Electrical activity in the gastroduodenal area--slow waves in the proximal duodenum. A comparison of man and dog

Intra-operative high-resolution mapping of slow wave propagation in the human jejunum: Feasibility and initial results

BACKGROUND

Bioelectrical slow waves are a coordinating mechanism of small intestine motility, but extracellular human studies have been restricted to a limited number of sparse electrode recordings. High-resolution (HR) mapping has offered substantial insights into spatiotemporal intestinal slow wave dynamics, but has been limited to animal studies to date. This study aimed to translate intra-operative HR mapping to define pacemaking and conduction profiles in the human small intestine.

METHODS

Immediately following laparotomy, flexible-printed-circuit arrays were applied around the serosa of the proximal jejunum (128-256 electrodes; 4-5.2 mm spacing; 28-59 cm² ). Slow wave propagation patterns were mapped, and frequencies, amplitudes, downstroke widths, and velocities were calculated. Pacemaking and propagation patterns were defined.

KEY RESULTS

Analysis comprised nine patients with mean recording duration of 7.6 ± 2.8 minutes. Slow waves occurred at a frequency of 9.8 ± 0.4 cpm, amplitude 0.3 ± 0.04 mV, downstroke width 0.5 ± 0.1 seconds, and with faster circumferential velocity than longitudinal (10.1 ± 0.8 vs 9.0 ± 0.7 mm/s; P = .001). Focal pacemakers were identified and mapped (n = 4; mean frequency 9.9 ± 0.2 cpm). Disordered slow wave propagation was observed, including wavefront collisions, conduction blocks, and breakout and entrainment of pacemakers.

CONCLUSIONS & INFERENCES

This study introduces HR mapping of human intestinal slow waves, and provides first descriptions of intestinal pacemaker sites and velocity anisotropy. Future translation to other intestinal regions, disease states, and postsurgical dysmotility holds potential for improving the basic and clinical understanding of small intestine pathophysiology.

Therapeutic potential of duodenal electrical stimulation for obesity: acute effects on gastric emptying and water intake

OBJECTIVES

No satisfactory treatment is available for obesity. Previous animal studies suggested the therapeutic potential of intestinal electrical stimulation for obesity. The aim of this study was to investigate the effects of duodenal electrical stimulation (DES) on gastric emptying and water intake in healthy humans.

METHODS

The study was performed in 12 healthy volunteers intubated with a feeding tube in the duodenum under endoscopy. There were three ring electrodes at the end tip of the tube and the two distal electrodes were used for recording and electrical stimulation. On two separate days, each subject underwent a session of DES with various stimulation parameters, a water-intake test with DES or with sham-DES, and a gastric-emptying test with DES or with sham-DES.

RESULTS

DES did not induce any noticeable dyspeptic symptoms. The amount of water drunk by the subjects was significantly reduced from 897 +/- 88 ml with sham-DES to 673 +/- 63 ml with DES (p < 0.002). The mean T(50) of gastric emptying was significantly increased from 113.1 +/- 10.0 min with sham-DES to 176.5 +/- 20.8 min with DES state (p < 0.005). The gastric retention at 2 h was increased with DES (42.8 +/- 4.5% vs 61.4 +/- 4.7%; p < 0.02).

CONCLUSIONS

DES delays gastric emptying and reduces water intake. It may have a potential application for the treatment of obesity.

Inter-digestive and post-prandial antro-pyloro-duodenal motor activity in humans: effect of 5-hydroxytryptamine 1 receptor agonism

BACKGROUND

Little is known about the effect of 5-hydroxytryptamine 1 (5-HT(1)) receptor agonism on the co-ordinated motor activity of the gastric antrum, pylorus and duodenum under fasting and fed conditions.

AIM

To evaluate the effect of sumatriptan, a 5-HT(1) agonist, on fasting and fed antro-pyloro-duodenal motility.

METHODS

In study 1, antro-pyloro-duodenal motility was recorded for two phase IIIs of the migrating motor complex and then, following either a subcutaneous injection of sumatriptan 6 mg or saline control, for at least one additional phase III in 11 healthy volunteers (21-36 years). In study 2, the post-prandial motility was recorded for 3 h after either a subcutaneous injection of sumatriptan 6 mg or saline control in 10 healthy volunteers (18-36 years).

RESULTS

Sumatriptan prolonged the migrating motor complex cycle (P = 0.009) by increasing the duration of phase II (P = 0.02) but not phases I and III. Post-prandially, sumatriptan reduced the activity index (P = 0.017) by reducing the frequency of co-ordinated motor activity involving the antrum and/or the duodenum (P < 0.05).

CONCLUSION

5-HT(1) receptor agonism increases the periodicity of the migrating motor complex and reduces the occurrence of post-prandial co-ordinated motor activity involving the gastric antrum, pylorus and duodenum.

Hyperglycemia induces abnormalities of gastric myoelectrical activity in patients with type I diabetes mellitus

BACKGROUND/AIMS

Blood glucose concentration has been shown to be an important factor in gastric motility. However, the effect of hyperglycemia on gastric myoelectrical activity has not yet been studied in patients with diabetes.

METHODS

Surface electrogastrography was performed in eight patients with type I diabetes mellitus under normoglycemic and hyperglycemic conditions (glucose clamp technique) and in eight normoglycemic control subjects.

RESULTS

In the early postprandial state, the frequency of the normal pacemaker rhythm tended to be higher during hyperglycemia than during normoglycemia (3.10 +/- 0.27 vs. 2.92 +/- 0.19 cycle/min; P = 0.061). The frequency decrease that occurs immediately after a meal was found less frequently during hyperglycemia (in 25% vs. 75% of the patients; P = 0.046). Higher harmonics of the 3-cycle/min component, indicating an electrogastrographic waveform change, were found less often during hyperglycemia (in 13% vs. 63% of the patients; P = 0.039). Dysrhythmias (in particular, tachygastrias) were more prevalent during hyperglycemia (40.6% vs. 6.5% of the time; P = 0.028). No differences were found between normoglycemic patients and control subjects.

