Biomedical Engineering Reference
In-Depth Information
5.3
Fatigue testing.
shape of this level is opposed to the concavity of the coronary sinus to
preserve the natural hemodynamic fl ow.
The lower conical part (
annulus level
) fi rmly anchors the prosthesis to
the aortic annulus, preventing any migration and paravalvular leaks
thanks to its high radial force. Because of the self-expanding nature of
the frame, it can adapt to non-circular local anatomies and does not
recoil following expansion.
The CoreValve frame has been submitted to various studies:
Finite element analysis
: this method simulates in a mathematical model
the behaviour of the ReValving frame and highlights the zones of
mechanical effort. These studies have shown that the stress of the valve
functioning is concentrated at the commissural level. The current frame
design is compatible with long-term mechanical durability.
Fatigue testing
: fatigue tests are conducted on the frame alone and on
the valve/frame combination using a durability tester. In this test, the
ReValving undergoes accelerated aging. A comparison with US Food
and Drug Administration (FDA)-approved valves showed equivalent
durability (Fig. 5.3).
Pulse duplicator test
: the functioning of the valve-frame combination is
evaluated with the same test. It shows that the leafl ets do not touch the
frame while opening. The opening area is very satisfactory and the fl ow
pattern is adequate. Compared with other FDA-approved valves, the
gradient is low.
5.2.3 The valve apparatus
The key elements of any new heart valve are to be both functional and
durable. The key to this challenge is to design optimal frame-to-valve inte-
gration. The CoreValve valve apparatus is made of a standard biological
tissue, porcine pericardium. In practice, it is sutured to the frame using
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