U.S. patent application number 09/344440 was filed with the patent office on 2002-01-24 for cardiac message apparatus.
Invention is credited to BRENNEMAN, RODNEY A, LENKER, JAY A.
Application Number | 20020010407 09/344440 |
Document ID | / |
Family ID | 22206525 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020010407 |
Kind Code |
A1 |
BRENNEMAN, RODNEY A ; et
al. |
January 24, 2002 |
CARDIAC MESSAGE APPARATUS
Abstract
A device for performing minimally invasive closed chest heart
massage comprises a support having a plurality of curved,
deployable struts, optionally carrying a sheet or inflatable
bladder for engaging the pericardium. The struts are delivered to
the space between the pericardium and the posterior rib cage in a
radially collapsed configuration and deployed radially outwardly
with minimum advancement in the axial direction.
Inventors: |
BRENNEMAN, RODNEY A; (SAN
JUAN CAPISTRANO, CA) ; LENKER, JAY A; (LAGUNA BEACH,
CA) |
Correspondence
Address: |
JAMES M HESLIN ESQ
TOWNSEND AND TOWNSEND AND CREW LLP
TWO EMBARCADERO CENTER 8TH FLOOR
SAN FRANCISCO
CA
941113834
|
Family ID: |
22206525 |
Appl. No.: |
09/344440 |
Filed: |
June 25, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09344440 |
Jun 25, 1999 |
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09087665 |
May 29, 1998 |
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6200280 |
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Current U.S.
Class: |
601/41 ;
606/185 |
Current CPC
Class: |
A61M 60/122 20210101;
A61M 60/857 20210101; A61M 60/50 20210101; A61H 2031/001 20130101;
A61H 31/007 20130101; A61M 60/268 20210101; A61M 60/40
20210101 |
Class at
Publication: |
601/41 ;
606/185 |
International
Class: |
A61H 031/00 |
Claims
What is claimed is:
1. A cardiac massage device comprising: a support; and a plurality
of struts reciprocatably attached to the support, said struts being
retractable to a radially contracted configuration and advancable
along arcuate, diverging paths to define a surface which
non-traumatically engages the pericardium to compress the heart
when advanced against the pericardium.
2. A device as in claim 1, wherein the contracted configuration has
a maximum width of 2 cm.
3. A device as in claim 2, wherein the surface spans an area of at
least 5 cm.sup.2 when the struts are fully advanced.
4. A device as in claim 3, wherein the struts have distal tips and
wherein said distal tips are advanced over an axial distance of 5
cm or less as the struts are fully advanced.
5. A device as in claim 1, wherein the surface comprises a flexible
sheet attached to at least some of the struts.
6. A device as in claim 1, wherein the surface comprising an
inflatable bladder attached to at least some of the struts.
7. A device as in claim 1, wherein the surface comprises a
non-elastic filament around the periphery thereof.
8. A device as in claim 1, wherein the support comprises a sheath
having a lumen and a shaft reciprocatably received in the sheath
lumen, wherein the struts are attached to the shaft.
9. A device as in claim 8, wherein the support further comprises a
blunt member.
10. A device as in claim 9, wherein the blunt member is disposed
distal to end of the sheath.
11. A device as in claim 9, wherein the blunt member is
reciprocatably received in the sheath lumen.
12. A device as in claim 1, wherein at least some of the struts
have enlarged atraumatic tips.
13. A device as in claim 12, wherein at least some of the enlarged
atraumatic tips are axially offset from others to reduce their
collective periphery when the struts are retracted.
14. A device as in claim 1, wherein at least some of the struts
have bent tips.
15. A device as in claim 1, wherein at least some of the struts are
composed of a shape memory alloy.
16. A device as in claim 15, wherein the struts have a first shape
at room temperature and a second shape at a temperature above or
below room temperature.
17. A device as in claim 16, wherein the first shape is the arcuate
shape and the second shape is a less arcuate shape.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application is a divisional application of
09/087,665 filed May 29, 1998, the full disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to medical devices
and methods. More particularly, the present invention relates to
devices and methods for performing minimally invasive direct
cardiac massage.
[0004] Sudden cardiac arrest is a leading cause of death in most
industrial societies. While in many cases it is theoretically
possible to re-establish cardiac function, irreversible damage to
vital organs, particularly the brain and the heart itself, will
usually occur prior to restoration of normal cardiac activity.
