5-4.9 cpm), 6 cpm (5.0-7.4 cpm), 8 cpm (7.5-9.9 cpm) and 10 cpm (10.0-12.9 cpm). Maximal power peaks in each spectral group, and electrode locations which were expressed by x-y coordinates were the indicators for making the isopower EGG maps by using a contour map program. Thereafter, the maximal power spots or foci in each spectral group were determined. The pre-operative maximal power foci of the 1, 8 and 10 cpm groups were distributed rather evenly on the epigastro-abdominal surface. Those of the 3 and 6 cpm groups, mainly concentrated in the epigastric region, were absent in almost all patients who had undergone total gastrectomy. The infra-umbilical foci of the 3 and 6 cpm groups completely disappeared after total colectomy. The infra-umbilical foci of the 3 and 6 cpm groups (2.5-7.4) may reflect the colonic activities and the epigastric 3 cpm foci, the gastric activities. The pre-operative maximal power of the 3 cpm foci decreased significantly after total or sub-total gastrectomy.

Local differences in electrogastrographic responses to the stress of the mirror drawing test (MDT) as determined by multichannel electrogastrography

“…Anxiety has also been reported to facilitate antral meal retention (Lorena et al, 2004). The epigastric 3-and 6-cpm groups electrical activity in the EGG were suggested to reflect those of the colon on the basis of the EGG results obtained after total gastrectomy (Pezzola et al, 1989;Homma et al, 1995Homma et al, , 1999. We have reported that gastric, intestinal and colonic myoelectric activity can be recorded using EGG (Homma et al, 1995: Homma, 1997: Homma et al, 1999, 2000.…”

“…The methods used for recording and analyzing EGGs were the same as in the previous studies (Homma et al, 1999: Homma, 2005. Briefly, unipolar EGGs were recorded from the 16 locations (channels, ch) from the thoraco-abdominal skin surface (Fig.…”

“…To make topographic EGG maps, the electrode positions were represented by two-dimensional standard coordinates, Xi and Yi, and a spectral peak at a certain electrode position was expressed as Zi = (Xi,Yi) (Homma, 1997: Homma et al, 1999: Homma, 2006. Thereafter, the contour map program (Shiono et al, 1988) was applied and EGG maps were drawn for the power content ratio (Homma, 1997).…”

“…Thereafter, the contour map program (Shiono et al, 1988) was applied and EGG maps were drawn for the power content ratio (Homma, 1997). The iso-power content ratio lines and iso-absolute power ratio lines were usually drawn at intervals of 1/20 of the maximal power content ratio and absolute power ratio of each spectral group to obtain the foci of the maximal power content ratio or maximal absolute power ratio as in the case of maximal power foci (MPFs) (Homma et al, 1999). The mean and standard errors (SE) were calculated and the Student's t-test was used to determine the statistical significance.…”

“…The epigastric 3-and 6-cpm groups electrical activity in the EGG were suggested to reflect those of the colon on the basis of the EGG results obtained after total gastrectomy (Pezzola et al, 1989;Homma et al, 1995Homma et al, , 1999. We have reported that gastric, intestinal and colonic myoelectric activity can be recorded using EGG (Homma et al, 1995: Homma, 1997: Homma et al, 1999, 2000. Topographical EGG maps were also drawn for the determination of maximal power foci (MPFs) in the resting state, during MDT and after consuming a meal (Homma, 1997: Homma et al, 1999, 2000: Zhou et al, 1997.…”