U.S. patent number 3,613,672 [Application Number 04/840,253] was granted by the patent office on 1971-10-19 for mechanical ventricular assistance cup.
Invention is credited to Peter Schiff.
United States Patent |
3,613,672 |
Schiff |
October 19, 1971 |
MECHANICAL VENTRICULAR ASSISTANCE CUP
Abstract
An improved mechanical ventricular assistance cup for assisting
a heart in the performance of its pumping operations or for aiding
the heart in achieving normal pumping rhythm, which cup assembly is
provided with a semiflexible or inflatable powder shell to reduce
the size of the incision required for implanting the mechanical
pump and further being comprised of constituent materials which
render the cup effectively indestructible, make the cup compatible
with blood and body tissue and further act to provide a sturdier
cup structure.
Inventors: |
Schiff; Peter (Lambertville,
NJ) |
Family
ID: |
25281856 |
Appl.
No.: |
04/840,253 |
Filed: |
July 9, 1969 |
Current U.S.
Class: |
601/21;
601/153 |
Current CPC
Class: |
A61M
60/268 (20210101); A61M 60/40 (20210101); A61M
60/122 (20210101); A61M 60/857 (20210101) |
Current International
Class: |
A61M
1/10 (20060101); A61h 029/00 () |
Field of
Search: |
;128/24,24.2,24.5,44,64 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Trapp; L. W.
Claims
The embodiments of the invention in which an exclusive privilege or
property is claimed are defined as follows:
1. A cup assembly for use in applying mechanical assistive pumping
action to the heart comprising:
a substantially flexible nonstretchable cup-shaped member having a
configuration generally conforming to the configuration of at least
a portion of the heart;
said cup having a first substantially large diameter opening for
receiving a portion of the heart and positioning said portion
within the interior of the cup, and having second and third small
diameter openings;
at least one of said second and third openings being located at the
apex of said cup which is furthest removed from said first opening
and the remaining one of said second and third openings being
located along the surface of said cup at a position intermediate
said first opening and the opening at the apex of said cup;
a flexible liner being positioned within said cup and having a
configuration substantially conforming to the interior of said cup
when the liner is in an unstressed condition;
a first continuous marginal edge of said liner being positioned
against the marginal exterior surface portion of said cup which
surrounds said first opening;
a second continuous marginal portion of said liner being positioned
against the interior surface of said cup and adjacent to and
surrounding the opening in said cup provided in the cup apex;
bonding means for securing the continuous marginal edges of said
liner to the exterior and interior cup surfaces, respectively,
located in the region of said first opening and the opening located
in the cup apex;
said liner cooperating with said cup to form a hollow interior
region communicating with said remaining one of said second and
third openings, which hollow region is adapted to receive pulsatile
pressure to cause the liner to expand and contract and thereby
assist the heart in the performance of its pumping activity; said
flexible cup being contractable to reduce the cup size when
implanted in the body of a patient to minimize the size of the
required incision.
2. A device of the type described in claim 1 further comprising a
metallic electrode positioned within the interior of the cup in the
region of the cup apex;
means for bonding said electrode to the marginal portion of said
liner surrounding the cup apex.
3. The device of claim 1 further comprising a tube connected to the
opening provided in the apex of the cup for communicating a
sustained negative pressure thereto for retaining said heart
portion within the cup.
4. The device of claim 1 wherein a major portion of said cup
extending between said electrode and said first opening is
comprised of an inflatable structure comprising inner and outer
flexible inelastic members defining a hollow interior;
a narrow diameter tubular member being connected to said inflatable
structure to fill said inflatable structure with air and thereby
form a substantially rigid cup configuration when mechanical
assistive pumping action is required.
5. The device of claim 4 wherein said inflatable structure is
comprised of an elongated tubular member being coiled to form the
configuration of the cup portion extending between said electrode
and said first opening;
bonding means for joining adjacent exterior surface portions of
said coiled tubular member.
6. The device of claim 4 wherein said inflatable structure is
comprised of first and second substantially flexible,
nonstretchable sheets of material extending between said electrode
and said first opening;
bonding means for joining said first and second sheets at spaced
intervals to form spaced, substantially parallel ribs defining
elongated hollow interior portions communicating with one another
to receive air under pressure from said narrow diameter tubular
member and thereby form an inflated substantially rigid cuplike
configuration generally conforming to the shape of the portion of
the heart positioned therein.