[0005] A number of techniques have been developed to provide
artificial circulation of blood to oxygenate the heart and brain
during the period between cardiac arrest and restoration of normal
cardiac activity. Prior to the 1960's, open chest cardiac massage
(OCM) was a standard treatment for sudden cardiac arrest. Open
chest cardiac massage, as its name implies, involved opening a
patient's chest and manually squeezing the heart to pump blood to
the body. In the 1960's, closed chest cardiac massage (CCM) where
the heart is externally compressed through the chest wall became
the standard of treatment. When CCM is combined with airway
support, it is known as cardiopulmonary resuscitation (CPR). CPR
has the advantage that it is much less invasive than OCM and can be
performed by less skilled individuals. It has the disadvantage,
however, that it is not generally effective. In particular, the
medical literature shows that CCM provides significantly less
cardiac output, neuroperfusion, and cardiac perfusion than achieved
with OCM.
[0006] Methods and devices for performing minimally invasive direct
cardiac massage have been described by Buckman et al. and by Drs.
Filiberto and Giorgio Zadini in the patent and literature
publications listed in the Description of the Background Art below.
While the methods of Buckman et al. and the Zadinis differ in a
number of respects, they generally rely on introducing a balloon,
shoe, or other deployable member to engage the heart through a
small incision through an intercostal space above the pericardium.
The heart may then be pumped by directly engaging and compressing
the pericardium, either by inflating and deflating the member or by
reciprocating a shaft attached to the member. Although these
approaches have been shown to be effective in animal models, the
particular devices described in the patents are awkward for
emergency use on human patients. In particular, the balloon-type
and shoe-type heart-engaging members described in the patents may
be difficult to deploy in the potential space between the posterior
surface of the rib cage and the pericardium. For example,
inflatable balloon members may lack sufficient rigidity to impart
the necessary compressive force, rigid shoe-like members risk
damage to the pericardium, and cup-shaped compressive members may
compress so much of the heart volume that the end diastolic volume
is compromised.
[0007] For these reasons, it would be desirable to provide improved
methods and devices for performing minimally invasive direct
cardiac massage. In particular, it would be desirable to provide
apparatus and methods which are simple to deploy and carry out and
in particular which do not require intervention by a physician. The
heart-engaging component(s) of the devices should reliably deploy
and expand within the region between the posterior rib cage and the
pericardium and should minimize risk to the pericardium from
perforation and other damage. The devices and methods should be
simple to introduce to the patient in the first place, and in at
least some circumstances, should eliminate the need to separately
make an incision before introducing the device. The apparatus and
method further should be compatible both with manual actuation,
i.e., manual reciprocation of a handle or shaft attached to the
heart-engaging member, and with automatic or powered systems for
reciprocating the member. At least some of these objectives will be
met by the invention described hereinafter.
[0008] 2. Description of the Background Art
[0009] U.S. Pat. Nos. 5,582,580; 5,571,074 and 5,484,391 to
Buckman, Jr. et al. and 5,683,364 and 5,466,221 to Zadini et al.,
licensed to the assignee of the present application, describe
devices and methods for minimally invasive direct cardiac massage
through an intercostal space. Published PCT application WO 98/05289
and U.S. Pat. No. 5,385,528 describe an inflatable device for
performing direct cardiac massage. U.S. Pat. No. 3,496,932
describes a sharpened stylet for introducing a cardiac massage
device to a space between the sternum and the heart. Cardiac assist
devices employing inflatable cuffs and other mechanisms are
described in U.S. Pat. Nos. 5,256,132; 5,169,381; 4,731,076;
4,690,134; 4,536,893; 4,192,293; 4,048,990; 3,613,672; 3,455,298;
and 2,826,193. Dissectors employing inflatable components are
described in U.S. Pat. Nos. 5,730,756; 5,730,748; 5,716,325;
5,707,390; 5,702,417; 5,702,416; 5,694,951; 5,690,668; 5,685,826;
5,667,520; 5,667,479; 5,653,726; 5,624,381; 5,618,287; 5,607,443;
5,601,590; 5,601,589; 5,601,581; 5,593,418; 5,573,517; 5,540,711;
5,514,153; and 5,496,345. Use of a direct cardiac massage device of
the type shown in the Buckman, Jr. et al. patents is described in
Buckman et al. (1997) Resuscitation 34:247-253 and (1995)
Resuscitation 29:237-248.
