Modular power system and method for a heart wall actuation system for the natural heart

An actuation system for assisting the operation of a natural heart is disclosed. The actuation system includes a framework for interfacing with the natural heart and a power system that can be coupled to the framework. The framework includes an internal framework element and an external framework element. The power system is configured to engage an exterior surface of the heart wall, and includes an actuator mechanism for exerting force on the heart wall, a driving mechanism for actuating the actuator mechanism, a transmission mechanism coupled between the actuator mechanism and the driving mechanism for transmitting power to the actuator mechanism, and a carrier device coupled between the actuator mechanism and the driving mechanism and configured for housing the transmission mechanism. The modular power system is configured for being freely exchanged and replaced in the actuation system while leaving the framework elements in place and generally undisturbed. A guide structure such as a wire or tube can also be included for guiding or advancing the power system to its position adjacent to the heart surface.

FIELD OF THE INVENTION

This invention relates generally to assisting the natural heart in operation and, more specifically, to powering a system for actuating a wall of the natural heart.

BACKGROUND OF THE INVENTION

The natural human heart and accompanying circulatory system are critical components of the human body and systematically provide the needed nutrients and oxygen for the body. As such, the proper operation of the circulatory system, and particularly, the proper operation of the heart, are critical in the life, health, and well-being of a person. A physical ailment or condition which compromises the normal and healthy operation of the heart can therefore be particularly critical and may result in a condition which must be medically remedied.

More specifically, the natural heart, or rather the cardiac tissue of the heart, can degrade for various reasons to a point where the heart can no longer provide sufficient circulation of blood for maintaining the health of a patient at a desirable level. In fact, the heart may degrade to the point of failure and thereby may not even be able to sustain life. To address the problem of a failing natural heart, solutions are offered to provide ways in which circulation of blood might be maintained. Some solutions involve replacing the heart. Other solutions are directed to maintaining operation of the existing heart.

One such solution has been to replace the existing natural heart in a patient with an artificial heart or a ventricular assist device. In using artificial hearts and/or assist devices, 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. Such contact may enhance undesirable clotting of the blood, may cause a build-up of calcium, or may otherwise inhibit the blood's normal function. As a result, thromboembolism and hemolysis may occur. Additionally, the lining of an artificial heart or a ventricular assist device can crack, which inhibits performance, even when the crack is at a microscopic level. Such drawbacks have limited use of artificial heart devices to applications having too brief of a time period to provide a real lasting health benefit to the patient.

An alternative procedure also involves replacement of the heart and includes a transplant of a heart from another human or animal into the patient. The transplant procedure requires removing an existing organ (i.e. the natural heart) from the patient 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, time consuming, and expensive to accomplish. Furthermore, even if the transplanted organ matches the recipient, a risk exists that the recipient's body will still 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 natural heart transplant. Although use of animal hearts would lessen the problem of having fewer donors than recipients, there is an enhanced concern with respect to the rejection of the animal heart.

Rather than replacing the patient's heart, other solutions attempt to continue to use the existing heart and associated tissue. In one such solution, attempts have been made to wrap skeletal muscle tissue around the natural heart to use as an auxiliary contraction mechanism so that the heart may pump. 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. This is especially true for those patients with severe heart failure.

Another system developed for use with an existing heart for sustaining the circulatory function and pumping action of the heart, is an external bypass system, such as a cardiopulmonary (heart-lung) machine. Typically, bypass systems of this type are complex and large, and, as such, are limited to short term use, such as in an operating room during surgery, or when 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 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, and increased risk of infection.

Still another solution for maintaining the existing natural heart as the pumping device involves enveloping a substantial portion of the natural heart, such as the entire left and right ventricles, with a pumping device for rhythmic compression. That is, the exterior wall surfaces of the heart are contacted and the heart walls are compressed to change the volume of the heart and thereby pump blood out of the chambers. Although somewhat effective as a short term treatment, the pumping device has not been suitable for long term use. Typically, with such compression devices, heart walls are concentrically compressed. The compressive movement patterns, which reduce a chamber's volume and distort the heart walls, may not necessarily facilitate valve closure (which can lead to valve leakage).

