Abstract:
A circulatory assist system is disclosed, the system including an implantable electrical device having an electric motor, an implantable controller connected to the implantable electrical device, and an implantable power source connected to the controller for supplying power to the controller. The controller is attachable to a first side of a percutaneous connector. A second side of the percutaneous connector, opposite to the first side, allows external connectivity to said controller.

Description:
[0001]    This application claims the benefit of U.S. Provisional Applications Nos. 61/399,315, filed Jul. 9, 2010 and 61/277,135, filed Sep. 21, 2009, the contents of each of which are hereby incorporated by reference into this application. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to implantable medical devices. Specifically, the invention relates to a system for controlling implantable medical devices. 
       BACKGROUND OF THE INVENTION 
       [0003]    Implantable medical devices such as ventricular assist devices are being developed for long term treatment of chronic heart failure. Such devices require a pumping mechanism to move blood. Due to the nature of the application, the pumping mechanism must be highly reliable. Patient comfort is also a significant consideration. 
         [0004]    Transcutaneous energy transfer (“TET”) systems are used to supply power to devices such as heart pumps implanted internally within a human body. An electromagnetic field generated by a transmitting coil outside the body can transmit power across a cutaneous (skin) barrier to a magnetic receiving coil implanted within the body. The receiving coil can then transfer the received power to the implanted heart pump or other internal device and to one or more batteries implanted within the body to charge the battery. 
         [0005]    One of the challenges of such systems is insufficient battery lifetime. The implanted battery may be required to supply the implanted device&#39;s entire power demand for one to several hours at a time, such as when the patient does activities that preclude wearing the external TET power unit, such as showering or swimming. When the implanted battery is first implanted into the patient, the battery capacity is large and can meet the power demand for the required amount of time. However, when subjected to frequent charging and discharging, the implanted battery&#39;s capacity decreases. With decreased battery capacity, the patient cannot spend as much time without the external TET power unit. Eventually, the battery may need to be replaced so that the patient can go without the external TET power unit for long enough periods of time again. 
         [0006]    In addition to the foregoing problems, the use of inductive coils by TET systems to wirelessly transfer power to an implanted battery results in slow recharging times, as inductive charging has lower efficiency and increased heating in comparison to direct contact. Thus, there is a need in the art for ventricular assist device (“VAD”) technology that improves patient lifestyle during internal battery operation (“tether free”) and reduces bulkiness of the external hardware during normal operation. Therefore, there is a need in the art for an implantable component design that solves the problems described above. 
       SUMMARY OF THE INVENTION 
       [0007]    The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later. 
         [0008]    In accordance with one embodiment of the invention, an implantable controller and implantable power source attach to an implantable electrical device, such as a VAD, for powering the implantable electrical device when tether-free operation is desired, for example. In another embodiment of the present invention, a second power source, which may be referred to herein as an external power source in embodiments where implantable elements are actually implanted, supplies power to the implanted system and recharges the implantable power source by direct contact through a percutaneous connector. 
         [0009]    In one embodiment, a backup controller is provided and it may have a hard wire communication link, through a percutaneous connector, to directly communicate with the implanted controller and serve as a programming/monitoring/diagnostic device). A back-up controller, which may be referred to herein as an external backup controller in embodiments where implantable elements are actually implanted, may also be plugged into the percutaneous connector to control the implantable electrical device. In one embodiment, a monitoring circuit of the implantable power unit can be used to monitor a condition of the implantable power source. The monitoring circuit can transmit a transcutaneous telemetry signal which represents the monitored condition to transfer control of the implantable electrical device to the backup controller or to trigger an alarm to alert a patient that an external power source should be connected to the percutaneous connector. In another embodiment the transcutaneous telemetry signal represents the monitored condition of the implantable controller for use by a control circuit to activate the backup controller. In one embodiment the backup controller transmits signals to the implantable controller through the percutaneous connector to disable the implantable controller and override the pump drive signals that are normally outputted by the implantable controller. In one embodiment, a logic signal used to switch between implantable controller and backup controller may be CMOS compatible (3.3 or 5 Volts, for example), depending on the internal logic design. 
