External drive unit for an implantable cardiac assist pump

Abstract

The present application relates to an external drive unit (7) for an implantable heart assist pump (4). The proposed drive unit (7) includes a motor housing (51), a percutaneous drive shaft (3), and a motor (35) for driving the heart assist pump (4). The motor (35) is connected to the heart assist pump (4) via the drive shaft (3), and the motor (35) is arranged within the motor housing (51). The drive unit (7) further includes a catheter (2) surrounding the drive shaft (3) and a purge tube (53) for injecting a purge medium into the lumen of the catheter (2) or into the gap (41) between the catheter (2) and the drive shaft (3). The purge tube (53) is in thermal contact (54, 55) with the outer surface of the motor housing (51) and / or with the outer surface of the proximal portion (52) of the catheter (2). Due to the thermal contact (54, 55), heat can be transferred from the outer surface of the proximal portion (52) of the catheter (2) and / or from the outer surface of the motor housing (51) to the purge medium.

Description

[0001] This application is a divisional application of the application with application number 201880023816.2 and invention title "External drive unit for an implantable heart assist pump" filed on April 6, 2018. Technical Field

[0002] This application relates to the field of medical technology. This application relates to an external drive unit for an implantable heart assist pump and a heart assist device including the drive unit and the implantable heart assist pump. This application relates to the assignee's U.S. Patent Application No. 15 / 482,513, filed on April 7, 2017, with the invention title "Method and System for an External Drive Unit for an Implantable Heart Assist Pump", which is incorporated herein by reference. Background Art

[0003] A heart assist device for assisting a patient's heart function is known from the prior art. The device may include an implantable blood pump that can be inserted into a heart ventricle by minimally invasive means. Further, an external (or extracorporeal) motor may be provided to drive the blood pump. The motor is connected to the blood pump by a percutaneous flexible drive shaft; the drive shaft is rotatably mounted within a percutaneous catheter. The implantable fittings of the device can be inserted into the patient's groin via a puncture site. Related devices are described, for example, in US8,489,190B2.

[0004] For such a heart assist device, problems related to heat dissipation of the external motor may occur. In some applications, when operating the blood pump, the motor may be positioned close to the patient's body, especially close to the patient's leg. If the heat generated by the motor is not effectively removed, the motor may overheat, which can cause motor failure. In addition, when the hot housing of the motor contacts the patient's skin, the overheating of the motor may pose a health risk to the patient, especially when the patient, for example, due to anesthetic, cannot notice the heat and react appropriately. For example, the safe heat absorption of human skin has been studied in the context of heat generated by ultrasonic and magnetic resonance imaging probes. For example, in "Human Skin Temperature Response to Absorbed Thermal Power" (SPIE Proceedings – The International Society for Optical Engineering 3037:129 - 134, March 1997), a method for determining the safe heat absorption level is described.

[0005] To prevent the motor of a cardiac assist device from overheating, the housing of such a motor may be provided with a plurality of heat sinks so that heat can be effectively discharged from the motor and dissipated into the surrounding air. However, if the motor is operated in an enclosed environment, such as under a blanket when the patient is resting or under a surgical drape during surgery, the amount of heat that can be transferred to the air may be insufficient. In addition, the surface of the housing with heat sinks may be difficult to clean. Summary of the Invention

[0006] In view of the above prior art, an object of the present application is to provide an improved external drive unit for an implantable cardiac assist pump and an improved cardiac assist device. In particular, an object of the present application is to provide a drive unit and a cardiac assist device with improved thermal management. Further, an object of the present application is to propose a drive unit that can operate a cardiac assist device safely and effectively.

[0007] These objects can be achieved by the technical features of the external drive unit in independent claim 1. The dependent claims, together with the description and the accompanying drawings, make optional further features and further improvements obvious.

[0008] The proposed external, i.e., extracorporeal, drive unit for an implantable cardiac assist pump includes a motor housing, a percutaneous drive shaft, and a motor for driving the cardiac assist pump. The motor is connected to the cardiac assist pump via the drive shaft and the motor is arranged within the motor housing. The drive unit further includes a catheter surrounding the drive shaft and a purge tube for injecting a purge medium into the lumen of the catheter or into the gap between the catheter and the drive shaft. The purge medium may be a solution, such as a glucose solution or a saline solution. The purge tube is in thermal contact with the outer surface of the motor housing and / or with the outer surface of the proximal portion of the catheter. Due to the thermal contact, heat can be transferred from the outer surface of the proximal portion of the catheter and / or from the outer surface of the motor housing to the purge medium.

[0009] The catheter generally includes a portion intended to be disposed within the patient's body and another portion intended to be disposed outside the patient's body. The proximal portion of the catheter is generally intended to be disposed outside the patient's body. Injecting the purge medium into the lumen of the catheter or into the gap between the catheter and the drive shaft prevents blood from penetrating into the catheter lumen or the gap and weakens the rotatability of the drive shaft.

[0010] In most embodiments, the purge tube is configured to direct a purge medium such that it first makes thermal contact with the outer surface of the motor housing and / or with the outer surface of the proximal portion of the catheter, and subsequently the purge medium is injected into the catheter lumen or into the gap between the catheter and the drive shaft. As described below, prior to the purge medium being injected into the catheter lumen or into the gap between the catheter and the drive shaft and after it has made thermal contact with the outer surface of the motor housing and / or with the outer surface of the proximal portion of the catheter, the purge medium may additionally be injected into the fluid gap between the stator and the rotor of the motor. The heart assist device and / or the drive unit may include a fluid transporter, e.g., a pump configured to flow the purge medium in any of the ways described above and / or below.

[0011] During operation of a heart assist device including a drive unit, the motor may become hot due to heat dissipation. Further, in some embodiments, the proximal portion of the catheter that may be disposed in proximity to the motor may also become hot during operation. Specifically, during operation, heat may be transferred from the motor to the proximal portion of the catheter and to the portion adjacent to the proximal portion of the catheter that may not be covered by the housing and may be in contact with the patient's skin. Due to the thermal contact of the purge tube with the outer surface of the motor and / or with the outer surface of the proximal portion of the catheter, heat may be transferred from the motor, and / or the proximal portion of the catheter to the purge medium within the purge tube. Thus, the motor, and / or the proximal portion of the catheter may be cooled, thereby reducing the risk of overheating of the drive unit. In particular, when the drive unit is disposed under a blanket (where it may not be adequately cooled by the surrounding air) and when the drive unit is in contact with the patient's body such that the risk of patient tissue burns is increased, the proposed drive unit improves the safety of operation of the heart assist device.

[0012] Compared with the prior art, the proposed drive unit does not require additional components because the purge tube serves two purposes simultaneously: First, the purge tube directs the purge medium into the patient's body to prevent blood from penetrating into the catheter lumen or into the gap between the catheter and the drive shaft. Second, the purge tube according to the present invention improves the thermal management of the drive unit. In addition, the purge medium may be preheated by making thermal contact with the motor and / or with the proximal portion of the catheter. Thus, the viscosity of the purge medium may be reduced, such that the rotatability of the drive shaft is improved. Since the purge medium first makes thermal contact with the outer surface of the motor housing and / or with the outer surface of the proximal portion of the catheter, and since the purge medium is subsequently injected into the catheter lumen or into the gap between the catheter and the drive shaft and ultimately into the patient's body, an improvement in the rotatability of the drive shaft can be achieved. Further, since the purge medium enters the patient's body only after making thermal contact with the motor housing or with the proximal portion of the catheter, the initial temperature of the purge medium during thermal contact may be relatively low, thereby enabling effective heat transfer away from the motor housing or the proximal portion of the catheter.

[0013] During operation of the heart assist device, the outer surface of the motor housing is typically hotter than the outer surface of the proximal portion of the catheter. In some embodiments, the purge tube is in thermal contact with both the outer surface of the motor housing and the outer surface of the proximal portion of the catheter. In these embodiments, cooling the drive unit and preheating the purge medium can be particularly effective. The purge tube can be configured to direct the purge medium to first be in thermal contact with the outer surface of the proximal portion of the catheter and subsequently with the outer surface of the motor housing to effect a gradual preheating of the purge medium and to enable effective cooling of the proximal portion of the catheter. As explained below, in some embodiments, the purge medium can be injected into the fluid gap of the motor. The purge medium can then be injected into the catheter lumen or into the gap between the catheter and the drive shaft.

[0014] The catheter can include one or more lumens. In some embodiments, the heart assist device can be configured such that the purge medium first flows distally through one lumen of the catheter into the patient and then out of the patient through another lumen of the catheter. In most embodiments, the catheter lumen or the gap between the catheter and the drive shaft extends into the proximal portion of the catheter. In particular, the lumen or gap can extend along the entire length of the proximal portion of the catheter and in some embodiments along the entire length of the catheter. In this embodiment, heat can be transferred to the proximal portion of the catheter or to the portion adjacent the proximal portion through the purge medium within the lumen or gap. Thus, cooling the proximal portion of the catheter by the purge tube can be highly advantageous in this embodiment.

