U.S. patent number 3,733,616 [Application Number 05/139,701] was granted by the patent office on 1973-05-22 for electromagnetically actuated artificial heart.
Invention is credited to Frederick Gordon Willis, Jr..
United States Patent |
3,733,616 |
Willis, Jr. |
May 22, 1973 |
ELECTROMAGNETICALLY ACTUATED ARTIFICIAL HEART
Abstract
An artificial heart pump which utilizes a plurality of
electromagnets to alternately repel and attract a corresponding
plurality of permanent magnets mounted on two flexible membranes
each of which forms one of the heart's two ventricle chambers.
Inventors: |
Willis, Jr.; Frederick Gordon
(Belmont, MA) |
Family
ID: |
22487903 |
Appl.
No.: |
05/139,701 |
Filed: |
May 3, 1971 |
Current U.S.
Class: |
623/3.11;
417/412; 600/12 |
Current CPC
Class: |
F04B
43/08 (20130101); A61M 60/40 (20210101); F04B
43/0063 (20130101); F04B 43/04 (20130101); A61M
60/122 (20210101); A61M 60/50 (20210101); A61M
60/562 (20210101); A61M 60/894 (20210101); A61M
60/148 (20210101); A61M 60/268 (20210101) |
Current International
Class: |
A61M
1/10 (20060101); F04B 43/04 (20060101); F04B
43/08 (20060101); F04B 43/02 (20060101); F04B
43/00 (20060101); A61M 1/12 (20060101); A61f
001/24 () |
Field of
Search: |
;3/1,DIG.2
;128/1R,214R,273 ;417/322,412,413 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Total Artificial Hearts With Built-In Valves" by T. Akutsu et al.,
Transactions Amer. Society For Artificial Internal Organs, Vol.
XVI, April 1970, pages 392-397..
|
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Frinks; Ronald L.
Claims
Therefore, what I claim and intend to secure by Letters Patent of
the United States is:
1. An artificial heart comprising:
1. a rigid shell means defining at least a right ventricle chamber
and a left ventricle chamber;
2. a right ventricle flexible bag positioned within said right
ventricle chamber, said bag defining a blood containing
chamber;
3. a left ventricle flexible bag positioned within said left
ventricle chamber, said bag defining another blood containing
chamber;
4. inlet and outlet unidirectional fluid valve means fluidly
coupled to said right ventricle flexible bag;
5. inlet and outlet unidirectional fluid valve means fluidly
coupled to said left ventricle flexible bag;
6. means forming a plurality of individual magnetic poles spaced
along a substantial area on the exterior surface of each of said
right and left ventricle flexible bags;
7. a plurality of individual electromagnetic means positioned on
said shell means at spaced points along an area overlying said
magnetic poles area for generating electromagnetic fields which
interact with the magnetic fields of said magnetic poles; and,
8. means for cyclically energizing said electromagnetic means.
2. The artificial heart of claim 1 wherein said means for forming a
plurality of magnetic poles on the exterior surface of each of said
flexible bags comprises a plurality of permanent magnets.
3. The artificial heart of claim 2 further characterized by said
permanent magnets being in abutting relation with the poles of said
electromagnetic means when said electromagnetic means are
de-energized.
4. The artificial heart of claim 1 further characterized by said
energizing means cyclically energizing said electromagnetic means
to cause repulsion between said electromagnetic fields and the
magnetic fields of said magnetic poles.
5. The artificial heart of claim 1 wherein each of the outlet
unidirectional fluid valve means is pre-loaded to open when a
predetermined pressure is reached.
6. The artificial heart of claim 1 further characterized by at
least a portion of each of said right and left ventricle flexible
bags being in side-by-side relation with at least some of said
electromagnetic means positioned therebetween and, with said right
and left ventricle flexible bags having opposite magnetic
polarities in the area of side-by-side relation so that both poles
of the electromagnetic means can be utilized during each cyclical
energization.