Therefore, mechanical pumping of the heart, such as through mechanical compression of the ventricles, must address these issues and concerns in order to establish the efficacy of long term mechanical or mechanically assisted pumping. Specifically, the ventricles must rapidly and passively refill at low physiologic pressures, and the valve functions must be physiologically adequate. The myocardial blood flow of the heart also must not be impaired by the mechanical device. Still further, the left and right ventricle pressure independence must be maintained within the heart.

The present invention addresses the issues of heart wall stiffness and the need for active refilling by assisting in the bending (i.e., indenting, flattening, twisting, etc.) of the heart walls, rather than concentrically compressing the heart walls. Because of the mechanics of deformation in hearts having proportions typical in heart failure (specifically, wall thickness/chamber radius ratios), the deformation from bending and the subsequent refilling of the heart requires significantly less energy than would the re-stretching of a wall that has been shortened to change the chamber volume a similar amount. The present invention facilitates such desirable heart wall bending and specifically protects the heart wall during such bending.

Another major obstacle with long term use of such pumping devices is the deleterious effect of forceful contact of different parts of the living internal heart surface (endocardium), one against another, due to lack of precise control of wall actuation. In certain cases, this coaptation of endocardium tissue is probably necessary for a device that encompasses both ventricles to produce independent output pressures from the left and right ventricles. However, it can compromise the integrity of the living endothelium.

Mechanical ventricular wall actuation has shown promise, despite the issues noted above. As such, devices have been invented for mechanically assisting the pumping function of the heart, and specifically for externally actuating a heart wall, such as a ventricular wall, to assist in such pumping functions.

Specifically, U.S. Pat. No. 5,957,977, which is incorporated herein by reference in its entirety, discloses an actuation system for the natural heart utilizing internal and external support structures. That patent provides an internal and external framework mounted internally and externally with respect to the natural heart, and an actuator device or activator mounted to the framework for providing cyclical forces to deform one or more walls of the heart, such as the left ventricular wall. The invention of U.S. patent application Ser. No. 09/850,554 further adds to the art of U.S. Pat. No. 5,957,977 and that application is incorporated herein by reference in its entirety. The application specifically sets forth various embodiments of activator or actuator devices which are suitable for deforming the heart walls and supplementing and/or providing the pumping function for the natural heart.

For such heart wall activation systems, an actuator device acts on the heart and is coupled to a mechanism necessary for powering or driving the actuator components of the system to mechanically act on the heart wall. The actuator device, driving mechanism and other associated components of the system may be considered to be power systems for the actuation system. The actuator device and other components of the power system involve moving parts which will wear. Therefore, the power system for a heart wall actuation system will generally have to be replaced and exchanged at least once, either due to wear, routine maintenance or malfunction. Since such power systems are interfacing with components positioned near the heart, their replacement and maintenance presents a significant issue to be addressed. Such power systems also must be able to readily interface with the heart or other components of the actuation system for ease of replacement. Furthermore, they should be readily and easily positioned with or inside the body to operate properly in the overall actuation system.

Accordingly, it is an objective of the present invention to provide a device and method for actively assisting the natural human heart in its operation.

It is still another objective of the present invention to provide the necessary actuation of a heart wall to assist the heart at a proper natural rate in a way suitable for long term usage.

It is further an objective to address the maintenance and replacement of components of a heart wall actuation system, particularly the dynamic activation and power components which deliver the actuation forces to the heart.

These objectives and other objectives and advantages of the present invention will be set forth and will become more apparent in the description of the invention below.

SUMMARY OF THE INVENTION

The present invention addresses the above objectives and other objectives and provides an actuation system for assisting the operation of a natural heart. The actuation system includes a framework for interfacing with the natural heart. The framework includes one or more framework elements such as an internal framework element and an external framework element or multiple such internal and external elements. The actuation system also includes a power system configured to be coupled to the framework and configured to engage a heart wall. The power system includes an actuator mechanism for exerting a force on the heart wall. A driving mechanism provides power for actuating the actuator mechanism and a transmission mechanism coupled between the actuator mechanism and the driving mechanism transmits the power to the actuator mechanism. A carrier device contains the actuator mechanism and the transmission mechanism together, generally as a unitary structure so that the power system may be manipulated as a unitary structure. The contained mechanisms are generally stationary with respect to the carrier device. In one embodiment of the invention, the power system is configured to be fixed to the framework.

