Pump for an Artificial Heart

The invention relates to a pump for an artificial heart, more specifically, to a device which is insertable into the blood circulatory system of a living being as an aid or substitute for a natural heart. Such devices are described, for example, in "Advances in Biomedical Engineering and Medical Physics" Volume 3, Cardiac Engineering, published by Interscience Publishers, a division of John Wiley & Sons, Inc.

Cardiac surgeons have set forth requirements for an artificial heart pump that have not been met in their entirety by the pumps presently known for this purpose. Essentially, these requirements call for a flat, rounded-off shape for a pump which is flexible throughout the largest possible area of its outer covering, and the connection conduits of which are attached in a releasable and/or swivelable manner, to the pump housing.

Furthermore, the pump shall operate smoothly, that is free of irregular shocks and it shall run as vibration-free as possible. For this purpose, gravity forces must be compensated.

The foregoing requirements pertain mainly to the application and body compatibility of the pump as such. As mentioned, these requirements have not been satisfied heretofore. However, other requirements, not relating directly to the invention, for example, requirements relating to the drive and to the pump control or to artificial heart valves to be inserted in the blood stream, have been met heretofore by a number of well known proposals.

In view of the foregoing, it is the aim of the invention to achieve the following objects, singly or in combination:

To provide an artificial heart pump with a flat, rounded-off configuration which is flexible to as large an extent as possible within its outer covering and which has good body compatibility;

To reduce irregular pressure changes or pressure shocks resulting from a pulsating pump output;

To provide a pump action that operates substantially without vibrations and to compensate gravity forces;

To provide a pump which can be easily handled during the implantation, placement, and for which the necessary connections may be easily made;

To provide a pump which may be driven by either gaseous or liquid pressure media;

to provide a pump having a drive system wherein sealing problems are minimized;

to provide a pump that is as suitable for a permanent implantation as an artificial heart as it is for a time limited use, for example, in a cardiac by-pass operation;

to provide an artificial heart pump having pressure and current flow characteristics during any work cycle which correspond substantially to those of a natural heart; and

to provide a pump may be adjusted to different form and dimension requirements with low alteration expenditures.

According to the invention, there is provided a pump for an artificial heart having a pump housing with a shape corresponding substantially to that of a rotational ellipsoid. The housing includes central, polar regions and an equatorial region where connectors or ports for inlet and outlet conduits are tangentially mounted. The pump housing is made of rigid material in the central, polar regions and of flexible material in the equatorial region. A connector terminal, which is able to rotate at least through 90.degree. is secured to the central region, for the connection of control and/or power supply conduits. Due to this flat, flexible shape it is easy to handle the pump during implantation and placement, and the required connections are also easily made. This flat shape also results in a good body compatibility of the pump.

Further embodiments of the invention compensate for inertia forces of moving bodies and fluids and assure the steady pulsating delivery of blood free of shocks. According to these further embodiments, a flat, torus shaped bellows made of elastic material is located between two oppositely driven pressures plates and encloses the pump volume. Inlet and outlet ports are formed as part of the bellows and extend in a tangential direction relative to the bellows. These ports penetrate or extend through the pump housing in its elastic region and are tightly sealed to the housing at the point of penetration. The pressure plates are spring loaded for the reduction of impact or shock forces by providing the pressure plates with radially extending and/or tangentially directed leaf springs which extend from the pressure plates in spaced apart fashion, for example, as fingers would from a hand. Especially where a relatively thin walled torus shaped bellows is used these springs may be bent to encircle the bellows whereby the springs of one pressure plate reach into the spaces between the "fingers" or springs of the other pressure plate and vice versa when the bellows is compressed.

According to a further feature of the invention, a rotatable connector terminal comprises a pipe or hose connection for a pressure medium conduit which supplies the drive power to the pump. The pressure medium is effective in interconnected sealed-off pressure chambers to move elastic membranes secured to rigid pressure plate drive members in opposite directions. The drive members are biased by a restoring spring force which returns the pressure plates into their starting positions. The pressure medium used may be a gas or liquid, preferably of a kind that is body compatible.

