Patent Description:
With one third of all causes of death, cardiovascular diseases account for the most frequent cause of deaths worldwide. One of the most common cardiovascular diseases is heart failure, which affects at least <NUM> million people. In severe cases of heart failure where pharmacologic treatment is not effective, heart transplantation is the therapy of choice. However, donor organs are rare. Therefore, mechanical blood pumps like ventricular assist devices (VAD) or total artificial hearts (TAH) have been developed to bridge the time until a donor heart is available or to replace the heart completely. With the rise of small, implantable rotary blood pumps (RBPs) used as ventricular assist devices, the importance of larger pulsatile pumps in the treatment of end-staged heart failure declined. Available pulsatile systems are based on positive displacement pumps with valves, and require large pneumatic driving units, which limits the quality of life substantially.

In spite of the efficacy of RBPs, patients suffer from several adverse events related to the compromised hemocompatibility of these devices, leading to von Willebrand factor deficiency, platelet activation, hemolysis, and resulting in major bleedings, cerebral strokes, and pump thrombosis. Although the shear rate in contemporary clinical pulsatile devices is lower, the valve regions are susceptible to thrombosis due to the long residence times and disturbed flow patterns around the valve discs or leaflets.

Existing mechanical circulatory support (MCS) devices ensure survival and improve the quality of life of most recipients, however, current RBPs are associated with serious adverse events (thromboembolic and bleeding complications) caused by their poor hemocompatibility. Pulsatile devices have the potential to reduce trauma to the blood cells. However, the risk of thrombosis, caused by the interaction between blood and artificial materials comprising the device, remains.

<CIT> discloses a pump and method for moving a fluid, as blood, having a body and end members forming a cylindrical chamber. A free floating piston located in the chamber is moved along the length of the chamber with a solenoid to pump blood into and out of opposite ends of the chamber. The end members containing inlet and outlet valves and sleeves are adapted to attach to veins or tubes to carry the blood to and from the pump. When electrical power is applied to the solenoid, a magnetic force operates to move the piston in the chamber, thereby pumping blood into and out of the chamber through the valves in the opposite end members.

<CIT>, discloses a hollow and firm cylindrical member of non-magnetic material has an inlet port and an outlet port at each end. A check valve is associated with each of the ports, so that blood may be both admitted and expelled from each end of the cylinder. A ball which is responsive to a magnetic field rolls or floats within the cylinder. A magnetic field, typically obtained from passing current through an electrical coil, is alternately established at one end of the cylinder and then the other end.

Recent observations highlight the medical need for hemocompatible blood pumps used as ventricular assist devices and total artificial hearts: Critical complications taint the long-term performance of all implantable rotary blood pumps. Serious adverse events are stirred by the non-physiological flow patterns and the interaction between pump and the cardiovascular system. Only <NUM>% of these patients are free from severe adverse events including right heart failure, bleeding or strokes after <NUM> months. Life quality is therefore strongly impaired and new developments are urgently needed. A small, implantable hemocompatible TAH with a low risk of complications constitutes the urgently needed treatment for adult patients with biventricular failure and children with congenital heart (e.g. Fontan patients).

It is thus an object of the present invention to overcome or reduce at least some of the drawbacks of the prior art and to develop a new pumping concept delivering pulsatile flow to the cardiovascular system.

Embodiments of the present disclosure seek to solve at least one of the problems existing in the prior art to at least some extent. In particular, the present disclosure refers to a blood pump as defined in claim <NUM> comprising:.

Features of the inventive concept and methods of accomplishing the same may be understood more readily by reference to the following detailed description of an embodiment and the accompanying drawings. The present invention, however, may be embodied in various different forms, and should not be construed as being limited to only the illustrated embodiments herein. Rather, this embodiment is provided as example so that this disclosure will be thorough and complete, and will fully convey the aspects and features of the present invention to those skilled in the art. Accordingly, processes, elements, and techniques that are not necessary to those having ordinary skill in the art for a complete understanding of the aspects and features of the present invention may not be described. Unless otherwise noted, like reference numerals denote like elements throughout the attached drawings and the written description, and thus, descriptions thereof will not be repeated.

