Abstract:
A catheter system and method are employed to implant components of a medical device inside an animal. The catheter system includes a plurality of coaxial catheters and sheaths between which electrically interconnected components of the medical device are releasably held. A guide wire is inserted to a desired location inside the animal and the plurality of catheters and sheaths is slid as an assembly along the guide wire to that location. One of the sheaths is moved with respect to the other catheters and sheaths to release one of the components. The guide wire and the remaining catheters and sheaths are repositioned to a second location inside the animal and manipulated to release another component. Additional components can be implanted by further repositioning and manipulating steps. The catheter system is removed from the animal leaving the components in place.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a continuation in part of U.S. patent application Ser. No. 11/112,181 filed on Apr. 22, 2005.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates to medical devices that are implanted into the vasculature of an animal, and more particularly to the apparatus for performing the implantation.  
         [0005]     2. Description of the Related Art  
         [0006]     A remedy for people with slowed or disrupted natural heart activity is to implant a cardiac pacing device which is a small electronic apparatus that stimulates the heart to beat at regular rates.  
         [0007]     Typically the pacing device is implanted in the patient&#39;s chest and has sensor electrodes that detect electrical impulses associated with in the heart contractions. These sensed impulses are analyzed to determine when abnormal cardiac activity occurs, in which event a pulse generator is triggered to produce electrical pulses. Wires carry these pulses to electrodes placed adjacent specific cardiac muscles, which when electrically stimulated contract the heart chambers. It is important that the electrodes be properly located to produce contraction of the heart chambers.  
         [0008]     Modem cardiac pacing devices vary the stimulation to adapt the heart rate to the patient&#39;s level of activity, thereby mimicking the heart&#39;s natural activity. The pulse generator modifies that rate by tracking the activity of the sinus node of the heart or by responding to other sensor signals that indicate body motion or respiration rate.  
         [0009]     U.S. Pat. No. 6,445,953 describes a cardiac pacemaker that has a pacing device, which can be located outside the patient, to detect abnormal electrical cardiac activity. In that event, the pacing device emits a radio frequency signal, that is received by a stimulator implanted in a vein or artery of the patient&#39;s heart. Specifically, the radio frequency signal induces a voltage pulse in an antenna on the stimulator and that pulse is applied across a pair of electrodes, thereby stimulating adjacent muscles and contracting the heart.  
         [0010]     The stimulator in that wireless system is powered by the energy of the received signal thus requiring that the pacing device transmit a relatively strong radio frequency signal in order to provide adequate energy to the stimulator implanted deep in the patient&#39;s chest. It is desirable to place the stimulator, or at least the antenna for the stimulator, in a blood vessel located closer to the skin of the patient with electrodes implanted in one or more cardiac blood vessels and connected to the stimulator by wires extending through the electronic circuit circulatory system. This would enable more of the energy from the frequency signal to reach the stimulator, however, the blood vessels close to the skin are not sufficiently large to accommodate the size of the stimulator.  
         [0011]     The antenna, usually in the form of a coil, must possess several characteristics in order to function within the blood vessel. The coil must retain its shape in order to remain tuned to the particular radio frequency being used. The conductors of the antenna have to be insulated so that the blood and other substances flowing through the vascular system do not provide a short circuit or otherwise detune the antenna. In addition the antenna must be biologically compatible with the blood vessel walls and with the blood.  
         [0012]     Therefore, it is desirable to provide an apparatus for positioning each of the components of the medical device in the patient.  
       SUMMARY OF THE INVENTION  
       [0013]     A catheter system is provided to implant a medical device in an animal, wherein the medical device has a plurality of components that are to be placed at different locations. The system is particular adapted to implant a medical device in which the components are electrically interconnected by wires.  
         [0014]     The catheter system comprises a guide wire, a first catheter with a guide wire lumen for slidably receiving the guide wire, and a tubular outer sheath through which the first catheter extends. A first cavity is formed between the first catheter and the outer sheath within which a first component of the medical device is releasably located. A second cavity also is formed between the first catheter and the outer sheath within which a second component of the medical device is releasably located.  
         [0015]     In a preferred embodiment, the catheter system further includes a second catheter with a lumen within which the first catheter is slidably received. Thus, the first and second catheters are both within the outer sheath. The first cavity is located between the first and second catheters and the second cavity is located between the second catheter and the outer sheath. As an option, an inner sheath may be provided between the first and second catheters, with the first cavity between the first catheter and the inner sheath. More catheters and sheaths may be added coaxially on the catheter system to deliver additional components into the animal.  
         [0016]     The catheter system is manipulatable to independently release each of the first and second components at different locations in the animal. Initially the guide wire is inserted into the animal to a first location. Then, the assembly of catheters is slid over the guide wire until reaching the first location. The outer sheath is moved over the second catheter to expose the second component, that is deposited at the first location.  
         [0017]     If a desired second location for implantation of the second first component is along the existing route of the guide wire through the animal, the first and second catheters are slid along the guide wire to place the first component at the second location. Otherwise, the guide wire can be repositioned to the second location before the first and second catheters are slid into place. Thereafter, the first and second catheters are moved with respect to each other to expose the first component, which is deposited at the second location.  
