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Patent 1069252 Summary

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(12) Patent: (11) CA 1069252
(21) Application Number: 226993
(54) English Title: POROUS CARDIOVASCULAR IMPLANTS
(54) French Title: IMPLANT CARDIOVASCULAIRE POREUX
Status: Expired
Bibliographic Data
Abstracts

English Abstract


CARDIOVASCULAR PROSTHETIC DEVICES AND IMPLANTS
WITH POROUS SYSTEMS

ABSTRACT OF THE DISCLOSURE

A novel cardiovascular prosthetic device or implant
having many useful cardiovascular applications comprises a
porous surface and a network of interconnected interstitial
pores below the surface in fluid flow communication with the
surface pores. Tissue forms a smooth thin adherent coating
of self-determining thickness on the porous surface making it
resistant to the formation of the blood clots normally associated
with the presence of foreign bodies in the blood stream.


Claims

Note: Claims are shown in the official language in which they were submitted.


The embodiments of the invention in which an
exclusive property or privilege is claimed are defined as
follows:
1. A heart valve constructed of metal substantially
inert to blood and having surfaces adapted to contact a
flowing blood stream entering or leaving a heart, said
surfaces being constituted by dense coherent substrate
having adhered thereto a porous coating consisting essen-
tially of a plurality of small discrete generally ball-
shaped particles bonded together at their points of contact
with each other and to said substrate to define a plurality
of connected, interstitial pores uniformly distributed
throughout said coating.

.
2. The heart valve of claim 1 wherein said particles
are of a size and spaced from each other to establish an
interstitial pore size of from about 1 to about 1000 microns.

3. The heart valve of claim 1 wherein said particles
have a size between about 50 and 200 microns.

4. The heart valve of claim 1 wherein said particles
have a size below about 50 microns.

5. The heart valve of claim l wherein said coating has
a thickness of about 1 to about 1000 microns.

6. The heart valve of claims 1, 2 or 5 wherein said
coating has a porosity of at least about 8%.



Description

Note: Descriptions are shown in the official language in which they were submitted.


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This invention relates to novel prosthetic devices
and implants for cardiovascular use.
It is well known that the introduction of foreign
bodies into the blood stream, for example, the polished metal
surfaces of artificial heart valves, tends to cause the
formation of blood clots which may break loose and embolize to
various parts of the body. Such throm~oembolic problems have
led to the administration of ant:icoagulants to patients with
artificial heart valves. The effects of these anticoagulants
on the blood clotting mechani~m cause difficulties in stopping
the flow of blood through even a minor flesh wound.
In addition, flexible plastic conduits are used for
vascular graft purposes and such surfaces also are thrombogenic.
To date, the art has been unable to avoid the dual
problem of avoiding thrombus formation while also avoiding the
bleeding problem associated with the use of antLcoagulants.
It has now been surprisingly found that these prior
art difficulties can be overcome and foreign bodies may be
introduced into thecardiovascular system without blood clotting

-
problems. The present invention provides a cardiovascular

~ prosthetic device or a cardiovascular implant having a blood-
.
engaging porous surface region in fluid flow communication with~
a subsurface net~ork of interconnected pores. Such a device
may beused bo prevent t~e formation of clots in the blood stream.
It was particularly surprising to find that nucleated
cells circulating in the blood stream colonize onto the porou9
blood-engagin~ suxface and subsequently differentiate into
other cell ty~es to form a thin, smooth, generally uniformly-
thick, firmly-attached tissue covering on the surface. The

tissue covering is formed rapidly over about a one month period
and does not appear to increase significantly in thickness~

thereafter. The tissue formation is not accom~ ~ ied by throm-
Go~
bosis or embolism owing to its blood- ~re.



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In U.S. Patent No. 3,855,638, there is described a
surgical prosthetic device consisting of a metal substrate
with a porous metal coating into which bone tissue may grow
- for incorporation of the prothesis into the body. ~he porous
coating used in this prior art device has several essential require- -
ments, including restrictions on coating thickness, interstitial
pore size and coating porosity. These parameters are dictated
by the strength requirementsof the surgical pros~hetic device,
namely, that the coating and the coating-substrate interface
have strengths at least that of bone, so that there is no danger
of failure of the prosthesis after ingrowth of bone tissue.
In cardlovascular uses, however, strength is less of
an important consideration, and the ranges of parameters chosen
are dictated to some degree by the intended use of the prosthetlc
aevice-or ~mplant.
Further, the mechanism of incorporation of the sur- `
gical prosthetic device of this prior art into the body is by
ingrowth of tissue into the coating while the present invention
involves quite a different mechanism which arises from the
different environment of the devices of the invention as
~ ~ .
compared with that of the prior art. ~--
The clK~ovascular prosthetic devices~Dr imDla~ use~ in the~ ~
present invention may, in some-cases, be wholly porous with the ;
network of interconnected pores extending throughout the body `~
,:
`~ ~ -of the device. Alternatively, the prosthetic device or implant
may be in the form of a porous coating on a coherent substrate,~
with the network of interconnected pores extending throughou~ ~ ~
the-coating only. ~ -
:, . . . . . .
~ An example of the use of the former type of device

;~ 30 is as the metal electrode tiP of a heart pacemaker


~ while an example of the use of the latter type of device is as a
,:
! heart valve prosthesis, typically having a statianary member
- ', ' .. -.