The present disclosure generally refers to a blood pump comprising:.

The new pumping concept delivers pulsatile flow to the cardiovascular system with a single moving part, without risk prone valves and the potential for an outstanding hemocompatibility. The size of the design theoretically facilitates implantation in pediatric and adult patients.

According to the present disclosure, the blood pump includes a first motor unit which is configured to generate an electromagnetically driven translational motion of the movable piston and at least one another second motor unit configured to generate an electromagnetically driven rotary motion of the movable piston around the longitudinal axis of the cylindrical piston chamber. The linear and rotational motions must be performed together only in so far as they lead to the two mentioned end positions of the piston. In other words, during the translational motion or movement of the piston from one end position towards the other end position, the rotational motion or movement can be uniform or over time at different speeds. The rotary motion is a continuously rotary motion. The same applies with respect to the translational motion.

Through the superposition of the two movement sequences the present blood pump combines the advantages of both pulsatile and rotary blood pumps of the state of art. In particular, the size of the blood pump may be comparable to other TAHs under development based on rotary principles. The single moving part, i.e. the piston, enhances reliability of a pulsatile valveless pump to levels of rotary blood pumps. The blood pump may prove superior to common pulsatile devices in terms of reliability and risk of thrombosis due to the valveless design. At the same time, the pulsatile pumping principle with much lower velocities and shear rates than in RBPs may demote adverse events related to the working principle of modern RBPs. The size of the pump for the adult population may be approx. <NUM> x <NUM>, which is much smaller than comparable systems. Additionally, the design can be downscaled for the use in pediatric patients.

According to one embodiment, the linear motor unit is construed as a multi-phase (for example <NUM>- or <NUM>-phase) linear induction motor (LIM) including an axially polarized ring-shaped permanent magnet array positioned within the piston and segmented windings wired around the cylindrical piston chamber. Generally, a linear electric motor's primary typically consists of a flat magnetic core with transverse slots that are often straight cut with coils laid into the slots, with each phase giving an alternating polarity so that the different phases physically overlap. The secondary is frequently a sheet of aluminium, often with an iron backing plate. Some LIMs are double sided with one primary on each side of the secondary, and, in this case, no iron backing is needed. However, according to the present embodiment, a regulated electromagnet serves as stator (i.e. represents the primary) whereas the secondary includes a permanent magnet positioned in the moveable piston. Thus, the electric motor is a brushless motor and any wear as well as spark formation could be avoided.

In addition to the use of the before mentioned multi-phase linear induction motor or separately thereof, the rotary motor unit may be construed as a multi-phase (for example <NUM>- or <NUM>-phase) rotational induction motor including a radially polarized permanent magnet array positioned within the piston and segmented windings wrapped along an axial side and circumference the cylindrical piston chamber. The segmented winding may include soft magnetic back yokes and multi (for example <NUM> or <NUM>) phases of wired coils wrapped along an axial side and circumference the cylindrical piston chamber. The radially polarized permanent magnet array may be positioned closed to each base surfaces of the piston facing the left chamber and the right chamber. Thus, the stator of rotary motor unit is represented by the wrapped coil arrangement and the part in motion includes a permanent magnet. Once again, such an arrangement allows a brushless implementation of the rotary motor unit.

According to another embodiment, the inlet and outlet of the left chamber are positioned on opposite sides of the cylindrical piston chamber, respectively the inlet and outlet of the right chamber are positioned on opposite sides of the cylindrical piston chamber.

Further, a piston length may be in the range of <NUM> to <NUM> and a piston radius may be in the range of <NUM> to <NUM>. Separately or in addition thereof, a volume of the left or right chamber may be in the range of <NUM> to <NUM>. If the before-mentioned dimensions are maintained, the blood pump may be used as a full implant.