SUMMARY OF THE INVENTION
[0010] The present invention provides improved devices and methods
for performing cardiac massage, particularly minimally invasive
direct cardiac massage where the heart is directly compressed
through a small incision formed through an intercostal space over
the pericardium. Devices according to the present invention
comprise a support and a heart-engaging member attached to the
support. The support may be any assembly, structure, system, or
other mechanical framework which is suitable for positioning and
manipulating the heart-engaging member so that it can engage and
compress the heart. Most simply, the support could be a simple
handle or shaft having the heart-engaging member attached at a
distal end thereof. Once the heart-engaging member is deployed,
cardiac massage can be performed by simple manual pumping or
reciprocation of the handle or shaft. In the exemplary embodiment
described hereinafter, the support comprises a shaft together with
a sheath which is coaxially received over the shaft. The shaft and
sheath may be manipulated relative to each other to deploy and
retract the heart-engaging member, as described in more detail
hereinbelow. A wide variety of other supports will also be
possible, including supports which comprise powered drivers, such
as electric, pneumatic, or other motors. Such drivers can be
provided as part of the support, where the driver may be disposed
externally, internally, or both externally and internally relative
to the patient when the heart-engaging member is deployed over the
pericardium.
[0011] The heart-engaging member of the present invention comprises
a plurality of struts which are reciprocatably attached to the
support. The struts are retractable to a radially contracted
configuration and advancable along arcuate, diverging paths to
define a surface which non-traumatically engages the pericardium to
compress the heart when advanced against the pericardium. The
struts will typically be composed of a resilient material, more
typically be composed of a shape memory alloy, such as nickel
titanium alloy, and will usually be formed to deploy radially
outwardly and advance along the desired arcuate, diverging paths as
they are advanced from a constraining member, usually a tubular
sheath. The struts may be advanced and retracted relative to the
sheath using any suitable mechanical system, typically a shaft
which reciprocates together with the struts through a lumen of the
sheath. In some instances, it will be desirable to provide at least
some of the struts with a temperature-responsive memory so that the
shape of the struts will change in response to a transition from
room temperature to body temperature and/or in response to an
induced temperature change after they have been deployed, e.g., by
electrically heating or cooling the struts and/or infusing a heated
or cooled medium into the space surrounding the struts.
[0012] The geometry of the retracted strut configuration will be
selected to facilitate introduction through the intercostal space
before strut deployment. Preferably, the struts will be contracted
within a space having a maximum width of 2 cm, preferably a maximum
width of 1.2 cm. After deployment by advancing the struts along the
arcuate, diverging paths, the heart-engaging surface which is
defined will have a surface area of at least 5 cm.sup.2, preferably
being in the range from about 10 cm.sup.2 to 100 cm.sup.2, usually
in the range from 20 cm.sup.2 to 75 cm.sup.2. Usually, the surface
will be generally circular or slightly oval with a diameter or
average diameter in the range from 3 cm to 18 cm, preferably from 5
cm to 10 cm.
[0013] An important advantage of the present invention is that the
struts may be radially deployed with only a minimum axial
advancement. That is, the struts will make a sharp radially outward
turn from the support as they are advanced into the region between
the pericardium and the posterior rib cage. Typically, the distal
tips of the struts will advance no more than 5 cm in the axial
direction before they are fully radially deployed. More preferably,
the maximum axial distance will be 2 cm or less, even more
preferably being 1.5 cm or less, and still more preferably being 1
cm or less.
[0014] In another preferred aspect of the present invention, the
surface defined by the plurality of struts will comprise a flexible
sheet attached to at least some of the struts. The sheet will
usually, although not necessarily, be inelastic or non-distensible,
permitting it to readily conform to the surface of the pericardium
as the struts are advanced while constraining the deployed tips of
the struts and preventing the struts from bending back from the
heart. Alternatively or additionally, the tips of the struts may be
constrained by a filament, strip, suture, or other element which
ties the tips together and prevents over deployment and expansion
of the struts. The sheet may be continuous, i.e., in the form of a
continuous fabric, membrane, or the like, or may be discontinuous,
i.e., in the form of a net, perforate sheet, permeable or
impermeable sheet, or the like. Optionally, the strut may be flat
(when not engaged against the pericardium) or may be slightly
concave to conform to the exterior surface of the pericardium.