[0015] In most embodiments, the purge tube is not formed as part of the catheter. In particular, in most embodiments, the purge tube is not formed by the lumen of the catheter. The purge tube can be a separate tube disposed outside the outer wall of the catheter.

[0016] The purge tube is generally entirely extracorporeal such that it does not include any implanted portion. The purge tube is generally arranged such that it is in fluid connection with the catheter lumen or gap. The drive unit generally includes a purge port in fluid connection with the gap or lumen. The purge tube can be attached to the purge port such that the purge tube is in fluid connection with the gap or lumen. Generally, during operation of the heart assist device, the purge medium flows distally within the gap or lumen.

[0017] The motor can be an electric motor. In some embodiments, the motor includes a stator and a rotor. The rotor can be connected to a drive shaft. The rotor typically includes magnets, especially permanent magnets. The stator includes a plurality of windings. The stator generally surrounds the rotor such that a magnetic gap is formed between the magnets of the rotor and the windings of the stator. The rotor is rotatably mounted. A fluid gap is formed between the rotor and the stator. The fluid gap can be in fluid communication with a purge port for injecting a purge medium into the fluid gap. A purge tube can be connected to or connectable to the purge port. The purge medium can be injected into the fluid gap and the inner cavity of the conduit or the void between the conduit and the drive shaft. The fluid gap of the motor is generally in fluid communication with the inner cavity of the conduit or the void between the conduit and the drive shaft. In a specific embodiment, the purge tube and the fluid gap are configured to direct the purge medium such that it first makes thermal contact with the outer surface of the motor housing and / or with the outer surface of the proximal portion of the conduit, and then is injected into the fluid gap between the rotor and the stator, and then is injected into the inner cavity of the conduit or the void between the conduit and the drive shaft.

[0018] When an unpurged motor is used, seals may be required to separate the gaps between the motor and the conduit and the drive shaft, thereby preventing air from entering the void and ultimately into the patient. The advantage of using a purged motor is that complex seals that generate friction and separate the gaps between the motor and the conduit and the drive shaft may not be required. Thus, the motor is easy to manufacture and frictional losses can be reduced, enabling the motor to operate in a more efficient manner. Further, since seals are generally prone to failure, the risk of failure of the heart assist device is reduced when no seals are provided.

[0019] When the motor is purged with a purge medium, the motor can be effectively cooled. Further, since the purge medium is preheated by making thermal contact with the proximal portion of the conduit and / or the motor housing, its viscosity is reduced when the purge medium enters the fluid gap of the motor. Thus, the drive unit reduces frictional losses in the fluid gap and / or the motor bearings and improves motor efficiency.

[0020] In some embodiments, the purge tube is configured to first direct the flow of the purge medium to an area in thermal contact with the outer surface of the proximal portion of the catheter, then to an area in thermal contact with the outer surface of the motor housing, then into the fluid gap between the rotor and the stator, and then into the catheter lumen or into the void between the catheter and the drive shaft and / or into the fluid gap of the motor (as described below). It has surprisingly been found that when using a drive unit according to this embodiment, the motor current required to pump a defined volume of blood using an implantable heart assist pump, i.e., the current applied to the stator windings, is independent of the flow rate of the purge medium. In contrast, in the absence of thermal contact between the purge tube and the outer surface of the motor housing and / or the outer surface of the proximal portion of the catheter, the motor current will increase with increasing purge flow rate, presumably because the purge medium in the fluid gap is colder due to the increased flow rate, which in turn leads to an increase in viscosity and thus an increase in the frictional losses of the motor. The preheating of the purge medium according to the invention then results in a constant motor current for different purge flow rates. Thus, since the undesired influence of the purge flow rate on the motor current does not have to be taken into account, the motor current can advantageously be used as a control parameter for the heart assist device. Thus, the electronic control of the heart assist device can be significantly simplified.

[0021] In some embodiments, the purge tube is configured to direct the purge medium to flow in a proximal direction in an area in thermal contact with the outer surface of the motor housing and / or the outer surface of the proximal portion of the catheter before injecting the purge medium into the catheter lumen or into the void between the catheter and the drive shaft. Heat transfer is particularly effective in this countercurrent flow arrangement. In this arrangement, the purge medium flows in the opposite direction (proximal direction) in an area in thermal contact with the outer surface of the proximal portion of the catheter compared to flowing in the catheter lumen or in the void between the catheter and the drive unit (distal direction flow); and / or the purge medium flows in the opposite direction (proximal direction) in an area in thermal contact with the outer surface of the motor housing compared to flowing in the fluid gap between the stator and the rotor (distal direction flow). In particular, the fluid transporter can be configured such that the purge medium flows distally within the fluid gap.

[0022] In some embodiments, the purge tube at least partially surrounds the motor housing and / or the proximal portion of the catheter in an area in thermal contact with the outer surface of the motor housing and / or the outer surface of the proximal portion of the catheter. By surrounding the motor housing and the proximal portion of the catheter, the heat transfer area will increase and thus the efficiency of heat transfer will be enhanced. The purge tube is typically in thermal contact with the motor housing and / or the proximal portion of the catheter from multiple sides (e.g., within an angle range of at least 180°). The purge tube can in particular completely surround the motor housing and / or the proximal portion of the catheter over the entire angular range.

[0023] In some embodiments, the purge tube is flexible. The purge tube may have a tubular shape and may further have a circular cross-section. The outer diameter of the purge tube may be at least 1 mm, preferably at least 2 mm and / or at most 5 mm, preferably at most 3 mm. The inner diameter of the purge tube may be at least 0.3 mm, preferably at least 0.7 mm and / or at most 2 mm, preferably at most 1.5 mm. The purge tube may comprise or consist of a biocompatible material. In some embodiments, the purge tube comprises a plastic material (such as PU, PEEK), or a metal (such as stainless steel), or consists of a plastic material (such as, PU, PEEK), or a metal (such as, stainless steel). The high thermal conductivity of the purge tube material can enhance the thermal contact between the purge medium and the motor housing and / or the proximal portion of the conduit.

[0024] The purge tube may be helically wound around the motor housing and / or the proximal portion of the conduit in a region where the purge tube is in thermal contact with the outer surface of the motor housing and / or with the outer surface of the proximal portion of the conduit. When the purge tube extends in a well-defined helical manner, recessed areas within the purge tube can be prevented and the risk of air trap residues within the purge tube when the purge tube is filled with the purge medium can be reduced. For example, for this purpose, the purge medium within the purge tube may comprise only one continuous flow path and not include parallel flow paths. Thus, reliable exhaust of the purge tube can be achieved. For example, the purge tube may be wrapped around the motor housing and / or the proximal portion of the conduit. In this embodiment, the drive unit is easy to manufacture. Further, a drive unit with the desired heat transfer efficiency can be easily fabricated simply by selecting the appropriate number of turns of the purge tube and thus generating the desired heat transfer area. In some embodiments, the purge tube forms at least 4 turns, preferably at least 8 turns, around the proximal portion of the conduit and / or at least 3 turns, preferably at least 5 turns, around the motor housing.

[0025] The purge tube may be attached to the motor housing and / or the proximal portion of the conduit. In most embodiments, the purge tube abuts against the outer surface of the motor housing and / or the outer surface of the proximal portion of the conduit in the heat contact area such that the motor housing and / or the proximal portion of the conduit are in direct contact with the purge tube. However, in other embodiments, a heat conducting element may be disposed between the motor housing, and / or the proximal portion of the conduit and the purge tube. The purge tube and the motor housing and / or the proximal portion of the conduit may then be in direct contact with the heat conducting element. This arrangement enables reliable heat contact. In some embodiments, the purge tube is at least partially integrated within the motor housing. For example, a portion of the purge tube may be formed by a lumen embedded within the motor housing. The total thermal conductivity (W / K) between the inner surface of the purge tube and the inner surface of the motor housing may be at least 5 times, preferably at least 10 times, the total thermal conductivity between the inner surface of the purge tube and the inner surface of the drive unit housing. Further, the total thermal conductivity between the inner surface of the purge tube and the interior of the motor, especially the windings of the motor, may be equivalent to at least the total thermal conductivity between the inner surface of the purge tube and the inner surface of the motor housing. This total thermal conductivity takes into account the thermal conductivity, cross-sectional area, thickness, and contact thermal conductivity of a series of materials disposed between the inner surface of the purge tube and the inner surface of the motor housing. Due to the relatively high thermal conductivity coefficient between the purge tube and the drive unit housing, heat generated by the motor may be dispersed into the drive unit housing, for example, by air convection, and local hot spots of the drive unit housing may be avoided. Further, the interior of the motor is in thermal contact with the motor housing such that heat generated by the motor is transferred to the outer surface of the motor housing. To achieve sufficient heat transfer from the motor fluid gap to the outer surface of the motor housing, the windings may be cast in a casting material, such as epoxy resin, thereby preventing air voids between the fluid gap and the outer surface of the motor housing. In some embodiments, the casting material directly binds the windings and the motor housing together.