7. The device of claim 6 wherein said ribs extend in a direction
transverse to the edge of the cup surrounding said first
opening.
8. The device of claim 6 wherein said ribs extend in a direction
substantially parallel to the edge of the cup surrounding said
first opening to form a singular helically shaped elongated hollow
interior portion.
9. The device of claim 1 wherein said liner material is a sheet of
flexible material having high-tensile strength.
10. The device of claim 9 wherein the surface of said sheet making
contact with the heart is coated with silicone rubber.
11. The device of claim 1 wherein all of the exposed surface of
said device is coated with silicon rubber.
Description
Conventional mechanical ventricular assistance cups, for example,
of the type described in copending application Ser. No. 785,652,
filed Dec. 20, 1968 are normally comprised of a rigid shell or cup
member having a large opening for receiving and positioning the
heart therein and at least first and second ports for applying
negative pressure and pulsatile pressure, respectively, to retain
the heart within the cup and to provide assistive pumping action.
When mechanical ventricular assistance cups of this general type
are employed, the rigid shell structure requires a relatively large
surgical incision to be made in the patient in order to insert and
position the cup assembly around the ventricles of the heart. In
addition thereto, it is frequently desirable to implant such a
circulator assistance cup for long periods of time and have the cup
remain in a dormant state around the heart during its implantation
period until it becomes necessary to mechanically activate the cup
so as to support any temporary or long term inadequacy of the
natural heart pumping function. In such instances, the rigid
assistance cup severely impairs the natural heart function when the
assistance cup is not mechanically activated.
The invention is characterized by providing a mechanical
ventricular assistance cup assembly which is made more readily
insertable through a relatively small surgical incision by the
provision of a semiflexible outer shell. In addition, the use of an
inflatable outer shell as one alternative embodiment advantageously
adapts the cup for long term implantations wherein the cup may
remain dormant and in an unimpairing state until it is inflated for
mechanical assistance.
BACKGROUND
This invention relates to improvements in mechanical ventricular
assistance so as to yield a more flexible, versatile and
effectively indestructible cup assembly. Mechanical ventricular
assistance may generally be utilized to provide either constant
short term circulatory support or partial periodic long-term
circulatory support.
When mechanical ventricular assistance devices are used in either
of the above-mentioned modes, it is desirable to be able to implant
the device with a surgical incision of minimal size. In order to
reduce the size of the surgical incision, a semiflexible cup shell
is utilized, which shell is of sufficient rigidity to aid in
mechanical assistance during the diastole cycle and yet be manually
compressible for insertion of the cup through a small surgical
opening. In addition, the cup has a construction which permits
recording of an electrocardiogram in spite of the electrical
insulating properties of the cup as well as providing long-term
reliability as a result of its unique mechanical design.
If such as cup assembly is utilized in a partial circulatory
support or in a periodic long-term circulatory support mode, a
rigid shell would severely interfere with the natural pumping of
the heart such as, for example, in cases where the heart, when
enlarged, would attempt to increase its size beyond the size of the
rigid cup and thereby be restrained by the cup. As a result
thereof, the cup shell is formed of a flexible material and is of
such a nature, when dormant, as to be similar to the sack or
periocardium which normally surrounds the heart. Upon demand, the
sacklike assistance device must be capable of being made rigid so
that it will support not only the systole action, but also the
diastole or filling action of the ventricles.
The present invention is comprised of a mechanical ventricular
assistance device having a flexible cup shell with the first large
opening provided for receiving the ventricles of the heart. A
second opening provided at or near the apex of the cup is adapted
to receive a negative pressure of an amplitude sufficient to retain
the heart within the cup at least during those periods in which the
mechanical ventricular assistance device is being activated.
A flexible shell or membrane is positioned within the interior of
the cup and is sealed about the margin of the cup large opening and
in the region of the opening located near the apex of the cup so as
to form a hollow enclosure which communicates with a third cup
opening for receiving alternating positive and negative (pulsatile)
pressure to alternately expand and contract the flexible membrane
and thereby impart a pumping action to the heart ventricles.
A conductive member positioned within the interior of the cup and
adapted to engage the heart ventricles is electrically connected
through a suitable lead to enable electrocardiograms of the heart
action to be taken when the cup is either in its dormant or active
state.
The flexibility of the cup shell permits it to be manually squeezed
or contracted together so as to reduce its overall size during
insertion and thereby reduce the size of the incision required for
insertion.
