Christopher Allen Potter MD, Presenter: Nothing to Disclose

Daniel S Hippe MS, Abstract Co-Author: Research Grant, Koninklijke Philips Electronics NV Research Grant, General Electric Company Research Grant, Koninklijke Philips Electronics NV

Elan Dahl Bomsztyk MD, Abstract Co-Author: Nothing to Disclose

Guy E. Johnson MD, Abstract Co-Author: Nothing to Disclose

Bruce E. Lehnert MD, Abstract Co-Author: Nothing to Disclose

Lorenzo Mannelli MD, PhD, Abstract Co-Author: Nothing to Disclose

Claire Kalsch Sandstrom MD, Abstract Co-Author: Nothing to Disclose

Martin Lee David Gunn MBChB, Abstract Co-Author: Medical Advisor, TransformativeMed, Inc Spouse, Consultant, Wolters Kluwer nv

CT angiography is sensitive and specific for diagnosis of intramural hematoma (IMH), aortic dissection (AD) and penetrating atherosclerotic ulcer (PAU). Most acute aortic syndrome (AAS) protocols use a pre-contrast phase to detect IMH, as contrast-enhanced phase alone is believed insufficiently sensitive for IMH, but there is little supporting data.

We retrospectively reviewed images of patients who presented to our Emergency Department with suspected AAS and received pre- and post-contrast CTA from 2/1/2005 to 2/1/2010 for isolated acute IMH, defined as IMH without visible intimal flap. 423 studies were reviewed. 11 cases of IMH were identified. 22 normal controls and 12 abnormal controls (AD or PAU) were age and sex matched and added. The 45 studies were randomized. Only contrast-enhanced images were evaluated by three blinded, independent fellowship-trained radiologists. Reviewers rated their confidence for IMH using a 5-point modified Likert scale, also indicating if they recommended a non-contrast study to exclude IMH. Inverse probability weighting was used to extrapolate ordering rates from the matched case-control sample to the original sample.

423 patients underwent CTA for AAS. 11 patients were diagnosed with IMH (incidence of 2.6%). On independent case review, overall rater sensitivity for IMH on contrast-enhanced images alone was 94% (CI 74-99%) and specificity 97% (CI 88-99%). For all false negative cases, confidence rating for exclusion was low and delayed non-contrast examination was recommended. If delayed CT were ordered due to suspicious findings on contrast-enhanced images, 7.1% of patients (CI 3.3-14%) would undergo a delayed CT to exclude IMH. More conservatively, if delayed CT were ordered when confidence rating of 1 or 5 (definitely not present or definitely present) cannot be assigned, only 14% (CI 7.5-25%) of patients would undergo additional delayed CT. While the present sample was not large enough to be definitive, no IMH cases would be missed using this approach.

Acute IMH is a very uncommon diagnosis in patients with suspected AAS. A pre-contrast examination is unnecessary for diagnosis of acute IMH. Dose and time savings may be achieved by eliminating the pre-contrast phase.

Exclusion of non-contrast phase on CTA for acute aortic syndrome, used in most ED protocols, may result in overall patient time and radiation dose savings.

Potter, C, Hippe, D, Bomsztyk, E, Johnson, G, Lehnert, B, Mannelli, L, Sandstrom, C, Gunn, M, Detection of Intramural Hematoma: Is a Non-contrast Phase Really Necessary?.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13012676.html