title: Pharmacologic exposure of an occult atrial septal defect.
abstract: OBJECTIVE
  To describe the diagnostic technique used to identify the presence of a symptomatic interatrial shunt obscured by normal intracardiac pressures and to discuss the unusual findings in this case and their relevance to the investigation of patients with unexplained hypoxemia.
  
  
  METHODS
  Case report.
  
  
  METHODS
  Intensive care unit of a university teaching hospital.
  
  
  METHODS
  A patient with a variant of the platypnea-orthodeoxia syndrome.
  
  
  METHODS
  Intravenous administration of metaraminol.
  
  
  RESULTS
  Clinical examination and routine investigations ruled out pneumonia or myocardial infarction as a cause of respiratory failure, and pulmonary angiography was normal other than for the demonstration of an interatrial communication. Repeated transthoracic echocardiograms failed to indicate the presence of a significant interatrial shunt that was eventually detected following temporary shunt reversal with intravenous metaraminol and confirmation by bubble-contrast transesophageal echocardiography and right heart catheter studies.
  
  
  CONCLUSIONS
  Symptomatic right-to-left intracardiac shunt may occur in patients with normal intracardiac and pulmonary artery pressures. The presence of a significant shunt cannot be ruled out by transthoracic echocardiography without the use of bubble contrast.
authors.affiliation: Nuffield Department of Anaesthetics, John Radcliffe Hospital, Oxford, UK.
authors.forename: I M
authors.initials: IM
authors.lastname: Mackenzie
authors.forename: A
authors.initials: A
authors.lastname: Banning
authors.forename: O
authors.initials: O
authors.lastname: Dyar
mesh_terms: D018663:Adrenergic Agents; D017548:Echocardiography, Transesophageal; D006344:Heart Septal Defects, Atrial / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008680:Metaraminol; D008875:Middle Aged
chemical_list: D018663:Adrenergic Agents; D008680:Metaraminol