[0026] In some embodiments, the drive unit further includes a heat sink. The heat sink may include a contact surface configured to contact and / or directly contact the patient's skin and / or be placed flat on the patient's skin. The contact surface is connected to the motor or connectable to the motor in a heat conducting manner so as to transfer heat generated by the motor to the patient tissue.

[0027] The drive unit including the heat sink provides a solution contrary to the common perception of the prior art, as discussed in U.S. Patent US2016 / 0213827A1, that heat in the motor of a heart assist pump must be effectively removed. Instead, effective removal of heat of the above drive unit may be achieved at least in part by transferring heat to the patient tissue. Thus, during operation of the heart assist pump, heat may be transferred from the motor to the contact surface of the heat sink. The thermal conductivity of the heat contact between the motor and the contact surface may be large enough to allow heat generated by the motor to be transferred through the heat sink to reach the patient tissue.

[0028] The contact surface can be planar or curved. In typical embodiments, the contact surface is stepless. In a preferred embodiment, the contact surface is flexible to maximize contact with the tissue. The contact surface can be provided for transferring heat from the motor to the tissue. When using the drive unit, the entire contact surface can be in contact with the skin. The drive unit can also include a bottom surface formed by the entire area of the drive unit designed to contact the patient's skin. The contact surface generally forms part of the bottom surface. However, in some embodiments, the contact surface forms the entire bottom surface.

[0029] This application also relates to a cardiac assist device, which includes the drive unit described above or below and also includes an implantable cardiac assist pump. The cardiac assist pump can be connected to the drive shaft of the drive unit, for example, inseparably. In another embodiment, the motor can be connected to the drive shaft through a coupling (such as through a magnetic clutch).

[0030] According to the operating method of the cardiac assist device, the drive unit drives the cardiac assist pump. The purge medium is injected into the lumen of the catheter or into the gap between the catheter and the drive shaft. The motor generates heat and transfers it to the motor housing. Further, the heat is transferred from the outer surface of the motor housing and / or the outer surface of the proximal portion of the catheter to the purge tube. In some embodiments, a radiator is provided and the heat generated by the motor is transferred to the radiator. In a further embodiment, the contact surface of the radiator contacts and / or directly contacts the patient's skin and / or lies flat on the patient's skin, such that the heat generated by the motor is transferred to the patient tissue. In a further embodiment, the contact surface of the radiator directly contacts the patient's skin. However, in some cases, another material, such as a piece of the patient's clothing, can be arranged between the skin and the contact surface.

[0031] The drive unit can include the housing of the drive unit. The motor housing, and / or the proximal portion of the catheter can be arranged within the drive unit housing. A portion of the purge tube can extend between the motor housing and the drive unit housing to effect the heat transfer to the purge tube as described above. Further, a portion of the purge tube can extend between the proximal portion of the catheter and the drive unit housing to effect the heat transfer to the purge tube as described above. The portion adjacent to the proximal portion of the catheter can be arranged outside the drive unit housing. Further, the purge tube can include a portion arranged outside the housing of the drive unit. This portion is generally attached to the supply of the purge medium. For simple and cost-effective manufacture of the drive unit, the diameter of the portion of the purge tube arranged outside the drive unit housing can be the same as the diameter of the portion in thermal contact with the motor housing and / or the proximal portion of the catheter.

[0032] The radiator can be attached to the housing of the drive unit. In a typical embodiment, when the drive unit is assembled, the drive unit housing is an outer housing that can be at least partially visible. The radiator can be arranged outside the drive unit housing. The radiator can be configured to enable heat conduction from the motor to the patient tissue. In most embodiments, the radiator is a passive component that does not require an electrical power supply. Further, in most embodiments, the radiator does not rely on moving parts and / or moving fluids. The radiator can be rigidly or movably connected to the drive unit housing. In some embodiments, the radiator is detachably connected to the drive unit housing. For example, the cardiac assist pump can be conveniently implanted in a catheterization laboratory without connecting the radiator. In this case, the drive unit housing can serve as the handle of the cardiac assist device. After the implantation process, the drive unit housing can be connected to the radiator so that the heat generated by the motor can be effectively transferred to the patient tissue. The heat can be transferred from the motor to the motor housing. The motor housing can be in thermal contact with the drive unit housing so that the heat generated by the motor can be transferred from the motor housing to the drive unit housing. Further, this heat can be transferred from the drive unit housing to the radiator.

[0033] The drive unit can include a holding device configured to attach the drive unit to the patient's thigh. When using the cardiac assist device, in a typical application scenario, at least the bottom surface of the drive unit is in contact with the patient's skin. The contact surface can also subsequently come into contact with the skin. During operation of the motor, the drive unit then allows for significantly effective removal of heat from the motor. Thus, overheating of the motor can be prevented.

[0034] The radiator acts in conjunction with the proposed purge tube and in thermal contact with the motor housing and / or the proximal portion of the catheter to optimize the thermal management of the cardiac assist device. In many embodiments, when operating the cardiac assist device, there is no need for heat transfer from the drive unit to the surrounding air. Thus, even when the drive unit is covered by a blanket or surgical drape, the cardiac assist device can be reliably operated without overheating. In a typical embodiment, there is no need for a heat sink. Thus, the proposed drive unit can be designed in a relatively compact manner, thereby improving the ease of attachment of the drive unit and the comfort of wearing the drive unit. Further, the amount of heat removed from the motor is predictable and is not greatly related to the temperature of the surrounding air or the flow rate of the surrounding air. Thus, the thermal management of the drive unit can be controlled in a reliable manner. In addition, since there is no need for a heat sink, the drive unit housing can have a partially or fully continuous and / or seamless surface. Thus, the drive unit can be easily cleaned.

[0035] Therefore, the drive unit can be advantageously used in different application scenarios:

[0036] First application scenario: During the implantation of a heart assist device in a catheterization laboratory, the motor can be placed on a sterile cloth because the area under the sterile cloth may be considered non-sterile. In this case, convection of the air around the motor is possible, which reduces the risk of overheating. Additionally, accidental contact between the patient and the motor is not possible, and the user (doctor) usually wears gloves when contacting the motor. Therefore, the acceptable motor temperature is higher than that in the second application scenario described below. Further, since the user may touch the motor with infected, especially blood-stained gloves, the risk of contamination of the drive unit is relatively high.

[0037] Second application scenario: During patient transportation or intensive care, it is particularly important for the pump to maintain its position within the patient. In this case, the motor should be reliably fixed relative to the puncture site due to its weight. For this purpose, the motor is usually placed under a blanket or quilt. Therefore, the heat transfer efficiency from the motor by convection is not high, and the risk of overheating of the motor during operation must be considered. Further, in this scenario, the patient may come into direct contact with the pump. Therefore, the effective heat transfer from the motor to the purge medium and / or patient tissue ensured by the drive unit described above or below is very beneficial. Further, since the motor may need to be cleaned after long-term use, the surface geometry obtained using the proposed drive unit is beneficial compared to the radiator designs known in the prior art (e.g., including heat sinks).

[0038] The surface area of the contact surface of the radiator can be larger than the surface area of the surface of the drive unit housing that faces the patient during operation. The size of the radiator can be set such that it extends beyond the drive unit housing. In some embodiments, the surface area of the contact surface is at least 25 cm 2 , preferably at least 50 cm 2 or at least 100 cm 2 . The surface area is generally less than 400 cm 2 . A sufficiently large surface area is required to achieve effective heat transfer from the motor to the patient tissue. Additionally, a sufficiently large surface area is crucial for preventing local overheating of the tissue and tissue damage. The amount of heat transfer to the patient tissue is generally at most 80 mW / cm of the surface area of the contact surface 2 , preferably at most 60 mW / cm 2 or at most 40 mW / cm 2 . Further, when designing the thermal management of the drive unit, the surface area is an important factor in the composition and enables the motor to operate at the required temperature. In most embodiments, during the operation of the drive unit, the ratio of the surface area of the contact surface to the heat dissipated by the motor is at least 13 cm 2 / W, preferably 25 cm 2 / W and more preferably 50 cm 2 / W, thus avoiding local overheating of the tissue.

[0039] Certain regions of the heat sink can be flexible. Thus, the contact surface can adapt to the skin contour surface. For example, when the drive unit is attached to the patient's thigh, the contact surface can adapt to the contour of the thigh. Therefore, the wearing comfort of the drive unit can be improved and thermal contact between the heat sink and the patient's skin can be ensured. All regions of the heat sink can be flexible.

[0040] The heat transferred to the tissue is generally not used for therapeutic purposes. In order to be able to effectively transfer heat from the motor to the patient's tissue, the heat exchanger can include at least one section of material with a relatively high thermal conductivity. This region can extend entirely on the contact surface. The thermal conductivity of this region can be at least 1 W / (m·K), preferably at least 10 W / (m·K), at least 50 W / (m·K), or at least 100 W / (m·K). In a preferred embodiment, the thermal conductivity of the heat sink in the direction parallel to the contact surface of the heat sink is higher than that in the direction perpendicular to the contact surface to ensure that the thermal energy is widely distributed on the surface and to avoid hot spots.