Another embodiment provides that a motion frequency of the translational motion of the piston is in the range of <NUM> to <NUM>. This ensures the generation of sufficient hydrodynamic forces to bear the piston within the cylindric housing.

The piston may be further construed such that in the first end position a lateral surface of the piston closes the inlet of the left chamber and the outlet of the right chamber, whereas the outlet of the left chamber and the inlet of the right chamber are open, and whereby the closing situation of the inlets and outlets is exactly reversed in the second end position. In other words, inlets and outlets of each chamber are alternately closed and opened, i.e. if the inlet of a certain chamber is open its outlet will be closed. In addition, if an inlet of one of the chambers is open, the inlet of the other chamber is closed.

In particular, the piston has a left base surface facing the left chamber and a right base surface facing the right chamber. According to an embodiment, a curved part of the left base surface is inwardly curved such that (i) in the first end position of the piston the outlet of the left chamber is open while the inlet of the left chamber is closed and (ii) in the second end position of the piston the inlet of the left chamber is open while the outlet of the left chamber is closed. In addition, a part of the right base surface is inwardly curved such that (i) in the first end position of the piston the inlet of the right chamber is open while the outlet of the right chamber is closed and (ii) in the second end position of the piston the outlet of the right chamber is open while the inlet of the right chamber is closed. In other words, the base surfaces on the left and right side of the piston do not extend perpendicular to the longitudinal axis of the piston. Said base surfaces are also not planar, but have a surface contour, which includes an inwardly (i.e. towards the piston) curved area. This allows pressure peaks to be avoided during pumping.

The surface contour of the left base surface and the surface contour of the right base surface may be point symmetrical to each other. In this way, the manufacturing process can be simplified.

According to another embodiment, a shunt is connected between at least one of the left and right chambers or the inlets of the left and right chambers. The shunt is configured to allow pressure balancing between both chambers. For example, the shunt may be realised by a groove within the pump housing extending between the two chambers, respectively ending into the left and the right inlet.

In alternative or additional the rotary motion of the piston around the longitudinal axis during the translational motion of the piston chamber between the first end position and the second end position is a non-synchronous or a non-uniform rotary motion. In other words, at least one of these two motions indicate a discontinuous behaviour. Thereby, an accurate balancing of the output of the left and right chamber is possible. In other words, by adapting the rotating speed the pump efficiency of each chamber can be adapted, thereby adapting the amount of discharged blood. This measure may for example prevent pulmonary congestion or so-called suction events.

According to another embodiment of the present disclosure, a hydrodynamic bearing may be provided between the outer surface of the piston and the inner surface of the piston chamber of the pump housing. This bearing ensures a smooth piston motion without the risk for dry friction and material wear. Specifically, the hydrodynamic bearing may have a gap clearance of less than <NUM>. In that case only a small amount of blood components may enter such small hydrodynamic bearings, consequently leading to low blood trauma in these regions.

<FIG> illustrate cross sectional views on an exemplary embodiment of the blood pump <NUM>. The blood pump <NUM> includes a pump housing <NUM> with a cylindrical piston chamber <NUM>. An axially and rotatably slidable free floating piston <NUM> centrally positioned within the cylindrical piston chamber <NUM> thereby dividing the cylindrical piston chamber <NUM> into a left chamber <NUM> and a right chamber <NUM>. The left chamber <NUM> and right chamber <NUM> each include an inlet <NUM>, <NUM> and outlet <NUM>, <NUM> transversely arranged to and communicating with the left chamber <NUM>, respectively right chamber <NUM>.

A linear motor unit <NUM> is configured to generate an electromagnetically driven translational (or translatory) motion of the piston <NUM> along the longitudinal axis of the piston chamber <NUM> alternately between a first end position shown in <FIG> and a second end position shown in <FIG>. Here, the linear motor unit <NUM> is construed as a <NUM>-phase linear induction motor including an axially polarized ring-shaped permanent magnet array <NUM> positioned within the piston <NUM> and segmented windings <NUM> wired around the cylindrical piston chamber <NUM>.