The transmission mechanism, which may be housed by the carrier device, may be electrical wire, traction cable, torque cable, or hydraulic tubing for example. The power supplied by the driving mechanism may be electrical, mechanical, or hydraulic power. The power of the power system refers to the delivery of an electrical signal or current, delivery of a mechanical motion or delivery of hydraulic fluid, all for the purposes of actuating the actuator mechanism. Therefore, the terms power transmission or power delivery or power supply are not limiting to a particular mode of actuating the actuation mechanism. In one embodiment, the carrier device houses the actuator mechanism and is configured for coupling the actuator mechanism to the framework. The carrier device is elongated and flexible in one embodiment for positioning in the body.

In one embodiment of the invention, the actuator mechanism can include a plurality of juxtaposed elements, such as blocks, which are configured to be drawn together in the actuated state. The juxtaposed elements can cooperate with each other, when drawn together, to assume a predetermined shape or curvature. In another embodiment of the invention, the actuator mechanism may include an inflatable deforming tube structure coupled to a hydraulic fluid supply.

In another embodiment of the invention, the actuation system includes a guide structure for aiding in the placement of the power system in the body. One suitable guide structure is a wire. Another suitable guide structure is a flexible tube.

The present invention, together with other and further objectives thereof, is set forth in greater detail in the following description, taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to an actuation system for assisting the operation of a natural heart. The actuation system disclosed as one example herein comprises a framework for interfacing with the heart, through the wall of the heart, which includes one or more internal framework elements configured to be positioned within the interior volume of the heart and one or more external framework elements configured to be positioned proximate an exterior surface of the heart. A power system is coupled to the framework and configured to engage an exterior surface of the heart. For example, if the left ventricle of the heart is to be actuated utilizing the invention, the external framework can be positioned approximate the exterior left ventricular wall, and the power system will be similarly positioned. This specification discloses a modular power system, which may be exchanged and replaced in a heart wall actuation system as required for repair or for routine maintenance. The modular power system provides a generally unitary structure for positioning and powering the actuator mechanism.

One particular advantage of the present invention is that it provides for simplified replacement of the power and actuator mechanisms which deliver a force or motion to a heart wall to change the volume of a heart chamber. Replacement is done via a limited operation which accesses a driving mechanism or power source near the body surface (e.g. within the abdominal wall) rather than through a major trans-thoracic (open chest) operation to access the heart directly. In one embodiment, the driving mechanism for delivering power to actuate the actuator mechanism can be positioned remotely from the framework, from the heart, and from the actuator mechanism, and can be coupled to the actuator mechanism. In this way, the driving mechanism can be surgically positioned in the body at a site which is readily accessible and particularly more accessible than the chest cavity and the heart. Thus, in this embodiment, the driving mechanism may also be repaired or upgraded without having to perform cardiothoracic surgery on the patient.

The invention operates by coupling a mechanism for exerting a force, that is, an actuator mechanism of the power system, onto an external framework element that has been surgically placed onto the cardiac wall. The actuator mechanism may be selectively and cyclically operated between an actuated state and a relaxed state and may be operable, when in the actuated state, to assume a predetermined shape or curvature and thereby indent a portion of the heart wall to effect a reduction in the volume of the heart and specifically a reduction in one of the chambers of the heart for assisting the heart in its pumping function. The power system includes a driving mechanism for supplying power for actuating the actuator mechanism. The actuator mechanism can be housed in a carrier device, generally at one end, and the driving mechanism can be coupled with the carrier device, generally at the other end. In one embodiment, a transmission mechanism is coupled between the driving mechanism and the actuator mechanism and is housed in the carrier device.

Besides being a conduit of power transmission, the carrier device also serves to help withdraw the power system when being replaced and to advance the new power system when being installed. The invention may also include a guide structure, such as a guide wire or guide tube, as a guidance system for guiding or advancing the power system to its position adjacent to the heart surface.

