David Boyd Melvin, M.D.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a device and method for assisting in the activation

and operation of a living heart, and more specifically, for mechanically deforming cardiac

tissue such that the circulation of blood is maintained.

BACKGROUND OF THE INVENTION

The natural heart, and specifically, the cardiac tissue ofthe natural heart can fail

for various reasons to a point where the natural heart cannot provide sufficient circulation

of blood for a body so that life can be maintained. As a solution for the failing natural

heart, several attempts have been made in the past to provide a device to maintain

circulation.

One such approach has been to either assist or to entirely replace the existing

natural heart in a patient with an artificial heart, or to transplant a natural heart from

another human into a patient. Several drawbacks have limited use of prior devices to

applications having far too brief of a time period to provide a real lasting benefit, and to

transplant use in a tiny fraction of those afflicted with heart disease or malfunction.

A particular problem stems from the fact that the materials used for the interior

lining of the chambers of an artificial heart are in direct contact with the circulating

blood, which can enhance undesirable clotting of the blood, build up of calcium, or

otherwise inhibit the blood's normal function. Hence, thromboembolism and hemolysis

could occur with greater ease. Additionally, an artificial heart lining can crack, which

inhibits performance, even if the crack is at a microscopic level.

The transplant procedure requires removing an existing organ (i.e., the natural

heart) for substitution with another organ (i.e., another natural heart) from another

human, or potentially, from an animal. Before replacing an existing organ with another,

the substitute organ must be "matched" to the recipient, which can be, at best, difficult

and time consuming to accomplish. Furthermore, even if the transplanted organ matches

the recipient, a risk exists that the recipient's body will reject the transplanted organ and

attack it as a foreign object. Moreover, the number of potential donor hearts is far less

than the number of patients in need of a transplant. Although use of animal hearts would lessen the problem with fewer donors than recipients, there is an enhanced concern with

rejection ofthe animal heart.

In an effort to use the existing natural heart of a patient, other attempts have been

made to wrap skeletal muscle tissue around the natural heart to use as an auxiliary

contraction mechanism to pump the natural heart. As currently used, skeletal muscle

cannot alone typically provide sufficient and sustained pumping power for maintaining

circulation of blood through the circulatory system of the body, especially for those

patients with severe heart failure.

Still another concept for maintaining the existing natural heart as the pumping

device involves enveloping a substantial portion ofthe natural heart, such as the entire

left and right ventricles, with a pumping device for rhythmic compression. Although

somewhat effective as a short term treatment, the pumping device has not been suitable

for long term use. Typically, a vacuum pressure is needed to overcome cardiac

tissue/wall stiffness so that the chambers can return to their original volume and refill

with blood. This "active filling" of the chambers with blood limits the ability of the

pumping device to respond to the need for adjustments in the blood volume pumped

through the natural heart, and can adversely affect the circulation of blood to the coronary

arteries. Natural heart valves are quite sensitive to wall and annular distortion, and

movement patterns that reduce a chamber's volume do not necessarily facilitate valve

closure (which can lead to valve leakage). Another major obstacle with long term use of

such pumping devices is the deleterious effect of extensive mechanical contacting of

living internal surfaces (endocardium). In certain cases, this coaption of endocardium

tissue is probably mechanically necessary for a device that encompasses both ventricles

to produce independent output pressures, but it can compromise the integrity ofthe living

endothelium.

Another device developed for use with an existing heart for sustaining the

circulatory function of a living being and the pumping action of the natural heart is an

external bypass system, such as a cardiopulmonary (heart-lung) machine. Typically,

bypass devices of this type are complex and large, and, as such, are limited to short term

use in an operating room during surgery, or to maintaining the circulation of a patient

while awaiting receipt of a transplant heart. The size and complexity effectively prohibit

use of bypass systems as a long term solution, as they are rarely even portable devices.

Furthermore, long term use of a heart lung machine can damage the blood cells and blood

borne products, resulting in post surgical complications such as bleeding,

thromboembolism function, and increased risk of infection.

