Characterization of Ascending Aortic Flow in Patients With Degenerative Aneurysms

Abstract

Objectives: Degenerative thoracic aortic aneurysm (TAA) patients are known to be at risk of life-threatening acute aortic events. Guidelines recommend preemptive surgery at diameters of greater than 55 mm, although many patients with small aneurysms show only mild growth rates and more than half of complications occur in aneurysms below this threshold. Thus, assessment of hemodynamics using 4-dimensional flow magnetic resonance has been of interest to obtain more insights in aneurysm development. Nonetheless, the role of aberrant flow patterns in TAA patients is not yet fully understood. Materials and Methods: A total of 25 TAA patients and 22 controls underwent time-resolved 3-dimensional phase contrast magnetic resonance imaging with 3-directional velocity encoding (ie, 4-dimensional flow magnetic resonance imaging). Hemodynamic parameters such as vorticity, helicity, and wall shear stress (WSS) were calculated from velocity data in 3 anatomical segments of the ascending aorta (root, proximal, and distal). Regional WSS distribution was assessed for the full cardiac cycle. Results: Flow vorticity and helicity were significantly lower for TAA patients in all segments. The proximal ascending aorta showed a significant increase in peak WSS in the outer curvature in TAA patients, whereas WSS values at the inner curvature were significantly lower as compared with controls. Furthermore, positive WSS gradients from sinotubular junction to midascending aorta were most prominent in the outer curvature, whereas from midascending aorta to brachiocephalic trunk, the outer curvature showed negative WSS gradients in the TAA group. Controls solely showed a positive gradient at the inner curvature for both segments. Conclusions: Degenerative TAA patients show a decrease in flow vorticity and helicity, which is likely to cause perturbations in physiological flow patterns.The subsequent differing distribution of WSS might be a contributor to vessel wall remodeling and aneurysm formation.

The effect of smoking on quantification of aortic stiffness by ultrasound time-harmonic elastography

“…Evidence exist, that ultrasonographic elastography methods provide additional information on pure morphological information that can be helpful after endovascular repair of aortic aneurysms or in multiparametric vascular ultrasound imaging 22 , 23 . Furthermore, in the last years, 4D-flow and MR elastography have been used to investigate the complex interaction of aortic wall and diameter changes in patients with aneurysm 24 – 26 . In a recent study, Dong et al found lower abdominal aortic stiffness and stiffness ratio measured by MR elastography to be associated with aneurysmal events 27 .…”

Impact of Field Strength in Clinical Cardiac Magnetic Resonance Imaging

“…Flow velocities, flow volumes, and wall shear stress could provide additional and potentially complementary information for clinical guidance and therapy. Four-dimensional PC flow offers a comprehensive overview and potentially new insights into the pathophysiology of different disease entities (eg, aortic aneurysms, 83 mitral and aortic valve pathology, 84,85 intracardiac pathology 86 ) and might ultimately help to predict disease outcome and patient prognosis 87,88 . Detailed protocol recommendations for cardiac 89 and aortic 90 4D flow can be found elsewhere.…”

Combined Curvature and Wall Shear Stress Analysis of Abdominal Aortic Aneurysm: An Analysis of Rupture Risk Factors

“…Numerous studies have shown that in AAA, rupture sites occur in areas of low WSS and in most cases are close to areas of flow stagnation with higher intraluminal thrombus deposition [ 5 – 8 ]. In addition, WSS is also used to assess hemodynamics in the patients with thoracic aortic aneurysm and aortic dissection [ 9 , 10 ].…”