7. The artificial heart of claim 1 further characterized by:
1. said shell means defining a right atrium chamber and a left
atrium chamber with each of said chambers having an inlet and an
outlet;
2. means for fluidly coupling the outlet of said right atrium
chamber to said right ventricle inlet unidirectional fluid valve
means; and,
3. means for fluidly coupling the outlet of said left atrium
chamber to said left ventricle inlet unidirectional fluid valve
means.
8. The artificial heart of claim 1 further characterized by:
1. said shell means defining a right atrium chamber and a left
atrium chamber;
2. a right atrium flexible bag positioned within said right atrium
chamber, said bag having an inlet and an outlet with the outlet
fluidly coupled to the inlet valve means for said right ventricle
flexible bag;
3. a left atrium flexible bag positioned within said left atrium
chamber, said bag having an inlet and an outlet with the outlet
fluidly coupled to the inlet valve means for said left ventricle
flexible bag;
4. means forming a plurality of magnetic poles on the exterior
surface of each of said right and left atrium flexible bags;
5. a plurality of electromagnetic means positioned on said shell
means for generating electromagnetic fields which interact with the
magnetic fields of the magnetic poles on said right and left atrium
flexible bags, said electromagnetic means being cyclically
energized by said energizing means.
Description
BACKGROUND OF THE INVENTION
This invention relates to artificial hearts in general, and more
particularly, to an artificial heart which duplicates as closely as
possible the functional aspects of the human heart.
Considerable effort has been expended in recent years to develop a
substitute for the human heart. Representative examples of recent
technology in the field of implanted pumps are found in the
following U.S. Pat. Nos. 3,182,335; 3,206,768; and 3,327,322.
Various other types of blood pumps for external use have been
described in U.S. Pat. Nos. 2,815,715; 2,971,471; and 3,021,793. To
date, no known pumping system adequately duplicates the heart's
pumping action within a volume which would permit implantation of
the pumping system in the human body.
It is accordingly, a general object of the present invention to
provide an artificial heart for implantation in the human body
which duplicates as closely as possible the operation of the human
heart.
It is a specific object of the present invention to provide an
artificial heart which occupies substantially the same volume as
the human heart.
It is another object of the present invention to provide an
artificial heart which minimizes the mechanically induced damage to
the blood caused by the pumping action of the artificial heart.
It is a feature of the present invention that the materials
employed in the artificial heart are readily available and
compatible with the human body.
It is still another feature of the present invention that the
artificial heart does not require excessive electrical power so
that a light, compact power source can be employed.
These objects and features and other objects and features of the
present invention will best be understood by a detailed description
of a preferred embodiment thereof, selected for purposes of
illustration and shown in the accompanying drawings in which:
FIG. 1 is a generalized, diagrammatic view in cross-section of a
single chamber pump illustrating he basic components of the
artificial heart pump;
FIG. 2 is an enlarged view in cross-section showing a portion of
the blood containing, flexible membrane wall together with the
permanent magnets mounted thereon and the associated
electromagnets;
FIG. 3 is a similar view to that of FIG. 2 showing another
arrangement for the membrane wall and permanent magnets;
FIG. 4 is still another view similar to that of FIG. 2 showing an
alternative embodiment of the membrane in which the membrane is
filled with discrete magnetized particles;
FIG. 5 is a view in perspective of the artificial heart split open
along line A--A in FIG. 5; and,
FIG. 6 is a view in block form showing the associated electrical
circuitry for the artificial heart pump's electromagnets.
Turning now to the drawings and particularly to FIG. 1 thereof
there is shown in generalized diagrammatic view a single chamber
pump constructed in accordance with the present invention and
indicated generally by the reference numeral 10. The pump 10
comprises a flexible bag or membrane 12 which defines a fluid
containing chamber 14. Unidirectional inlet and outlet fluid valves
16 and 18, respectively, are provided for the pump chamber 14. For
purposes of illustration, the inlet and outlet valves shown in FIG.