Consequently, none of the previous available techniques or devices for

maintaining circulation of blood provided an adequate or practical long-term use device

or technique for adequately maintaining sufficient blood pressure and circulation of blood

through the circulatory system ofthe body.

SUMMARY OF THE PRESENT INVENTION

It is the object of the present invention to provide a device and method for

activation of a natural heart that provides different independent pressures to the left and right side of the natural heart.

It is another object ofthe present invention to provide a device and method for

activation of a natural heart that minimizes damage to the coronary circulatory and the endocardium (lining tissue).

It is still a further another object ofthe present invention to provide a device and

method for activation of a natural heart that allows one or more ofthe heart chambers

to rapidly and passively refill at low pressure after an activation stroke.

Another object ofthe present invention is to provide a device and method for the

activation of a natural heart that supports and maintains competence ofthe heart valves

so the heart valves can function as designed.

Still another object ofthe present invention is to provide a device and method for

the activation ofthe heart that functions at the proper rate.

Yet another object ofthe present invention is to provide an apparatus and method

for the activation of a natural heart on a long term basis.

It is yet still an object ofthe present invention to provide a device and method for

the activation of a natural heart to provide an implant device that does not require

removal of an existing natural heart.

Additional objects, advantages, and other features ofthe present invention will

be set forth and will become apparent to those skilled in the art upon examination ofthe

following, or may be learned with practice ofthe invention.

To achieve the foregoing and other objects, and in accordance with the purpose

herein, the present invention comprises an activator device for use with a natural heart

having an internal stint for placement within the interior volume of a natural heart adjacent cardiac tissue. The device also includes a yoke for placement around a portion

of the exterior surface of the natural heart in general alignment with the stint and is

connected to the stint by at least one cord.

Preferably, the activator device includes a first ring for placement around at least

one ofthe atrioventricular valve annuli, a second ring for placement around at least one

ofthe outflow valve or semilunar annuli, and a septal splint having a frame and sutures

in a net-like configuration to stabilize the septal wall between chambers ofthe natural

heart. The first ring, second ring, and the septal splint are connected to each other using

fastening elements.

In a preferred embodiment, the yoke is sized and configured for placement

adjacent at least a portion of the interventncular groove, preferably adjacent at least a

portion of the anterior and posterior portions of the interventricular groove, and more

preferably adjacent at least a substantial portion ofthe anterior and posterior portions of

the interventricular groove. In another embodiment, the yoke is sized and configured for

placement adjacent at least a portion ofthe atrioventricular groove.

The present invention also includes an activator attached to the yoke for

deforming the natural heart, which preferably includes a hydraulic lateral arm.

The present invention also includes a method for cardiac tissue deformation using

the above-described device. The activator deforms a portion of the cardiac tissue by

moving an arm from a relaxed condition to an activated condition. As the activator is

pressing against the natural heart, the volume of at least one chamber ofthe natural heart is decreased so that blood is pumped out of the natural heart and into the circulatory

system. Thereafter, the activator releases from against a portion of the cardiac tissue

returns to the relaxed condition. The combination ofthe stint and yoke assist in returning

the volume ofthe chamber so that at least one ofthe chambers ofthe natural heart refills

with blood and thus, the steps can be repeated.

Different forces can be applied to a natural heart for reducing the volume of at

least one ofthe chambers. These forces can include applying a torsion force or a shearing

to the natural heart, flattening a portion ofthe cardiac tissue, applying a uniform pressure

to the natural heart, and/or applying an indentation against at least one point on the

exterior wall ofthe natural heart.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and

distinctly claiming the present invention, it is believed the same will be better understood

from the following description taken in conjunction with the accompanied drawings in

which:

Fig. 1 is a partial frontal anterior perspective view of an exemplary natural heart;

Fig. 2 is a perspective view of an internal stint and exterior yoke made in

accordance with the present invention;

Fig. 3 is a partial cross-sectional view of a natural heart with a septal splint made

in accordance with the present invention placed within a natural heart;

Fig. 4 is a partial frontal perspective view of a natural heart with an external yoke

placed on a natural heart;

Fig. 5 A is a frontal perspective view of one embodiment ofthe external yoke and

activator ofthe present invention;

