The effects of varying the extent of the vagotomy on the myoelectrical and motor activity of the stomach

Origins and patterns of spontaneous and drug-induced canine gastric myoelectrical dysrhythmia

The aim of this study was to investigate the characteristics and orientation of gastric dysrhythmia using multichannel serosal recordings in dogs. Ten dogs chronically implanted with four to eight pairs of electrodes were studied. Gastric slow waves were recorded in four sessions: postsurgical and after atropine, vasopressin, and glucagon. A total of 554.7 min of bradygastria, 201 min of tachygastria and 22.3 min of arrhythmia were observed in the recordings. The majority of bradygastria (80.5 +/- 9.4%) originated in the proximal stomach (P < 0.04, vs other locations) and propagated all the way to the distal antrum. In contrast, tachygastria mainly originated in the distal antrum (80.6 +/- 8.8%) (P < 0.04, vs other locations) and propagated partially or all the way to the proximal stomach. Dysrhythmia appeared intermittently with normal gastric slow waves. In all recordings, normal slow waves were present 38.0 +/- 5.3% of the time, while bradygastria, tachygastria, and arrhythmia were present 35.9 +/- 5.3%, 23.0 +/- 1.6%, and 2.4 +/- 0.5% of the time, respectively. The prevalence of dysrhythmia was highest in the distal antrum (80.4%) (P < 0.01) and lowest in the proximal part of the stomach. In conclusion, tachygastria originates from an ectopic pacemaker in the distal antrum. It may completely or partially override the normal slow waves. Bradygastria is attributed to a decrease in the frequency of the normal pacemaker in the corpus. The prevalence of gastric dysrhythmia is different in different locations of the stomach and is highest in the distal antrum.

Electrical control of gastric emptying in denervated and reinnervated canine stomach: a pilot study

Gastric emptying of solids is abnormally slow after vagotomy. To determine whether it was possible to accelerate emptying by electrical stimulation either of the gastric wall directly or of a "foreign" nerve brought in to reinnervate the stomach, eight dogs underwent truncal vagotomy (TV); five of the dogs received intercostal nerve muscle pedicle (NMP) implants. Gastric atony was demonstrated postoperatively in all animals up to 4 months later by means of radiological contrast studies. After allowing time for neurotization to occur (mean 78 days), the cervical vagi were stimulated to confirm that TV was complete. Gastric peristalsis, intraluminal pressures, and emptying were assessed during stimulation of the NMPs and of the gastric wall, followed by sacrifice for histologic study. Neither reinnervation alone nor stimulation of the NMPs improved emptying. Although viable somatic nerve was found in the gastric wall, nerve sprouting was not. By contrast, stimulation of the gastric wall with trains of pulses (20 Hz, 2-10 ms, 2-5 mA) evoked peristalsis in all animals. We conclude that somatic nerve tissue cannot produce functional reinnervation of a visceral organ; however, direct muscular stimulation can accelerate gastric emptying after TV.

Coordinated motor activity of the human gastroduodenal region

Using real-time ultrasonic imaging, and a test meal of 500 ml of dilute orange juice, we have studied the temporal relationships among contractions of the terminal antrum, pylorus, and proximal duodenum of 22 normal subjects. A total of 259 cyclical periods of motor activity were observed. Individual mean gastroduodenal cycle times ranged from 17.9 to 29.6 seconds (2.0-3.3 cycles/min). Terminal antral contractions (TACs) were observed in 98% of cycles and pyloric closure invariably occurred at the midpoint of these contractions. The pylorus then opened as the terminal antrum relaxed and remained open until the next TAC. Only 67% of TACs were associated with contractions of the proximal duodenum (DC), but 94% of these occurred about 1 sec (range 1 sec before to 2 sec after) after pyloric closure. Only 6% of DCs were ectopic, in that their occurrence was apparently uncoordinated with the TACs. Our observations demonstrate that after ingestion of a test meal, the human terminal antrum, pylorus, and proximal duodenum usually contract in a sequential coordinated manner, presumably under the control of the gastric slow wave. No evidence of independent pyloric closure was obtained.

Alterations in gastrointestinal emptying of 99m-technetium-labeled solids following sequential antrectomy, truncal vagotomy and Roux-Y gastroenterostomy