A rotary motor unit is configured to generate an electromagnetically driven partially rotary motion of the piston <NUM> around the longitudinal axis during the translational motion within the piston <NUM> between the first end position and the second end position. For sake of clarity, <FIG> do not illustrate details thereof, but the rotary motor unit will be described in detail below. For the understanding of the pumping mechanism in <FIG> it is only important that the rotary motor unit allows to make the piston a <NUM>° turn during movement from the first end position into the second end position, respectively a <NUM>° turn back from the second end position into the first end position.

The two inlets <NUM>, <NUM> of the pump <NUM> are connected to the left and right atria, respectively. The outlets <NUM>, <NUM> are anastomosed to the pulmonary artery and the aorta. The piston <NUM> is electromagnetically driven in a shuttling translationally and in a uniform rotatory motion inside a cylindrical piston chamber <NUM>. Thereby the piston <NUM> divides the pump housing <NUM> into left and right chambers <NUM>, <NUM>, with one inlet <NUM>, <NUM> and outlet <NUM>, <NUM> each. The translational motion from the first end position illustrated in <FIG> towards the second end position illustrated in <FIG> causes a filling of one chamber, here the right chamber <NUM> while the other chamber - here the left chamber <NUM> - is emptied simultaneously. Through the rotation, the opening of the inlet <NUM>, <NUM> and outlet <NUM>, <NUM> of both chambers <NUM>, <NUM> are controlled, so mechanical check valves are obsolete. With this combination of rotation and translation, the entire pump function of both the right and the left heart is accomplished by only one moving part.

In <FIG> the pumping and actuation principle is depicted by arrows. The filling of the right chamber <NUM> is accompanied with simultaneously discharging of the left chamber <NUM>. The translational movement is achieved by energizing wired coil of the windings <NUM> causing a Lorentz force FL on the piston <NUM>. The translational movement is superimposed by a rotational <NUM>° movement of the piston <NUM>. The inlet <NUM> of the right chamber <NUM> and the outlet <NUM> of the left chamber <NUM> is closed in the second end position of the piston <NUM> without the need of valves. When the current in the wired coils is inverted, the piston <NUM> is forced backwards to the first end position discharging the right chamber <NUM> while filing the left chamber <NUM>. The dashed lines indicate the magnetic flux path of the permanent magnet array <NUM>.

The motion frequency of the piston <NUM> may be in the range of <NUM> to <NUM> to support a patient at rest, causing relatively low velocities compared to state-of-the-art rotary blood pumps and potentially resulting in significantly lower blood trauma. A superior washout potential is expected because of marginal stagnation areas within the pump <NUM> and a low priming volume. The simple geometry permits the use of ultrahigh precision leading to smooth surfaces in blood contact, mitigating the risk for thrombus formation.

The outer surface of the piston <NUM> and the inner surface of the piston chamber <NUM> of the pump housing <NUM> may be manufactured with ultrahigh precision because of their simple rotational symmetry. A hydrodynamic bearing may be provided between the outer surface of the piston <NUM> and the inner surface of the piston chamber <NUM> of the pump housing <NUM> (not shown). The hydrodynamic bearing may have a gap clearance of less than <NUM>. This bearing ensures a smooth piston motion without the risk for dry friction and material wear. Recent findings suggest that only a small amount of blood components may enter such small hydrodynamic bearings, consequently leading to low blood trauma in these regions.

The electromagnetic motor composed of the linear motor unit <NUM> and at least one rotary motor unit actuates the piston <NUM> in an efficient way compared to other pulsatile blood pumps: For the translational motion, two wired coils around the middle part of the pump <NUM> housing are energized in opposite current directions for an optimal force generation. The rotary motion will be achieved by one or two radial flux motors.

