Abstract:
A medical implant system comprises an implant proportioned for implantation within a blood vessel, a lead coupled to the implant, and an anchor coupled to the lead, the anchor configurable in a radially compressed position so as to be positioned in the blood vessel, and a radially expanded position for engagement with the wall of blood vessel. The anchor functions as an antenna for telemetric communication with an extracorporeal device and/or as a receiver for inductive recharging of secondary cells in the implant using an extracorporeal charging device.

Description:
[0001]    The present application claims the benefit of U.S. Provisional Application No. 61/078,408 filed Jul. 6, 2008. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of systems and methods for communicating with and/or supplying recharging energy to medical implants using external devices. 
       BACKGROUND 
       [0003]    Applicants&#39; prior applications disclose intravascular leads used to deliver energy stimulus to the heart, or to nervous system structures such as nerves and nerve endings, and/or used to deliver agents into the bloodstream. See U.S. 2005/0043765 entitled INTRAVASCULAR ELECTROPHYSIOLOGICAL SYSTEM AND METHOD; U.S. 2005/0234431, entitled INTRAVASCULAR DELIVERY SYSTEM FOR THERAPEUTIC AGENTS; U.S. 2007/0255379 entitled INTRAVASCULAR DEVICE FOR NEUROMODULATION, U.S. Ser. No. 12/413,495 filed Mar. 27, 2009 entitled SYSTEM AND METHOD FOR TRANS VASCULARLY STIMULATING CONTENTS OF THE CAROTID SHEATH; and U.S. Ser. No. 12/419,717 filed Apr. 7, 2009 and entitled INTRAVASCULAR SYSTEM AND METHOD FOR BLOOD PRESSURE CONTROL. 
         [0004]      FIG. 1  shows such one such system positioned in the vasculature. The illustrated system includes an elongate device body  12 , one or more leads  14 , and a retention device or anchor  16 . 
         [0005]    The leads may be used to electrically couple the device body  12  to elements  26  such as electrodes, ultrasound transducers, or other elements that will direct energy to target tissue. When they are to be used for delivering agents into the vasculature, the leads fluidly couple the device body to fluid ports such as valves, openings, or fluid transmissive membranes. Some leads might include sensors that are positioned for detecting certain conditions of the patient and for transmitting signals indicative of the sensed conditions. 
         [0006]    The leads  14  are connected to the device body  12 , which is also positioned in the vasculature. The device body houses a power source which may include a battery and a power generation circuit to produce operating power for energizing the stimulation elements and/or to drive a pump for delivery of agents and/or to operate sensors. Where the implant is an electrical stimulator, the intravascular housing includes an electrical pulse generator for generating stimulation pulses for transmission to the patient via electrodes associated with the leads and optionally to other electrodes directly on the body of the implantable device. A processor may be included in the intravascular housing for controlling operation of the device. 
         [0007]    Some of the disclosed leads are anchored in blood vessels using expandable anchors  16  which may have stent-like or other suitable configurations. Stimulation elements such as the electrodes  26  may be carried by the anchor  16 . As shown in  FIG. 1 , the anchors expand into contact with the vessel walls to maintain the position of the lead and to position electrodes  26  in contact with the vessel wall. Similar anchoring devices may be used to anchor the device body  12  if needed. 
         [0008]    Use of external charging devices for inductively recharging batteries of medical implants has been previously described. Use of external programmers to remotely communicate with implants has also been described. See, for example, U.S. Pat. No. 5,967,986 which describes a stent having ultrasonic sensors where an antenna on or forming the stent is used to communicate with an external device and to receive electrical power electromagnetically transmitted from an external device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  shows an intravascular implant having leads anchored in the internal jugular veins and an implant disposed in the inferior vena cava. 
           [0010]      FIG. 2  is a block diagram illustrating an exemplary embodiment of an intravascular implant system having recharging and/or telemetric communication capabilities. 
           [0011]      FIGS. 3-7  are perspective views showing embodiments of intravascular anchoring devices having telemetric antennas and/or recharging coils. 
