Antral Frequency Research Articles

Transpyloric propagation and liquid gastric emptying in children with foregut dysmotility.

Gastric emptying (GE) requires precise antropyloroduodenal coordination for effective transpyloric flow, the mechanisms of which are still unclear. We aimed to correlate gastric antral function assessed by antroduodenal manometry (ADM) with GE scintigraphy (GES) for liquid feeds in children with suspected gastrointestinal dysmotility. Children who underwent both ADM and GES over a five-year period were reviewed. ADM tracings were re-analyzed to assess antral frequency, amplitude, and motility index (MI) pre-prandially and postprandially. Transpyloric propagation (TPP) was defined as antegrade propagated antral activity preceding duodenal phase III of the migrating motor complex (MMC). TPP was defined as "poor" if occurring in <50% of all presented duodenal phases III. For GES, regions of interest over the whole stomach, fundus, and antrum were drawn to calculate GE half-time (GE-T1/2 ) and retention rate (RR) in each region at 1 and 2h. Forty-seven children (median age: 7.0years) were included. Twenty-two had PIPO, 14 functional GI disorders, and 11gastroparesis. Children with poor TPP had longer GE-T1/2 (113.0 vs 66.5min, p=0.028), higher RR of the whole stomach and fundus at 1h (79.5% vs 63.5%, p=0.038; 60.0% vs 41.0%, p=0.022, respectively) and 2h (51.0% vs 10.5%, p=0.005; 36.0% vs 6.5%, p=0.004, respectively). The pre-prandial antral amplitude of contractions inversely correlated with GE-T1/2 , RR of the whole stomach, and fundus at 2h. TPP during phase III of the MMC correlated with gastric emptying of liquid and its assessment on ADM might predict abnormalities in postprandial gastric function.

Enhanced Gastric Emptying Scintigraphy to Assess Fundic Accommodation Using Intragastric Meal Distribution and Antral Contractility.

Gastric emptying scintigraphy (GES) as now commonly performed measures only total gastric emptying. Intragastric meal distribution (IMD) immediately after meal ingestion (t = 0 min) (IMD0) can assess fundic accommodation, and dynamic antral contraction scintigraphy (DACS) can assess antral motility. Our goals were to incorporate IMD and DACS into GES, compare IMD0 using gastric division into anatomic proximal and distal halves versus more physiologic separation of the antrum from the proximal stomach using DACS, and establish reference values. Methods: Healthy subjects (n = 20) underwent GES using a solid-liquid meal. DACS (1 frame/3 s) was performed for 20 min after each static imaging time. IMD0 was measured using both semiautomated software to divide the gastric long axis into anatomic halves and Fourier analysis to identify antral pixels with phasic contractions. Results: Using halving of the stomach, IMD0 averaged 0.75 ± 0.15 (SD). Using phasic contractions to define the antrum, mean IMD0 was 0.85 ± 0.14 (P = 0.004). Sustained antral contractions started at a mean of 11.24 ± 12.98 min after meal ingestion and originated in the gastric midbody with a starting location at 40.5% ± 10.8% from the distal to the proximal stomach along its long axis. Antral frequency and ejection fraction peaked 30 min after meal ingestion at 3.30 ± 0.71 contractions per minute and an ejection fraction of 30.3% ± 13.69%, when mean antral filling peaked at 36.7% ± 14%. Maximum antral contraction speed was 3.54 ± 0.90 mm/s at 60 min after meal ingestion. Gastric retention was 39.8% ± 12.8% at 2 h and 5.8% ± 6.0% at 4 h. Conclusion: Addition of DACS to GES permits physiologic characterization of both fundic accommodation and antral contractility to supplement routine GES.

Muscarinic regulation of pacemaker frequency in murine gastric interstitial cells of Cajal.

Peristaltic contractions in the stomach are regulated by the spread of electrical slow waves from the corpus to the pylorus. Gastric slow waves are generated and propagated by the interstitial cells of Cajal (ICC). All regions distal to the dominant pacemaker area in the corpus are capable of generating slow waves, but orderly gastric peristalsis depends upon a frequency gradient in which the corpus pacemaker frequency exceeds the antral frequency. Cholinergic, muscarinic stimulation enhances pacemaker frequency. We investigated this phenomenon using intact murine gastric muscles and cultured ICC. Acetylcholine (ACh) increased the frequency of slow waves in antrum and corpus muscles. The increase was significantly greater in the antrum. ACh and carbachol (CCh) increased the pacemaker currents in cultured ICC. At high doses of CCh, transient pacemaker currents fused into sustained inward currents that persisted for the duration of stimulation. The effects of CCh were blocked by low doses of the M(3) receptor antagonist 1-dimethyl-4-diphenylacetoxypiperidinium. Frequency enhancement by CCh was not affected by forskolin, but the phospholipase C inhibitor U-73122 inhibited both the increase in frequency and the development of tonic inward currents. 2-Aminoethyldiphenyl borate also blocked the chronotropic responses to CCh. Inhibitors of protein kinase C did not block responses to CCh. These studies show that mice are an excellent model for studying mechanisms that regulate gastric slow-wave frequency. CCh, apparently via production of inositol 1,4,5-trisphosphate, accelerates the frequency of pacemaker activity. High concentrations of CCh may block the entrainment of pacemaker currents, resulting in a tonic inward current.

