Animal And Human Studies Of Surface Gastrointestinal Pacing For The Treatment Of Gastrointestinal Motility Disorders

Objective: To investigate the effects of surface gastric pacing on gastric emptying,gastric myoelectrical activity and plasm motilin level in a canine model of gastric motility disorders and the correlation between gastric myoelectrical activity and plasm motilin level, and between gastric emptying and plasm motilin level before and after pacing. In addition, we evaluated the therapeutic efficacy of surface gastrointestinal (GI) pacing in patients with gastrointestinal motility disorders and also explored the probable mechanism of gastric pacing. Methods: In animal studies, ten adault healthy mongrel dogs were divided randomly into two groups: experimental group of six dogs and control group of four dogs. A model of gastric motility disorders was established in experimental group with bilateral truncal vagotomy combined with injection of glucagon. Gastric half-emptying time (GEt1/2) was monitored with single photon emission computerized tomography (SPECT), and the semi-solid test meal was labeled with an isotope-99mTc sulfur colloid. Gastric serosal myoelectrical activity was recorded using four-channel computer analysis instrument. Plasm motilin concentration was measured with radioimmunoassay (RIA) kit. Surface gastric pacing with the optimal pacing parameters were applied postprandial for entrainment of gastric slow wave, gastric pacing was performed for 45 min dayly for a month in conscious dogs.In human studies , fifty patients with gastrointestinal motility disorders were divided randomly into two groups: experimental group (low-frequency gastric pacing ) of 30 patients and control group (high-frequency gastric pacing) of 20 patients. A eight-channel electrogastrogram (EGG) recorder was applied to record gastric myoelectrical activities. Low-frequency gastric pacing at a basic frequency of 1.1～1.2 times the intrinsic frequency superimposed a series of high frequency pulses (10～30 Hz) was performed in experimental group. And high-frequency gastric pacing at a basic frequency of 12.0 cpm superimposed a series of high frequency pulses (10～30 Hz) was carried out in control group for 45 min daily for 15 consecutive days. The therapeutic efficacy of GI pacing was evaluated by total symptom score (TSS) and gastric myoelectrical activities at baseline andpost-treatment with a self-administered questionnaire .Results:1. Compared with before surgery, GEt1/2 in the dogs with vagotomy was increased significantly from 56.35 ± 2.99 min to 79.42 ± 1.91 min ( P < 0.001), but a long-term surface gastric pacing markedly accelerated gastric emptying in animals with vagotomy, and significantly decreased GEt1/2 to 64.94±1.75 min (P < 0.001).2. GEt1/2 in all animals received glucagon injection was clearly higher than that before glucagon was administered, only GEt1/2 of the dogs with vagotomy was significantly increased(108.24 ± 10.75 min,P < 0.01). However, the delay of gastric emptying of intact dogs after injection of glucagon was not statistically significant (57.73±1.65 min vs. 56.15±2.34 min, P > 0.05). 3. After acute gastric pacing, the GEt1/2 of the dogs with vagotomy and injection of glucagon was significantly less with pacing than that without pacing(108.24±10.75 min vs. 76.93±8.55 min, P < 0.05). However ,such acute pacing had no significant effect on the GEt1/2 of intact dogs (56.15±2.34 min vs. 58.52 ± 4.77 min,P=0.4)or when only vagotomy was performed (79.42±1.91 min vs. 74.41±6.10 min,P =0.3).4. Basic electrical rhythm (BER) frequency (4.85±0.40 cpm, cycles per min), amplitude(2.32±0.35 mV)and propagation velocity(4.06 ± 0.40 cm/s)of dogs with bilateral truncal vagotomy in the fed state was decreased significantly compared with the intact dogs(5.37 ± 0.36 cpm,4.25 ± 0.12 mV,6.92 ± 0.24 cm/s)(P < 0.03).After a long-term treatment of surface gastric pacing, BER frequency(5.49±0.31 cpm),amplitude(3.97 ± 0.19 mV)and propagation velocity(5.57±0.48 cm/s)was increased significantly compared with before pacing (P < 0.05).5. Postprandial gas...