title: Four-dimensional magnetic resonance imaging-derived ascending aortic flow eccentricity and flow compression are linked to aneurysm morphology†.
abstract: OBJECTIVE
  The impact of specific blood flow patterns within ascending aortic and/or aortic root aneurysms on aortic morphology is unknown. We investigated the interrelation of ascending aortic flow compression/peripheralization and aneurysm morphology with respect to sinotubuar junction (STJ) definition.
  
  
  METHODS
  Thirty-one patients (aortic root/ascending aortic aneurysm >45 mm) underwent flow-sensitive 4D magnetic resonance thoracic aortic flow measurement at 3 Tesla (Siemens, Germany) at two different institutions (Freiburg, Germany, and San Francisco, CA, USA). Time-resolved image data post-processing and visualization of mid-systolic, mid-ascending aortic flow were performed using local vector fields. The Flow Compression Index (FCI) was calculated individually as a fraction of the area of high-velocity mid-systolic flow over the complete cross-sectional ascending aortic area. According to aortic aneurysm morphology, patients were grouped as (i) small root, eccentric ascending aortic aneurysm (STJ definition) and (ii) enlarged aortic root, non-eccentric ascending aortic aneurysm with diffuse root and tubular enlargement.
  
  
  RESULTS
  The mean FCI over all patients was 0.47 ± 0.5 (0.37-0.99). High levels of flow compression/peripheralization (FCI <0.6) were linked to eccentric aneurysm morphology (Group A, n = 11), while low levels or absence of aortic flow compression/peripheralization (FCI >0.8) occurred more often in Group B (n = 20). The FCI was 0.48 ± 0.05 in Group A and 0.78 ± 0.14 in Group B (P < 0.001). Distribution of bicuspid aortic valve (P = 0.6) and type of valve dysfunction (P = 0.22 for aortic stenosis) was not found to be different between groups.
  
  
  CONCLUSIONS
  Irrespective of aortic valve morphology and function, ascending aortic blood flow patterns are linked to distinct patterns of ascending aortic aneurysm morphology. Implementation of quantitative local blood flow analyses might help to improve aneurysm risk stratification in the future.
authors: Department of Cardiovascular Surgery, Heart Center Freiburg University, Freiburg, Germany fabian.alexander.kari@universitaets-herzzentrum.de.
authors: Fabian A
authors: FA
authors: Kari
authors: Department of Cardiovascular Surgery, Heart Center Freiburg University, Freiburg, Germany.
authors: Nadja
authors: N
authors: Kocher
authors: Department of Cardiovascular Surgery, Heart Center Freiburg University, Freiburg, Germany.
authors: Friedhelm
authors: F
authors: Beyersdorf
authors: Department of Cardiovascular Surgery, Heart Center Freiburg University, Freiburg, Germany.
authors: Anke
authors: A
authors: Tscheuschler
authors: Department of Cardiovascular Surgery, Heart Center Freiburg University, Freiburg, Germany.
authors: Philipp
authors: P
authors: Meffert
authors: Department of Cardiovascular Surgery, Heart Center Freiburg University, Freiburg, Germany.
authors: Bartosz
authors: B
authors: Rylski
authors: Department of Cardiovascular Surgery, Heart Center Freiburg University, Freiburg, Germany.
authors: Matthias
authors: M
authors: Siepe
authors: Department of Diagnostic Radiology, University Medical Center Freiburg, Freiburg, Germany.
authors: Maximilian F
authors: MF
authors: Russe
authors: Department of Diagnostic Radiology, University of San Francisco, San Francisco, CA, USA.
authors: Michael D
authors: MD
authors: Hope
mesh_terms: D000328:Adult; D000368:Aged; D001011:Aorta / Q000473:pathology* / Q000601:surgery; D001014:Aortic Aneurysm / Q000175:diagnosis* / Q000601:surgery; D001783:Blood Flow Velocity / Q000502:physiology; D015331:Cohort Studies; D019245:Compressive Strength; D016001:Confidence Intervals; D003287:Contrast Media; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care / Q000379:methods; D011856:Radiographic Image Enhancement; D012039:Regional Blood Flow / Q000502:physiology; D012189:Retrospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D003287:Contrast Media
keywords: Aortic regurgitation; Aortic stenosis; Aortopathy; Ascending aortic aneurysm; Bicuspid aortic valve; Blood flow; Circumferential wall tension; Phase contrast magnetic resonance imaging; Wall shear stress
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