Distribution of pacemaker function through the tunica muscularis of the canine gastric antrum.

1. Interstitial cells of Cajal (ICC) have been shown to generate pacemaker activity in gastrointestinal (GI) muscles. Experiments were performed to characterize the ICC within the canine gastric antrum and to determine the site(s) of pacemaker activity and whether active propagation pathways exist within the thick-walled tunica muscularis of large mammals. 2. Immunohistochemistry and electron microscopy revealed four populations of ICC within the antral muscularis on the basis of anatomical location. Typical ICC were found in the myenteric region of the small intestine (IC-MY). Intramuscular ICC (IC-IM) were intermingled between muscle fibres of circular and longitudinal muscle layers. ICC were also found within septa (IC-SEP) between muscle bundles and along the submucosal surface of the circular muscle layer (IC-SM). ICC were identified in each location by ultrastructural features. 3. Intracellular electrical recordings demonstrated nifedipine-insensitive slow waves throughout the circular muscle layer. Separation of interior and submucosal circular muscle strips from the dominant (myenteric) pacemaker region dramatically slowed frequency but did not block spontaneous slow waves, suggesting that pacemaker cells populate all regions of the circular muscle. 4. Slow waves could be evoked in interior and submucosal circular muscles at rates above normal antral frequency by electrical pacing or by acetylcholine (0.3 microM). Active slow wave propagation occurred in all regions of the circular muscle, and propagation velocities were similar in each region. 5. In summary, antral muscles of the canine stomach have pacemaker capability throughout the circular muscle. Normally, a dominant pacemaker near the myenteric plexus drives slow waves that actively propagate throughout the circular layer. Pacemaker activity and the active propagation pathway may occur in networks of ICC that are distributed in the region of the myenteric plexus and throughout the circular muscle layer.

Post-synchronized scintigraphic data to estimate antral motility

We evaluated an improved dynamic antral scintigraphy (DAS) technique, without any frequency filtering or computation of an autocorrelation function. This DAS was performed in 15 consecutive patients and 10 healthy volunteers. Antral frequency was first estimated and was given as an input parameter to compute phase and amplitude values in each antral pixel. Motility indices were calculated by multiplying the frequency by a normalized amplitude in the whole antrum. In addition, a gastric emptying (GE) test was performed. Only 10 patients had a delayed GE when using a cut-off value of the mean of half emptying time (T +2SD) obtained in controls. Antral frequencies were significantly increased but motility indices were significantly lower in patients than in controls. These results in patients were accounted for by a retention of food in the antrum. Therefore, amplitude normalization by the antral mean count activity of each set of data was essential for discriminating between patients and controls and normalized indices appeared early predictors of hypomotility in patients with normal GE. This improved DAS technique should be a useful tool to assess antral dysmotility noninvasively, and may be of physiological and clinical interest.

Electrical arrhythmias in gastric antrum of the dog.

Antral electrical arrhythmias were investigated in 32 unanesthetized chronic dog preparations implanted with serosal electrodes and transducers. Five of these animals underwent surgical removal of the duodenal cap and the adjacent hypomuscular segment. In the intact dogs two distinct types of arrhythmias of the basic electric rhythm (BER) were observed. During phase I (basal activity) arrhythmias were recorded in 17 of 32 dogs. In 9 of the 32 dogs, arrhythmias were present in more than 10% of recorded phase I activity. These arrhythmias included tachygastria as well as mixed gastric rhythms. A second type of arrhythmia consisting of premature and delayed BER occurred in all dogs during phase III (burst activity). In all five dogs, duodenal cap removal produced a marked increase in antral arrhythmias as well as the disruption of normal interdigestive motor and electrical patterns. The changes in terminal antral electrical rhythmicity after surgery may be due to an interaction with the higher frequency duodenal pacemaker tissue. Antral frequencies of 15-18 cycles/min in two of five dogs several days after cap removal were evidence of a duodenal influence. Antral arrhythmias may be present during both normal and pathophysiological states. Their importance is as an indicator of the functional status of the antral smooth muscle and its responsiveness to normal physiological and pharmacologic stimuli.