The flexible membrane is preferably formed of a material having a
high tensile strength so as to be capable of being easily collapsed
while being substantially incapable of being stretched. The
flexible membrane is preferably secured within the interior of the
cup in the region of the apex by suitable adhesive means and is
sandwiched between the metallic electrode and the semiflexible cup
shell. The remaining seal between the flexible diaphragm and the
cup is obtained through the use of an adhesive material which
adheres a marginal portion of the flexible membrance along the
marginal exterior surface of the cup shell in the region of the cup
shell large opening so as to eliminate tearing stresses at the
seals between shell and membrane and causing the flexible membrane
to experience only tensile or pulling stresses. The use of a
flexible membrane having a high tensile strength renders the shell
structure substantially indestructible due to the nature of the
seals employed.
The cup shell may alternatively be formed of a ribbed inflatable
structure having a plurality of internally inflatable chambers
preferably communicating with one another for the receipt of air
pressure therein so as to form a substantially rigid shell
structure when inflated and a highly flexible shell structure when
deflated and in the dormant state. This structure also serves to
minimize the size of the surgical incision required during
implantation of the device.
It is therefore one object of the present invention to provide a
mechanical ventricular assistance cup for assisting a heart in the
performance of its pumping operations for aiding the heart in
achieving normal pumping rhythm.
Another object of the present invention is to provide a novel
mechanical ventricular assistance assembly having a cup shell which
is flexible and inflatable to facilitate implantation within the
body of a patient and necessitating only a minimal size incision
for insertion thereof.
Still another object of the present invention is to provide a novel
mechanical ventricular assistance assembly having a cup shell which
is flexible and inflatable to facilitate implantation within the
body of a patient and necessitating only a minimal size incision
for insertion thereof and whereby the flexible membrane of the
assembly which assists in the pumping action is formed of materials
and is of a design such as to render the cup totally compatible
with body tissue and substantially indestructible.
These as well as other objects of the present invention will become
apparent when reading the accompanying description and drawings in
which:
FIG. 1 is a perspective view showing one mechanical ventricular
assistance cup assembly designed in accordance with the principles
of the present invention.
FIG. 2 is a sectional view of the assembly shown in FIG. 1.
FIG. 3 is a perspective view of a cup assembly showing another
preferred embodiment of the invention.
FIG. 4 is a sectional view of the cup assembly of FIG. 3.
FIG. 5 is a perspective view showing another preferred embodiment
of the cup assembly of the present invention.
FIG. 6 is a sectional view of a portion of the cup assembly of FIG.
5 looking in the direction of arrows A--A'.
FIG. 7 is a perspective view of a single tubular, inflated ring
portion of the assembly of FIG. 3 useful in describing the
effectiveness of the cup assembly shown therein.
FIG. 8 shows a portion of the cup assembly of FIG. 2, for example,
in detail for purposes of explaining the structural advantages of
the invention.
FIG. 8a shows a detailed sectional view of a portion of a
conventional cup assembly for purposes of further explaining the
advantages of the cup structure of the present invention.
FIG. 9 shows a sectional view of a portion of the flexible membrane
which may be employed in the present invention.
FIG. 1 illustrates a perspective view of a mechanical ventricular
assistance cup. The assembly is comprised of a semiflexible cup
shell 21 which may, for example, be formed of a rubber or plastic
material having a fibrous matrix so as to prevent the cup material
from being stretched while being yieldable and capable of being
bent or contracted. A large opening 21a is provided at the top end
of the cup shell 21 as designated by numeral 21a, and is adapted to
receive the ventricles of the heart. The apex of the cup is
provided with an opening, as shown best in FIG. 2, communicating
with a fitting 10 which acts to secure a hollow tubular member 14
to the apex opening of the cup. A sustained vacuum or negative
holding pressure is applied through tube 14 to fitting 10 to retain
the ventricles of the heart within the cup interior. Pulsatile
(i.e. alternating positive and negative) pumping pressures are
applied through a hollow tubular member 11 and a fitting 12 to an
opening provided intermediate the openings 21a and 21b. This
opening 21c, which is provided along one surface of the cup,
communicates with an enclosed interior volume to be more fully
described. A lip member 38 maintains a seal between the cup
assembly and the AV groove, not shown, of the heart.