[0015] Alternatively or additionally, an inflatable bladder may be
attached to at least some of the struts. The inflatable bladder may
comprise a generally flat structure extending over all the struts,
or may comprise an annular or torroidal structure extending over
only the outer regions of the struts. The bladder may be inflatable
using a liquid or gas, preferably be inflatable with a
physiologically acceptable liquid, such as saline, contrast medium,
or the like.
[0016] In a still further preferred aspect of the apparatus of the
present invention, the support may include a blunt member which can
bluntly dissect a space between the anterior surface of the
intercostal muscle and the posterior surface of the rib cage in
order to facilitate deployment of the struts into the space. For
example, the blunt member may be provided as a leading edge or tip
of the support which enters through the intercostal space into the
region over the pericardium. The struts may then be advanced
through or over the blunt member, or the blunt member may be
retracted prior to strut deployment.
[0017] In a particularly preferred embodiment of the device of the
present invention, a blunt member will be provided as the leading
edge of the support. The blunt member may include a blade which may
be axially advanced from the blunt member, point, or other cutting
element to make an incision partially through the skin overlying
the intercostal space before the blunt member is introduced through
the intercostal space. Usually, the blade or other cutting element
will be automatically retractable so that the blade cannot enter
into the space immediately above the pericardium in order to reduce
the risk of injury to the pericardium and the heart. By providing
the blade and blunt member on the cardiac massage apparatus, the
device can be introduced in a single step with minimum preparation
of the patient prior to such introduction. The user need only
properly locate the cardiac massage device over the intercostal
space and then advance the device through the skin prior to
radially deploying the struts to engage the pericardium.
[0018] Methods according to the present invention for performing
cardiac massage comprise advancing a plurality of struts through an
intercostal space to a region over a pericardium. The struts are
opened along arcuate, radially diverging paths (to form a trumpet
horn geometry) between a posterior rib surface and the pericardium.
The open struts are then engaged against the pericardium to
periodically compress the heart and induce artificial blood
circulation. Preferably, the struts are introduced by first bluntly
dissecting a space between the posterior rib surface and the
pericardium, typically by advancing a blunt member through the
intercostal space, where the blunt member is disposed between the
struts. Optionally, a blade may be advanced from the blunt member
to partially cut through the intercostal skin, where the blade is
retracted prior to advancing the blunt member into the space
between the ribs and the pericardium. Still further optionally, a
flexible sheath may be unfurled as the struts are open.
Alternatively, an inflatable bladder may be attached to at least
some of the struts and be inflated as the struts are deployed
and/or to effect deployment of the struts.
[0019] In another aspect of the method of the present invention,
cardiac massage is performed by engaging a plurality of struts
arranged in radially diverging arcuate paths against the
pericardium. The struts are then reciprocated against the
pericardium to induce artificial circulation. Usually, either a
flexible sheet or an inflatable bladder will be suspended between
at least some of the struts as the struts are reciprocated.
[0020] In a still further aspect of the methods of the present
invention, the region between a posterior rib surface and a
pericardium may be bluntly dissected by advancing a blunt member
through an intercostal space into said region. In particular, the
advancement is enhanced by deploying a blade from the blunt member
to partially cut through the intercostal skin prior to advancing
the blunt member. Preferably, the blade is automatically retracted
back into the blunt member before the blunt member can pass
completely through the skin and the intercostal space.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a perspective view of a cardiac massage device
constructed in accordance with the principles of the present
invention.
[0022] FIGS. 2A and 2B illustrate alternative configurations for
single struts which may be employed in the device of FIG. 1.
[0023] FIG. 3 is a cross-sectional view of the distal end of the
device of FIG. 1, showing a pair of struts carrying flexible sheet
therein with the struts being shown in a partially deployed
configuration in broken line.
[0024] FIG. 4 illustrates the struts and sheet of FIG. 3 shown in a
fully deployed configuration.
[0025] FIGS. 5 and 6 illustrate cardiac massage devices having
struts with enlarged distal, atraumatic tips, where the tips are
axially offset from each other in order to minimize the peripheral
space required to accommodate the enlarged tips.
[0026] FIGS. 7 and 8 illustrate a cardiac massage device having a
radially directing blunt member with struts shown in a retracted
configuration (FIG. 7) and in a radially deployed configuration
(FIG. 8).