In <FIG> the actuation system is depicted in more detail. Besides the centrally positioned linear motor unit <NUM> two rotary motor units <NUM>, <NUM> are arranged left and right thereof. Each rotary motor unit <NUM>, <NUM> unit is construed as a multi-phase rotational induction motor including a radially polarized permanent magnet array <NUM>, <NUM> positioned within the piston <NUM> and segmented windings <NUM>, <NUM> including soft magnetic back yokes and multi phases of wired coils wrapped along an axial side and circumference the cylindrical piston chamber <NUM>. Here, the rotary motor units <NUM>, <NUM> are realized as <NUM>-phase unipolar permanent magnet type stepper motors. A magnetic flux path of the rotary motor unit <NUM> is illustrated by the dashed line in <FIG> resulting in a torque moment that causes the rotation of the piston <NUM>.

<FIG> are cross sectional views of the piston chamber <NUM> and the piston <NUM> according to the exemplary embodiment. The two inlets <NUM>, <NUM> may have a diameter in the range of <NUM> to <NUM> and are connected to the left and right atria for example via conically shaped textile materials, respectively. The outlets <NUM>, <NUM> may have a similar diameter of <NUM> to <NUM> and may be connected to graft materials and anastomosed to the pulmonary artery and the aorta. As already mentioned above, the piston <NUM> is electromagnetically driven in a shuttling translationally and in a uniform rotatory motion inside the cylindrical piston chamber <NUM>. As illustrated in <FIG>, the translational motion from the left chamber <NUM> in direction to the right chamber <NUM> pumps blood and fills through the outlet <NUM> into the aorta. Simultaneously, the right chamber <NUM> is filled through the inlet <NUM>. The left inlet <NUM> and the right outlet <NUM> are closed by the piston <NUM>. As shown in <FIG>, the rotation of the piston <NUM> opens the inlet <NUM> of the left chamber <NUM> and closes the inlet <NUM> of the right chamber <NUM>. The translational movement from the right to the left discharges the right chamber <NUM> and fills the left chamber <NUM>. Only exemplary: for an adult population pump a total length L<NUM> may be <NUM>, a length L<NUM> of the piston 20may be <NUM>, and a diameter D of the piston chamber <NUM> may be <NUM>.

Furthermore, the piston <NUM> has a left base surface <NUM> facing the left chamber <NUM> and a right base surface <NUM> facing the right chamber <NUM>. A curved part <NUM> (or notch) of the left base surface <NUM> is inwardly curved such that (i) in the end position of the piston <NUM> illustrated in <FIG> the inlet <NUM> of the left chamber <NUM> is open while the outlet <NUM> of the left chamber <NUM> is closed and (ii) in the end position of the piston <NUM> illustrated in <FIG> the inlet <NUM> of the left chamber <NUM> is open while the outlet <NUM> of the left chamber <NUM> is closed. In addition, a curved part <NUM> (or notch) of the right base surface <NUM> is inwardly curved such that (i) in the first end position of the piston <NUM> the inlet <NUM> of the right chamber <NUM> is open while the outlet <NUM> of the right chamber <NUM> is closed and (ii) in the second end position of the piston <NUM> the outlet <NUM> of the right chamber <NUM> is open while the inlet <NUM> of the right chamber <NUM> is closed. In other words, the base surfaces <NUM>, <NUM> on the left and right side of the piston <NUM> do not extend perpendicular to the longitudinal axis of the piston <NUM>. Said base surfaces <NUM>, <NUM> are also not planar, but have a surface contour, which includes an inwardly (i.e. towards the piston <NUM>) curved area. This allows pressure peaks to be avoided during pumping, so that the hemocompatibility is improved.