FIG. 2 shows the internal structure of the cup assembly in greater
detail and includes an electrode member adapted to permit
electrocardiogram recording, fibrillation and defibrillation in the
manner set forth in detail, for example, in copending application
Ser. No. 785,652, filed Dec. 20, 1968. For example, FIG. 2 of this
copending application shows the particular pressure sources
employed for sustaining the heart within the cup and for providing
the assistive mechanical pumping action.
The cup assembly further incorporates a flexible shell or membrane
35 having a construction which insures against the possible
bursting of the membrane due to weaknesses in the design or
material of the liner. The lip 38 surrounding the large opening 21a
of the cup is secured to liner 35 such as, for example, by a
heating-sealing or by a suitable adhesive. Liner 35 extends at its
upper end about the margin of the cup defining opening 21a and the
marginal portion of the liner extends downwardly along the outer
surface of the cup and is secured to the marginal exterior portion
of the cup 21 immediately adjacent opening 21a. Liner 35 is
preferably cemented by a suitable cement or adhesive applied at
22.
Liner, or membrane, 35 is further cemented in the region of the
apex of the cup wherein one surface of liner 35 is cemented at 19
to the portion 21d of reduced cup thickness and is further cemented
in the region 19a to the convex surface of stainless steel
electrode 18 so that the liner 35 is "sandwiched" between electrode
18 and the reduced thickness portion 21d of cup 21. A wire 15 is
electrically connected to the stainless steel electrode 18 and
extends through a suitable opening 21e provided in the reduced
thickness portion 21d of cup 21 for connection to peripheral
circuitry. For example, this electrode may be employed to couple
the signals detected from the heart ventricle to an
electrocardiogram. As was previously mentioned, the material of cup
shell 21 is preferably of flexible nonstretchable material which
may be, for example, a plastic material or a combination of a
plastic or rubber material in conjunction with a fiberlike matrix
embedded therein.
In operation, the negative pressure applied through tubular member
14 retains the heart ventricles within the cup assembly.
Alternating positive and negative pressure pulses applied through
tubular member 11 cause the flexible membrane 35 to alternately
expand in the manner shown in FIG. 2 and contract so as to move
closer to the interior surface of cup 21, thereby assisting the
heart in the performance of its pumping action.
Another preferred embodiment of the present invention is shown in
FIGS. 3 and 4 wherein the inflatable shell structure is comprised
of a continuously helically wound tubular coil 52. The coil 52
forms the outer shell of the cup and is joined at its lower edge
52a to a solid, substantially rigid cup portion 21d. It should be
noted that the bottom portion of the cup assembly is substantially
identical to that shown in FIG. 2 wherein like elements have been
designated by like numerals. A tubular member 57 of small diameter
is connected to the coiled tubular structure 52 and serves to
selectively either inflate or deflate coiled section 52 to form a
rigid cup structure. In cases where the structure is deflated, the
upper shell portion may lie dormant when implanted into the body of
a patient in cases where the pumping action of the patient is
satisfactory and requires no mechanical pumping assistance.
The sectional view of FIG. 3, shown in FIG. 4, depicts the cup lip
member 38 as being bonded to the exterior surface of liner 35 which
is stretched about the marginal exterior portion of the tubular
coil 52 in a manner similar to that shown in FIG. 2. The liner is
cemented in the region 22 which comprises the marginal exterior
surface of the outer cup shell immediately surrounding opening 21a.
Adjacent coils of elongated helically coiled tube 52 are preferably
cemented to one another by a suitable adhesive or alternatively may
be heat-sealed to one another.
The design principles employed in the attachment of liner 35 in
FIGS. 1 through 4 provide extremely high tensile strength and
substantially eliminate any tear stresses in the structure in a
manner to be more fully described.
FIG. 8a shows a sectional view of an upper cup portion of a
conventional cup assembly such as, for example, of the type
described in the above-mentioned application Ser. No. 785,652. As
shown in FIG. 8a, the liner or membrane 35 is joined to the upper
marginal interior surface portion 22a of cup 22, which marginal
portion is immediately adjacent the large cup opening 21a. The
portion 35a of membrane 35 is bonded to marginal portion 22a of the
rigid glass cup by a suitable adhesive 36. Assuming that a membrane
35 of high tensile strength is employed, the membrane itself,
although bendable, will undergo almost no stretching. Thus, when
the hollow interior region defined by membrane 35 and cup 21 is
filled with a positive pressure pulse, the high-tensile strength of
the membrane places a strong tear stress upon the bonding cement
36, causing the liner portion 35a to be pulled away from glass
shell 22 in the direction substantially as shown by arrow 37. The
application of repeated positive pressure pulses over prolonged
periods of time will weaken the bonding agent and thereby tear the
membrane away from marginal portion 22a of the cup shell.