CONCLUSIONS

This study has shown that hyperglycemia is an important factor in the generation of gastric myoelectrical disturbances and tachygastrias in particular.

Signal preprocessing system for the small intestinal electromyogram

The intestinal EMG obtained from chronically implanted electrodes in canine preparations provides for the evaluation of intestinal motor activity and its control. The basic electrical rhythm (BER) and spike components on the EMG signal provide evidence of control activity and a measure of contraction intensity, respectively. A hardware system is presented in which these two components are separated by filters and the contraction spikes counted in fixed epochs to yield a contraction spike per unit time record against time. The signal is also available in parallel binary form at the end of each epoch, together with a data-ready signal for direct acquisition by computer. Tests of system performance and operating protocols are given. The preprocessor is used as a fast front end to a digital signal processing system specifically built for intestinal EMG analyses.

Motor activity of the gastric antrum, pylorus, and duodenum under fasted conditions and after a liquid meal

Because the mechanisms that control the movement of food and digestive juices across the human pylorus are not completely understood, the aim of this study was to document the normal patterns of pressure activity in the antrum, pylorus, and duodenum and the associated pH changes in 9 healthy volunteers. Studies were carried out under fasting conditions and after ingestion of 300 ml of chocolate milk, using a unique 11-channel intraluminal probe that incorporated a sleeve sensor positioned across the pylorus and pH electrodes situated in the terminal antrum and proximal duodenum. The most common motor pattern recorded under fasting conditions consisted of regular coordinated contractions, most of which (a) involved the antrum and duodenum, (b) showed evidence of propagation through two or more adjacent channels, and (c) were associated with transient reductions in duodenal pH and transient elevations in antral pH. Ingestion of milk changed the motor pattern to one that was composed of pressure waves, which were confined to the pylorus with few or no pressure waves in the terminal antrum or proximal duodenum. Isolated pyloric pressure waves were gradually replaced by propagated antroduodenal contractions, which eventually occurred at a regular frequency that was higher than that observed under fasting conditions. After ingestion of milk, only the coordinated contractions were associated with transient reductions in duodenal pH. Isolated pyloric pressure waves were also observed under fasting conditions just before or just after phase III of the migrating motor complex, and 17% of these were accompanied by episodes of duodenal acidification.

A study of motility of normal human gastroduodenal region

A method of recording continuously and simultaneously the intraluminal pressure in the antrum, pylorus, and duodenal bulb has been used to study gastroduodenal motility during intragastric infusion of saline. Twenty-two studies were performed in 15 normal individuals. Two types of contraction were recorded: (1) independent contractions of the individual parts of the gastroduodenal region, and (2) related contractions of the antrum, pylorus, and duodenal bulb, resulting in a concerted contraction of the whole region. The majority of pyloric contractions were part of a concerted contraction of the whole gastroduodenal region during which the pylorus behaved as the terminal part of the antrum. The majority of duodenal contractions were not associated with pyloric contractions, only 21.7% of duodenal contractions coincided with closure of the pylorus. This suggests that under the conditions of this study the pylorus was not acting as a barrier to reflux. An elevated basal pressure was never recorded from within the pylorus; apart from a brief closure during contraction, the pylorus is always open.

Duodenal pressure activity recorded by an intraluminal electrical transducer in man

The duodenal pressure activity was studied by means of an intraluminal electrical transducer, and the recordings were compared to those of a traditional open-tip tube. The physiological significance of different pressure waves was studied by means of combined pressure and cineradiographic recordings. The recordings obtained by the intraluminal transducer were found to be essentially similar to those obtained by the open-tip tube. Most pressure waves observed in this study were found to cause a propulsive, mixed, or retropulsive movement of the intraluminal contents, and no significant displacement of the contents could be observed without simultaneous pressure waves. A difference in physiological significance of single and complex waves could not be detected. Rhythmic activity caused a rapid propulsion of intraluminal contents. It is concluded that the pressure recordings obtained by the intraluminal transducer are reliable in the study of duodenal motility.

Large bowel myoelectrical activity in man

The myoelectrical activity of human colon and rectum has been studied by three types of electrode in man--intraluminal (suction), serosal and cutaneous. The patterns obtained indicate a high degree of consistency between the methods and the value of surface electrodes is emphasized. Gradient along the large bowel of both frequency and percentage electrical activity have been observed and possible physiological roles are postulated for them. By correlating the features of regular electrical and corresponding regular motor waves an alteration in the myoelectrical pattern is observed in the region of the rectosigmoid junction.

Electrical activity of gastrointestinal smooth muscle

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The effect of stimulation on the myoelectrical activity of the rectosigmoid in man

The myoelectrical activity of the rectosigmoid has been studied in 66 subjects at rest and after stimulation with either pentagastrin 6.0 mug/kg hr intravenously in 21 cases, neostigmine 0.5 mg intramuscularly in 20 cases, or two bisacodyl suppositories in 19 cases. Two electrical rhythms were present at rest. A faster rhythm (frequency 6-9 cycles/min) predominated and its incidence was significantly increased by neostigmine at all levels in the rectosigmoid and by bisacodyl in the rectum only. The incidence of the slower rhythm (frequency 2.5-4.0 cycles/min) was significantly increased by pentagastrin which had no effect on the faster rhythm. The amplitude of each basic electrical rhythm rose when its incidence was increased. Motor waves were augmented corresponding to which of the two electrical rhythms was increased after stimulation.