title: A type A aortic dissection missed by non-cardiac gated contrast-enhanced computed tomography due to an aortic root dissection flap masquerading as an aortic valve apparatus: a case report.
abstract: BACKGROUND
  Though computed tomographic angiography has very high sensitivity and specificity to diagnose acute aortic dissection, false-negative studies can occur and secondary tests may be required to make the diagnosis.
  
  
  METHODS
  We report the case of a 57-year-old Caucasian man with a typical presentation for acute type A aortic dissection in whom the initial non-cardiac gated computed tomographic angiogram was negative, leading to a delay in surgical management. Transesophageal echocardiography and post hoc 3D reconstruction of the original computed tomographic scan revealed a dissection flap confined to the aortic root, immediately superior to the sinuses of Valsalva and masquerading as part of the aortic valve apparatus.
  
  
  CONCLUSIONS
  This case demonstrates that false-negative computed tomographic angiograms taken to rule out type A aortic dissection can occur and that secondary imaging tests, such as echocardiography, should be performed in cases in which the pre-test probability of aortic dissection is high. Cardiac gating of computed tomographic angiograms to exclude aortic dissection may enhance diagnostic accuracy.
authors.forename: Karan
authors.initials: K
authors.lastname: Nagra
authors.forename: Richard
authors.initials: R
authors.lastname: Coulden
authors.affiliation: Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta, 2C2 WMHSC, 8440 112th Street, Edmonton, AB T6G 2B7, Canada. mcmurtry@ualberta.ca.
authors.forename: Michael Sean
authors.initials: MS
authors.lastname: McMurtry