title: Abnormal gastric myoelectrical activity in postural tachycardia syndrome.
abstract: OBJECTIVE
  Postural tachycardia syndrome (PoTS) is an important cause of orthostatic intolerance resulting from cardiovascular autonomic dysfunction. In addition to postural symptoms, PoTS patients may have allied features, including gastrointestinal (GI) symptoms, which have not yet been thoroughly investigated. We evaluated gastric myoelectrical activity in PoTS patients.
  
  
  METHODS
  Using cutaneous electrogastrography (EGG), we recorded gastric myoelectrical activity before and after standard liquid meal ingestion in 15 PoTS patients (age 27 ± 4 years); including 7 with and 8 without GI symptoms, and in 11 healthy individuals (age 23 ± 7 years). We performed spectral analysis of EGG recordings to obtain the dominant frequency of gastric pacemaker rhythm (DF), instability coefficient of DF (ICDF), and low (LFR%), normal (NFR%), and high (HFR%) range power percentages of the total power.
  
  
  RESULTS
  Instability coefficient of DF, an index of variability of gastric pacemaker rhythm, was significantly elevated both pre- and post-prandially (30-45 min after the meal) in the PoTS group (8.8 ± 6, 10.0 ± 8 %) compared with controls (4.0 ± 3, 4.0 ± 3 %; both p < 0.05). Patients with GI symptoms had significantly higher post-prandial ICDF (15.0 ± 5 %) than those without GI symptoms (5.6 ± 4 %; p < 0.05). There were no significant differences in DF, LFR%, NFR% and HFR% before and after the meal between the PoTS and control groups, or between PoTS patients with and without GI symptoms.
  
  
  CONCLUSIONS
  Our study revealed increased variability of gastric pacemaker rhythm in PoTS, and these findings might be related to pathophysiology of functional GI symptoms in PoTS.
authors.affiliation: Department of Medicine, Autonomic and Neurovascular Medicine Unit, Imperial College London, 2nd Floor QEQM Wing, St. Mary's Hospital, Praed Street, London, W2 1NY, UK. william.seligman@magd.ox.ac.uk
authors.forename: William H
authors.initials: WH
authors.lastname: Seligman
authors.forename: David A
authors.initials: DA
authors.lastname: Low
authors.forename: Masato
authors.initials: M
authors.lastname: Asahina
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Mathias
mesh_terms: D000328:Adult; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D016065:Myoelectric Complex, Migrating / Q000502:physiology*; D019518:Postprandial Period; D054972:Postural Orthostatic Tachycardia Syndrome / Q000503:physiopathology*