title: Patent foramen ovale and high-altitude pulmonary edema.
abstract: BACKGROUND
  Individuals susceptible to high-altitude pulmonary edema (HAPE) are characterized by exaggerated pulmonary hypertension and arterial hypoxemia at high altitude, but the underlying mechanism is incompletely understood. Anecdotal evidence suggests that shunting across a patent foramen ovale (PFO) may exacerbate hypoxemia in HAPE.
  
  
  OBJECTIVE
  We hypothesized that PFO is more frequent in HAPE-susceptible individuals and may contribute to more severe arterial hypoxemia at high altitude.
  
  
  METHODS
  Case-control study of 16 HAPE-susceptible participants and 19 mountaineers resistant to this condition (repeated climbing to peaks above 4000 m and no symptoms of HAPE).
  
  
  METHODS
  Presence of PFO determined by transesophageal echocardiography, estimated pulmonary artery pressure by Doppler echocardiography, and arterial oxygen saturation measured by pulse oximetry in HAPE-susceptible and HAPE-resistant participants at low (550 m) and high altitude (4559 m).
  
  
  RESULTS
  The frequency of PFO was more than 4 times higher in HAPE-susceptible than in HAPE-resistant participants, both at low altitude (56% vs 11%, P = .004; odds ratio [OR], 10.9 [95% confidence interval {CI}, 1.9-64.0]) and high altitude (69% vs 16%, P = .001; OR, 11.7 [95% CI, 2.3-59.5]). At high altitude, mean (SD) arterial oxygen saturation prior to the onset of pulmonary edema was significantly lower in HAPE-susceptible participants than in the control group (73% [10%] vs 83% [7%], P = .001). Moreover, in the HAPE-susceptible group, participants with a large PFO had more severe arterial hypoxemia (65% [6%] vs 77% [8%], P = .02) than those with smaller or no PFO.
  
  
  CONCLUSIONS
  Patent foramen ovale was roughly 4 times more frequent in HAPE-susceptible mountaineers than in participants resistant to this condition. At high altitude, HAPE-susceptible participants with a large PFO had more severe hypoxemia. We speculate that at high altitude, a large PFO may contribute to exaggerated arterial hypoxemia and facilitate HAPE.
authors.affiliation: Department of Cardiology, Swiss Cardiovascular Center Bern, University Hospital, Inselspital, Bern, Switzerland. yves.allemann@insel.ch
authors.forename: Yves
authors.initials: Y
authors.lastname: Allemann
authors.forename: Damian
authors.initials: D
authors.lastname: Hutter
authors.forename: Ernst
authors.initials: E
authors.lastname: Lipp
authors.forename: Claudio
authors.initials: C
authors.lastname: Sartori
authors.forename: Hervé
authors.initials: H
authors.lastname: Duplain
authors.forename: Marc
authors.initials: M
authors.lastname: Egli
authors.forename: Stéphane
authors.initials: S
authors.lastname: Cook
authors.forename: Urs
authors.initials: U
authors.lastname: Scherrer
authors.forename: Christian
authors.initials: C
authors.lastname: Seiler
mesh_terms: D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000503:physiopathology*; D001783:Blood Flow Velocity; D016022:Case-Control Studies; D003326:Coronary Circulation; D015150:Echocardiography, Doppler; D017548:Echocardiography, Transesophageal; D005260:Female; D006344:Heart Septal Defects, Atrial / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D006976:Hypertension, Pulmonary / Q000503:physiopathology*; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009051:Mountaineering; D010092:Oximetry; D011651:Pulmonary Artery; D011654:Pulmonary Edema / Q000209:etiology*