The control, for example, a closed loop control, for a drive means which itself is not part of the invention may comprise an electromechanical displacement transducer located inside the space surrounded by the torus shaped bellows. The signal conductors of the transducer lead to a connector plug on the rotatable connector terminal. In this way, through little expense, it is possible to obtain very accurate, proportional signals corresponding to the delivery or conveying efficiency of the pump, under all operating conditions. These signals may be transmitted to a suitable control arrangement for the drive means of the pump.

In order that the invention may be clearly understood, it will now be described, by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 is a sectional view of a pump according to the invention, for an artificial heart, wherein the section extends along line II--II in FIG. 2;

FIG. 2 is a top plan view of the pump of FIG. 1;

FIG. 3 is a side view, partially in section, of a further embodiment according to the invention, of a pump for an artificial heart;

FIG. 4 is a top plan view of the pump in FIG. 3; and

FIG. 5 is a top plan view of one type of a pressure plate with tangentially extending leaf spring means.

According to the invention, the pump 1 for an artificial heart as shown in FIGS. 1 and 2, includes a pump housing 2 comprising centrally located polar regions 3 and a peripheral, equatorial region 4. The central, polar regions are made of rigid material, for example, a body compatible metal or of synthetic material. The equatorial region 4 of said pump housing 2 is made of flexible material, e.g., synthetic material. Certain internal elements, for example 11, respectively 12, 13, of the pump, are also made of flexible material, e.g. synthetic material respectively; spring steel, as will be described below. The pump housing 2 also includes two elastically deformable inlet and outlet port means 5 and 6, mounted to the housing 2 to extend in tangential directions relative to the equatorial region 4, as shown in FIG. 2. Said port means 5 and 6 are adapted for connection to known valves such as artificial heart valves, located in respective conduits, not shown. The central region 3 of said pump housing 2 is provided with a connector means or terminal plate 7 rotatably secured to the housing means in at least one polar region. A coupling plug 8, for example, for control means, is part of the connector means. Said connector terminal plate 7 also includes a releasable coupling 9 for a power supply conduit which, for the pump of FIG. 1, is a pressure medium conveying conduit, not shown. The terminal plate is rotatable at least through 90.degree..

A flat, torus shaped bellows 11 confines a pump volume 10. The bellows is made of elastic material and positioned between two oppositely driven pressure plates 12 and 13, as shown in FIG. 1. The pressure plates are secured to dished power application members 23' and 24' having central cylinder chambers 23 and 24 as will be described in more detail below.

Two inlet and outlet pipe or hose conectors, of which only the connector 14 is shown in FIG. 1, are formed to extend in a tangential direction out of the bellows 11. Said connectors penetrate the pump housing 2 in the elastic, equatorial region 4 and are tightly attached to the housing 2 at the point of penetration by an adhesive bond or, as shown, by means of a fastening screw 16 and a retaining nut 17. The pressure plates 12 and 13 are constructed to have a built-in spring action. For example, the pressure plates may be made of elastically deformable material providing a spring loading by radially or tangentially extending fingers as shown in FIGS. 3 and 5.

The present pump is easily implanted into and placed in the body of a living being, due to the flexibility of the entire pump in its equatorial region, and due to its flat configuration as well as due to the rotatability of the connector terminal 7. Further, the connection to a power supply also contributes to a relatively easy implantation and placement.

By using a relatively thin walled, torus shaped bellows 11, which requires only a small amount of work or energy for its deformation, it is possible to construct the pressure plates 12 and 13 so that they provide a spring action, for example by means of elastic fingers, which encircle the bellows 11 in the equatorial region, whereby the fingers, such as shown at 40, 41 in FIG. 3, of one plate reach into spaces between the fingers in the other plate and vice versa, when the bellows 11 is compressed.