[0041] To safely and effectively transfer heat from the motor to the patient's tissue, the heat distribution on the surface area is of utmost importance. By designing the heat sink, the weight and the amount of material required for the drive unit can be reduced to make it flat. Thus, the heat sink can have a thickness of less than 2 cm, especially less than 1 cm or less than 0.5 cm. For example, the heat sink is a foil.

[0042] The heat sink can include a thermal conductive layer. The thermal conductive layer can quickly and effectively achieve heat transfer in the region of the contact surface, thus avoiding hot spots on the skin. The heat sink can also include a carrier layer. The carrier layer can have a lower thermal conductivity than the thermal conductive layer. The carrier layer can contain an elastomer and / or a plastic. In this way, the thermal conductive layer, especially a relatively thin and / or flexible layer, can achieve sufficient heat transfer, while the carrier layer can provide sufficient mechanical stability for the heat sink. The thermal conductive layer can contain a metal, especially copper, aluminum, and / or pyrolytic carbon. In some embodiments, the heat sink can include multiple thermal conductive layers.

[0043] In addition, the heat sink may include a biocompatible coating. For example, the contact surface of the heat sink may include a biocompatible coating. The coating may form part of the bottom surface of the heat sink or be entirely formed as the bottom surface of the heat sink. The coating may cover and / or surround the heat-conducting layer. In particular, if the heat sink or its heat-conducting layer includes harmful substances soluble in sweat, the coating may be provided. The coating can prevent the harmful substances from reaching the patient's skin at this time. For example, the biocompatible coating may include parylene, polyurethane, silicone, PEEK, or biocompatible metals such as implantable metals. The biocompatible coating may have a thickness of less than 2 mm, preferably less than 0.5 mm or less than 0.1 mm. The biocompatible coating may be the same as the carrier material for constructing the biocompatible carrier.

[0044] Furthermore, the motor and / or the motor housing and / or the drive unit housing may be elongated. When the drive unit is attached to the patient's thigh, the elongation direction of the motor and / or the motor housing and / or the drive unit housing may be consistent with the axial direction of the thigh. The holding device is generally connected to the drive unit housing. The holding device of the drive unit may include a strap and / or a hook-and-loop fastening device. The holding device may also include an adhesive. The adhesive attaches the drive unit to the thigh to achieve a particularly reliable fixation of the drive unit relative to the puncture site. In particular, when the drive unit is attached to the patient's thigh, the adhesive fixation can form an effective holding device that prevents the drive unit from sliding along the tapered portion of the thigh towards the knee. For example, the mechanical stress applied to the puncture site can be reduced by the proposed holding device. In some embodiments, the heat sink includes an adhesive surface for attaching the heat sink to the skin. For example, the heat sink may be formed by an adhesive patch. According to this embodiment, the heat generated by the motor can be transferred to the patient tissue through the patch. The thermal conductivity of the patch can be large enough to effectively transfer heat to the tissue. The adhesive surface may form part of the contact surface and / or the entire contact surface. The adhesive may be a biocompatible adhesive, such as a well-known wound closure adhesive patch.

[0045] Furthermore, the drive unit may include a fastening device for preventing the drive unit from moving to different positions on the patient's skin. For example, the fixing device may include a rubber-coated area. The bottom surface of the drive unit may also include bumps.

[0046] The heat sink may include openings or recesses, particularly through-holes or grooves, to allow sweat to evaporate from the skin. The openings or recesses may be arranged to be at least partially adjacent to the contact surface. In a typical embodiment, the heat sink includes at least three, at least five or at least eight openings or recesses. During operation of the motor, the heat transferred to the tissue may cause the patient to sweat more. Therefore, the openings or recesses can significantly improve the wearing comfort of the drive unit. To effectively transfer water vapor to the surrounding air, the minimum or uniform diameter of the openings or recesses is typically at least 1 mm or at least 5 mm. The maximum or uniform diameter of the openings or recesses is typically at most 20 mm or 80 mm.

[0047] In some embodiments, the openings are elongated. The ratio of the maximum diameter to the minimum diameter may be at least 1.2 or at least 2. In this way, sweat (in the form of water vapor) can be effectively transferred from the body to the surrounding air while ensuring sufficient mechanical stability of the heat sink and effective two-dimensional heat conduction. For example, the openings may be elongated such that when the drive unit is attached to the patient's thigh, the openings have a larger diameter along the circumference of the thigh and a smaller diameter along the axis of the thigh. If the motor is elongated along the axis, the elongation of the holes may allow heat to be effectively transferred circumferentially while water vapor is effectively removed from the skin.

[0048] In some embodiments, the heat sink includes holes for allowing the evaporated sweat to be transferred from the skin to the surrounding air. The heat sink may include a thin film having holes. The holes may have a diameter of at least 0.02 μm and / or at most 0.3 μm.

[0049] The heat sink may include a sweat-absorbing material, particularly a fabric or cotton. The sweat-absorbing material may form part of the bottom surface of the heat sink. The sweat-absorbing material can absorb sweat from the patient's skin and thus enhance the wearing comfort of the drive unit.

[0050] In some embodiments, the heat sink includes a heat pipe. The heat pipe may be flat. For example, the heat pipe may be a heat spreader. Generally, the bottom surface of the heat pipe is in contact with the patient's skin. In other embodiments, the heat pipe may be arranged between the motor and the heat sink and connected to the motor and the heat sink. The top surface of the heat pipe may be in thermal contact with the motor. The heat pipe can achieve effective heat transfer from the motor to the tissue or to the contact surface.

[0051] Compared with a motor without purge, it is expected that the frictional losses in the purge medium result in a reduced efficiency of the purged motor. Surprisingly, the adverse low efficiency of the motor can be circumvented by any one of the above or below features and combinations of these features. The width of the fluid gap can be at least 0.1 mm, preferably at least 0.2 mm, and / or at most 1 mm, preferably at most 0.5 or at most 0.3 mm. It must be taken into account that the minimum size of the magnetic gap is limited by the size of the fluid gap. Typically, the rotor and / or stator includes a sleeve or coating, which can limit the fluid gap. The limiting surface of the fluid gap can be smooth and / or stepless and can avoid undercut surfaces to ensure a reliable exhaust process. Thereby, the rotor magnet and / or the stator winding can be protected from corrosion by the purge medium. Thus, the magnetic gap is generally larger than the fluid gap. Although it is expected that the magnetic losses increase with the increase in the width of the fluid gap (magnetic gap), it is surprisingly found that a relatively wide fluid gap results in an overall improvement in the motor efficiency. This improvement is related to the reduction of frictional losses in the purge medium.

[0052] As explained above, the proposed drive unit allows for precise control of the thermal management of the heart assist device in various application scenarios. In particular, the temperature of the purge medium within the fluid gap can be precisely controlled. This effect can be achieved by preheating the purge medium due to thermal contact with the outer surface of the proximal portion of the catheter and / or the outer surface of the motor housing or by removing heat from the motor to the purge tube and / or radiator. In a typical embodiment, in the steady state of operation, the temperature of the purge medium in the fluid gap is at least 50 °C, preferably at least 60 °C. Further, in the steady state of operation, the temperature of the purge medium in the fluid gap is at most 100 °C, preferably at most 90 °C. By correspondingly controlling the temperature of the purge medium, the viscosity of the purge medium can be reduced while maintaining the temperature of the purge medium safe for the patient and preventing the purge medium from boiling. Thus, the motor can be operated in a particularly efficient manner by controlling the temperature of the purge medium to make the frictional losses in the fluid low.

[0053] To precisely control the temperature of the purge fluid, it is necessary to analyze and adjust the temperature of the preheated fluid medium and the heat transfer between the fluid gap and the patient's skin and / or between the fluid gap and the purge tube. For example, the heat transfer from the fluid gap to the purge tube may be affected by the material of the motor housing. The motor housing may comprise or consist of a metal (such as stainless steel or aluminum). In some embodiments, the motor windings may be disposed within the motor housing. In some embodiments, the motor housing may be partially or completely formed of a plastic casting material encapsulating the windings. The windings may include one or more copper wires. Further, the heat transfer from the fluid gap to the radiator may be affected by the material of the drive unit housing. The drive unit housing may comprise or consist of a plastic material (such as PEEK or ABS). The plastic material is particularly suitable for enabling the operation of the motor within the desired temperature range. In some embodiments, the drive unit housing is shaped to be able to serve as a handle of the drive unit.

[0054] In some embodiments, the drive unit includes a thermal insulator disposed between the purge tube and the drive unit housing. The thermal insulator may be disposed in the area of thermal contact with the proximal portion of the catheter and the drive unit housing. Additionally or alternatively, the thermal insulator may be disposed in the area of thermal contact with the motor housing and the drive unit housing. The thermal insulator may surround the purge tube. Further, the thermal insulator may be tubular. The thermal insulator may include a plastic material, particularly a foam plastic material. In some embodiments, an air gap or a vacuum gap is formed between the purge tube and the drive unit housing to achieve thermal insulation between any one or both of the thermal contact areas and the drive unit housing. The air gap can evenly distribute the heat generated by the motor within the drive unit housing by convection, thereby avoiding local hot spots on the drive unit housing. Further, the purge tube may be partially surrounded by a heat shrink tube in the area of thermal contact with the motor housing and / or the proximal portion of the catheter to improve thermal contact.

