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The Vulcan Syndrome – Asymptomatic Healthy Volunteers with Pathologic Esophageal Acid Exposure

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Gardner, Jerry D., M.D.; Sloan, Sheldon, M.D.; Robinson, Malcolm, M.D.; Miner, Phillip B. Jr., M.D.

American Journal of Gastroenterology: September 2005 - Volume 100 - Issue - p S23–S24
Supplement Abstracts Submitted for the 70th Annual Scientific Meeting of the American College of Gastroenterology: ESOPHAGUS
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Science for Organizations, Inc., Chatham, NJ; Janssen Pharmaceutica, Titusville, NJ and Oklahoma Foundation for Digestive Research, Oklahoma City, OK.

Purpose: Much attention has been given to the excessive esophageal acid exposure that occurs in subjects with gastroesophageal reflux disease (GERD). No attention, however, has been given to normal subjects with excessive esophageal acid exposure, apparently because they have been assumed to represent the tail of a normal Gaussian distribution.

Aim: To examine the distributions of values for esophageal acidity in normal and GERD subjects, paying particular attention to high values from normal subjects.

Methods: Esophageal pH was recorded for 24 hours in 26 asymptomatic healthy control subjects on 2 separate occasions 1 week apart, and in 57 subjects with GERD on 1 occasion. Normal subjects were asymptomatic. GERD subjects experienced heartburn at least 4 times/ week for at least 6 months. All subjects received standardized meals at 8:00, 12:00 and 18:00.

Results: Using receiver operating characteristic (ROC) analysis, the value for 24-hour integrated esophageal acidity that was optimal for distinguishing normal from pathologic esophageal reflux was 8.1 mmol.hr/L. This cut point had a sensitivity of 72%, specificity of 88% and area under the ROC curve [95% confidence interval] of 0.86 [0.77, 0.94; P < 0.0001]. Three of 26 healthy subjects (12%) had integrated esophageal acidity >8.1 mmol.hr/L. The distribution of values from healthy subjects was skewed toward high values and was significantly different from a normal Gaussian distribution (Kolmagorov Smirnov statistic = 0.28; P = 0.036) indicating that these 3 subjects represent a distinct subset of healthy subjects.

Conclusions: As many as 12% of healthy subjects may have the Vulcan syndrome, i.e. values for 24-hour esophageal acid exposure in the range seen in GERD subjects, but without accompanying symptoms of gastroesophageal reflux. Investigation of the factors that prevent symptoms in the Vulcan syndrome despite pathologic esophageal acid exposure could provide important insight into the pathophysiology and treatment of GERD.[figure 1]

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