         [0010]    One object of the invention is to provide VAD technology that improves a patient&#39;s lifestyle during tether free operation. Another object of the invention is to reduce the external hardware required during normal operation. 
         [0011]    The following description and the annexed drawings set forth in detail certain illustrative aspects of the invention. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed and the present invention is intended to include all such aspects and their equivalents. Other advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  illustrates components and operation of an implantable therapeutic electrical system in accordance with one embodiment of the invention; 
           [0013]      FIG. 2  illustrates a backup controller and a power source connected to an implantable therapeutic electrical system in accordance with one embodiment of the invention; 
           [0014]      FIG. 3  illustrates a power source connected to an implantable therapeutic electrical system in accordance with one embodiment of the invention; 
           [0015]      FIG. 4  illustrates an implantable therapeutic electrical system in accordance with one embodiment of the invention; and 
           [0016]      FIG. 5  illustrates a backup controller and a power source connected to an implanted therapeutic electrical system in accordance with one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    The embodiments described below provide an alternate configuration to the prior art implantable systems. In some of these embodiments power is provided by an external power source, including a battery, cigarette lighter adapter, AC adaptor or DC power source, through a percutaneous connector. This configuration may be used as an alternative to the TET power transfer disclosed in U.S. Provisional Application No. 61/191,595, assigned to the same assignee of the present application. In some embodiments the percutaneous connector includes extra pin connections to allow a backup controller to be connected in case the implantable controller were to fail. 
         [0018]    In some embodiments, signals are transmitted by the backup controller to inhibit or block the implantable controller&#39;s drive circuits so that the backup controller&#39;s drive circuits tap into pump drive connections. When the implantable controller&#39;s drive MOSFETS are not disabled, the internal circuitry may sink the signal from the external motor drive and not properly drive the pump. 
         [0019]      FIG. 1  illustrates an embodiment of the present invention, including an implantable therapeutic electrical device  101 , such as a VAD device, implantable power sources including a rechargeable power source  103 , a controller  105 , and a skin button  107 . In the illustrated embodiment, the power source  103  supplies power to the controller  105 . In turn, the controller  105  sends driving signals to a motor in the electrical device  101 . The skin button  107  may be implemented as a percutaneous connector that allows external modules to connect to the implantable controller  105 , as well as to the implantable power source  103  and implantable device  101  (through wire lines inside the controller). In one embodiment of the present invention, controller  105 , power source  103  and device  101  are all implanted inside a patient&#39;s body. 
         [0020]    In one embodiment DC power may be supplied through the skin button  107  to the controller  105 , the power source  103  and the device  101 . If the implantable device  101  is a VAD, its power demands may not be supplied by the implantable power source  103  for long periods of time. In such case, the implantable power source  103  may act as a supplemental power source, the primary power being supplied externally through skin button  107 , but the implanted power source  103  may still be used to supply power for short periods of time. 
         [0021]      FIG. 2  illustrates another embodiment of the present invention. The figure illustrates implantable therapeutic electrical device  201 , implantable power source  203 , implantable controller  205 , and wires  233 ,  255 ,  265  and  223 . Also illustrated are external power source  213 , external backup controller  235 , external telemetry transceiver  227 , as well as external wired connections  245  and  243  and wireless connection  217 . 
         [0022]    The controller  205  may include Drive MOSFETs  225  connected to a motor controller  215 . The motor controller  215  may produce control signals for controlling a pump in the illustrated VAD  201 . These control signals may be relayed to the VAD  201  by the Drive MOSFETs  225 . The signals may also be conditioned by the Drive MOSFETs  225 . 
         [0023]    In one mode of operation, the Drive MOSFETs  225  operate as switches that interrupt the signal from the motor controller  215 . In this mode of operation, the backup controller  235  sends the signal through wired connection  265  to command the interruption of the control signal from motor control  215 . Also, the backup controller may supply a backup motor control signal  255  to drive the VAD  201 . In one embodiment, this mode of operation is triggered after the remote telemetry transceiver  225  detects a signal sent over the wireless connection  217  indicative of a malfunction of motor controller  215 . In another embodiment, the backup controller may receive the signal indicative of a malfunction through a wired connection. 
