Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Patent
1996-05-28
2000-03-21
Yu, Mickey
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
623 12, A61F 206
Patent
active
060397543
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the invention
The arterial system consists largely of curved and branching vessels. Arterial flow is generally laminar but is strongly influenced by inertial forces (Reynolds numbers>>1). Almost all studies of arterial fluid dynamics consider the curvature and branching to be planar. The mechanics of steady flow (Reynolds number>>1) in planar bends and branches are reasonably well understood and involve: the inner wall of the bend (where flow separation may occur) and high wall shear at the outer wall; and low wall shear at the outer wall of a branch (where flow separation may occur) together with high wall shear at the inner wall (flow divider).
2. Description of the Related Art
Several findings indicate that the local blood velocity field influences: (a) the dimensions and mechanical properties of vessels and the morphology, mechanics and metabolism of the endothelium (Yoshida et al, 1988), and (b) the development of vascular disease, in particular atherosclerosis (which causes heart attack and stroke) which develops preferentially in low shear regions in arteries (Yoshida et al, 1988); intimal hyperplasia (which causes the occulusion of vascular grafts) and which develops preferentially in low shear regions in side-to-side veno-arterial bypass grafts (Dobrin et al, 1988; Rittgers and Bhambhani, 1993), and thrombosis which occurs preferentially in low shear regions.
There has been limited consideration in the physiological literature of the mechanics of flow in non-planar bends and branches.
The aortic arch is recognised to curve three-dimensionally and rotational flow has been detected in the aortic arch and descending thoracic aorta (Caro et al, 1971; Frazin et al, 1990).
The branching of the left common coronary artery is recognised to be non-planar and studies in a curved bifurcation model show skewing of the velocity profile away from the `plane` of bifurcation, both upstream of the bifurcation and in a daughter tube (Batten and Nerem, 1982).
Studies of the velocity field in a realistic model of the abdominal aorta and aortic bifurcation show centrifugal effects caused by the curvature of the abdominal aorta and aortic bifurcation inducing helical flow structures and influencing the localisation of separation zones (Pedersen et al, 1992).
There has been study of the exact anatomical locations of atherosclerotic lesions and of the detailed flow patterns at these locations in transparent isolated human arteries (Asakura and Karino, 1990).
SUMMARY OF THE INVENTION
Recent model experiments by the present inventor led to an investigation as to whether non-planar curvature and branching may be more common than planar curvature and branching in the arterial tree.
With non-planar curvature and branching there is the expectation of skewing of the secondary motion (with the possible development of swirl flow) and alteration of the distribution of wall shear stress from that present with planar curvature and branching. The present inventor has undertaken several studies as a means of determining whether non-planar curvature and branching are common in the circulation. Inspection of a cast of a human aorta and of a rabbit aorta showed the origins of several branches of the aortic arch and abdominal aorta to be tangential to the axis of the parent vessel in more than one plane; non-planar curvature at some bifurcations, for example at the aortic bifurcation; and curvature of the inlet to some bifurcations in a plane other than the `plane` of bifurcation, as at the lower abdominal aorta.
Phase-shift-based MRI studies have been undertaken with steady laminar flow in a planar model of the aortic bifurcation. When the inlet tube was straight, thin-slice dynamic flow imaging, sensitive to the axial component of the flow, shows the secondary motion in a daughter tube to be in the plane of bifurcation (see FIGS. 1 and 1A). When the inlet tube was curved in a plane normal to the plane of bifurcation, the secondary motion in the daughter tube was skewed (see FIGS. 2
REFERENCES:
patent: 4098571 (1978-07-01), Miyata et al.
patent: 4225979 (1980-10-01), Rey et al.
patent: 4313231 (1982-02-01), Koyamada
patent: 4345414 (1982-08-01), Bornat et al.
patent: 4441215 (1984-04-01), Kaster
patent: 4501263 (1985-02-01), Harbuck
patent: 4795465 (1989-01-01), Marten
patent: 4938740 (1990-07-01), Melbin
patent: 5139515 (1992-08-01), Robicsek
patent: 5156619 (1992-10-01), Ehrenfeld
patent: 5236446 (1993-08-01), Dumon
patent: 5236447 (1993-08-01), Kubo et al.
patent: 5258027 (1993-11-01), Berghaus
Frazin et al. Circulation, "Functional Chiral Asymmetry in Descending Thoracic Aorta," vol. 82, No. 6, Dec. 1990, 1985-1994.
Imperial College of Science Technology & Medicine
Nguyen Tram A.
Yu Mickey
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