Cardiac autonomic function and oesophageal acid sensitivity in patients with non-cardiac chest pain

Background-Acid reflux can elicit noncardiac chest pain (NCCP), possibly th rough altered visceral sensory or autonomic function. The interactions betw een symptoms, autonomic function, and acid exposure are poorly understood. Aim-To examine autonomic function in NCCP patients during exposure to oesop hageal acid infusion. Subjects and methods-Autonomic activity was. assessed using power spectral analysis of heart rate variability (PSHRV), before and during oesophageal a cidification (0.1 N HCl), in 28 NCCP patients (40.5 (10). years; 13 females ) and in 10 matched healthy controls. Measured PSHRV indices included high frequency (HF) (0.15-0.5 Hz) and low frequency (LF) (0.06-0.15 Hz) power to , assess vagal and sympathetic activity, respectively. Results-A total of 19/28 patients had angina-like symptoms elicited by acid . There were no significant manometric changes observed in either acid sens itive or insensitive patients. Acid sensitive patients had a higher baselin e heart rate (82.9 (3.1) v 66.7 (3.5) beats/min; p <0.005) and lower, basel ine vagal activity (HF normalised area: 31.1 (1.9)% v 38.9 (2.3)%; p <0.03) than, acid insensitive patients. During acid infusion, vagal cardiac outfl ow increased (p <0.03) in acid sensitive but not in acid insensitive patien ts. Conclusions-Patients with angina-like pain during acid infusion have decrea sed resting vagal activity. The symptoms elicited by perception of acid are further associated with a simultaneous increase in vagal activity in keepi ng with a vagally mediated pseudoaffective response.