           [0012]      FIG. 8  shows a lead and anchor positioned in the vasculature of a human subject for use in receiving recharging energy or telemetrically communications from an external device. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The present application discloses the use of an anchor of the type disclosed with respect to  FIG. 1  as an antenna for telemetric communication and/or as a receiver for inductive recharging of secondary cells in the implant. Embodiments are shown and described with respect to use of the antenna in an intravascular system for use in delivering electrical stimulation to nervous system targets or tissue of the heart. However it is to be understood that these concepts may be used with other types of intravascular implants without departing from the scope of the present invention. 
         [0014]    In the system  100  shown in  FIG. 2 , implant device  12  houses a power source  11  which may include a battery and a power generation circuit to produce operating power for stimulation. Device  12  also includes a pulse generator  13  for generating stimulation pulses for transmission to the patient via electrodes  26  on leads  14  and optionally to electrodes on the body of the implantable device  12 . A processor  30  may be included for controlling operation of the device  12 . 
         [0015]    In one embodiment, the system  100  includes a battery  11  that is rechargeable. An external charger  32  positioned outside the patient inductively couples to a coil mounted on the anchor  16  associated with the lead  14  or device  12  ( FIG. 1 ). This internal coil is electrically connected to a charging circuit  33  within the device  12  to recharge the battery. The external charger  32  includes a primary charging coil energizable to create an electromagnetic field that in turn induces current in the implanted coil associated with the anchor. The external charger may be mounted to a waist pack, wearable skin-contacting/adhering patch, purse, backpack, collar, garment (e.g. a vest that communicates with components in the torso), or wheelchair cushion so that it can be carried by the patient in sufficient proximity to the internal coil. Alternatively, the coil may be positioned within a pad positionable on a patient&#39;s mattress, allowing for charging of the battery while the patient rests. 
         [0016]    The system  100  may also (or alternatively) include an external programmer  34  that communicates with a telemetry interface  36  within the implantable device  12  using radio frequency encoded signals or other telemetric methods. In this embodiment, the antenna for receiving the telemetric signals is coupled to an anchor  16  used for the lead  14  or device  12  ( FIG. 1 ). Telemetry systems permitting external devices to communicate with implanted medical devices are known in the art. See, for example, U.S. Pat. Nos. 6,824,561, 5,312,453 and 5,127,404. A user may use the programmer  34  to configure the device  12  (e.g. to set dosing schedules, to set the thresholds above/below which stimulation will be given, to set stimulation parameters), to review the history of therapy given by the implant, to test the implant, to allow the patient to direct release of analgesics for pain control, etc. Where multiple electrodes are employed, the programmer  34  may be used to identify the most optimal electrode pair for stimulating the target structure as discussed in greater detail below. 
         [0017]    Sensors  38  can be positioned for detecting certain conditions of the patient and for transmitting signals indicative of the sensed conditions. Signals corresponding to the sensed conditions may be used to trigger the delivery of and/or sensor output may be stored within the device for subsequent retrieval using external programmer  34 . 
         [0018]    Where both telemetry and inductive recharging are used, the external charger  32  and external programmer  34  may be part of a single external device. 
         [0019]    In some arrangements, the anchors having telemetric antennas and/or recharging coils are preferably positioned in areas of the vasculature that are closer to the surface rather than deep within the body. For example, in the  FIG. 1  arrangement in which leads are positioned in one or both of the internal jugular veins, one or both of the anchors  16  might be equipped with antennas or coils, allowing charging or telemetry to be carried out using an external device positioned near the neck (e.g. in a collar positioned around the neck or a pillow underneath the neck while the patient sleeps). Use of an external coil within a garment worn by the patient may be used for various embodiments. 
         [0020]    In the anchor embodiments discussed below, the anchor used for the device  12  or lead  14  includes structural features that allow the anchor to radially engage a vessel wall. For example, a band, sleeve, mesh, laser cut tubing, or other framework formed of one or more shape memory (e.g. nickel titanium alloy, nitinol, thermally activated shape-memory material, or shape memory polymer) elements or stainless steel, Elgiloy, or MP35N elements. In some embodiments, the anchor and antenna/coil are integral components. Forming the anchors using an electrically conductive structural materials is particularly advantageous in that it allows the metal structure of the anchor to serve as the antenna or coil, thus eliminating the need for additional components. In other embodiments, the antenna may be a separate feature mounted to the structure of the anchor. 