Fig. 5B is a frontal perspective view of another embodiment of an external yoke

and activator ofthe present invention;

Fig. 6 is a top sectional schematic view of a natural heart with an internal splint

and an external yoke ofthe present invention illustrated being connected by transmural

cords;

Fig. 7A is a partial schematic view of an exemplary activator of the present

invention in a relaxed condition; and

Fig. 7B is a partial schematic view of an exemplary activator of the present

invention in an activated condition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the figures in detail wherein like numerals indicate the same

elements throughout the views, a natural heart, generally indicated in Figure 1 as 10, has

a lower portion comprising two chambers, namely a left ventricle 12 and a right ventricle

14, which function primarily to supply the main force that propels blood through the

circulatory system. A natural heart 10 also includes an upper portion having two

chambers, a left atrium 16 and a right atrium 18, which primarily serve as an entry way

to the left and right ventricles 12 and 14, respectively, and assist in moving blood into the left and right ventricles 12 or 14. The interventricular wall of cardiac tissue separating

the left and right ventricles 12 and 14, respectively, is defined by an interventricular

groove 20 on the exterior wall of the natural heart 10. The anterioventricular wall of

cardiac tissue separating the lower ventricular region from the upper atrium region is

defined by anterioventricular groove 22 on the exterior wall ofthe natural heart 10.

Generally, the ventricles are in fluid communication with the atria through an

atrioventricular valve. More specifically, the left ventricle 12 is in fluid communication

with the left atrium 16 through the mitral valve, while the right ventricle 14 is in fluid

communication with the right atrium 18 through the tricuspid valve. Generally, the

ventricles are in fluid communication with the circulatory system (i.e., the pulmonary

and peripheral circulatory system) through semilunar valves. More specifically, the left

ventricle 12 is in fluid communication with the aorta 26 of the peripheral circulatory

system, through the aortic valve, while the right ventricle 14 is in fluid communication

with the pulmonary artery 28 ofthe pulmonary, circulatory system through the pulmonic

valve.

By way of a non-limiting example, the present invention will be discussed in

terms of embodiments that are used to primarily assist in the activation and operation of

the left ventricular portion of the natural heart 10, however, it is noted that the present

invention can also be used to assist in the activation and operation of other portions of

the natural heart 10, such as the atria, or the right ventricular portion ofthe natural heart

10. The present invention is a mechanical activator, illustrated in Figure 2 as 50, which

includes an internal stint 52. Furthermore, the present invention includes an external

yoke 70 fixed to the internal stint 52 by transmural cords 86. The internal stint 52 is sized

and configured for placement within the interior volume of the natural heart 10, and

includes a generally triangular shaped frame 53 that can be assembled from a plurality

of interlocking struts, preferably an anterior, a posterior and a basal strut. The stint 52

also includes at least two separate ring structures, namely a first ring 56 sized and

configured for placement adjacent the atrioventricular valve annuli, and preferably

suprajacent the mitral valve annuli in the left atrium 16, and a second ring 58 sized and

configured for placement adjacent the semilunar valve annuli preferably subjacent the

aortic valve annuli in the left ventricle 12.

Figure 3 further illustrates a septal splint 54, which can include one or more

strands of sutures affixed to the frame 53 through loops positioned on the frame 53,

preferably the loops are affixed to the inner portion of frame 53, and more preferably,

at about 1.5 cm intervals. The splint 54 can take the form of a tennis racket-like shaped

configuration or a snowshoe like shaped configuration to brace or stabilize one side of

the septum, preferably the right side ofthe interventricular septum without distortion of

the chordae. Preferably, the septal splint 54 is positioned by stringing a heavy

monofilament polypropylene suture, such as a #5 polypropylene suture, under, through,

and behind the trabeculae, and through the loops as will be discussed later in great detail. The first and second rings 56 and 58 and the septal splint 52 are attached at least to each

other using a connector element 59, such as a pin to assist in maintaining the relative

position so that the first and second rings 56 and 58, respectively, and the splint 52 are

supported while the natural heart 10 is being activated.

