Biomedical Engineering Reference
In-Depth Information
Cut-down of the aorta to the distal end of the prosthesis; verifi cation
that the left and right coronary arteries ostia stayed uncovered and were
perfectly free from mechanical intrusion.
Search for paravalvular leaks with a 1 mm metal tip inserted between
the aortic wall and the external rim of the frame.
Further dissection of the aorta to the annulus, and verifi cation of ade-
quate positioning of the prosthesis relative to the annulus and the sub-
annular zone.
In these investigations the CoreValve delivery was routinely event-free. The
P12.1 prosthesis (fi rst-generation prosthesis), lacking the subannular frame,
was never in contact with the mitral valve for more than 3 mm, while the
leafl et complete length was measured at 30 mm. No reduction of the EOA
was noted and there was no reduction in mobility of the anterior and pos-
terior leafl ets. The implantation of the CoreValve prosthesis left a free
passage to both coronary orifi ces. The P12.1 prosthesis has a constraint on
the upper layer of the frame that allows for optimal valve prosthesis func-
tion and also prevents the frame from interfering in any way with the coro-
nary ostia. The assembly of the P12.1 prosthesis (mounting the valve on
the frame) was changed to a running suture, thus limiting leaks between
pericardium tissue and frame. On three implantations, balloon expansion
following the implantation was shown to reduce the leaks by pushing the
frame further inside the aortic wall. Leaks of a lesser diameter were still
observed, but were minimal, meaning that the 1 mm probe could be pushed
in these leaks with repeated strong applications. Since these leaks have not
been signifi cant in animal implantations, the model of cadaver hearts, which
of course lack blood pressure to extend the vessel and anatomy, can be
questioned.
5.4
Cadaver studies
The implantation mechanics associated with the deployment of the Core-
Valve technology has also been investigated using intact cadavers. This
approach represents a near-clinical deployment environment, and despite
the absence of blood fl ow and pressure, is capable of informing upon the
adequacy of the deployment technology. In these investigations, access
was carried out via the right femoral artery/external iliac artery and left
subclavian artery. An extra-stiff guidewire was inserted up to the aortic
valve. The ascending aorta was opened for visualization. The delivery
catheter was pushed on the wire, and after delivery of the prosthesis,
analysis was carried out to determine the seating of the valve, the
mechanical integrity of the deployment and the extent of any paravalvu-
lar leakage.
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