         [0021]      FIGS. 3-5  illustrate designs of anchors incorporating antennas useful for telemetric communication. Referring to  FIG. 3 , anchor  16   a  is an electrically conductive anchor functioning as both anchor and antenna. In this embodiment, the anchor  16   a  is one used to retain a lead within the vasculature. Antenna transmission wires  40  extend from the anchor  16   a  to the device body  12  ( FIG. 1 ). Electrodes  26  are mounted to the anchor  16   a . Conductors  42  extend from the electrodes  26  to the device body. Electrically insulative material  44  insulates the electrodes  26  from the anchor. Conductors  40 ,  42  may be packaged together within the lead  14 , or they may be in separate leads. 
         [0022]    In the  FIG. 4  embodiment, anchor  16   b  includes an undulating antenna portion  46  and electrodes  26  isolated from the antenna portion  46  by insulating material  44 . Electrically insulated electrode wires and antenna wires (coupled to the communication circuitry within the device  12 ) extend through the lead  14  to the device  12 . 
         [0023]      FIG. 5  shows an antenna/anchor coupled to device body  12  rather than to a lead. In this embodiment, telemetric signals between the communication circuitry within the device  12  and the antenna may be conducted through the mechanical couplings between the antenna/anchor  16   c  and the device  12 . 
         [0024]      FIGS. 6 and 7  show anchors equipped with recharging coils. The ability to recharge the batteries can significantly prolong the life of an implanted device. In these embodiments, AC charging current from a primary coil in the external charger  32  induces a current in the pick-up coil on the anchor. A rectifier (preferably within the device  12  but optionally mounted to the anchor) converts the AC current to DC current, which is used to charge the battery contained within the device  12 . 
         [0025]    In other embodiments, electrical power from the external device may be used to power the implant rather that to, or in addition to, its use for recharging the battery. 
         [0026]    In the  FIG. 6  embodiment of an anchor coil  16   d , the coil functions both as anchor and as a recharging coil. Electrodes  26  are electrically insulated from the coil using insulative material  44  as shown. Electrically insulated electrode wires and recharge wires (coupled to the recharging circuitry within the device  12 ) extend into the lead  14 . 
         [0027]    In an alternate embodiment shown in  FIG. 7 , the anchor  16   e  is formed of coiled struts  48  that function as recharging coils. Here the electrodes  25  are positioned on a strip of insulating material  44  attached to the free ends of the coiled struts. 
         [0028]    It should be noted that while in the  FIGS. 3 ,  4  and  6  embodiments the electrodes are described as being mounted to the anchor, they may instead be separate components that are sandwiched between the anchor and the vessel wall upon expansion of the anchor. For example, electrodes on an insulative pad may be positioned adjacent the vessel wall prior to expansion of the anchor, so that expansion of the anchor retains the electrodes in contact with the vessel wall. In this modified embodiment, the conductors associated with the electrode extend to the device body  12  separate from the lead  14 . 
         [0029]    Although much of the prior discussion has addressed the anchors that are used for anchoring electrodes on a lead or device, an anchors may be specifically positioned only for its use in recharging and/or communicating. Such anchors may be positioned in vessels selected for their proximity to the median cubital vein in the region of the inner elbow as shown in  FIG. 8 , thus allowing the external charger or telemetry interface to be worn on the arm (e.g. using an arm band, cuff or garment). Other suitable locations include the inferior vena cava, femoral vein, brachial vein, basilica vein or pulmonary artery. Other locations may be suitable, particularly where the implant system is used for other clinical applications. For example, antennas or coils may also be positioned subcutaneously, the superior mesenteric vein, the portal vein, the celiac trunk, the pancreatic duodenal vein (e.g. in a system used for pancreatic stimulation to regulate insulin production). 
         [0030]    All prior patents and applications referred to herein are incorporated by reference for all purposes. 
         [0031]    It should be recognized that a number of variations of the above-identified embodiments will be obvious to one of ordinary skill in the art in view of the foregoing description. Accordingly, the invention is not to be limited by those specific embodiments and methods of the present invention shown and described herein. Rather, the scope of the invention is to be defined by the following claims and their equivalents.