The present invention relates to heart assist devices, cannulae and filters therefor, and in particular to implantable blood pumps, such as ventricular assist devices.
Thrombogenesis is considered a potential issue heart assist devices including, but not limited to, extracorporeal cardiac bypass machines and implantable blood pumps such as left ventricular assist devices.
Cannulation is normally required to fluidly connect the heart assist device to the body's blood flow system, sometimes directly connecting the heart assist device to the heart. Some known outflow cannulae include filters to remove blood clots from the blood flow. For example, cardiac bypass machines have traditionally included a filter on outflow cannulation. These filters are generally limited to ameliorating blood clots, prior to the blood flow entering the patient's body, generated during processing by the pump of the bypass machine.
Some newer heart assist devices include low thrombogenic technology, such as the implantable blood pump described in U.S. Pat. No. 6,227,797. U.S. Pat. No. 6,227,797 describes a centrifugal-type flow pump incorporating a hydro-dynamic thrust bearing to reduce thrombogenesis. This type of pump produces very low haemolysis and low thrombogenesis compared with other known blood pumps, and as such has generally removed the need for filters to be mounted in their corresponding outflow cannulae as this new pump technology no longer generates significant amounts of blood clotting.
However, the inventors have found that such newer styles of blood pumps may be generally more susceptible to interference by blood clots interfering with the pumping mechanism than the earlier style of blood pumps, such as peristaltic or pulsatile blood pumps.
It is an object of at least one of the embodiments of the present invention to overcome or at least to ameliorate one or more of the disadvantages associated with the above mentioned prior art.
According to a first aspect there is provided a cannula for an implantable blood pump, the cannula comprising:
a body having a bore extending between an inlet and an outlet for fluid communication therebetween; and
a filter is disposed in, on or at the body and arranged to filter blood clots from at least a portion of fluid passing through the body.
Advantageously, the use of a filter helps to avoid or reduce the risk of blood clots entering the blood pump. The ability to reduce the risk of thrombus in relation to the pump is desired, as thrombus in the pump may detrimentally alter its desired operation parameters. This may particularly be the case with regard to blood pumps using rotatable impellers for blood flow, such blood pumps which use rotatable impellers for axial or centrifugal blood flow through the pump.
Optionally, the cannula is an implantable inflow cannula.
Optionally, the body is tubular. The body may also be flexible.
Optionally, the cannula is arranged to be mounted between a patient's left ventricle and an implantable blood pump. The outlet of the cannula may be mountable to an inlet of the pump.
The filter may be located at or adjacent the inlet. The filter may be located between the inlet & the outlet or at the outlet.
The filter may be located in or on the body such that all the fluid passing through the body will pass through the filter. Alternatively, the filter may be annular defining an outer screening portion and a central non-screening aperture and is located in or on the body such that some of the fluid passing through the body will pass through the outer screening portion and some of the fluid will pass through the central aperture.
The filter is optionally constructed of a mesh. For example, the mesh may have a three-dimensional porous-type structure, or a two-dimensional matrix-type structure. Alternatively, the filter may have a two or three-dimensional woven mesh type structure. The filter may be stiff and/or flat and/or planar.
Optionally, the filter is constructed of titanium alloy.
The filter may be coated with a biocompatible substrate. The substrate may carry a charge appropriate to attract and capture clots.
Optionally, the body is constructed of silicone.
Optionally, the inlet may be configured to be inserted within the left ventricle of the patient such that the filter is located on the inlet within the left ventricle.
Optionally, the first end comprises a funnel shaped tip.
According to another aspect, there is provided a heart assist device comprising:
a blood pump;
a blood inlet and a blood outlet;
a blood passage from the inlet to the outlet through the pump; and
a filter in cooperation with the blood pump arranged to filter at least a portion of blood passing through the blood pump.
Optionally, the filter is located upstream of the pump. The filter may be arranged to filter all the blood passing through the pump.
The filter may comprise a titanium alloy mesh or matrix and/or may be coated with a biocompatible substrate. The substrate may carry a charge appropriate to attract and capture clots.