[0027] FIG. 9 illustrates a cardiac massage device according to the
present invention with an inflatable bladder extending over the
deployed struts.
[0028] FIG. 10 illustrates a cardiac massage device according to
the present invention with a torroidal bladder spanning the distal
tips of the deployed struts.
[0029] FIGS. 11 and 12 illustrate a cardiac massage device having a
blunt member at its distal end with a blade retracted (FIG. 11) and
a blade advanced (FIG. 12).
[0030] FIG. 13 is a cross-sectional view illustrating the heart
beneath a patient's rib cage.
[0031] FIGS. 14A and 14B illustrate a method according to the
present invention employing the cardiac massage device of FIGS. 1,
3, and 4.
[0032] FIGS. 15A and 15B illustrate a method according to the
present invention employing the device of FIGS. 11 and 12.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0033] Referring now to FIG. 1, an exemplary device 10 constructed
in accordance with the principles of the present invention
comprises an outer sheath 12, an inner shaft 14, and an plurality
of struts 16 which are shown in a partially deployed configuration
extending from a distal end of the sheath 12. The struts 16 may be
deployed by axially reciprocating the shaft 14, typically by
manually grasping and moving a handle 20 at the proximal end of the
shaft 14.
[0034] The device 10 will have a plurality of struts 16, typically
having at least 3 struts, usually having from 8 to 20 struts,
preferably from 10 to 15 struts. The struts will usually have
atraumatic distal tips, typically having enlarged elements 24
(e.g., epoxy beads) at their distal tips, as shown in FIGS. 2A and
2B. In some instances, the distal tip of the elements 16 will be
bent so that it will immediately turn radially outward as the strut
is axially advanced from the sheath 12, as shown in FIG. 2B. As
discussed above, it is desirable that advancement of the struts in
the axial direction relative to the sheath or other components of
the support be limited in order to reduce the risk of damage to the
pericardium. Bending the tip, as shown in FIG. 2B, can help achieve
that goal. The tip may be bent relatively sharply, as shown in FIG.
2B, or alternatively may be formed in a "ski" tip or otherwise
deflected in order to permit its outward movement.
[0035] The struts 16 will usually be resilient so that they may
spring radially outwardly from the support as they are distally
advanced. For example, the struts 16 may be formed from a
spring-type stainless steel where the struts are formed to have the
configuration shown in FIGS. 2A, 2B, or other configurations, when
they are in their non-constrained state. Preferably, the struts 16
will be formed from a shape memory alloy, such as nickel-titanium
alloy, and will similarly have a memorized shape such as that shown
in FIGS. 2A, 2B, at least when they are being employed in their
superelastic form. In some instances, it will be desirable to
employ a temperature-induced shape change in the struts as part of
their radial deployment. For example, the struts could have a
sharply curved configuration as they are extended from the support
into the space between the pericardium and the posterior surface of
the rib cage. The shape could then at least partially straighten as
the struts reach body temperature in order to reduce the profile of
the struts in the axial direction, i.e., facilitate movement of the
struts into the restricted space between the pericardium and
overlying rib cage. Alternatively, other shape changes may be
induced by the changed body temperature and/or by temperature
changes induced by electrical heating, exposure to heated or cooled
media, or the like.
[0036] Referring now to FIGS. 3 and 4, struts 16 may be carry a
flexible sheet 26 which is deployed to span between the distal tips
of at least some of the struts as the struts are radially expanded,
as shown in FIG. 4. The flexible sheet may be any of the materials
or in any of the forms described above, and will serve as an
interface surface for engaging the pericardium as the devices of
the present invention are used for direct cardiac massage.
[0037] Referring now to FIGS. 5 and 6, provision of enlarged distal
tips 24 on the struts 16 can increase the profile of the struts
since there is more material being accommodated within a limited
cross-sectional area. Such an increase in area increases the
profile of the device being introduced through the intercostal
space. Such increased profile is undesirable. To reduce the
profile, the distal tips of the struts 16 may be axially spaced
apart, either in a uniformly receding arrangement, as shown in FIG.
5, or in an alternating arrangement as shown in FIG. 6.
