Gastric electrical activity becomes abnormal in the upright position in patients with postural tachycardia syndrome

Some patients with functional abdominal pain report worsening of symptoms in the upright position. Many of these have a postural tachycardia syndrome (POTS). We investigated whether the electrical activity of the stomach changes during the upright portion of a tilt table test in patients with and without POTS. All of the children undergoing autonomic testing were offered enrollment in this institutional review board-approved prospective study between October 2007 and January 2009. Electrogastrography was recorded 10 minutes in the supine position and during the entire upright portion of tilt. Children were divided into 2 groups: POTS and No-POTS. Findings were correlated with this grouping using Fisher exact test and either Student t test or Wilcoxon rank sum test as appropriate. Forty-nine patients participated (35 girls), with a mean age of 14.7 + 3.5 years, 25 with POTS and 24 without. The POTS and No-POTS groups did not differ in baseline normal gastric activity. The change from supine to standing showed a significant difference in the electrogastrographic tracing between the POTS and No-POTS groups (P < 0.04-0.09), best seen in channels 1 and 4. In particular, gastric activity became more abnormal in the upright position in the POTS group, whereas the opposite occurred in the No-POTS group. The electrical activity of the stomach changes during the upright position in children with POTS, but not in children without this diagnosis. These changes could relate to their report of worsening pain in the upright position.