[0055] According to some embodiments of the cardiac assist device, the drive unit may or may not include a purge tube in thermal contact with the proximal portion of the catheter and / or with the motor housing. Further, the drive unit may not include the radiator described above or below and / or the drive unit may include a radiator not intended to be in contact with the patient's skin. The means for removing heat from the motor may, for example, be formed through the purge tube or through the radiator described above or below, formed through fins attached to the motor housing or attached to the drive unit housing, or formed through a heat pipe thermally connected to the motor. Further embodiments become apparent through the combination of various aspects and / or in combination with the description above or below.

[0056] In particular, the present application further relates, among other things, to the following aspects:

[0057] 1. A method for operating a cardiac assist device, the cardiac assist device comprising an external drive unit and an implantable or implanted cardiac assist pump, wherein the drive unit comprises a motor for driving the cardiac assist pump, and wherein the motor is connected to the cardiac assist pump by a percutaneous drive shaft, wherein the motor comprises a stator and a rotatably mounted rotor connectable to the drive shaft, wherein a fluid gap is formed between the rotor and the stator, wherein the fluid gap is in fluid connection with a purge port for injecting a purge medium into the fluid gap, wherein the cardiac assist device comprises a catheter surrounding the drive shaft, and wherein the purge medium is injected into the fluid gap and into the void between the catheter and the drive shaft or into the catheter lumen.

[0058] 2. The method according to the first aspect, wherein the temperature of the purge medium in the fluid gap is at least 50 °C, preferably at least 60 °C, in the steady state of operation.

[0059] 3. The method according to any of the preceding aspects, wherein the temperature of the purge medium in the fluid gap is at most 100 °C, preferably at most 90 °C, in the steady state of operation.

[0060] 4. The method according to any of the preceding aspects, wherein the purge medium is a glucose solution or a saline solution.

[0061] 5. The method according to any of the preceding aspects, wherein the drive unit comprises a purge tube attached to the purge port, wherein the purge tube is in thermal contact with the outer surface of the motor housing and / or the outer surface of the proximal portion of the catheter, and wherein the purge medium is preheated by being in thermal contact with the outer surface of the motor housing and / or the outer surface of the proximal portion of the catheter before being injected into the fluid gap.

[0062] 6. An external drive unit for an implantable cardiac assist pump, the external drive unit comprising a motor for driving the cardiac assist pump, wherein the motor is connected or connectable to the cardiac assist pump by a percutaneous drive shaft, and wherein the drive unit comprises a heat pipe connected to the motor in a heat-conducting manner.

[0063] 7. The drive unit according to the sixth aspect, wherein the drive unit comprises a housing, in particular a motor housing or a drive unit housing, and wherein the heat pipe is connected to the housing in a heat-conducting manner.

[0064] 8. A cardiac assist system, comprising the drive unit according to any of the sixth or seventh aspects, and further comprising a console or a control unit having a radiator, wherein a part of the heat pipe is connected to the radiator in a heat-conducting manner to remove heat from the motor.

[0065] 9. An external drive unit for an implantable heart assist pump, the external drive unit comprising a motor for driving the heart assist pump, wherein the motor is connected to the heart assist pump by a percutaneous drive shaft, characterized by a heat sink, the heat sink comprising a contact surface configured to contact the patient's skin, wherein the contact surface is thermally conductively connected to or connectable to the motor to transfer heat generated by the motor to the patient's tissue.

[0066] 10. A method of operating a heart assist device, the heart assist device comprising an external drive unit and an implantable or implanted heart assist pump, wherein the drive unit comprises a motor for driving the heart assist pump, and wherein the motor is connected to the heart assist pump by a percutaneous drive shaft, wherein the drive unit further comprises a motor housing, wherein the motor is disposed within the motor housing, the drive unit further comprises a catheter surrounding the drive shaft and a purge tube for injecting a purge medium into the lumen of the catheter or into the gap between the catheter and the drive shaft, wherein

[0067] the purge tube is in thermal contact with the outer surface of the motor housing and / or the outer surface of the proximal portion of the catheter such that heat is transferred from the outer surface of the proximal portion of the catheter and / or from the outer surface of the motor housing to the purge medium.

[0068] 11. The method according to aspect ten, wherein the purge tube directs the purge medium such that it first makes thermal contact with the outer surface of the motor housing and / or with the outer surface of the proximal portion of the catheter and is then injected into the lumen of the catheter or into the gap between the catheter and the drive shaft.

[0069] 12. The method according to aspect eleven, wherein the purge tube directs the purge medium such that it first makes thermal contact with the outer surface of the motor housing and is then injected into the lumen of the catheter or into the gap between the catheter and the drive shaft.

[0070] 13. The method according to aspect ten, wherein the motor comprises a stator and a rotatably mounted rotor connected to the drive shaft, wherein a fluid gap is formed between the rotor and the stator, wherein the fluid gap is in fluid communication with a purge port for injecting the purge medium into the fluid gap, and wherein the purge tube is connected to the purge port.

[0071] 14. The method according to aspect thirteen, wherein the purge tube and the fluid gap direct the purge medium such that it first makes thermal contact with the outer surface of the motor housing and / or with the outer surface of the proximal portion of the catheter, is then injected into the fluid gap between the rotor and the stator, and is then injected into the lumen of the catheter or into the gap between the catheter and the drive shaft.

[0072] 15. The method according to aspect thirteen, wherein the purge medium flows in a distal direction in the fluid gap. Description of the Drawings

[0073] Exemplary embodiments will be described with reference to the following drawings:

[0074] Figure 1 FIG. is a schematic view of a cardiac assist device having an implantable cardiac assist pump and an extracorporeal drive unit.

[0075] Figure 2 FIG. is a schematic view of the drive unit.

[0076] Figure 3 FIG. is another schematic view of the drive unit.

[0077] Figure 4 FIG. is another schematic view of the drive unit.

[0078] Figure 5 FIG. is a cross-sectional view of the radiator and the drive unit housing.

[0079] Figure 6 FIG. is a cross-sectional view of the radiator.

[0080] Figure 7 FIG. is a cross-sectional view of the drive unit housing and the motor.

[0081] Figure 8 FIG. is a cross-sectional view of the drive unit according to another embodiment.

[0082] Figure 9 FIG. is a perspective view of the purge tube and the motor housing.

[0083] Figure 10 FIG. is a graph showing a comparison of measured operating parameters of a drive unit having and not having thermal contact between the purge tube and the motor housing and the proximal portion of the conduit.

[0084] Figure 11 FIG. is a schematic view of the drive unit according to another embodiment. DETAILED DESCRIPTION

[0085] Figure 1 A schematic view of a cardiac assist device 1 is depicted. The cardiac assist device 1 includes a conduit 2. A flexible drive shaft 3 is guided within the conduit 2. The distal ends of both the conduit 2 and the drive shaft 3 are connected to the pump head of a cardiac assist pump 4. The cardiac assist pump 4 includes a housing 5 and an impeller 6. The impeller 6 is connected to the distal end of the drive shaft. The proximal end of the drive shaft 3 is connected to an extracorporeal drive unit 7 including a motor. The drive unit 7 is configured to drive the rotational movement of the impeller to move the patient's blood.

[0086] The heart assist pump 4, as well as the catheter 2 and the drive shaft 3, are inserted via a puncture site 8 located in the patient's groin into the patient's femoral artery. The arrangement shows the use of the heart assist device 1 to assist the left ventricular function of the heart, where the heart assist pump 4 is partially arranged in the region of the aortic valve 11 within the patient's left ventricle 10. When the heart assist device 1 is operated, the drive shaft 3 is driven by a motor of the drive unit 7, and the heart assist device 1 conveys blood from the left ventricle 10 to the aorta 12 in the direction towards the proximal end 14, that is, from the distal end 13 of the heart assist device 1 to the aorta 12. In other embodiments, the heart assist device 1 can be configured to convey blood in the direction from the proximal end 14 to the distal end 13 of the heart assist device 1. This arrangement is particularly suitable for assisting the right ventricular function of the heart.

[0087] As Figure 2 schematically depicted in the figure, the drive unit 7 can be attached to the patient's thigh 15. Figure 2 And repeating features in the following figures are denoted by the same reference numerals. In the illustrated embodiment, the drive unit 7 is held in place relative to the puncture site 8 by a strap 16, such as an elastic strap. In most embodiments, the length of the strap is between 45 and 60 cm. However, as described below, other fixing devices are also possible. The motor is arranged within a motor housing. The motor housing is arranged within the housing 17 of the drive unit 7, for example, formed by an injection-molded ABS component. The surface of the housing 17 of the drive unit 7 is smooth and continuous in most embodiments so that the housing 17 of the drive unit 7 is easy to clean and can be used as a handle for the heart assist device 1. The catheter 2 is rigidly connected in a fluid-tight manner to the proximal part of the housing 17 of the drive unit 7. Further, a supply line 18 is schematically shown in the figure. In the illustrated embodiment, the supply line 18 is connected to the proximal end of the housing 17 of the drive unit 7 and includes a power supply line for the motor and a fluid supply line or purge line for a purge medium. In other embodiments, the fluid supply line or purge line and the power supply line are each guided within one of a plurality of individual supply lines. Further, in some embodiments, the supply line 18 and / or the fluid supply line or purge line exit at the distal or side surface of the housing 17 of the drive unit 7.