1 are depicted as ball check valves having a moveable ball 20 which
seats against valve seats 22 in the closed direction and is held
within the valve in the open condition by check valve ball
retaining members 24. However, it should be understood that other
valve configurations can be employed for inlet and outlet valves 16
and 18. Conduit means 26 and 28 are employed to connect the pump
chamber 14 through the inlet and outlet valves respectively to a
source of pumped fluid (not shown) and to utilization means (not
shown) for the fluid pumped out of the chamber 14.
In the preferred embodiment, the flexible bag 12 is formed from a
plastic material or from a rubber latex. Existing technology has
provided suitable plastics and latex materials which are compatible
with human blood. A plurality of magnetic poles 30 are formed on
the exterior surface 12a of the flexible bag. Preferably, the
magnetic poles comprise separate permanent magnets that are affixed
to the exterior surface of the flexible bag 12, as shown in greater
detail in FIG. 2. Other structural configurations for forming the
magnetic poles 30 on the exterior surface of the flexible bag 12
are illustrated in FIGS. 3 and 4 and will be described below in
greater detail. For the moment, it is sufficient to note that the
magnetic poles 30 are oriented in a predetermined pattern of
magnetic polarities.
Surrounding at least a portion of the flexible bag 12 is a "rigid"
support means or shell 32 which contains a corresponding plurality
of electromagnets 34. The electromagnets 34 are positioned on shell
32 so that the electromagnetic fields generated by the
electromagnets 34 will interact with the corresponding flexible bag
magnetic poles 30. Assuming for purposes of illustration that the
magnetic poles 30 on the flexible bag 12 have a fixed plurality, as
would be the case with permanent magnets, it can be seen that when
the electromagnets 34 are energized by a current flow in one
direction, the magnets 30 will be repelled from the electromagnets
34 and, conversely, when the electromagnets are energized in the
reverse direction, the magnets 30 will be attracted to the
electromagnets 34.
If the support means or shell 32 is sufficiently "rigid" to resist
the repulsion and attraction forces generated by the interaction of
the electromagnetic and magnetic fields of electromagnets 34 and
magnets 30, it can be seen that the flexible bag 12 will be
compressed when the magnets 30 are repelled from the electromagnets
and expanded outwardly when the magnets are attracted to the
electromagnets.
The term "rigid" as used in the description and in the claims
covers any substance or material which has sufficient rigidity to
resist the forces generated by the interaction of the
electromagnetic and magnetic fields. Expressed in a slightly
different way, the shell should remain stationary while the
flexible bag moves away from or toward the shell under the
influence of the interacting magnetic fields. It will be
appreciated that this definition of the term "rigid" covers many
items which would normally not be considered "rigid" and that the
term is relative given the various operating parameters e.g.,
electromagnetic and magnetic field strengths, of the pump.
In order to maximize the effectiveness of the magnetic repulsion
forces, it is desirable to have the exterior surface 12a of the
flexible bag touching the inner surface 32a of the support means or
shell 32 with the corresponding magnets 30 and electromagnets 34 in
abutting relationship. Thus, in the rest or neutral condition, the
flexible bag 12 will be in substantial contact with the inner
surface 32a of the exterior shell 32.
Given the structural and electrical configuration depicted in FIG.
1, it will be appreciated that if the flexible bag chamber 14 is
filled with a fluid, such as, blood, when the electromagnets 34 are
energized to cause repulsion of the permanent magnets 30, the
flexible bag 12 will be compressed thereby forcing the fluid within
chamber 14 out through the unidirectional outlet valve 18 into
outlet conduit 28. At the end of the compression stroke, the bag
can be returned to its rest position by reversing the current flow
through the electromagnets 34. However, in many instances, it is
not necessary to provide a current reversal through the
electromagnets 34 in order to return the flexible bag to its
uncompressed, rest condition as shown in FIG. 1. For example, if
the flexible bag 12 is constructed from a resilient material, it
will return to its rest or neutral condition automatically. The
return of the flexible bag 12 to the rest condition is further
assisted in an inlet gravity flow system by the force of gravity
pulling the fluid in inlet conduit 26 through the inlet
unidirectional flow valve 16. This situation occurs in the normal
human heart and is utilized in the artificial heart illustrated in
FIG. 5.