So that the components of the stint 52 (e.g., the septal splint 54 and first and

second rings 56 and 58) are not totally rigid and can exhibit an elastic quality, the

components are preferably made of a stiff coil spring material covered with braided

polyester. Localized adjustments can be made to the elasticity ofthe various components

ofthe stint 52 to reduce the potential for problems, such as damaging the cardiac tissue

or compromising the coronary circulation.

As illustrated in Figure 4, the device 50 also includes an external yoke 70 for

placement around a portion of the exterior surface of a natural heart 10. The generally

stirrup shaped yoke 70 restricts free motion of the natural heart 10 so that the natural

heart 10 can be activated. Preferably, the yoke 70 can be between about 1 and 2 cm wide

and includes a semi-rigid collar portion, preferably made of polypropylene, for providing

rigidity to the yoke 70. Additionally, the yoke 70 can include a gel-filled cushion portion

that is positioned immediately adjacent exterior surface of the natural heart 10 for

providing equalized pressure over the irregularities in the epicardial surface ofthe natural

heart 10, and preferably, any of the coronary arteries 30 within each region under the

yoke 70. Preferably, the yoke 70 is sized and configured for placement adjacent at least

a portion of the atrioventricular groove 22, more preferably, at least a portion of the

anterior and posterior portions ofthe interventricular groove 20, and most preferably, at

least a substantial portion of the anterior and posterior portion of the interventricular

groove. In yet another embodiment, the yoke 70 is sized and configured for placement adjacent at least a portion ofthe atrioventricular groove 22.

Referring now to Fig. 6, general alignment of the yoke 70 is maintained by at

least one transmural cord 86, and preferably, a plurality of cords 86 that penetrate the

walls ofthe natural heart 10 and connect to the stint 52. The cord 86 is preferably made

of a heavy braided, polymer-impregnated polyester suture core (such as # 5 Ethiband®

by Ethicon, Inc.) covered in the intermyocardial portion with a braided sleeve of

polyester yarn to promote firm tissue growth around the cord 86. When it is necessary

to utilize more than one cord 86 with the present invention, spacing of the cords 86

should preferably be at intervals of between about 15 mm to 20 mm along the yoke 70,

from the septal splint 54 and the first ring 56 extending obliquely outwardly toward the

left ventricle exterior wall for insertion into the left ventricle margin of the yoke 70.

More preferably, the cords 86 should be positioned for avoiding contact with the

coronary vessels 30. The cords 86 vary in length such that the splint 54 and first ring 56

are oriented beneath the gel-filled cushion portion while the septum stint 52 and the first

ring 56 are held stable in general alignment with the natural heart 10, and are generally

not allowed to move away from the ventricular exterior wall when pressure is applied to a natural heart 10 via by activator 74.

As mentioned above, the present invention also includes an activator 74 attached

to at least a portion of the yoke 70, preferably the apical portion 70a, as illustrated in

Figures 5A and 5B. The activator 74 includes a lateral flexible arm 75 generally having

an "L" shaped configuration that extends approximately two-thirds of the distance

between the apical portion 70a and base portion 70b ofthe yoke 70.

Connected to the arm 75 is at least one, and preferably a plurality of, bands 84 extending away from the arm 75 sized and configured for placement adjacent the exterior

surface ofthe natural heart 10. The distal ends ofthe bands 84 are typically affixed and

secured along portions of yoke 70.

One embodiment of the yoke 70 and activator 74 is illustrated in Figure 5 A in

which the bands 84 extend perpendicularly away from the arm 75 and connect to the

anterior and posterior portions of yoke 70. In another embodiment ofthe yoke 70 and

activator 74 as illustrated in Figure 5B, bands 84 extend radially away from the distal

end ofthe arm 75.

Referring now to Figures 7A and 7B, the activator 74 preferably has a hydraulic

lateral arm 75 having a tubed-shape corrugated configuration with rings 77 affixed to the

inner aspect of each corrugation. A plurality of longitudinally extending cords 76,

preferably three or more, are affixed to the inner portion of arm 75, preferably the distal

end of arm 75 and also preferably to each of the rings 77. The cords 76 can vary in

length, especially between the fixation points to each ring 77 for controlling the

separation distance between rings 77. In fluid communication with the arm 75 via a

driveline 92 is a pump unit "P", such as pneumatic or a hydraulic pump for controlling

or altering the fluid volume within the arm 75.

