Four-dimensional magnetic resonance imaging-derived ascending aortic flow eccentricity and flow compression are linked to aneurysm morphology

• Published in: Interactive cardiovascular and thoracic surgery Vol. 20; no. 5; pp. 582 - 588
• Main Authors: Kari, Fabian A., Kocher, Nadja, Beyersdorf, Friedhelm, Tscheuschler, Anke, Meffert, Philipp, Rylski, Bartosz, Siepe, Matthias, Russe, Maximilian F., Hope, Michael D.
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.05.2015
• Subjects: Adult; Aged; Aorta - pathology; Aorta - surgery; Aortic Aneurysm - diagnosis; Aortic Aneurysm - surgery; Blood Flow Velocity - physiology; Cohort Studies; Compressive Strength; Confidence Intervals; Contrast Media; Female; Follow-Up Studies; Humans; Imaging, Three-Dimensional - methods; Magnetic Resonance Imaging, Cine - methods; Male; Middle Aged; Preoperative Care - methods; Radiographic Image Enhancement; Regional Blood Flow - physiology; Retrospective Studies; Risk Assessment; Severity of Illness Index; Statistics, Nonparametric; Treatment Outcome; Young Adult; Phase contrast magnetic resonance imaging; Aortic stenosis; Bicuspid aortic valve; Ascending aortic aneurysm; Circumferential wall tension; Aortopathy; Wall shear stress; Aortic regurgitation; Blood flow
• ISSN: 1569-9293; 1569-9285
• DOI: 10.1093/icvts/ivu446

OBJECTIVES 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.