FIGS. 2 through 4 illustrate, in greatly enlarged form, a portion
of the flexible bag 12, the magnetic poles 30 and the
electromagnets 34. Looking at FIG. 2, the flexible bag 12 has three
permanent magnets 30a, 30b, and 30c secured by appropriate means
such as for instance, adhesive, to the exterior surface 12a of the
flexible bag. The electromagnet 34 is shown in greater detail and
comprises a core portion 34a and coil windings 34b. Preferably, the
electromagnetic coils 34 are mounted within the shell 32 and flush
with the inner surface 32a thereof. The physical arrangement of the
magnetic poles 30 is governed by the particular configuration of
the electromagnet poles 34c. The magnetic polarity arrangement
between the magnetic poles 30 and the electromagnetic poles 34 is
designed to provide a uniform repulsion or attraction between the
magnetic and electromagnetic fields established thereby.
For purposes of illustration, the polarity of the magnetic poles 30
has been arbitrarily shown in the sequence of north, south, north
which is indicated in FIG. 2 by the small letters, "N," "S," "N."
The corresponding electromagnetic polarities for the
electromagnetic poles 34c are shown by similar small letters. In
this configuration, it can be seen that the flexible bag magnet
poles 30 will be repelled from the corresponding electromagnet
poles. The converse or attraction condition is shown in FIG. 2 by
the North and South polarity indications within a circle.
FIG. 3 illustrates an alternative construction for the mounting of
the magnets 30 with respect to the flexible bag 12. As shown in
FIG. 3, the magnets 30 are mounted within the flexible bag wall
and, preferably, with the exterior surfaces thereof flush with the
exterior surface 12a of the flexible bag. If plastic or latex
materials are employed for fabricating the flexible bag 12, the
magnets 30 can be directly molded in the wall of the flexible
bag.
FIG. 4 illustrates still another method for forming the magnetic
poles on the exterior surface of the flexible bag 12. In this
instance, the flexible bag 12 acts as a binder for a plurality of
discrete magnetizable elements such as ferromagnetic filings. The
technology of metal filled plastics is well known at the present
time and need not be discussed in any further detail. One currently
available material which is satisfactory for the pump of the
present invention is an iron filled plastic sold by the 3M Company
under the tradename "Plastiform." Unlike the case of separate
magnets, as shown in FIGS. 2 and 3, the use of magnetized discrete
elements within a binder, as shown in FIG. 4, does not product
sharp transitions between the magnetic polarities. Thus, as shown
in FIG. 4, there is a transition region 36, between each magnetic
polarity. This transition is indicated by the dotted lines between
the magnetic polarities.
Although the preceding discussion in connection with FIGS. 1
through 4 has focused upon the use of magnetic poles and,
preferably, permanent magnets on the exterior surface of the
flexible bag 12, conceptually, it is possible to use electromagnets
on the flexible bag 12. Conversely, the magnetic fields for the
support means or outer shell 32 can be generated by permanent
magnets. However, this configuration is generally undesirable for
an artificial heart because of the increased weight of the
electromagnets and associated wiring on the flexible bag 12 and the
concommitant complexity of providing electrical connections to the
moveable flexible bag 12. Therefore, it is recommended that in the
case of an implantable artificial heart, the permanent
magnet-flexible bag configuration with electromagnets on the
exterior shell be employed.
Having described the generalized concepts of the pump of the
present invention, I will now describe in detail an artificial
heart which utilizes magnetic field interaction to provide a
pumping action which very closely duplicates the functional aspects
of the human heart. FIG. 5 is a view in perspective of an
artificial heart constructed in accordance with the present
invention and split open along lie A--A. For purposes of clarity,
certain elements of an actual human heart have been omitted from
the FIG. 5. However, the omitted elements are not necessary for the
operation or understanding of the artificial heart. The major
elements of the artificial heart are depicted in FIG. 5 and will be
discussed below. To one skilled in the art, it will be apparent
that the structural elements illustrated in FIG. 5 will provide a
substitute for the human heart which can be connected to the
existing blood conduits by well known and currently available
surgical techniques.