According to the exemplary embodiment, the motion frequency of the piston <NUM> may be in the range of <NUM> to <NUM>. The course of resulting flow and pressure in the left chamber <NUM> is shown in in <FIG>. The simple geometry of the blood piston <NUM> and piston chamber <NUM> permits the use of ultrahigh precision leading to smooth surfaces in blood contact, mitigating the risk for thrombus formation. Each stroke pumps and fills the chambers <NUM>, <NUM> with a volume of <NUM> to <NUM>.

Only exemplary, the height H of the curved parts <NUM>, <NUM> may be <NUM> and the depth D of the curved parts <NUM>, <NUM> may be <NUM>. As could be further seen from <FIG>, the surface contour of the left base surface <NUM> and the surface contour of the right base surface <NUM> are point symmetrical to each other. In this way, the manufacturing process can be simplified and the pump volumes of the two chambers <NUM>, <NUM> are essentially equal. This way, also optimal operation with a minimum risk for blood trauma may be ensured.

The outer surface of the piston <NUM> (or piston shell area) and the inner surface of the piston chamber <NUM> (or inner shell area) of the pump housing can be manufactured with ultrahigh precision because of their simple rotational symmetry. Therefore, a hydrodynamic bearing with a gap clearance in the range of <NUM> to <NUM> can be realized. This bearing bears forces of ><NUM> N and ensures a smooth piston motion at a maximum eccentricity of <<NUM>% without the risk for dry friction and material wear. An example for the load capacity of such a bearing at a gap of <NUM> is presented in <FIG> showing the theoretical load capacity of the blood pump in dependency of the eccentricity at a rotating frequency of <NUM>.

The shuttling motion combined with the pressure differences between the left and right chamber <NUM>, <NUM> may lead to an additional bearing stabilization due to the Lomakin effect. A certain gap clearance is required to permit enough gap flow which is necessary to cool the bearing region (heat due to motor coils) and to comply with the requirement of a maximal local temperature increase of <NUM>°K. Additionally, due to the small gap only a small amount of blood components may enter such hydrodynamic bearing gaps, consequently leading to low blood trauma in these regions.

<FIG> illustrate another exemplary embodiment of the blood pump <NUM>. The electromagnetic motor system actuates the simultaneous translational and rotary piston motion. In the embodiment illustrated in the drawings, the translational motion is achieved by a linear motor unit <NUM>. The linear motor unit <NUM> includes an axially polarized ring-shaped permanent magnet array <NUM> creating a magnetic field and composed of a permanent magnet <NUM> and soft magnetic material rings <NUM>. The permanent magnet array <NUM> is positioned within the piston <NUM>. Further, segmented windings <NUM> wired around the cylindrical piston chamber <NUM> and including a back yoke <NUM> and segmented copper coils <NUM>. During operation, the soft magnetic material rings <NUM> lead the magnetic flux through the segmented copper coils <NUM> wired around the middle part of the piston chamber <NUM>. A position dependent energization of the coil segments <NUM> creates a Lorentz force in axial direction.

Claim 1:
A blood pump (<NUM>) comprising:
- a pump housing (<NUM>) with a cylindrical piston chamber (<NUM>);
- an axially and rotatably slidable free floating piston (<NUM>) centrally positioned within the cylindrical piston chamber (<NUM>) thereby dividing the cylindrical piston chamber (<NUM>) into a left chamber (<NUM>) and a right chamber (<NUM>), wherein the left chamber (<NUM>) and right chamber (<NUM>) each include an inlet (<NUM>, <NUM>) and outlet (<NUM>, <NUM>) transversely arranged to and communicating with the left chamber (<NUM>), respectively right chamber (<NUM>);
- a linear motor unit (<NUM>) configured to generate an electromagnetically driven translational motion of the piston (<NUM>) along the longitudinal axis of the piston chamber (<NUM>) alternately between a first end position and a second end position; and
- at least one rotary motor unit (<NUM>, <NUM>) configured to generate an electromagnetically driven continuous rotary motion of the piston (<NUM>) around the longitudinal axis during the translational motion of the piston (<NUM>) between the first end position and the second end position.