According to FIG. 1, the rotatable connector terminal 7 comprises a releasable coupling or connector 9, for a conduit conveying a pressure medium, as for example, a gas or liquid of a body compatible type, to drive the pressure plates 12 and 13 in opposite directions. The pressure medium acts in the pressure chambers 18 and 19, which are interconnected by pressure equalizing conduit means 20 and which are sealed by means of elastic membranes 21 and 22, respectively. The membranes 21 and 22 are stretched over the closed end of said cylinder chambers 23, 24 which are rigidly connected to the respective pressure plates 12, 13 by the members 23' and 24' respectively whereby the elastic pressure plates 12 and 13 are moved toward each other and against the force of a restoring spring 25 mounted in said cylinder chambers 23, 24 as shown in FIG. 1. Thus, a pump operation substantially free of vibrations is achieved and irregular pressure changes or shocks are suppressed while the pump delivers a smoothly pulsating pump action.

For an exact control of the pump and for an adaptation to varying pump power output requirements, and electromechanical displacement transducer 26 of known construction, for example an inductive displacement transducer 26, is located in the space 27 surrounded by said torus shaped bellows 11, as shown in FIG. 1. The signal conductors of the transducer 26 are connected to a connector plug 8 arranged on said connector terminal plate 7. The control means are not illustrated, since they are not part of the invention.

FIGS. 3 and 4 show as another embodiment a pump 30 for an artificial heart. The pump 30 is especially suitable to be driven by a pressure gas. The pump 1 of FIGS. 1 and 2 may be driven by liquid pressure, as well as by gaseous pressure media. However, the basic structure is the same in both embodiments. Hence, the above description also applies generally to FIGS. 3 and 4.

The pump housing 32 of the pump 30 comprises a surface 31 in its elastic equatorial region 34. The surface 31 has a callote or a hemispherical shape corresponding to the curvature of a diaphragm. Preferably, the opposite surface 31' also has an appropriate convex curvature whereby the pump achieves a good fit relative to the given form of an organism.

There is substantial conformity in the construction and configuration of the polar regions 3 in FIGS. 1 and 2 and 33 in FIGS. 3 and 4, whereby the pump 1 or 30 may be easily adapted to different shape and dimensional requirements at relatively low alteration costs.

According to FIG. 3, when a pressure gas is the driving means, it is possible to admit pressure to an area 35 lying between the torus shaped bellows 37 and the elastic part of the pump housing 32 through the pressure equalizing conduits 36. This air cushion protects the surrounding organs and the pump itself from severe loads due to movements of the user. Good sealing means are needed in the embodiment of FIGS. 1 and 2 while only relatively simple sealing means are needed in the embodiment of FIGS. 3 and 4. To increase the elasticity of the pump and to reduce the masses of moving weights, the torus shaped bellows 37 of the pump 30 is constructed with relatively thin walls. Referring to FIG. 3, the torus shaped bellows 37 is encircled by the elongated finger like leaf springs 40 and 41 forming part of the pressure plates 38 and 39, in the equatorial region. The springs 40 and 41 are so spaced that the springs of one pressure plate fit into the spaces between the springs of the other pressure plate. The pressure plates 13 and 12 of FIG. 1 may be similarly constructed, if desired. FIG. 5 shows a modification of a pressure plate 50 with spring fingers 51 extending substantially tangentially whereby the outer free ends 52 of the spring fingers 51 are shaped to conform to the shape of the bellows 37. The FIG. 3 embodiment also has a restoring spring 25 and transducer 26. Both configurations of the pump 1 or 30 are suitable for permanent insertion as an artificial heart as well as for time limited insertion required in a by-pass operation. The diagrams for the pressure and current flows correspond very well to the respective diagrams of a natural heart.

Although the invention has been described with reference to specific example embodiments, it is to be understood that it is intended to cover all modifications and equivalents within the scope of the appended claims.