Referring toFIG. 1, one embodiment of the present invention is shown. Power system10includes a force delivery mechanism, or actuator mechanism22, and a carrier device20, shown detached from a driving mechanism24(FIG. 2). Power system10is a modular power system configured for use, in one embodiment, with a framework61which interfaces with the heart60. The power system10is configured for engaging a heart wall. Specifically, part or a portion of the power system engages the heart wall. Referring briefly toFIG. 5, an external framework element30of the framework61is shown coupled to the exterior of heart60. External framework element30is in the form of a yoke and is coupled to internal framework elements (not shown) positioned inside the heart. Greater details of a suitable framework61for use with the present invention are set forth in U.S. Pat. No. 5,957,977, which is incorporated herein by reference. While that patent discusses one suitable framework for the modular power system10of the invention, it will be understood by a person of ordinary skill in the art that other structures and frameworks will also be suitable for coupling the power system10to engage an exterior surface of a heart wall. Furthermore, while the embodiment of the invention illustrated herein is shown coupled to an exterior heart wall surface proximate the left ventricle of the heart, it might as easily be coupled to other areas of the heart for heart wall actuation.

Referring again toFIG. 1, a guide structure, such as a wire28, is illustrated and is threaded through an elongated passage29which passes through a carrier device20and through or past the components housed in the carrier device. The guide structure is used as the guidance system for positioning of the actuator mechanism in this embodiment of the invention as discussed further below.

The modular power system10illustrated inFIG. 1generally incorporates an actuator mechanism22which is operable, when actuated, for exerting a force on the heart wall surface for the pumping of blood. When the power system10engages a heart wall, the actuator mechanism22actually engages an outer surface of the heart wall. The actuator mechanism22is coupled with the driving mechanism24for providing power for actuating the actuator mechanism22and contained by the carrier device. A transmission mechanism is coupled with the actuator mechanism22for transmitting power to the actuator mechanism22. In one embodiment, the transmission mechanism is coupled between the actuator mechanism and driving mechanism. Modular power system10includes a carrier device20coupling the actuator mechanism22together with the transmission mechanism. The carrier device may also couple with the driving mechanism24to couple the various mechanisms together for providing a generally unitary structure which may be readily and easily manipulated inside the body for maintenance or replacement of the force delivery components of a heart wall actuation system. The carrier device may provide actual mechanical coupling of the various mechanisms and components or, alternatively, may just contain the mechanisms as a housing.

In one embodiment of the present invention, the carrier device20is in the form of a generally tubular sleeve which houses the actuator mechanism22along with the transmission mechanism. The sleeve may be formed of a biomedically suitable material such as polyurethane or silicon rubber. The carrier device20may also be configured for coupling the actuator mechanism22to a suitable heart framework61. For example, as illustrated inFIGS. 1 and 5, and discussed further hereinbelow, the carrier device20may include a structure, such as a nipple26, for coupling the carrier device and actuator mechanism to a suitable framework61. The other end of the carrier device20, opposite the actuator mechanism22, is coupled to a driving mechanism24as illustrated inFIG. 2.

FIG. 2shows an embodiment of a complete power system10which includes the actuator mechanism22, the carrier device20, and the driving mechanism24. The driving mechanism24is operable for supplying the power for actuating the actuator mechanism22. To that end, the operation of the driving mechanism24and the power it supplies will depend upon the operation of the particular actuation mechanism which is utilized. In accordance with one aspect of the invention, the actuator mechanism22may operate electrically, mechanically, or hydraulically, for example. Alternatively, the actuator may utilize a combination of such operational features or may incorporate other operational characteristics. Therefore, the power transmitted to the actuator mechanism to actuate the mechanism may take various forms, including electrical, mechanical, or hydraulic. The term “power” as used herein is not limiting but generally refers to any mechanism or means for actuating the actuator mechanism. The driving mechanism, and the transmission mechanism coupling the driving mechanism to the actuator mechanism for transmitting power thereto, are configured for working with the actuator mechanism. Therefore, the driving mechanism will be configured for providing suitable power or forces to the actuator mechanism and may include a system which is electrical, mechanical, hydraulic, a combination of these or some other suitable system to provide the necessary power. The transmission mechanism may similarly be electrical, mechanical, and/or hydraulic, or a combination of such features for providing the proper interface between the actuator mechanism and carrier device.

The power system10depicted inFIG. 2is configured to be implanted replaceably into a patient from a space outside the chest, such as a space in the subcutaneous tissue, without having to perform cardiothoracic surgery on the patient. The driving mechanism24, in one embodiment, is detachable and replaceable separately from the carrier device20. Alternatively, the driving mechanism might be coupled with the carrier device so that the entire system10is replaceable as a modular unit.