[0038] Referring now to FIGS. 7 and 8, the cardiac massage devices
of the present invention may be provided with blunt members at
their distal ends to facilitate introduction into the space in
between the pericardium and the posterior surface of the ribs. For
example, a blunt member 30 may be mounted axially within the sheath
12 to define an annular space 32 for reciprocatably receiving the
struts 16. The struts may then be contained in the retracted
configuration, as shown in FIG. 7, and may be axially advanced to
deploy radially outwardly, as shown in FIG. 8. The blunt member 30
may optionally be used to define guide surfaces 34 which assist the
struts in making a rapid turn to a radially outwardly direction, as
shown in FIG. 8. The embodiment of FIGS. 7 and 8 may comprise a
flexible sheet suspended over the distal tips of the struts, as
described previously, or may employ an inflatable bladder, as will
be described below. Optionally, a mechanically advantaged
deployment device, such as a screw or gear mechanism, may be used
to axially advance the struts and deploy them over the guide
surfaces.
[0039] Referring to FIG. 9, the cardiac massage device as generally
described above may be provided with an inflatable bladder 40 which
is attached to at least some of the distal tips of individual
struts 16. The inflatable bladder will have in inflation tube 42
extending proximally outward from the device so that it may be
connected to a suitable inflation source, such as a syringe filled
with saline, contrast medium, or other suitable inflation medium.
The inflatable bladder 40 provides two useful features in the
present invention. First, inflation of the bladder 40 can assist in
the radial deployment of the struts 16 since mechanical force can
be imparted to urge the struts in a radially outwardly direction.
Second, the inflatable bladder can provide a non-traumatic surface
for engaging the heart and protecting the pericardium.
[0040] FIG. 10 illustrates a variation of the inflatable bladder
shown in FIG. 9. In particular, inflatable bladder 50 comprises a
torroidal geometry which can seat against the pericardium to in at
least some instances provide a more stable interface. The bladder
50 is inflated through an inflation tube 52.
[0041] Referring now to FIGS. 11 and 12, a further optional aspect
of the present invention will be described. The cardiac massage
device having a blunt member 30' at its distal end is constructed
generally the same as that shown in FIGS. 7 and 8. In addition to
the structure of FIGS. 7 and 8, however, FIGS. 11 and 12 show a
blade 60 having a sharpened distal tip 62 which is reciprocatably
disposed within the blunt member 30. The tip 62 of the blade may be
axially advanced, as shown in FIG. 12, in order to facilitate
introduction of the device through the skin over the intercostal
space. The blade should be retracted, as shown in FIG. 11, before
the device actually enters the space between the posterior surface
of the rib cage and the pericardium. Preferably, the blade will be
automatically retracted before the device can enter beyond the
posterior surface of the rib cage.
[0042] Referring now to FIG. 13, the patient's heart H is shown in
cross-section between ribs R.sub.n where n indicates the rib
number. The aorta A is also shown extending from the top of the
heart.
[0043] In a first exemplary method according to the present
invention, sheath 12 of the cardiac massage device of FIGS. 1, 3
and 4 is introduced through the intercostal space between R.sub.4
and R.sub.5, as shown in FIG. 14A. Shaft 14 is then advanced in a
distal direction to radially extend the struts 16, as shown in FIG.
14B. The flexible sheet 26 is thus engaged against the pericardium
P, and the device as a whole may be reciprocated through the
intercostal space to depress the heart, as shown in broken line.
Such reciprocation will preferably be performed at a rate from 40
cycles/minute to 150 cycles/minute, preferably between 40
cycles/minute and 130 cycles/minute either manually or employing a
powered drive (not shown).
[0044] The use of the device of FIGS. 11 and 12 is illustrated in
FIGS. 15A and 15B. The device is introduced by engaging the blunt
member 30' against the patient's skin at a region over the heart
and between R.sub.4 and R.sub.5. Blade 60 is advanced so that tip
62 extends partly through the thickness of the patient's skin
overlying the intercostal space. The blade is then retracted as the
blunt member 30 is advanced inwardly. Struts 16 may be deployed
radially outwardly to engage the pericardium P, as shown in FIG.
15B, and the device then reciprocated to alternately compress and
relieve the heart to induce circulation, as shown in broken line.
Relief of the compression allows the ventricle to refill prior to
the next compression step.
[0045] While the above is a complete description of the preferred
embodiments of the invention, various alternatives, modifications,
and equivalents may be used. Therefore, the above description
should not be taken as limiting the scope of the invention which is
defined by the appended claims.
* * * * *