FIG. 8 shows the upper marginal portion of the cup structures of
FIGS. 2 or 4, for example, wherein the membrane 35 formed of a
material having high-tensile strength extends upwardly over the lip
of the cup shell and downwardly along its outer marginal portion
where it is bonded in the region 22 by a suitable bonding cement
36. Dotted line portion 35' shows the membrane in the collapsed
state. When a positive pressure pulse is applied through tubular
member 11, the membrane moves to the expanded position shown by the
solid line portion 35. Due to the high tensile strength of the
membrane, substantially no tear stress is placed upon the bond
between the membrane and the liner. Alternatively, the tensile
stress as represented by arrow 38a is distributed substantially
equally over the entire bond between membrane 35 and cup 21. Thus,
even after repeated application of positive pressure pulses over
prolonged periods of time, the bond between liner and shell will be
unaffected, yielding a substantially indestructible structure.
In a similar manner, the "sandwiching" of the bottom portion of
liner 35 between electrode 18 and reduced thickness shell portion
21d (by a suitable bonding cement) similarly distributes the
pulling stress substantially equally along the length of the
membrane portion sandwiched between electrode 18 and shell portion
21d so as to provide a substantially indestructible structure in
the apex region of the cup.
The flexible characteristics of either shell 21 of FIG. 2 or coiled
shell 52 of FIG. 4 permits the cup to be squeezed (for example, by
the hand) so as to be inserted through a relatively small surgical
incision. If desired, the fitting 12 shown in FIGS. 1 through 4 may
be replaced by a "right-angle" fitting of the type shown by fitting
10 of FIGS. 1 through 4 to further reduce the amount of clearance
required for insertion and implantation into the body of a patient.
Upon demand, the cup shown in FIGS. 3 and 4 may be made rigid by
the injection of a high-pressure pulse applied through tube 57.
Alternatively, the cup shown in FIGS. 3 and 4 may be caused to
remain in a dormant state by removal of the pressure pulse, thereby
deflating the coiled cup section. When in a dormant state, the cup
assembly provides minimal interference to a heart unassisted by the
mechanical pumping action.
FIG. 7 serves to explain the reason why the coiled cup assembly
will remain rigid when in the inflated condition. FIG. 7 shows in
schematic fashion one full turn of the coiled cup 52. When
inflated, the air pressure within each coil will be substantially
equally distributed throughout. Thus, the pressure along the
interior surface of the coil shown in FIG. 7 will be equal to
Kh.pi.d, where d is equal to the diameter of the coil shown in FIG.
7; h is equal to the height of the interior surface of the coil
(assuming the coil to be of a square cross-sectional configuration
for purposes of simplifying the description set forth herein); and
where K is equal to a constant. The pressure along the outer wall
of the single loop of coil is equal to Kh(d+.DELTA.r) wherein
(d+.DELTA.r) is equal to the diameter of the outer wall of the
single loop coil. Since the surface area of the outer wall of the
single loop of coil is greater than the surface area of the inner
wall of the single loop of coil (due to the increased diameter
d+.DELTA.r), the equally distributed air pressure will cause the
coiled shell portion 52 to assume the shape as shown best in FIG.
3, which structure will remain substantially rigid when
inflated.
