title: Comparison of the size of persistent foramen ovale and atrial septal defects in divers with shunt-related decompression illness and in the general population.
abstract: BACKGROUND
  Decompression illness (DCI) is associated with a right-to-left shunt, such as persistent foramen ovale (PFO), atrial septal defect (ASD) and pulmonary arteriovenous malformations. About one-quarter of the population have a PFO, but considerably less than one-quarter of divers suffer DCI. Our aim was to determine whether shunt-related DCI occurs mainly or entirely in divers with the largest diameter atrial defects.
  
  
  METHODS
  Case control comparison of diameters of atrial defects (PFO and ASD) in 200 consecutive divers who had transcatheter closure of an atrial defect following shunt-related DCI and in an historic group of 263 individuals in whom PFO diameter was measured at post-mortem examination.
  
  
  RESULTS
  In the divers who had experienced DCI, the median atrial defect diameter was 10 mm and the mean (standard deviation) was 9.9 (3.6) mm. Among those in the general population who had a PFO, the median diameter was 5 mm and mean was 4.9 (2.6) mm. The difference between the two groups was highly signiﬁcant (P < 0.0001). Of divers with shunt-related DCI, 101 (50.5%) had an atrial defect 10 mm diameter or larger, but only 1.3% of the general population studied had a PFO that was 10 mm diameter of larger.
  
  
  CONCLUSIONS
  The risk of a diver suffering DCI is related to the size of the atrial defect rather than just the presence of a defect.
authors.affiliation: The Royal Shrewsbury Hospital, Shrewsbury, UK.|Royal Stoke University Hospital Stoke-on-Trent, ST4 6QG, UK, E-mail: peter.wilmshurst@tiscali.co.uk.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Wilmshurst
authors.affiliation: Liverpool Heart and Chest Hospital, Liverpool, UK.
authors.forename: W Lindsay
authors.initials: WL
authors.lastname: Morrison
authors.affiliation: Our Ladys Hospital for Sick Children, Dublin, Ireland.
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Walsh
authors.affiliation: The Royal Shrewsbury Hospital, Shrewsbury, UK.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Pearson
authors.affiliation: The Royal Shrewsbury Hospital, Shrewsbury, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Nightingale
mesh_terms: D000293:Adolescent; D000328:Adult; D001344:Autopsy; D016022:Case-Control Studies; D003287:Contrast Media; D003665:Decompression Sickness / Q000209:etiology*; D004242:Diving; D004618:Embolism, Air / Q000150:complications; D005260:Female; D054092:Foramen Ovale, Patent / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology* / Q000628:therapy; D006344:Heart Septal Defects, Atrial / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology* / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D012016:Reference Values; D012189:Retrospective Studies; D055989:Septal Occluder Device; D014463:Ultrasonography
chemical_list: D003287:Contrast Media
keywords: Patent foramen ovale (PFO); decompression illness; migraine; neurology; persistent foramen ovale; right-to-left shunt; venous gas embolism