FIGS. 1A and 1Bdepict one embodiment of the invention in which actuator mechanism22utilizes a plurality of juxtaposed elements, such as articulating blocks34, for actuating a heart wall. One suitable embodiment of an actuator mechanism22is described in U.S. patent application Ser. No. 09/850,554, which is incorporated herein by reference, whereby traction on an actuator cable32or other tether or cord effects a change in alignment of the articulating blocks34and thus creates a predetermined shape. That is, the blocks34are configured to be drawn together in an actuated state and to cooperate with each other, when drawn together, to assume a predetermined shape. The blocks are drawn together when cable32is drawn by a force provided by driving mechanism24. That is, the power associated with the embodiment ofFIGS. 1A,1B is mechanical power and that mechanical power is transmitted to the blocks34by cable32, which acts as the transmission mechanism.

The actuator mechanism22, when positioned against an exterior surface of a heart wall, moves the heart wall when it takes its predetermined actuated shape and effects a reduction in volume of a chamber of the heart60, such as the left ventricle50. This action on the heart wall assists the pumping action of the heart60. Greater detail of such an actuator mechanism is set forth in U.S. patent application Ser. No. 09/850,554, butFIGS. 1A and 1Bshow the basic mechanism in relaxed and actuated states, respectively.

The configuration ofFIG. 1Adepicts the end of cardiac chamber refilling. During filling of the heart chamber, the actuator mechanism22is relaxed. As seen inFIG. 1A, a transmission mechanism, in the form of actuator cord32is secured at an end33inside the actuator mechanism22and inside the carrier device20. For example, the cable might be anchored to an end block by a suitable anchor connection. for example, the cable might be anchored to an end block by a suitable anchor connection. In the embodiment ofFIGS. 1A,1B, the carrier device20acts as a casing over the blocks34to contain the blocks and form a unitary structure with the transmission mechanism32. InFIG. 1A, the cable32is relaxed and is not drawn so that the blocks34are not pulled together at this point in the cardiac cycle. The relaxed actuator mechanism22will then generally take the shape of the filling or filled cardiac chamber.

FIG. 1Bdepicts the configuration of the actuator mechanism imposed in actuation to produce or aid ejection of blood from the cardiac chamber. For ejection of blood, the power system changes the configuration of the actuator blocks34by tightening or drawing the actuator cord32and pulling or drawing the actuator blocks34together to form a predetermined shape to indent or move the heart wall.

The carrier device contains the actuator mechanism and the transmission mechanism in the embodiment ofFIGS. 1A,1B. The cable32interfaces with the blocks and passes through passages35formed therein. The cable portion away from actuator mechanism22may progress generally loosely through carrier device20. Alternatively, the carrier device has a passage formed therein, similar to the passages35in the blocks, for containing the cable so that it may be drawn and relaxed in a controlled manner.

The actuator mechanism22is coupled to the driving mechanism24through the carrier device20, which may be flexible. The driving mechanism24supplies power (i.e., draws the cable) and the power is transmitted via the actuator cable32to draw the blocks together to achieve the predetermined shape of the actuator mechanism22. The driving mechanism24is configured and operable for cyclically drawing and relaxing the cable32to effect the shape change of the actuator mechanism to actuate the heart wall. Such an embodiment is an example of a mechanical power system and the driving mechanism provides the mechanical power by drawing the cable. In such an embodiment, driving mechanism24may include an electrical power source such as a battery, and other mechanical structure, such as an electromechanical converter, for drawing cable34. The drawing mechanism may include any suitable mechanism for drawing cable34, such as a motor, a solenoid, a muscle, etc.

FIGS. 3 and 4show one possible implementation of the invention, showing positioning of the power system10near the heart60through the abdominal wall84of a patient. The power system10is configured to operate in conjunction with the framework61for providing an actuation system for assisting the operation of a natural heart60. Generally, the framework61is positioned to interface with the heart60through cardiothoracic surgery as discussed in U.S. Pat. No. 5,957,977. However, in accordance with one aspect of the present invention, the modular power system10, which includes an actuator mechanism22, may be installed in position without such cardiothoracic surgery. Rather, access from a site between the abdominal wall and the overlying skin, or within or deep to the muscular abdominal wall, may be utilized. Therefore, the modular power system10of the invention is readily replaceable, such to address maintenance or malfunction. The driving mechanism24may already be positioned between skin and muscular fascia of the abdominal wall, as illustrated inFIGS. 3 and 4. In such a case, the carrier device20, actuator mechanism and any transmission mechanism which is housed in the carrier device would then be selectively uncoupled and coupled with the driving mechanism24during installation of the system or during removal and replacement. Alternatively, the entire power system10, including the driving mechanism24, might be installed as illustrated inFIGS. 3 and 4.