Referring now to FIG. 5, the "rigid" support means of shell 32 is
formed in a generally cardioid shape with the interior sections
thereof defining a plurality of chambers which correspond to the
major chambers within a human heart. Positioned within each chamber
is a flexible bag corresponding to the flexible bag 12 illustrated
in FIG. 1 and discussed above. For purposes of identification in
connection with the following description of FIG. 5, separate
reference numerals will be used for each shell-formed chamber and
corresponding flexible bag. The artificial heart shown in FIG. 5
has been split along an axis A--A which represents generally the
axis of symmetry for the heart. The left hand section of the outer
shell 12 forms portions of four separate chambers, namely, a right
atrium chamber 38, a right ventricle chamber 40 and a left atrium
chamber 42 and a left ventricle chamber 44. In a corresponding
manner, the right hand section of the outer shell 12 also forms
portions of the right atrium chamber 38, right ventricle chamber
40, left atrium chamber 42, and left ventricle chamber 44.
Positioned within each of these chambers in the preferred
embodiment of the artificial heart, is a corresponding flexible bag
i.e., a right atrium bag 46, a right ventricle bag 48, a left
atrium bag 50, and a left ventricle bag 52. The right and left
atria bags 48 and 50 can be omitted, if desired, but they are
recommended in order to duplicate as closely as possible the
operation of the human heart. Each of the flexible bags is provided
with a plurality of magnetic poles 30 shown representationally in
FIG. 5. Similarly, each of the outer shell chambers 38,40,42 and
44, is provided with a corresponding plurality of electromagnets
34, which are also shown representationally in FIG. 5.
The fluid or blood flow paths through the artificial heart
corresponds to the fluid paths within the human heart. Looking at
the left hand side of FIG. 5, blood enters the right atrium bag 46
through an upper vena cava 54 and a lower vena cava (not shown).
When the electromagnets on the right atrium inner shell surface 38
are energized, the right atrium bag 46 is compressed forcing the
blood therein through a unidirectional inlet valve, such as cusp
valve 56, and into the right ventricle flexible bag 48. In similar
fashion, the right ventricle bag is compressed to force the blood
therein out through another unidirectional valve 58 into the
pulmonary aorta 60 to the lungs (not shown). The oxygenated blood
from the lungs returns to the heart through pulmonary vein 62 and
enters the left atrium flexible bag 50. Upon compression of the
left atrium flexible bag, the blood therein is forced through a
unidirectional valve such as flat plate valve 64 into the left
ventricle bag 52. Subsequent compression of the left ventricle bag
52 forces the blood outwardly through another unidirectional valve
66 into the systemic aorta 68. Although cusp and flat plate valves
have been shown in FIG. 5, these types of valves are merely
illustrative and other types of unidirectional valves can be used
in the artificial heart.
It will be appreciated from the preceding description that the
fluid flow paths within the artificial heart shown in FIG. 5
duplicate the corresponding blood flow paths through the human
heart. By properly energizing the electromagnets 34, a uniform
compression over a volume of liquid is obtained without scraping or
local compressive peaks. The field action of the cardiac muscle is
approximated in the artificial heart of the present invention by a
uniform magnetic field that is applied to the pumping chamber bags
12.
In the preferred embodiment, the flexible bags 12 generally and
reference numerals 47,48,50 and 52, specifically, carry an external
permanent magnetic field either through magnets attached to the
outside surface of the bag or by direct magnetic imprinting as
depicted in FIG. 4. The outer shell 32 contains a corresponding
number of electromagnets 34 in close proximity to the flexible
bags. Preferably, in the relaxed position as noted above, each of
the flexible bag magnets is in abutting relationship to the
corresponding electromagnet in order to maximize the magnetic
forces generated by the interaction of the electromagnet and
permanent magnet fields. To compress any one of the flexible
chamber bags, it is only necessary to activate the desired
electromagnetic coils to produce the same polarity as the polarity
of the abutting flexible bag magnets. Since there is no direct
conversion of electrical to mechanical energy, there are no moving
parts to wear out. The only motion is in the flexible bags, and
therefore, an extremely favorable meantime between failures can be
achieved.