Figure 7A illustrates the arm 75 in a relaxed condition when fluid pressure within

arm 75 is at or below ambient levels and where the shape of arm 75 is determined by the

external forces and the intrinsic stiffness of arm 75. To utilize the present invention,

pressure within the arm 75 can be increased, preferably above ambient levels, so that the

shape of the arm 75 is altered to an activated condition, as illustrated in Fig. 7B. The

length difference of the various cords 76 between the rings 77 controls the radius of

curvature of the arm 75 and the direction of curvature at various portions along the

longitudinal length ofthe arm 75. The amount of pressure required within the arm 75

must be sufficient to overcome the intrinsic stiffness ofthe arm 75 at ambient condition,

and to facilitate the proper deformation of both the arm 75 and bands 84 so that the

proper amount of pressure is applied to the exterior wall ofthe natural heart 10 to assist

in altering (i.e., reducing) the volume of one or more chamber of a natural heart 10 (e.g.,

the left ventricle 12) to maintain circulation ofthe blood through the circulatory system.

In a preferred embodiment, the arm 75 can be customized to apply different

pressure to different portions ofthe natural heart 10. For example, varying the diameter

of arm 75 along the longitudinal length can assist in controlling the curvature of arm 75.

Regions ofthe arm 75 needing less bending moment can have a smaller diameter and

regions ofthe arm 75 where greater bending moments are preferred can have a larger

diameter.

Various embodiments of an activator 74 can be utilized with the present invention

to achieve a change in the volume of one or more heart chambers. It is noted that any

activator 74 used with the present invention should be sufficient so that the cardiac output

of a typical adult is between about 3 1/min and about 30 1/min, and preferably between

about 5 1/min and 20 1/min.

In addition, there are various possible forces which can be used for activating, and

thus altering the chamber volumes ofthe natural heart 10. The present invention can be

utilized to flatten the exterior wall of the natural heart 10 in a plane substantially

perpendicular to the plane of the atrioventricular valves (e.g., a mitral valve) or

substantially parallel to the septum. When utilizing such a force, the activator 74 should

be configured to produce a flexion in the convex direction limited to between about 2.5

to 3.0 times the curvature value of the exterior wall of the natural heart 10 during the

diastolic portion ofthe cardiac cycle. Deflection in a concave direction is restricted only

to those bands 84 extending away from the arm 75 and connecting to the base portion 70b

of yoke 70.

Also, an activator 74 can be used to apply a uniform pressure to substantially the

entire exterior wall ofthe natural heart 10.

Furthermore, the activator 74 can be used to indent the exterior wall ofthe natural

heart 10 at more than one location, and preferably at two or three locations on either an

exterior wall or the septum in a hemispheric or hemiellipsoid profile.

Additionally, an activator 74 can apply a torsion force to at least a part of the

natural heart 10 at various angles.

In yet another embodiment, the activator 74 can apply a shearing force to a

portion ofthe lateral exterior wall, which is directed apically and is a basal sheer force

applied on the right side of the stint 52.

When the orientation ofthe arm 75 is altered from the relaxed condition, which

is illustrated in Fig. 7A, to the activated condition, which is illustrated in Fig 7B, the arm

75 and the bands 84 deform and apply pressure against the exterior wall ofthe natural

heart 10 for assisting with or facilitating activation ofthe natural heart 10 (the systolic

portion of the cardiac cycle). As a result, the volume of one or more chambers of the

natural heart 10 is reduced and blood is pumped out ofthe natural heart 10 and into the

circulatory system.

Following the activation (i.e., systolic portion ofthe cardiac cycle), the arm 75

and bands 84 release from against the cardiac tissue and return to their relaxed condition.