Recent reviews have documented significant delayed gastric emptying following Roux-Y biliary diversion for alkaline gastritis. This study establishes the use of radionuclide imaging in the experimental model and evaluates the following: (1) gastric emptying following antrectomy with and without vagal denervation; (2) the effect of Roux-Y diversion on gastric and upper gastrointestinal emptying using animals as their own controls; and (3) the role of truncal vagotomy in the "Roux-Y delayed emptying syndrome." Upper gastrointestinal emptying was evaluated in 8 dogs using the radionuclide technetium 99 labeled egg white method with continuous visualization by gamma camera. Eight dogs underwent B-II antrectomy without vagotomy and were divided into two groups. Four underwent vagotomy, re-evaluation, and Roux-Y diversion. Four underwent Roux-Y diversion first, re-evaluation, then truncal vagotomy. Control dogs retained 65% +/- 4% (SEM) and 45% +/- 6% of ingested food at 2 and 4 hours, respectively. Following antrectomy only, rapid gastric emptying of radionuclide solid is observed with 35% +/- 7%, 16% +/- 4% and 7% +/- 4% retention and 2, 3, and 4 hours, respectively. Roux-Y antrectomy without vagotomy results in similar rapid gastric emptying. Truncal vagotomy following B-II antrectomy delays gastric emptying compared to antrectomy only. Truncal vagotomy and Roux diversion results in varied patterns of gastrointestinal emptying. Significant gastric retention and gastric and Roux limb retention are observed in 25% of trials. Significant Roux limb retention is observed in 45% of the group. Prior to vagotomy there is no retention or altered transit in the Roux limb. In general, no delay in gastrointestinal emptying is observed in the absence of vagal denervation. These data corroborate our clinical experience in observing both Roux and gastric retention following radionuclide evaluation in Roux-Y patients.

Effects of various operations on the electrical activity of the human stomach recorded during the postoperative recovery period

This study attempts to characterize any changes occurring in the human gastric control electrical rhythm (CER), following a variety of gastric surgical procedures. Pairs of electrodes were implanted in selected specific sites on the stomachs of 57 patients undergoing either antrectomy and vagotomy, proximal gastric vagotomy (PGV), vagotomy and drainage, gastric resection without vagotomy, or fundoplication. Five patients undergoing nongastric operations served as controls. After operation recordings were obtained with differential preamplifiers, an oscilloscope, and a dual-channel tape recorder. An electrical signal compatible with a CER was found almost always in the distal body or antrum, regardless of whether vagotomy was performed. In contrast, a CER was found only occasionally in the fundus, and was never found following PGV. Although there was a difference in the frequency of occurrence of fundic CER in patients with and without vagotomy, it was not statistically significant (p = 0.0668). Patients with prolonged postoperative convalescence because of gastric atony were compared with patients with normal postoperative courses regarding the presence or absence of CER in the gastric antrum or fundus. A statistically significant relationship between abnormal gastric motility and absence of CER was not established.

Human gastric pacesetter potential. Site of origin, spread, and response to gastric transection and proximal gastric vagotomy

Gastric electrical activity was recorded from twenty-six patients at celiotomy. The human gastric pacemaker was localized to an area in the midcorpus along the greater curve. Pacesetter potentials were generated regularly by the pacemaker at a mean frequency of 3.2 cycles/min and were propagated circumferentially and aborally from the pacemaker, increasing in amplitude and velocity as they approach the pylorus. The pattern of pacesetter potenitals in patients with gastric ulcer, gastric cancer, and duodenal ulcer was similar to that of patients without such diseases. Complete transection of the gastric corpus isolated the distal stomach from the natural pacemaker and resulted in the appearance of a new pacemaker in the distal stomach with a slower frequency. The fact that proximal gastric vagotomy did not greatly alter the frequency of generation or the pattern of propagation of the pacesetter potential provided further evidence that both are myogenic phenomena.

Gastric emptying in control subjects and patients with duodenal ulcer before and after vagotomy

The emptying of a solid meal labelled with Indium 113mDTPA from the stomach was studied with a gamma camera in 26 normal subjects, 27 patients with duodenal ulcer, on 41 occasions after truncal vagotomy and pyloroplasty and 38 times after highly selective vagotomy. Applying the method of principal component analysis to the results, differences were detected between control and duodenal ulcer subjects and two probable subgroups of duodenal ulcer were observed. Half emptying times did not reveal these patterns. After vagotomy, delayed emptying was general at one week. At one month, patients after highly selective vagotomy had a more normal result than those with truncal vagotomy and pyloroplasty (TV), but by six months no significant difference in overall emptying rate was found, although changes in the pattern of gastric emptying persisted in some patients after TV.

The immediate and delayed effects of different types of vagotomy on human gastric myoelectrical activity

The immediate and delayed effects of different types of vagotomy on the antral myoelectrical activity have been studied in 52 patients who had previously undergone either highly selective vagotomy (HSV) or truncal vagotomy and pyloroplasty (TV + P) for the treatment of chronic duodenal ulceration up to eight years previously. The frequency of the electrical activity was not statistically different between the two types of operation. After HSV the triphasic waveshape of the antral myoelectrical activity was retained; it was recorded more frequently in the delayed tests (98.0 plus or minus 1-7%) of the recording period than in immediate tests (74-7 plus or minus 6-5%) whereas mean amplitude in the immediate tests (1-59 plus or minus 0-13 mV) was not significantly changed in the delayed tests (1-49 plus or minus 0-08mV). After TV + P the waveform was more sinusoidal in shape, being recorded more often in the delayed tests (91-7 plus or minus 2-7%) than in the immediate tests (41-4 plus or minus 8-9%) although the mean amplitude between the immediate (0-090 plus or minus 0-06 mV) and delayed tests (0-94 plus or minus 0-07 mV) was not significantly different. The only significant change in the myoelectrical activity with the passage of time after vagotomy was an increase in the percentage activity.

Electrical activity of gastrointestinal smooth muscle

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