[0088] The drive unit 7 further includes a heat sink 19. The heat sink 19 is rigidly connected to the housing 17 of the drive unit 7 such that the heat generated during motor operation is transferred to the heat sink 19. The heat sink 19 can be thin and have a thickness of 4 mm or less. For example, the heat sink 19 can be formed by the following patch or by a flat two-dimensional heat pipe. The bottom surface of the heat sink 19 lies flat or directly contacts the skin contact surface of the patient, so that heat can be transferred from the heat sink 19 to the patient tissue. During operation of the motor, before the heat sink 19 is fixed to the thigh 15, the outer surface temperature of the housing 17 of the drive unit 7 may exceed 43 °C. However, the thermal conductivity of the heat sink 19 ensures that the heat is evenly distributed over a sufficient area and is transferred to the thigh 15, thereby quickly reducing the surface temperature of the housing 17 of the drive unit 7 to below 42 °C, which defines the critical temperature for tissue damage.

[0089] The heat sink 19 includes a region with a thermal conductivity greater than 100 W / (m·k) for laterally spreading the heat, so that the heat is effectively transferred to the entire contact surface. In some embodiments, the surface area of the contact surface can be as large as 200 cm 2 . The heat sink 19 further includes openings (through holes), where two openings are marked with reference numerals 20 and 20'. The openings 20 and 20' allow the evaporated sweat to be transferred to the surrounding air and thus improve the wearing comfort.

[0090] Figure 3 A perspective view of the drive unit 7 is shown. In the illustrated embodiment, the heat sink 19 has a recess 22 for receiving the housing 17 of the drive unit 7. The strap 16 includes a hook-and-loop fastening mechanism having an annular surface 23 for engaging a corresponding hook-shaped surface (not shown in the figure) provided at the end of the strap. When the heart assist device 1 is used, the housing 17 of the drive unit 7 is received in the recess 22, and the strap 16 circumferentially wraps around the thigh such that a part of the strap 16 covers the housing 17 of the drive unit 7 and the drive unit 7 is held in place.

[0091] Figure 4 The openings 20 and 20' of the heat sink 19 are schematically shown to be elongate. In this case, the openings 20 and 20' have a larger diameter in the circumferential direction 24 relative to the thigh 15 so that the heat sink 19 performs effective heat transfer in this direction 24. The housing 17 of the drive unit 7 is elongate in the vertical direction 25 corresponding to the axial direction 25 of the thigh 15.

[0092] The heat sink 19 can be curved and / or flexible to adapt to the shape of the thigh 15. For example, the heat sink 19 can include a foil or a patch. Figure 5Shows an exemplary cross-section of the heat sink 19 formed by the first patch 26 and the second patch 27 and the housing 17 of the drive unit 7. Both patches 26 and 27 are bendable and each includes an adhesive bottom surface 28, 29 facing the thigh 15. In the illustrated embodiment, the patches 26, 27 surround the housing 17 of the drive unit 7 to effectively remove the heat of the motor. In the illustrated embodiment, the adhesive surface of the heat sink 19 forms a holding device for holding the drive unit 7 in place relative to the puncture site 8. Thus, another holding device such as the strap 16 described above may not be necessary, but may still be provided in some embodiments.

[0093] Figure 6 An exemplary cross-section of the heat sink 19 is shown. The heat sink 19 can be a multi-layer structure. The heat sink 19 includes a carrier layer 30 which forms the top layer of the heat sink 19. The carrier layer 30 can be formed by an elastomer and / or plastic material. For effective heat transfer on the contact surface area, i.e., in the horizontal direction shown in the figure, the heat sink 19 further includes a thin heat-conducting layer 31 which can be formed by a thin-layer material with a high heat-conductivity coefficient, for example, copper, aluminum or pyrolytic carbon. Either side of the heat-conducting layer 31 is wrapped by an inert and biocompatible coating 32 which is composed of parylene, polyurethane, silicone, PEEK or a biocompatible material such as implantable metal. The biocompatible coating 32 also covers the heat-conducting layer 31 on the inner wall of the opening 20 of the heat sink 19. The bottom surface of the heat sink without a step is formed by an adhesive layer 33 which, for example, contains glue to adhere the heat sink 19 to the patient's skin.

[0094] Furthermore, Figure 6 The sweat-absorbing part 34 of the heat sink 19 or the drive unit 7 is schematically shown. The sweat-absorbing part 34 can be made of, for example, fabric and / or cotton. In addition, the heat sink 19 or the drive unit 7 includes a rubber-coated area 48 having rubber blocks 49, 49' to prevent the heat sink 19 from slipping relative to the puncture site 8. The sweat-absorbing part 34 and the rubber-coated area 48 can be evenly distributed on the bottom surface of the heat sink 19.

[0095] Figure 7 A schematic diagram of the motor 35 is shown. The motor 35 is arranged within a motor housing which is arranged within the housing 17 of the drive unit 7. The motor 35 includes a rotor 36 having a permanent magnet and a stator 37 having windings 38. The rotor 36 is rotatably mounted using a first bearing 39 and a second bearing 40 and can rotate when current flows through the windings 38 of the stator 37. The rotor 36 is rigidly connected to the drive shaft 3 to drive the thruster 6.

[0096] The catheter 2 is rigidly connected to the housing 17 of the drive unit 7, and a gap 41 is formed between the catheter 2 and the drive shaft 3. The gap 41 is in fluid connection with the fluid gap 43 formed between the rotor 36 and the stator 37, with the purge port 42, and with the supply line 18. The radial width of the fluid gap 43 can be between 0.2 mm and 0.3 mm. When the heart assist device 1 is operated, a purge medium, such as a glucose solution, is supplied through the supply line 18 and flows through the fluid gap 43 and the gap 41 between the catheter 2 and the drive shaft 3 (and finally flows into the patient's body at the proximal end of the heart assist device 1).

[0097] During the operation of the motor 35, a power dissipation of, for example, 2 W may cause the motor 35 to heat up. As schematically shown by the arrow labeled 44, heat is removed from the motor 35 to keep the temperature of the glucose solution in the fluid gap 43 constant at 75 °C in the steady state of operation. To remove heat, the heat can be transferred, for example using the radiator 19 described above, to the patient tissue 45, for example using the fins on the housing 17 of the drive unit 7 to transfer to the surrounding air 46, and / or for example through an elongated heat pipe connected to the housing 17 of the drive unit 7 to transfer to the fins 47 of the console or control unit. Further, additionally or alternatively, the heat can be transferred to the fluid supply line or purge tube as described below. Any combination of these heat removal mechanisms is possible.

[0098] Further, when the motor 35 is not driven with full block commutation, inductors 50 can be provided to reduce eddy current losses. These inductors 50 can also be located within the housing 17 of the drive unit 7, but in a preferred embodiment, the inductors 50 are located at the end of the motor cable 18 (or within the control unit itself), and the motor cable 18 is connected to the control unit of the motor 35 to avoid adding additional weight and heat sources to the motor 35 and the patient's leg.

[0099] The heat removal of the purge tube is described in conjunction with the following figures. Figure 8 Another embodiment of the drive unit 7 is schematically shown. The drive unit 7 can include any feature of the aforementioned drive unit 7. Further, in Figure 8 the drive unit 7, the purge tube 53 serves a dual role, namely as a supply line for the purge medium and as a heat removal device. As Figure 8As shown, the winding 38 of the stator 37 is enclosed within the motor housing 51. The motor housing 51 is disposed at the central position of the housing 17 of the drive unit 7. However, in other embodiments, the motor housing 51 is disposed at the proximal position of the housing 17 of the drive unit 7. Further, the conduit 2 includes a proximal portion 52, and the proximal portion 52 is disposed within the housing 17 of the drive unit 7. As shown, the supply line 18 is attached to the proximal end of the housing 17 of the drive unit 7. The supply line 18 contains electrical leads for the power supply to the motor 35. In this embodiment, the purge tube 53 is not included within the supply line 18. The purge tube 53 extends through an opening on the side surface of the housing 17 of the drive unit 7 in the distal region of the housing 17 of the drive unit 7.

