Patent Publication Number: US-2007106274-A1

Title: Control systems for implantable medical devices

Description:
FIELD OF THE INVENTION  
      The present invention relates to improvements to control systems for implantable medical devices.  
     BACKGROUND OF THE INVENTION  
      In the past, there have been many implantable medical devices that require bulky and sophisticated control systems. These control systems are generally mounted within a solid external housing or other mounting box. This housing or box is generally bulky and cumbersome to carry and use, particularly so for elderly or sick patients, and if they are to be carried for an extended period of time. Some implantable medical devices may require the patient to carry around the control system and/or the medical device for the rest of their life. These sorts of implantable medical devices may include implantable blood pumps or left ventricular assist devices.  
      U.S. Pat. No. 6,895,280—Meadows et al, discloses a control system for an implantable medical device wherein the control circuit is mounted in a relatively bulky and rigid box type housing. U.S. Pat. No. 6,889,084—Thompson et al, discloses a control system that includes a miniaturized control circuit with an RF transmission system. Even though this control system and circuit has been miniaturized, the control system may be considered to be relatively bulky as the control system is housed within a box that is not mounted on the skin of the patient.  
      Therefore, there has been a long-felt need for a control system for use with an implantable medical device that minimises the bulk and addresses patient&#39;s physical needs. There has also been a long-felt need to improve patient comfort. Many previous devices and systems are not designed with consideration to the needs of patients using medical devices for extended periods of time.  
      The present invention aims to, or at least address or ameliorate, one or more of the disadvantages associated with the above-mentioned prior art.  
     SUMMARY OF THE INVENTION  
      In accordance with a first aspect the present invention consists of a control system for use with an implantable medical device, wherein said control system includes a control circuit carried by a skin patch that is adapted to be attached to the outer surface of the skin layer of a patient.  
      Preferably, said control circuit is encapsulated within said skin patch.  
      Preferably, said skin patch is made from a mouldable material.  
      Preferably, said mouldable material is silicone.  
      Preferably, said patch is bendable or deformable to suit anatomical positioning.  
      Preferably, said control circuit includes a vibrating alarm.  
      Preferably, the outer surface of said patch is partially coated with adhesive.  
      Preferably, said implantable medical device is an implantable rotary blood pump.  
      In accordance with a second aspect the present invention consists of a skin patch adapted to be attached to the outer surface of the skin layer of a patient, said patch carrying a control circuit for use with an implantable medical device.  
      Preferably, said skin patch is made from a mouldable material.  
      Preferably, said control circuit is encapsulated within said mouldable material.  
      Preferably, said patch is bendable or deformable to suit anatomical positioning.  
      Preferably, said control circuit includes a vibrating alarm.  
      Preferably, the outer surface of said patch is partially coated with adhesive.  
      In accordance with a third aspect the present invention consists of a control system for use with an implantable blood pump, said system comprising a control circuit carried by a bendable skin patch adapted to be attached to the outer skin layer of a patient.  
      Preferably, said control circuit includes a vibrating alarm.  
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
      The embodiments of the present invention will now be described with reference to the accompanied drawings wherein:  
       FIG. 1  depicts a top view of a first embodiment of the present invention;  
       FIG. 2  depicts a side cross-sectional view of the first embodiment as depicted in  FIG. 1 .  
       FIG. 3  depicts a perspective view of a control circuit in accordance with a second embodiment of the present invention. 
    
    
     BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS  
      In  FIGS. 1 and 2 , a first embodiment of the present invention is depicted and includes a control system  110 . The control system  110  includes a control circuit  101  encapsulated within a patch  102  mounted on the skin layer  103  of a patient.  
      Preferably, the control circuit  101  is electrically connected to a power source  104  via a first set of wires  107 . The control circuit  101  is also electrically connected to an implantable medical device  111 , which in this embodiment is a left ventricle assist device, via a second set of wires  105 . This left ventricular assist device  111  may be an implantable rotary blood pump such as the VentrAssist™ as described in U.S. Pat. No. 6,227,797—Watterson et al. This particular US patent is included within the description of the present invention forms part of this description.  
      In this arrangement, the control circuit  101  regulates, provides power to, and extracts data from, the left ventricle assist device  111 . Power source  104  provides electrical power to power circuit  101  which then supplies electrical power onto the implantable medical device  111 .  
      The power source  104  may be replaced with either: a mains power connection; a single battery; or a combination thereof. Please note that this power source  104  may be adapted to be suitable for various implantable medical device  111 .  
      Preferably, the second set of wires  105  may be in the form of a percutaneous lead which exits the skin layer  103  of a patient through a permanent exit wound  105 .  
      Preferably, control circuit  101  may be encapsulated within a patch  102 . The patch  102  may be generally flexible (or bendable) so the patch may be twisted, bent or otherwise deformed so as to adapt to the region of the outer skin layer  103  upon which it is mounted. Preferably, the patch  102  includes either a biocompatible or external use medical adhesive which is capable of adhering said patch  102  to the outer skin layer  103  of a patient. The patch  102  may be moulded from a materials including silicone. Preferably, the adhesive  112  is suitably strong enough to resist pulling or tearing associated with accidental movement of the first set of wires  107  or the power source  104 .  
      The control circuit  101  may also preferably include a control system as disclosed in U.S. Pat. No. 6,866,625—Ayre et al. The description of this patent is included within this specification herein.  
      The control circuit  101 , being encapsulated within patch  102 , may allow the entire control arrangement  110  to be overall less bulky than comparable systems. The reduction of bulk may lead to increases in patient comfort. The reduction of weight may also lead to reduced incidence of accidental wear and tear on the percutaneous lead assembly formed by the combination of the first set of wires  107  and the second set of wires  105 .  
      The portion of the percutaneous lead assembly exiting through skin layer  103  may be replaced with a Transcutaneous Energy Transmission System (“TETS”) and eliminating the need for a permanent exit wound  106  in the skin layer  103  of the patient. TETS is a system whereby energy, power, and data may be transmitted transcutaneously across the skin layer  103  by use of RF transmission to the implantable medical device  111  using electromagnetic coils (not shown) mounted on either side of the skin layer of the skin to provide a means for power transmission by RF frequencies.  
      In a second embodiment the control system of the present invention may comprise a control circuit  200  on a printed circuit board  208  that includes a specialised alarm, as shown in  FIG. 3 . The control circuit  200  is encapsulated in a patch (not shown) that is similar to patch  102  of the first embodiment, and would be used for an implantable medical device  111  similar to that referred to earlier. The specialised alarm may be in the form of a miniature motor  202  mounted on or in the control circuit  200  via a support bracket  210 . The rotor  204  of the miniature motor  202  is connected to an extrinsic arm  206 , that is not balanced around the centre of its rotation, such that rotation of the arm  206  causes a small vibration. This vibration, when the motor  202  is mounted to the control circuit  200 , is sufficient to cause a vibration of the control circuit  200  and the patch. This vibration may be then passed to the skin layer of the patient wherein the patient will feel a small vibration and be alerted, when necessary. This alarm may be a significant improvement over previous audible or visual alarms as it will alert the patient to a problem raised by the control circuit  200  no matter what the physical conditions of the patient are including, but not limited to, high levels of background noise or high levels of background light, which would otherwise make other types of alarms inappropriate.  
      Whilst the implantable medical device  111  referred to in the abovementioned first embodiment is a left ventricle assist device, it should be understood that the present invention may be used with other types of implantable medical devices.  
      The above descriptions detail only some of the embodiments of the present invention. Modifications may be obvious to those skilled in the art and may be made without departing from the spirit and the scope of the present invention.