In this embodiment the surgeon accesses the heart60from a position that is posterior to the xyphoid process86of the sternum88but anterior to the diaphragm82. The embodiment ofFIGS. 3 and 4uses a guide wire28as the guide structure, but other guide structures and systems might be utilized as well. The guide wire28is initially coupled to the framework61, such as to a yoke element30. The power system, and particularly the carrier device which contains and/or couples together the actuator mechanism and the transmission mechanism, is configured to glide on wire28for positioning. In one embodiment, the carrier device20includes an elongated passage29(seeFIG. 1) and the wire slides through the passage. More specifically, the power system is guided into positions along wire28. The carrier device20and the actuator mechanism22are advanced between surgical retractors64that hold open the surgical incision. The modular system, including the actuator mechanism and any associated transmission mechanism may be readily positioned and manipulated with respect to the remotely located heart. The power system10readily and relatively easily slides into working position over the guide wire28. In this embodiment, the actuator mechanism22is effectively coupled to or includes a locking device or structure26such as a nipple. In one embodiment, the nipple or other structure26is configured as part of the carrier device. This nipple26interacts with a mating component27, such as an opening or some other structure present on the external framework element30, which is interfaced with the heart60as discussed further below. As illustrated in phantom by reference numeral78, the modular carrier device20and actuator mechanism22depicted inFIG. 3illustrate how the modular power system assembly is advanced into working position as it slides over the guide wire28. As shown inFIG. 1, the cross-sectional size and shape of the actuator mechanism22may differ moderately from that of the carrier device20when a guide wire28is used as the guide structure, because the tube of encapsulating scar tissue that will form after the power system has been implanted can be somewhat elastic to allow the power system to be removed and replaced.

FIG. 4illustrates the carrier device20and the actuator mechanism22completely advanced into working position and coupled with the framework element30. The surgical incision through the abdominal wall84is closed, and the driving mechanism24rests near the diaphragm82. The driving mechanism24is attached to the carrier device and coupled to the appropriate transmission mechanism, such as a cable32. In this embodiment, the framework interfaces with the left ventricle50of the heart60.

In addition to the upper abdominal surface depicted inFIGS. 3 and 4, the upper chest, below the clavicle, is another non-limiting example of a site for superficial body access. Pathways can be between the clavicle and upper ribs and over the top surface of the clavicle or sternum or between ribs or through the bed of one or more resected ribs, in addition to the illustrated pathway below the lower rib margin.

FIG. 5is a more detailed view of a heart60with a framework61fixed to it to enable use of the replaceable modular power system10of the invention. In this embodiment, the framework is also fixed adjacent the exterior wall of the left ventricle50. Such a framework and the power system10of the invention alternatively may be fixed to another section or the wall of the heart or to multiple sections of walls of the heart. This embodiment illustrated includes a nipple26coupled to the actuator mechanism22of the power system10, such as with part of the carrier device20. The nipple is shown, in one form, as being formed as part of carrier device20, but that is not necessary. The nipple is fixed to a corresponding opening or mating component27on the external framework element30. The nipple26couples or locks into place with a portion of the framework when the power system10is positioned in place with framework61to provide an anchor point for the actuator mechanism. For example, the nipple might be snapped into an aperture27. As will be understood by a person of ordinary skill in the art, this example of a mating component is intended to be non-limiting. Other mating components or structures may include those which are engaged or released by traction or torsion on a cable designed for such a purpose. Another example is a screw-in fixation system. Numerous other possibilities will be obvious to those ordinarily skilled in the art for anchoring remotely accessible devices for various medical or non-medical applications.