         [0024]    In one embodiment of the present invention, the VAD&#39;s motor may be a permanent magnet brushless, sensorless DC motor. The motor is desirably highly reliable and maintenance free. The drive signals that are input to the stators(s) may be multiphase and biphasic to create a requisite rotating magnetic field excitation for normal operation of the motor. The stator drive signals may range from nearly zero volts to 16 volts, and from zero to three (3) amps. Typical power dissipation may be between 1 to 45 Watts, depending upon selected RPM and resultant flow rate. 
         [0025]    Also, the backup controller may have a hard wire communication link to directly communicate with the implanted controller and serve as a programming/monitoring/diagnostic device. The transceiver  225  may also detect other signals representative of measurements of operational parameters of the implanted module. These can be routed to the external controller  235  for remedial or corrective action. Examples of these parameters include low battery, excessive voltage applied to implanted electrical device (e.g., VAD), high temperature of implanted module, etc. When a signal indicative of low power is received, power may be supplied externally by power source  3131 , the power signal being routed through backup controller. 
         [0026]    Also, with reference to  FIG. 2 , in another mode of operation of the illustrated embodiment, the external rechargeable battery  213  is connected to the skin button  207  (instead of backup controller) and may supply power to the controller  205  through wired connections  223  and  243 . The cable  223  may be of a lesser width and composition from the cable  243 , as cable  223  is implantable. The skin button  207  serves not only as the percutaneous physical interface between external and internal modules, it also serves as the electrical interface. 
         [0027]    The mode of operation where the external power source  213  supplies power to the controller  205  may be triggered by receipt by the transceiver  227  of a signal over wireless connection  217  which is indicative of implanted battery  203  having low power. The “low power” signal may be generated by monitoring the signal fed to the controller  205  over cable  233 . The signal indicative of a malfunction (e.g., low power) may trigger a visual or audible alarm to alert the patient to connect external power source to the skin button. 
         [0028]      FIG. 3  illustrates another configuration of the system of the present invention. In the illustrated embodiment the backup controller  213  is not connected to the skin button  207 . When the backup controller is not plugged into the skin button, the skin button may mechanically ground the input MOSFET disable signal  265  to avoid accidental disabling of controller  205   
         [0029]    In the embodiment illustrated in  FIG. 3 , the telemetry transceiver  227  may still detect whether the controller  205  functions properly and may activate a visual and/or audible alarm to alert the patient of any malfunctioning of the implanted controller  205 . In one embodiment, the alarm may be inserted in a wristwatch for use by the patient. 
         [0030]      FIG. 4  illustrates the system components that may be used in one mode of operation. In this embodiment, neither the external battery (or power sources)  213  nor the backup controller is connected to the skin button  207 , allowing the patient to move freely without any external physical connections. 
         [0031]    In the embodiment illustrated in  FIG. 4 , the external transceiver  227  is still able to detect anomalies in the operation of the implanted controller  205  or in the supply of power through cable  233  and alert the patient of these. In the event that there are any anomalies, the patient may plug in either the battery  213  or the backup controller  235  as illustrated in  FIG. 3 . Alternatively, the power source  213  and the controller  235  may be connected in series as illustrated in  FIG. 5 , with the signal for providing power being routed through the controller  235 . 
         [0032]    The foregoing description of possible implementations consistent with the present invention does not represent a comprehensive list of all such implementations or all variations of the implementations described. The description of only some implementation should not be construed as an intent to exclude other implementations. For example, an embodiment described as including implantable components should not be construed as an intent to exclude an implementation whereby those components are actually implanted in a patient&#39;s body. Artisans will understand how to implement the invention in many other ways, using equivalents and alternatives that do not depart from the scope of the following claims. Moreover, unless indicated to the contrary in the preceding description, none of the components described in the implementations are essential to the invention.