FIGS. 5 and 6 show another alternative embodiment of the present
invention wherein the helically coiled portion of FIG. 3 is
replaced by a vertically ribbed inflatable portion 52' which is
comprised of first and second plastic sheets 53 and 54 (shown best
in FIG. 6) which are joined by a suitable adhesive 55 at regularly
spaced intervals to form the vertical ribs 56. Inflating of the
structure may occur in a manner similar to that shown in FIGS. 3
and 4 wherein a positive pressure pulse is applied through narrow
diameter tube 57 to fill the inflatable structure with air. Each of
the hollow interior portions 58 may be joined to adjacent hollow
interior portions by providing narrow communicating passageways 59
arranged in alternating fashion near the bottom edge of the
structure 52' and providing similar narrow communicating portions
(not shown) near the top edge of structure 52' interspersed with
portions 59 so that a positive pressure pulse applied through
narrow diameter tube 57 will pass through each of the hollow
interior sections 58 in a serpentine fashion, until the air
pressure is equally distributed throughout interior hollow sections
58. Although the ribs 56 are shown as being vertically aligned in
FIG. 5, it should be understood that these ribs may be arranged in
horizontal fashion similar to the coiled tubular arrangement shown
in FIG. 3. Whether vertically or horizontally aligned ribs are
employed, the shell structure 52' will form a substantially rigid
structure when inflated for the reasons as set forth in connection
with the description of FIG. 7. Thus, the structure of FIG. 5 is
equally as versatile as that shown in FIGS. 1 and 3 insofar as
being capable of being retained in either a dormant or active state
while implanted within a patient.
The flexible membrane 35 shown in the present invention has a
further advantage of the membrane structure 35 employed in
conventional cup assemblies (for example, of the type described in
copending application 785,652) in that the liner, by being bonded
to the outside of the cup, increases the effective pumping area of
the diaphragm as compared with conventional design, which has the
liner bonded to the inside of the shell just below the cup lip 38.
For this reason, higher pumping volumes and pressures are
obtainable with the structure described herein.
FIG. 9 shows one preferred embodiment for the cup liner 35 wherein
the liner may be comprised of a sheet of material 60 having
high-tensile strength. Some materials which have been found
advantageous for use in this application are polyurethane which has
a tensile strength of approximately 7,000 p.s.i. or Mylar which has
a tensile strength of about 40,000 p.s.i. Such materials are
substantially nonstretchable when employed as a membrane in the
present invention and are, therefore, practically indestructible.
However, these materials, if sharply bent or creased, will deform
along the crease and possibly develop a weakness along the crease
which may be caused to tear after prolonged use essentially due to
the repeated application of positive and negative pressure pulses
to the cup assembly.
In addition thereto, it is most advantageous to provide a cup
assembly whose materials are most favorably compatible with body
tissue and blood cells. It has been found that silicone rubber
exhibits excellent compatibility with body tissue and blood.
However, the tensile strength of silicone rubber is of the order of
400 p.s.i., making it highly stretchable as compared with
polyurethane or Mylar. Thus, in order to make most advantageous use
of these materials, the sheet 60 of high-tensile strength material
shown in FIG. 9 is coated along both surfaces thereof by silicone
rubber layers 61 and 61a, which coating process may be performed,
for example, by dipping the high-tensile strength sheet 60 into a
bath of silicon rubber in liquid form contained in an enclosure
having a moisture-free atmosphere. The dipping operation may be so
timed and so performed so as to preferably form a coating of
approximately 3 mils thickness on a sheet of high-tensile strength
material having a thickness of the order of 0.5 to 1 mil. Likewise,
the cup assembly 22 or 52 may be dipped in the liquid silicone
rubber to provide a similar coating thereon. Alternative approaches
which may be taken consist either of coating the membrane 35 on
both sides thereof, as shown in FIG. 9, and then bonding the
membrane to the cup shell, or, alternatively, initially bonding the
cup membrane to the cup shell and then dipping the entire structure
within a liquid bath of silicone rubber. The latter method can be
seen to provide a silicone rubber coating on only the exposed
surface of the membrane which has been found to be satisfactory,
since only this surface will be exposed to body tissue. Coating the
entire exposed surface of the cup shell 22 or 52 renders it
compatible with body tissue. The lip 38 of the shell structure may
also be formed of silicone rubber of a thickness of the order of 40
mils. Alternatively, the membrane 35 may be formed exclusively of
silicone rubber of a thickness of the order to 30 mils.
It can be seen from the foregoing description that the present
invention provides a novel mechanical ventricular assistance cup
assembly which is capable of being contracted when implanted within
the body of a patient to permit incisions of minimal size for
insertion thereof wherein the cup assembly may lie dormant for
prolonged periods of time when implanted so as to have no impairing
effect upon normal heart pumping action, and may further be
inflated to form a substantially rigid cup structure upon demand
when assistive mechanical pumping action is desired.
Although this invention has been described with respect to its
preferred embodiments, it should be understood that many variations
and modifications will now be obvious to those skilled in the art,
and it is preferred, therefore, that the invention be limited not
by the specific disclosure herein but only by the appended
claims.
* * * * *