The device may comprise an inflow cannula in fluid communication with the blood inlet. The filter may be located in the cannula, for example, it may be located at or adjacent an inlet end of the cannula.
Optionally, the cannula has two ends, a first said end being connectable to the blood inlet and a second said end being mountable to a patient's left ventricle.
Alternatively, the filter may be located adjacent an inlet of the device.
Optionally, the device is a ventricular assist device.
Optionally, the heart assist device comprises a cannula according to the above described first cannula aspect.
According to another aspect, there is provided a heart assist device filter for filtering blood passing through the device, the device comprising a blood pump having a blood inlet and a blood outlet and a pumping means for pumping blood through the device, wherein the filter is positionable upstream of the pumping means to filter at least a portion of blood entering the device.
According to an alternative arrangement, there is provided an inflow cannula for an implanted blood pump, said cannula including a tubular body having a bore extending between at least first and second ends for fluid communication therebetween, and wherein at least one matrix is disposed within said bore for capturing blood clots.
Preferably, said inflow cannula is mounted between the left ventricle and the implanted blood pump.
Preferably, said matrix is positioned proximal to the first end.
Preferably, said matrix is constructed of a mesh.
Preferably, said mesh is constructed of titanium alloy.
Preferably, said mesh is coated with a biocompatible substrate.
Preferably, said substrate carries a charge appropriate to attract and capture clots.
Preferably, said tubular body is constructed of silicone.
Preferably, said first end is inserted within the left ventricle of the patient and matrix is positioned on the first end within the left ventricle.
Preferably, said first end is a funnel shaped tip.
Preferably, said at least one aperture is disposed in said tubular body near said funnel shaped tip.
Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
In a first preferred embodiment, as depicted in
The inflow cannula 12 is connected near an inlet end 16 thereof through an incised hole 17 of the left ventricle LV, such that the inlet end 16 is wholly within the left ventricle LV. Referring to
The inlet end 16 incorporates a generally funnel shaped tip 26. This generally funnel shaped tip 26 may have the effect of reducing the risk of blood clots and also may function to stand the left ventricle open by preventing partial or full collapse of the septum S or left ventricle LV onto the inlet 16. In an alternative embodiment, the inlet end 16 does not incorporate a funnel shaped tip, but rather is cylindrical.
Referring to
The tubular body 20 may be made of a biocompatible polymeric material such as: polyurethane (‘PU’); polyetheretherketone (‘PEEK’); or silicone moulding. The tubular body 20 of this embodiment is constructed so as to prevent collapse when under negative pressure but flexible enough so that a surgeon or clinician is able to bend or flex the inflow cannula 12 during implantation.
Referring to
The filter 28 has been described above with reference to
The pore size of each of the above described filters is small enough to capture at least some blood cots in blood passing therethrough, yet large enough at least to allow individual blood cells to pass therethrough. For example, the pore size of the filter of any of the embodiments ranges from about 20 μm to 500 μm, or preferably 20 μm to 300 μm, or preferably 30 μm to 300 μm, or preferably 50 μm to 300 μm.
In other embodiments, the filter may not be flat, but may be cup-shaped, concave, or similar.
The above embodiments have been described with reference to the use of an LVAD. In alternative embodiments, other types of blood pumps can be used, such as right ventricular assist devices, axial flow blood pumps, pulsatile blood pumps, and so on.
As will be understood, unless the context requires or suggests otherwise, features of any one of the above described embodiments may be used in conjunction with another one or more of the above described embodiments.
While the invention has been described in reference to its preferred embodiments, it is to be understood that the words which have been used are words of description rather than limitation and that changes may be made to the invention without departing from its scope as defined by the appended claims.
In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.
A reference herein to a prior art document is not an admission that the document forms part of the common general knowledge in the art in Australia or elsewhere.
Number | Date | Country | Kind |
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2007901448 | Mar 2007 | AU | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/AU08/00385 | 3/18/2008 | WO | 00 | 3/29/2010 |