One of the advantages of the pumping system of the present
invention is the ability to utilize both poles of an electromagnet.
Looking at FIG. 5, it can be seen that for a major distance, the
left and right ventricle flexible bags 52 and 50, are in a
side-by-side relation. Therefore, by providing each flexible bag
with a single magnetic polarity and by making the magnetic
polarities of the two adjacent bags opposite, it is possible to
obtain the appropriate interaction of the magnetic electromagnetic
fields to produce a repulsion force i.e., compression of the bags,
with a single electromagnet.
The control circuitry for energizing the electromagnets 34 is
readily available in current electro-cardiac technology. Looking at
FIG. 6, there is shown in block form the timing and waveform
generating circuitry for energizing the electromagnetic coils of
the artificial heart. The initial timing signals are obtained from
a heart trigger circuit 70 now generally known under the generic
term of a "pacemaker." The pacemaker 70 can be triggered by signals
from the cardiac nerve or by a separate internal clock 72. The
output of the pacemaker 70 comprises a pulse train of relatively
sharp pulses 74. The pulses 74 are converted by a waveform
generator 76 into a waveform 78 having a relatively steep ramp
portion 78a, a plateau portion 78b and a sharp trailing edge 78c.
The general shape of the pulse waveform, the repetition rate and
the pulse duration can be adjusted to accommodate the particular
electrical circuitry of the artificial heart and to produce the
desired pumping action.
On the basis of current electro-cardiac technology, it is believed
that the waveform shown in FIG. 6 will produce the closest
approximation of the human heart pumping action. Specifically, it
is desirable to duplicate the isovolumentric compression of the
human heart which produces the readily discernable pumping or
"beat" action of the human heart. To this end, the cusp valves 56
and 66 in the artificial heart depicted in FIG. 5 are preloaded in
the closed position and will not open until a predetermined
pressure has been reached. Using the waveform 78 shown in FIG. 6,
the electromagnet coils 34d provide a rapid build-up of the
magnetic repulsion along the steep leading edge of the voltage
waveform and a constant pressure along the plateau of the
waveform.
The power requirements for the electrical circuits shown in FIG. 6
are relatively low and can be supplied by a number of sources
including an externally carried lightweight battery belt, a
biological battery, or by a scaled-up version of the atomic
thermocouple pacemaker power source which has been developed by the
National Institute of Health.
Having described in detail the preferred embodiment of my
artificial heart, it will be appreciated that the artificial heart
closely duplicates the functional aspects of the human heart.
Specifically, it can be seen that unlike piston and other
reciprocatory pumps, no mechanical abrasive forces are exerted upon
the blood. Furthermore, turbulance is minimized and the blood is
subjected only to the normal compressive actions found in a human
heart.
Although the artificial heart depicted in FIG. 5 duplicates each of
the four chambers of the human heart, i.e., the left and right
atria and the left and right ventricles, the basic pumping action
can be achieved by using only two pumping chambers corresponding to
the left and right ventricles. However, in order to minimize the
deleterious effects created by the pumping shock wave it is
desirable to interpose between the artificial heart and the normal
body blood conduits a mechanical equivalent of the human left and
right atria. Therefore, it is recommended that the artificial heart
be constructed in accordance with the chamber configuration shown
in FIG. 5. The use of corresponding left and right atria flexible
bags is also preferable, as mentioned previously. However, it
should be understood that the present invention is not limited to a
four chamber artificial heart, but instead can be constructed, if
desired, with only two chambers.
From the preceding detailed description of a preferred embodiment
of my invention, it will be appreciated that various modifications
can be made therein without departing from the scope of the
invention as defined in the appended claims.
* * * * *