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,

069252

and at least one moving member, the latter being freely moving
or connected to the stationary me~ber.
Both of these applications use metal as the material
of construction. The present invention is not limited to metal
as the material of construction and many other constructional
materials inert to blood may be used, either alone or in
combinations of two or more such materials, provided that they
can be provided in a porous form. Typical materials include
flexible or rigid plastics, cera~ics and carbon.
The present invention may be used for a variety of
cardiovascular applications in addition to those mentioned, `
including partially or totally implantable blood pumps, such as
artificial hearts and ventricular assist devicas, heart valve
- - components, such as flexible flap-type valve members, other
heart pacemaker electrode parts, rigid or flexible blood
vessel grafts and patches, blood stream fil~ rs, intracardiac
patches or baffles and in vascular access tubes.
In the latter case, typically for use in haemodialysis,
the inner surface of the tube is porous coated to promote
.
; 20 colonization and tissue growth, while the outer surface also may
bè porous coated for soft vessel tissue, soft tissue and skln
tissue ing,rowth.
In many applications of the present invention, the .
promotiQn of colonization and tissue growth is accompanied
by true soft tissue ingrowth into the porous surface at the
. . . : :- margins or on the outer surface from adjacent body tissue, to
provide bonding between the host and the member. ~ ;
The body tissue ingrowth combined with promotion ~f
tissue growth c?n the porous surface from the nucleated blood
~3Q stream cells is important in many applications of the present

invention.
For example, in an artificial heart, a ~orous

~69Z52

coating on all the elements provides a means of fixation to
host tissues by soft tissue ingrowth and provides surfaces
which are blood compatible arising from colonization and tissue
formation on the blood-contacting surfaces.
The parameters of the porous surface may vary widely.
The surface must, however, have an interconnected network of
pores underneath the surface in fluid flow communication with
the surface pores to promDte the colonization by nucleated cells
and subsequent differentiation into other cell types so that
the tissue which is formed is interlocked in the subsurface
network.
- The interstitial surface pore size may vary widely,
typically from about 1 micron such as up to about 1000 microns,
although it may be preferred to use pore sizes below 20 microns.
- As the pore size decreases, the surface becomes smoother,
decreasing blood turbulence and abrasion on movin~ parts of
the device.
. . .
The porosity also may vary widely, from about 8%
upwards. Where a coating is provided on a coherent substrate,
the thickness may vary from a single layer of particles upwards, ~ ;
- typically from about 1 to about 1000 microns. Thin layers are
prefèrred in devices having close tolerances.
- The devices may be made porous in any desired manner,
the manner chosen usually depending on the material of construc- ~
tion. Where the material is metal, for example, powder metal- -
lurgy techniques may be used to form a coating consisting of
a plurality of small, discrete generally ball-shaped particles
of the metal bonded together at their points of contact with
each other and the substrate to define the network of connected
interstitial pores uniformly distributed throughout the coating.
After formation of theporous ooating, it may be machined ~ ~
and refined, ii.- desired, to improve its surface characteristics. ~;
The formation of the adherent tissue coating from ` -

~ 5 - ~ ~ -
: .: .

~s~zsz
nucleated blood cells also alla~s thecardiovascular prosthetic device
or implant of the present invention to be incorporated into the
cardiovascular system, thereby achieving a more secure attachment
than has previously been the case.
The invention is illustrated by the following
Example:
Example
Conventionally-cast heart ball-valve cages of cobalt
base alloy composition were coated with a porous suxface layer.
'0 The surface to be coated was initially roughened by sand blasting
and then cleaned and degreased using ultrasonic cleaning
methods. A uniform Co-Cr-Mo alloy powder coating of about
500 micron thickness was applied to the surface using an aqueous
methylcellulose binder.
After air drying, the coated samples were sintered
in a dry hydrogen atmosphere at about 1220C for 2~ hour ~-
periods to form an integral structure well-bondea to the sub
strate surface.
Both coarse and fine powder coated samples were formed,
2Q the coarse powder having a particle size between 50 and 200 ;
microns and the fine powder having a particle size less than
50 microns.
: . . .,:: ,:
. ~ . .
; Ten of the coated cages, with either fine or coarse
powder-made metallic surfaces, were implanted in the right atria ~ -
in five dogs for periods-of time ranging from two weeks to
`~ three months. Upon removai, each valve was examined grossly
.: . : : -
and by light and scanning electron microscopy. Ten uncoated ~ -
. .
control valves were similarly implanted in five additional
dogs. No prophylactic anticoagulants were used in either the
experimental or the control group.
, ,:
All porous-coated valve cages developed a thin, smooth
firmly-attached tlssue coverlng with no evidence of thrombosis

~:

6925;Z
or embolism in the coated region. The process of coating
appeared to be well established at two weeks and complete at one
month.
On the other hand, the uncoated polished metal valve
cages sho~ed no evidence of tissue ingrowth and massive thrombus
formation was a consistent findillg.
The present invention/ therefore, provides a novel
cardiovascular prosthetic device or implant which avoids prior
art thro~bogenic problems. Modifications are possible within the
scope of the invention. -


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Representative Drawing

Sorry, the representative drawing for patent document number 1069252 was not found.

Administrative Status

For a clearer understanding of the status of the application/patent presented on this page, the site Disclaimer , as well as the definitions for Patent , Administrative Status , Maintenance Fee  and Payment History  should be consulted.

Administrative Status

Title Date
Forecasted Issue Date 1980-01-08
(45) Issued 1980-01-08
Expired 1997-01-08

Abandonment History

There is no abandonment history.

Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
MACGREGOR, DAVID C.
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Drawings 1994-03-23 1 12
Claims 1994-03-23 1 43
Abstract 1994-03-23 1 39
Cover Page 1994-03-23 1 25
Description 1994-03-23 6 318