Abstract
Since the first observation of a helical flow pattern in aortic blood flow, the existence of helical blood flow has been found to be associated with various pathological conditions such as bicuspid aortic valve, aortic stenosis, and aortic dilatation. However, an understanding of the development of helical blood flow and its clinical implications are still lacking. In our present study, we hypothesized that the direction and angle of aortic inflow can influence helical flow patterns and related hemodynamic features in the thoracic aorta. Therefore, we investigated the hemodynamic features in the thoracic aorta and various aortic inflow angles using patient-specific vascular phantoms that were generated using a 3D printer and time-resolved, 3D, phase-contrast magnetic resonance imaging (PC-MRI). The results show that the rotational direction and strength of helical blood flow in the thoracic aorta largely vary according to the inflow direction of the aorta, and a higher helical velocity results in higher wall shear stress distributions. In addition, right-handed rotational flow conditions with higher rotational velocities imply a larger total kinetic energy than left-handed rotational flow conditions with lower rotational velocities.
Highlights
Modeling and printing techniques facilitate the fabrication of patient-specific flow phantoms
The direction of helical blood flow is more dependent on the direction of the aortic valve flow than the angle of the flow; an increase in the aortic flow angle from 15° to 30° does not change the direction of helical blood flow
The major findings of our present study included the following: (a) the rotational direction and strength of helical blood flow in the thoracic aorta varies according to the direction of the aortic valve flow; (b) aortic flows with higher helical velocity components have higher wall shear stress (WSS) distributions, even when the blood flow rate and diameter of the aortic valve are controlled; and (c) right-handed rotational flow conditions with higher rotational velocities have larger turbulence kinetic energy (TKE), Mean kinetic energy (MKE), and total kinetic energy (KE) values than left-handed rotational flow conditions with lower rotational velocities
Summary
Modeling and printing techniques facilitate the fabrication of patient-specific flow phantoms. While in vivo studies do not predict hemodynamic changes due to various vascular modifications, vascular flow phantoms facilitate in-depth fluid-dynamic experiments with various modifications for vascular geometries[15,16]. Previous studies show that patients with aortic stenosis frequently demonstrate various types of helical blood flow in the thoracic aorta[5], and we hypothesized that the direction and angle of aortic valve flow can influence the flow patterns in the thoracic aorta. In the present study, our aim was to investigate the influence of the aortic flow angle on the hemodynamic features in the thoracic aorta using 3D-printed vascular flow phantoms and 4D PC-MRI measurements and quantifications. The development of helical blood flow, which depends on the direction of aortic valve flow, and the associations between helical blood flow and various fluid-dynamic indices such as the streamline, WSS, and turbulence kinetic energy (TKE), were investigated to understand if helical flow characteristics are appropriate fluid-dynamic risk predictors of vascular disease
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