In accordance with another aspect of the present invention, the actuator mechanism may be coupled to the framework in other positions for securing the actuator mechanism to actuate a wall of the heart. Particularly,FIGS. 3 and 4disclose the actuator mechanism coupled at the proximal end to framework element30through nipple26and the mating component27. As alternatively illustrated inFIG. 5, a distal end21of the actuator mechanism22may also be coupled to another point on the framework element30. As illustrated inFIG. 5, the carrier device20and actuator mechanism22may be positioned so that the distal end21of actuator mechanism22passes through an aperture23formed in the framework element30. In that way, the distal end21is further secured to secure the actuator mechanism22. Alternatively, distal end21of the actuator mechanism22might otherwise interface with the framework. For example, another nipple and mating component might be utilized similar to the elements26and27, to couple the distal end21of the actuator mechanism with the framework element30.

FIG. 5also depicts in greater detail the natural heart60incorporating a heart wall actuation system in accordance with an embodiment of the invention. Heart60includes a lower portion comprising two chambers, namely a left ventricle50and a right ventricle54which function primarily to supply the main force that propels blood through the circulatory system. The heart60also is composed of coronary arteries74as well as an upper portion having two chambers, a left atrium52and a right atrium56which primarily serve as an entryway to the ventricles and assist in moving blood into the ventricles. Generally, the ventricles are in fluid communication with the atria via an atrioventricular valve. More specifically, the left ventricle50is in fluid communication with the left atrium52through the mitral valve, while the right ventricle54is in fluid communication with the right atrium56through the tricuspid valve. Generally, the ventricles are in fluid communication with the circulatory system (i.e., the pulmonary and peripheral circulatory system), through semi-lunar valves. More specifically, the left ventricle50is in fluid communication with the aorta58of the peripheral circulatory system through the aortic valve while the right ventricle54is in fluid communication with the pulmonary artery62of the pulmonary circulatory system through the pulmonic valve.

Now referring toFIG. 6, an alternative embodiment of the invention utilizes a guide structure in the form of a guide tube18of a suitable prosthetic material. Rather than sliding along a guide wire as discussed above, the carrier device20and actuator mechanism22(with the transmission mechanism housed in the carrier device) are passed through the guide tube18when positioning components of the power system proximate a heart. In accordance with one aspect of the invention, The guide tube18is left in position in the body when the power system components are removed and replaced, thereby leaving a passage for guiding the carrier device20and actuator mechanism22into position. In one embodiment, the guide tube is a flexible tube through which the power system will pass to be positioned in the proper place with respect to a heart to be actuated. However, effective elasticity of such guide tubes18may not be sufficient to allow substantial deformation in cross section, particularly after extended periods of implantation. Therefore, in one embodiment, the cross-sectional profile of tube18will need to be generally similar to the carrier devices and actuator mechanisms which are used with these types of tubular guide structures so that the carrier (with enclosed transmission and actuator units) can slide freely through the guide structure. With the guide structure18in place, the modular power system10of the invention may be readily placed in position, removed, repaired or replaced, and again placed in position, with minimal disruption to the body.

FIGS. 7 and 8show an alternative embodiment of an actuator mechanism22as a force delivery system in the form of an inflatable and deformable tube structure, such as a corrugated tube38having alternating regions of tethered regions68and non-tethered regions66, or tethered regions of different flexibility. The hydraulic tube38has multiple corrugations and can be expanded, and thereby shaped, by the injection of hydraulic fluid36into the tubing. In such a case, the hydraulic fluid may be provided by the driving mechanism24, which may include a source of such fluid. The transmission mechanism may be in the form of an elongated tube or hose to deliver the fluid to the inflatable hydraulic tube38. For example, the carrier device20might be configured to form such an elongated hose. Alternatively, as discussed below, a separate hose37might extend inside the carrier device. In another alternative embodiment, the carrier device might form both the actuator mechanism38and the tube or hose to deliver hydraulic or other fluid. That is, the actuator mechanism and transmission mechanism might be simply different sections of a unitary tubular structure. As such, the invention does not require that the actuator mechanism, transmission mechanism, and carrier device all be separate pieces. Expansion of and the delivery of the fluid36to tube38flexibly extends non-tethered or less tethered corrugated regions66of the tube wall by pressure produced by an influx of the fluid36. The tethered or more tethered corrugated regions68of the tube wall are generally extended less than regions66. The non-tethered or less tethered regions66cooperate with the tethered regions or more tethered regions68to make tube38assume a predetermined shape when the hydraulic fluid36delivered thereto.