The combination ofthe stint 52 and the yoke 70 assists in returning the deformed portion

of the natural heart 10 back to its pre-activation volume so that it can refill with blood

during the diastolic portion of the cardiac cycle, so that the entire cardiac cycle can be

repeated.

To position the device 50 into and around an existing natural heart 10, open heart

thoracic surgery is required. Clinically, sufficient anesthesia is administered to the

patient and the thoracic cavity is opened using standard thoracic procedures.

Once the thoracic cavity is opened, circulation of blood to the natural heart 10

must be bypassed so the present invention can be inserted into the patient. Referring

initially to Fig. 2, the superior vena cava 26, the inferior vena cava (not shown), and aorta

26 are cannulated. The circulatory system is connected to a cardiopulmonary bypass

machine so that circulation and oxidation of the blood are maintained during the

procedure. By way of example, the procedure discussed in detail will be for insertion of

the present invention to assist in the activation and operation ofthe left ventricle 12.

Through an aortotomy and an interatrial groove left atriotomy, the first and

second rings 56 and 58, respectively, are inserted and sutured in position. Preferably, the

first ring 56 is positioned suprajacent the mitral annuli and the second ring 58 is

positioned subjacent the aortic annuli.

The interlocking struts ofthe septal frame 53 (e.g., anterior, posterior, basal struts)

are inserted into the right ventricle 14 through an apical ventriculotomy, a right atriotomy

with partial temporary detachment ofthe septal tricuspid leaflet of the tricuspid valve,

and an outflow tract ventriculotomy, respectively. Suture strands are then passed back and forth against the interventricular septum, threading through loops to provide a septal

splint 54. In placement of both the various struts of frame 53 and the strands that form

splint 54, care is taken to maneuver behind chordae and behind or through major

trabeculae and bases of papillary muscles. The suture strands are tied to form the net-like

configuration ofthe septal splint 54 that lies snugly against the septum, but allows it to

maintain normal rightward convexity. Separate connector elements 59, preferably pins,

are placed to joint the first ring 56 and the second ring 58, the second ring 58 and the

septal splint 54, and the septal splint 54 and the first ring 56.

Next, the left pleural cavity is opened and the yoke 70 is positioned behind the

natural heart 10. Cords 86 are assembled as 12" strands of suture with a polyester bead

fused to one end and blunt straight needle on the other. Each suture is passed through a

hole in the margin of the yoke 70, through the cardiac tissue, and preferably the

ventricular wall, and through the internal stint 52 (i.e., first ring 56 or septal splint 54)

and anchored after length adjustment, with the excess portion of the sutures cut and

removed. Cords 86 are tightened to render the intrinsically flexible stint 52 relatively taut and control bulging, preferably in a rightwardly direction.

Cardiotomies are closed, and the activator 74 is attached to the yoke 70. The

driveline 92 is attached to the drive unit "P" and all indicated monitoring lines are

positioned. Preferably, Heparin-filled Teflon-coated polyurethane 5 Fr. catheters are

brought through the posterior cervical incision into the chest and into the atrial

appendages and an identical one into a branch ofthe innominate artery. Termination of

a cardiopulmonary bypass is attempted and, if successful, the thoracotomy is closed.

An alternative method for positioning the present invention includes removing

the natural heart 10 from the patient, positioning all the components of the present

invention, as discussed above, and auto-transplanting the natural heart 10 back into the

patient using standard cardiectomy and cardiac transplant techniques known in the

industry.

Having shown and described the preferred embodiments to the present invention,

further adaptations ofthe activation device for the living heart and method of deforming

the living heart as described herein can be accomplished by appropriate modifications by

one of ordinary skill in the art without departing from the scope o the present invention.

For example, the present invention can be used with any one or even a plurality ofthe

various chambers of a living heart, and also could be used with different activators 74.

Other examples of an activator 74 usable with the present invention include a girdle

assembly that can be activated by hydraulics forces or other forces, such as an

electromagnetic for using magnets and electrical current. Several such potential

modifications have been discussed and others will be apparent to those skilled in the art.

Accordingly, the scope of the present invention should be considered in terms of the

following claims and is understood not to be limited in the details, structure and operation

shown and described in its specification and drawings.