[0100] The end of the purge tube 53 is attached to a purge medium supply source (not shown). The purge tube 53 extends into the interior of the housing 17 of the drive unit 7. Within the housing 17 of the drive unit 7, the purge tube 53 abuts against the outer surface of the proximal portion 52 of the conduit 2. Thus, as indicated by the arrow labeled 54, a thermal contact is formed between the proximal portion 52 of the conduit 2 and the purge tube 53. Further, the purge tube 53 abuts against the outer surface of the motor housing 51. Thus, as indicated by the arrow labeled 55, a thermal contact is formed between the motor housing 51 and the purge tube 53. The purge tube 53 is further attached to the purge port 42. When the purge medium is supplied, it flows through the drive unit 7 as indicated by the arrows (some arrows are labeled by the reference numeral 56). The purge medium first passes through the regions of the thermal contacts 54, 55, then enters the fluid gap 43 and subsequently enters the void 41 between the conduit 2 and the drive shaft 3. In a further embodiment, the purge medium enters the lumen of the conduit 2. The purge medium mainly flows in the proximal direction when passing through the thermal contacts 54, 55. Then, when the purge medium flows through the fluid gap 43 and the gap 41 between the conduit 2 and the drive shaft 3, the purge medium flows in the distal direction.

[0101] During the operation of the heart assist pump, the injected purge medium cools the proximal portion 52 of the conduit 2 and the motor 35 due to the thermal contacts 54, 55 and its relatively low temperature. Thus, the portion 63 of the conduit 2 is significantly cooled, and the portion 63 is disposed distally adjacent to the proximal portion 52 of the conduit 2 and outside the housing 17 of the drive unit 7, such that the portion 63 of the conduit 2 that is not disposed within the housing 17 of the drive unit 7 can be touched without the risk of injury. Further, the risk of deformation of the conduit 2 due to the heating of the portion 63 of the conduit 2 (and thus the risk of deformation and failure of the flexible drive shaft 3 disposed within the conduit 2) is reduced. Further, before the purge medium enters the fluid gap 43, it is preheated due to the thermal contacts 54, 55. Thus, the purge medium enters the fluid gap 43 at a higher temperature and a lower viscosity, thereby reducing the frictional losses within the motor 35 and enabling the motor 35 to operate more efficiently.

[0102] In most embodiments, the motor housing 51 is cylindrical. As Figure 9 shown, the purge tube 53 is tubular and wraps around the motor housing 51 such that the purge tube 53 is in direct contact with the outer surface of the motor housing 51, thereby achieving good thermal contact 55. Further, the purge tube 53 wraps around the proximal portion 52 of the conduit 2 in a similar manner. To manufacture the drive unit 7, the purge tube 53 can be preformed by hot pressing to form the helical shape of the purge tube 53. After the purge tube 53 wraps around the proximal portion 52 of the conduit 2 and the motor housing 51, the purge tube 53 can be embedded in a flexible silicone casting material, or fastened to the motor housing 51 by a heat shrink tube around the purge tube 53 or by an adhesive disposed between the motor housing 51 and the purge tube 53. In most embodiments, the proximal portion 52 of the conduit 2 is also cylindrical. The diameter of the purge tube 53 can be uniform. The conduit 2 and especially the proximal portion 52 of the conduit 2 can comprise a plastic material, such as PU or polyether block amide (PEBA), for example the conduit 2 can be braided with metal.

[0103] The drive unit 7 can further include a thermal insulator (not shown) disposed between the purge tube 53 and the housing 17 of the drive unit 7 to prevent the housing 17 of the drive unit 7 from getting hot. Further, the efficiency of the heat exchanger can be increased in this way through the thermal contacts 54, 55. The thermal insulator can completely surround the purge tube 53 in the area of the thermal contacts 54, 55 and can be a heat insulating foam tube made of plastic. The thermal insulator can also be formed by an air gap between the purge tube 53 and the housing 17 of the drive unit 7.

[0104] Figure 10 Graphs showing the measured operating parameters of different heart assist devices 1 are presented: The first heart assist device has according to Figure 8The drive unit 7, i.e., including the thermal contacts 54, 55 (forks), the second heart assist device has with respect to the drive unit 7. However, its purge tube 53 is neither in thermal contact with the proximal portion 52 of the conduit 2 nor in thermal contact with the motor housing 51 (circle). The left vertical axis 57 represents temperature, while the right vertical axis 58 represents the motor current that must be applied to achieve a predetermined blood transfer rate. The horizontal axis 59 represents the flow rate of the purge medium. The uppermost measured values 60, 60' correspond to the right vertical axis representing the motor current. The middle values 61, 61' and the lowermost measured values 62, 62' correspond to the left vertical axis and represent the temperature 61, 61' of the motor 35 and the temperature 62, 62' of the portion 63 of the conduit 2, the portion 63 of the conduit 2 being arranged adjacent to the proximal portion 52 of the conduit 2. The motor temperature 61, 61' decreases as the purge rate increases, while the temperature 62, 62' of the portion 63 of the conduit 2 increases as the purge rate increases. These measurements show that both the motor and the portion 63 of the conduit 2 can be effectively cooled by using the thermal contacts 54, 55 with the motor housing 51 and with the proximal portion 52 of the conduit 2. When the thermal contacts 54, 55 are not provided, the motor current 60 increases with the purge rate. In contrast, when the proposed thermal contacts 54, 55 are used, the motor current 60' can be significantly reduced at a reasonable purge rate. Therefore, the proposed thermal contacts 54, 55 make the heart assist device 1 more effective. Surprisingly, due to the thermal contacts 54, 55, the motor current 60' is completely independent of the flow rate. Therefore, the influence of the purge rate on the motor current 60' can be neglected when the motor current 60' is used as an important control parameter of the heart assist device 1 (e.g., indicating a malfunction of the heart assist device 1). Therefore, the proposed thermal contacts 54, 55 can simplify the monitoring circuit of the heart assist device 1.

[0105] Figure 11 Fig. 4 shows a drive unit 7 according to another embodiment. The drive unit 7 may include any one or all of the above features. The upper part of the housing 17 of the drive unit 7 is not shown in the drawing so that the interior of the drive unit 7 is visible. The housing 17 of the drive unit 7 serves as a handle of the drive unit 7 and for this reason presents a curved shape that can be easily lifted by a hand. A supply line 18 (not shown) including the power electrical leads of the motor may be attached to a power plug 64 provided at the proximal end of the housing 17 of the drive unit 7. Other electrical leads (not shown for clarity) connect the supply line to the motor 35, the motor 35 being arranged within the motor housing 51. The conduit 2 includes a portion 63 arranged adjacent to and outside the housing 17 and also includes a proximal portion 52 arranged within the housing 17 and connecting the portion 63 to the motor 35.

[0106] The purge tube 53 enters the housing 17 of the drive unit 7 in the proximal part of the housing 17. Further, as described above, the purge tube 53 wraps around the proximal part 52 of the conduit 2 and the motor housing 51 to form thermal contacts 54, 55. The purge tube 53 is further connected to the proximal end of the motor housing 51 to form a fluid connection with the fluid gap 43 of the motor 35. To further improve the thermal contact between the purge tube 53 and the motor housing 51, the purge tube 53 is wrapped within a heat shrink tube 65 (the position of the purge tube 53 below the heat shrink tube 65 is shown in dashed lines). The heat shrink tube 65 pushes the purge tube 53 towards the motor housing 51, thus improving the thermal contact. The part of the purge tube 53 that is wrapped around the proximal part 52 of the conduit 2 can also be wrapped within a heat shrink tube (not shown). Further, air gaps 66, 66' are formed between the housing 17 of the drive unit 7 and the parts where the purge tube 53 forms thermal contacts with the motor housing 51 and the proximal part 52 of the conduit 2. The air gaps 66, 66' provide thermal insulation for the motor housing 51 (the above-mentioned adiabatic foam tube can alternatively or additionally be provided). Further, the air gaps 66, 66' allow, to some extent, the heat generated by the motor to be dispersed into the housing 17 by convection, thus avoiding local hot spots.

Claims

1. An external drive unit (7) for an implantable heart assist pump (4), comprising The motor housing (51), the percutaneous drive shaft (3), and the motor (35) for driving the heart assist pump (4), wherein, The motor (35) is connected to the heart assist pump (4) through the drive shaft (3), and wherein the motor (35) is arranged within the motor housing (51), further comprising: a conduit (2) surrounding the drive shaft (3), and a purge tube (53) for injecting a purge medium into the lumen of the conduit (2) or into the gap (41) between the conduit (2) and the drive shaft (3); characterized in that the purge tube (53) is in thermal contact (55) with the outer surface of the motor housing (51) and / or in thermal contact (54) with the outer surface of the proximal portion (52) of the conduit (2); wherein the motor (35) comprises a stator (37) and a rotatably mounted rotor (36) connected to the drive shaft (3), wherein a fluid gap (43) is formed between the rotor (36) and the stator (37), and wherein the fluid gap (43) is in fluid communication with a purge port (42) for injecting a purge medium into the fluid gap (43), and wherein the purge tube (53) is connected or connectable to the purge port (42); wherein the purge tube (53) and the fluid gap (43) are configured to direct the purge medium such that it first makes thermal contact (55) with the outer surface of the motor housing (51) and / or makes thermal contact (54) with the outer surface of the proximal portion (52) of the conduit (2), and is then injected into the fluid gap (43) between the rotor (36) and the stator (37), and is then injected into the lumen of the conduit (2) or into the gap (41) between the conduit (2) and the drive shaft (3).