Alternatively, the regions described and illustrated as “untethered” or “less tethered” may also, in fact, be tethered, but tethered at a limiting length that is greater relative to passive length than is the limiting length of those regions described as “tethered.” For example, one of the tethered regions may allow a 20% expansion, while an opposite tethered region might allow expansion by only 0–5% to provide controlled curvature. In that way, the greatest resulting curvature may be controlled.

In particular,FIG. 7depicts the shape or configuration of hydraulic tube38assumed during the relaxed state of the actuator mechanism22, at the end of cardiac chamber filling. The pressure or amount of hydraulic fluid36in the tube (shown formed as carrier device20) is not sufficient to deform it and actuate it such that it significantly acts on the heart.FIG. 8depicts the shape or configuration assumed by the actuator mechanism22in the actuated state to produce or aid ejection of blood from the cardiac chamber. During filling of the heart chamber, the actuator mechanism22is relaxed and has a configuration of that inFIG. 7. During ejection of blood, the system is actuated and tube38changes configuration from that inFIG. 7to that inFIG. 8. This actuation or change of configuration of the actuator mechanism22can be affected by the delivery of hydraulic fluid36which is directed into and out of the actuator mechanism22through a suitable transmission mechanism, such as a tube formed by the carrier device20or a separate hydraulic hose, such as a hose37shown inFIG. 9.

FIG. 9is a non-limiting example of a driving mechanism24awhich may be used with the actuator mechanism22illustrated inFIGS. 7 and 8. Specifically, the mechanism in24aincludes a hydraulic cylinder42containing a piston44driven by a solenoid40that is, in turn, driven by an electric current delivered by electrical wires46or an induction system. Piston44might also be driven by an electric motor or other suitable device. In this embodiment, the driving mechanism24ais operable, in response to signals on electrical wires46, to drive piston44and pump hydraulic fluid36, or other suitable fluid, through hose37to actuate the tube38embodiment of the actuator mechanism22depicted inFIGS. 7 and 8. As shown inFIG. 9, the transmission mechanism is a hose37which passes through the elongated carrier device20.

FIG. 10illustrates another embodiment of a system employing a skeletal muscle70coupled to a prosthetic cable72by an appropriate coupling73as part of the driving mechanism. For example, an appropriate coupling, such as that described in U.S. Pat. No. 6,214,047, and pending application Ser. No. 09/889,195, may be utilized. That patent and pending application are incorporated herein by reference in their entireties. The prosthetic cable72couples to the driving mechanism24to provide power for actuation of the actuator mechanism22. In one example, the driving mechanism24may be configured to drive or draw an actuator cable32for shaping the blocks34of the embodiment of the actuator mechanism22depicted inFIG. 1in response to action by muscle70. As such, the driving mechanism24may include a structure for operably coupling the actuator cable32with cable72leading from a muscle or muscle group. The driving mechanism, alternatively, may include, levers, ratchets, gears, or other mechanical members which alternatively engage a series of sequentially contracting muscles, to alter the force/displacement ratio of the muscle, or to alter the time for which force is maintained. In the embodiment ofFIG. 10, the power source associated with driving mechanism24is a muscle or muscles of the human body.

Note that the described embodiments of driving mechanisms, actuating mechanisms and transmission mechanisms are only examples of the way in which various driving mechanisms may drive various force delivery systems or actuator mechanisms in a modular design. Among many feasible alternative combinations, the muscle power source may be adapted to provide hydraulic power transmission to an actuator mechanism. Alternatively, an electric power source (either motor or solenoid) may be adapted to traction a cable for power transmission to the actuator mechanism.

As noted above, one advantage of the present invention is that the modular power system may be replaced, either due to observed functional problems or on a routine schedule, via a limited operation accessing the driving mechanism near the body surface (i.e., within the abdominal wall) rather than through a major transthoracic operation to access the heart directly. The invention is an improvement relative to other heart wall actuators whose force delivery components cannot be replaced without replacing the entire system via a major cardiothoracic operation.

Although the figures and the accompanying text for purposes of clarity show only a single linearly configured power system and a single carrier device, the invention may include multiple actuator mechanisms either with their own carrier devices, or alternatively, with multiple actuator systems coupled with a common carrier device. Furthermore, one or more power systems and carrier devices may be associated only with a single actuator mechanism.