title: Psychophysiological responses to visceral and somatic pain in functional chest pain identify clinically relevant pain clusters.
abstract: BACKGROUND
  Despite chronic pain being a feature of functional chest pain (FCP) its experience is variable. The factors responsible for this variability remain unresolved. We aimed to address these knowledge gaps, hypothesizing that the psychophysiological profiles of FCP patients will be distinct from healthy subjects.
  
  
  METHODS
  20 Rome III defined FCP patients (nine males, mean age 38.7 years, range 28-59 years) and 20 healthy age-, sex-, and ethnicity-matched controls (nine males, mean 38.2 years, range 24-49) had anxiety, depression, and personality traits measured. Subjects had sympathetic and parasympathetic nervous system parameters measured at baseline and continuously thereafter. Subjects received standardized somatic (nail bed pressure) and visceral (esophageal balloon distension) stimuli to pain tolerance. Venous blood was sampled for cortisol at baseline, post somatic pain and post visceral pain.
  
  
  RESULTS
  Patients had higher neuroticism, state and trait anxiety, and depression scores but lower extroversion scores vs controls (all p < 0.005). Patients tolerated less somatic (p < 0.0001) and visceral stimulus (p = 0.009) and had a higher cortisol at baseline, and following pain (all p < 0.001). At baseline, patients had a higher sympathetic tone (p = 0.04), whereas in response to pain they increased their parasympathetic tone (p ≤ 0.008). The amalgamating the data, we identified two psychophysiologically distinct 'pain clusters'. Patients were overrepresented in the cluster characterized by high neuroticism, trait anxiety, baseline cortisol, pain hypersensitivity, and parasympathetic response to pain (all p < 0.03).
  
  
  CONCLUSIONS
  In future, such delineations in FCP populations may facilitate individualization of treatment based on psychophysiological profiling.
authors.affiliation: Centre for Digestive Diseases, Blizard Institute, Wingate Institute of Neurogastroenterology, Barts and the London School of Medicine & Dentistry, Queen Mary University of London, London, UK.
authors.forename: A D
authors.initials: AD
authors.lastname: Farmer
authors.forename: S J
authors.initials: SJ
authors.lastname: Coen
authors.forename: M
authors.initials: M
authors.lastname: Kano
authors.forename: H
authors.initials: H
authors.lastname: Naqvi
authors.forename: P A
authors.initials: PA
authors.lastname: Paine
authors.forename: S M
authors.initials: SM
authors.lastname: Scott
authors.forename: P L
authors.initials: PL
authors.lastname: Furlong
authors.forename: S L
authors.initials: SL
authors.lastname: Lightman
authors.forename: C H
authors.initials: CH
authors.lastname: Knowles
authors.forename: Q
authors.initials: Q
authors.lastname: Aziz
mesh_terms: D000328:Adult; D002637:Chest Pain / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D016000:Cluster Analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D059226:Nociceptive Pain / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D010147:Pain Measurement / Q000379:methods / Q000523:psychology; D011602:Psychophysiologic Disorders / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D059265:Visceral Pain / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D055815:Young Adult
keywords: Functional chest pain of presumed esophageal origin; pain clusters; pathophysiology