2. The drive unit (7) according to claim 1, characterized in that, The purge tube (53) is configured to direct the purge medium such that it first makes thermal contact (55) with the outer surface of the motor housing (51), and is then injected into the fluid gap (43) between the rotor (36) and the stator (37), and is then injected into the lumen of the conduit (2) or into the gap (41) between the conduit (2) and the drive shaft (3).

3. The drive unit (7) according to claim 1 or 2, characterized in that, The purge tube (53) is in thermal contact (55) with the outer surface of the motor housing (51) and in thermal contact (54) with the outer surface of the proximal portion (52) of the conduit (2), and wherein the purge tube (53) is configured to direct the purge medium such that it first makes thermal contact (54) with the outer surface of the proximal portion (52) of the conduit (2), and then makes thermal contact (55) with the outer surface of the motor housing (51) to effect gradual preheating of the purge medium and to effectively cool the proximal portion (52) of the conduit (2).

4. The drive unit (7) according to claim 3, characterized in that, The purge tube (53) is entirely outside the body.

5. The drive unit (7) according to claim 1 or 2, characterized in that, The purge tube (53) is configured to direct the purge medium to flow in the proximal direction in a region where the purge tube (53) is in thermal contact (55) with the outer surface of the motor housing (51) and / or in thermal contact (54) with the outer surface of the proximal portion (52) of the conduit (2) before injecting the purge medium into the inner lumen of the conduit (2) or into the gap (41) between the conduit (2) and the drive shaft (3).

6. The drive unit (7) according to claim 1 or 2, characterized in that, The purge tube (53) surrounds the proximal portion (52) of the conduit (2) in a region where the purge tube (53) is in thermal contact (54) with the outer surface of the proximal portion (52) of the conduit (2).

7. The drive unit (7) according to claim 6, characterized in that, The purge tube (53) spirally surrounds the proximal portion (52) of the conduit (2) in the region where the purge tube (53) is in thermal contact (54) with the outer surface of the proximal portion (52) of the conduit (2).

8. The drive unit (7) according to claim 1 or 2, characterized in that, Also included is a housing (17) of the drive unit (7).

9. The drive unit (7) according to claim 8, characterized in that, The proximal portion (52) of the conduit is disposed within the housing (17) of the drive unit (7).

10. The drive unit (7) according to claim 8, characterized in that, The housing (17) of the drive unit (7) serves as a handle of the drive unit (7) and for this reason has a curved shape that can be easily lifted by one hand.

11. The drive unit (7) according to claim 8, characterized in that, A portion of the purge tube (53) extends between the proximal portion (52) of the conduit (2) and the housing (17) of the drive unit (7).

12. The drive unit (7) according to claim 8, characterized in that, Also included is a thermal insulator disposed between the purge tube (53) and the housing (17) of the drive unit (7).

13. A heart assist device (1) comprising an external drive unit (7) and an implantable heart assist pump (4), wherein said drive unit (7) comprises: A motor housing (51), a percutaneous drive shaft (3), and a motor (35) for driving the heart assist pump (4), wherein the motor (35) is connected to the heart assist pump (4) by the drive shaft (3), and wherein the motor (35) is disposed within the motor housing (51). The drive unit (7) further includes: a conduit (2) surrounding the drive shaft (3). And a purge tube (53) for injecting a purge medium into the inner lumen of the conduit (2) or into the gap (41) between the conduit (2) and the drive shaft (3). Wherein the heart assist device (1) and / or the drive unit (7) includes a fluid conveyor configured to flow a purge medium. Wherein the motor (35) includes a stator (37) and a rotatably mounted rotor (36) connected to the drive shaft (3), wherein a fluid gap (43) is formed between the rotor (36) and the stator (37), wherein the fluid gap (43) is in fluid communication with a purge port (42) for injecting a purge medium into the fluid gap (43), and wherein the purge tube (53) is connected or connectable to the purge port (42). Wherein the purge tube (53) and the fluid gap (43) are configured to direct the purge medium such that it first makes thermal contact (55) with the outer surface of the motor housing (51) and / or makes thermal contact (54) with the outer surface of the proximal portion (52) of the conduit (2), and is subsequently injected into the fluid gap (43) between the rotor (36) and the stator (37), and is then injected into the lumen of the conduit (2) or into the void (41) between the conduit (2) and the drive shaft (3).

14. An external drive unit (7) for an implantable heart assist pump (4), comprising: A motor housing (51), a percutaneous drive shaft (3), and a motor (35) for driving the heart assist pump (4), wherein the motor (35) is connected or connectable to the heart assist pump (4) via the percutaneous drive shaft (3), and wherein the motor (35) is disposed within the motor housing (51). Wherein the drive unit (7) further comprises: a conduit (2) surrounding the drive shaft (3). And a purge tube (53) for injecting a purge medium into the lumen of the conduit (2) or into the void (41) between the conduit (2) and the drive shaft (3). Characterized in that the drive unit (7) further comprises a housing (17). Wherein the housing (17) of the drive unit (7) serves as a handle of the drive unit (7) and thus has a curved shape that can be easily lifted by one hand for this reason. Wherein the motor (35) comprises a stator (37) and a rotatably mounted rotor (36) connected to the drive shaft (3), wherein a fluid gap (43) is formed between the rotor (36) and the stator (37), wherein the fluid gap (43) is in fluid communication with a purge port (42) for injecting a purge medium into the fluid gap (43), and wherein the purge tube (53) is connected or connectable to the purge port (42). Wherein the purge tube (53) and the fluid gap (43) are configured to direct the purge medium such that it first makes thermal contact (55) with the outer surface of the motor housing (51) and / or makes thermal contact (54) with the outer surface of the proximal portion (52) of the conduit (2), and is subsequently injected into the fluid gap (43) between the rotor (36) and the stator (37), and is then injected into the lumen of the conduit (2) or into the void (41) between the conduit (2) and the drive shaft (3).

15. An external drive unit (7) for an implantable cardiac assist pump (4), comprising: A motor housing (51), a percutaneous drive shaft (3), and a motor (35) for driving the heart assist pump (4), wherein the motor (35) is connected or connectable to the heart assist pump (4) via the percutaneous drive shaft (3), and wherein the motor (35) is disposed within the motor housing (51). Wherein the drive unit (7) further comprises: a conduit (2) surrounding the drive shaft (3). and a purge tube (53) for injecting a purge medium into the lumen of the catheter (2) or into the gap (41) between the catheter (2) and the drive shaft (3), wherein the drive unit (7) includes a heat pipe thermally connected to the motor (35); wherein the motor (35) includes a stator (37) and a rotatably mounted rotor (36) connected to the drive shaft (3), wherein a fluid gap (43) is formed between the rotor (36) and the stator (37), wherein the fluid gap (43) is in fluid connection with a purge port (42) for injecting a purge medium into the fluid gap (43), and wherein the purge tube (53) is connected or connectable to the purge port (42); the purge tube (53) and the fluid gap (43) are configured to direct the purge medium such that it first makes thermal contact (55) with the outer surface of the motor housing (51) and / or makes thermal contact (54) with the outer surface of the proximal portion (52) of the catheter (2), and is then injected into the fluid gap (43) between the rotor (36) and the stator (37), and is subsequently injected into the lumen of the catheter (2) or into the gap (41) between the catheter (2) and the drive shaft (3).

16. An external drive unit (7) for an implantable heart assist pump (4), comprising: A motor housing (51), a percutaneous drive shaft (3), and a motor (35) for driving the heart assist pump (4), wherein the motor (35) is connectable to the heart assist pump (4) via the percutaneous drive shaft (3), and wherein the motor (35) is arranged within the motor housing (51), wherein the drive unit (7) further includes: a catheter (2) surrounding the drive shaft (3), and a purge tube (53) for injecting a purge medium into the lumen of the catheter (2) or into the gap (41) between the catheter (2) and the drive shaft (3), wherein the drive unit (7) further includes: a heat sink (19), the heat sink (19) including a contact surface configured to contact the patient's skin, wherein the contact surface is thermally connected to or connectable to the motor (35) to transfer heat generated by the motor (35) to the patient's tissue; wherein the motor (35) includes a stator (37) and a rotatably mounted rotor (36) connected to the drive shaft (3), wherein a fluid gap (43) is formed between the rotor (36) and the stator (37), wherein the fluid gap (43) is in fluid connection with a purge port (42) for injecting a purge medium into the fluid gap (43), and wherein the purge tube (53) is connected or connectable to the purge port (42); The purge tube (53) and the fluid gap (43) are configured to direct the purge medium such that it first makes thermal contact (55) with the outer surface of the motor housing (51) and / or makes thermal contact (54) with the outer surface of the proximal portion (52) of the conduit (2), and is subsequently injected into the fluid gap (43) between the rotor (36) and the stator (37), and is then injected into the lumen of the conduit (2) or into the void (41) between the conduit (2) and the drive shaft (3).

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