Objectives: Mechanisms of chest pain in gastroesophageal reflux disease (GERD) are poorly understood. The recent demonstration in healthy subjects that lower esophageal acid exposure induces pain hypersensitivity within the non-acid-exposed upper esophagus (secondary allodynia) raises the possibility that an increase in spinal neuronal excitability (i.e., central sensitization) contributes to chest pain in GERD. The aim of this study was to determine whether in patients with unexplained chest pain, acid reflux contributes to esophageal pain hypersensitivity.
Methods: In 14 patients with chest pain and GERD and 8 healthy volunteers, electrical pain thresholds (PT) were recorded from the upper esophagus before, and then repeatedly for 90 min after either hydrochloric acid (0.15 M) or saline (0.15 M) infusion into the lower esophagus. Six patients underwent a repeat study after 6 wk of high-dose proton pump inhibitor (PPI) therapy.
Results: GERD patients had lower resting upper esophageal PT than in healthy subjects (40.8 +/- 9 mA and 70.4 +/- 11 mA, respectively; p= 0.018). Acid infusion reduced PT in the non-acid-exposed upper esophagus in healthy subjects, but not in the patients (area under curve [AUC] - 304 +/- 333 and 786 +/- 464; p= 0.03, respectively). Following PPI therapy, resting PT increased (34.65 +/- 13.4 to 40.5 +/- 12.5 mA; p= 0.03), and a reduction in PT now occurred in acid infusion (AUC - 369 +/- 321; p= 0.03).
Conclusions: Patients with unexplained chest pain and occult GERD have esophageal pain hypersensitivity that is PPI responsive. The increase in resting PT and secondary allodynia only following PPI therapy suggests that pain hypersensitivity in these GERD patients may partially be the result of central sensitization.