         [0018]     A second embodiment of a catheter system having two guide wires and two catheter assemblies, one for each guide wire, also is described. The two catheter assemblies cooperate to implant a greater plurality of components, that are electrically interconnected by wires.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is a representation of a cardiac pacing system attached to a medical patient;  
         [0020]      FIG. 2  is an isometric, cut-away view of a patient&#39;s blood vessels in which a receiver antenna, a stimulator and an electrode of an intravascular medical device have been implanted at different locations;  
         [0021]      FIG. 3  is a longitudinal cross sectional view through a distal end of a catheter system for implanting the components of the intravascular medical device;  
         [0022]      FIG. 4  is a transverse cross sectional view through a catheter system along line  4 - 4  of  FIG. 3 ;  
         [0023]      FIG. 5  is a transverse cross sectional view through a catheter system along line  5 - 5  of  FIG. 3 ;  
         [0024]      FIG. 6  is a transverse cross sectional view through a catheter system along line  6 - 6  of  FIG. 3 ;  
         [0025]      FIGS. 7-14  depict a sequence of steps by which the components of the intravascular medical device are implanted in the patient; and  
         [0026]      FIGS. 15-25  illustrate an alternative sequence of steps by which the medical device components are implanted in a patient&#39;s vascular system. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]     Although the present invention is being described in the context of implanting components of a cardiac pacing system, it can be used to implant other types of medical devices into a patient&#39;s body. Furthermore, the present apparatus and method are not limited to implanting items in an animal&#39;s vascular system, but can be employed to implant elements elsewhere in the animal.  
         [0028]     Initially referring to  FIG. 1 , a cardiac pacing system  10  for electrically stimulating a heart  12  to contract comprises an external power source  14  and a medical device  15  implanted in the circulatory system of a human medical patient. The medical device  15  receives a radio frequency (RF) signal from the power source  14  worn outside the patient and the implanted electrical circuitry is electrically powered from the energy of that signal. At appropriate times, the medical device  15  delivers an electrical stimulation pulse into the surrounding tissue of the patient.  
         [0029]     The power source  14  may be the same type as described in U.S. Pat. Nos. 6,445,953 and 6,907,285 and includes a radio frequency transmitter that is powered by a battery. The transmitter periodically emits a signal at a predefined radio frequency that is applied to a transmitter antenna in the form of a coil of wire within a band  22  that is placed around the patient&#39;s upper arm  23 . In a basic version of the cardiac pacing system  10 , the radio frequency signal merely conveys energy for powering the medical device  15  implanted in the patient. In other systems, the transmitter modulates the radio frequency signal with commands received from optional circuits that configure or control the operation of the medical device  15 .  
         [0030]     Referring to  FIGS. 1 and 2 , the exemplary implanted medical device  15  includes an intravascular stimulator  16  located a vein or artery  18  in close proximity to the heart. Because of its electrical circuitry, the stimulator  16  is relatively large requiring a blood vessel that is larger than the arm vein, e.g. the basilic vein, which is approximately five millimeters in diameter. Therefore, the stimulator  16  may be implanted in the superior or inferior vena cava. Electrical wires lead from the stimulator  16  through the cardiac vascular system to one or more locations in smaller blood vessels  19 , e.g. the coronary sinus vein, at which stimulation of the heart is desired. At such locations, the electrical wire  25  are connected to a remote electrode  21  secured to the blood vessel wall.  
         [0031]     Because the stimulator  16  of the medical device  15  is near the heart and relatively deep in the chest of the human medical patient, a receiver antenna  24  for the RF signal is implanted in a vein or artery  26  of the patient&#39;s upper right arm  23  at a location surrounded by the transmitter antenna within the arm band  22 . That arm vein or artery  26  is significantly closer to the skin and thus receiver antenna  24  picks up a greater amount of the energy of the radio frequency signal emitted by the power source  14 , than if the receiver antenna was located on the stimulator  16 . Alternatively, another limb, neck or other area of the body with an adequately sized blood vessel close to the skin surface of the patient can be used. The receiver antenna  24  is connected to the stimulator  16  by a micro-coaxial cable  34 .  
         [0032]     As illustrated in  FIG. 2 , the intravascular stimulator  16  has a body  30  constructed similar to well-known expandable vascular stents. The stimulator body  30  comprises a plurality of wires formed to have a memory defining a tubular shape or envelope. Those wires may be heat-treated platinum, Nitinol, a Nitinol alloy wire, stainless steel, plastic wires or other materials. Plastic or substantially nonmetallic wires may be loaded with a radiopaque substance which provide visibility with conventional fluoroscopy. The stimulator body  30  has a memory so that it normally assumes an expanded configuration when unconfined, but is capable of assuming a collapsed configuration when disposed and confined within a catheter assembly, as will be described. In that collapsed state, the tubular body  30  has a relatively small diameter enabling it to pass freely through the vasculature of a patient. After being properly positioned in the desired blood vessel, the body  30  is released from the catheter and expands to engage the blood vessel wall. The stimulator body  30  and other components of the medical device  15  are implanted in the patient&#39;s circulatory system using a novel technique that employs a unique catheter system described hereinafter.  
         [0033]     The body  30  has a stimulation circuit  32  mounted thereon and, depending upon its proximity to the heart  12 , may hold a first electrode  20  in the form of a ring that encircles the body. Alternatively, when the stimulator  16  is relatively far from the heart  12 , the first electrode  20  can be remotely located in a small cardiac blood vessel much the same as a second electrode  21 . The stimulation circuit  32 , which may be the same type as described in the aforementioned U.S. patents, includes a power supply to which the micro-coaxial cable  34  from the receiver antenna  24  is connected. The power supply utilizes electricity from that antenna to charge a storage capacitor that provides electrical power to the stimulation circuit. A conventional control circuit within the stimulation circuit  32  detects the electrical activity of the heart and determines when electrical pulses need to be applied so that the heart  12  contracts at the proper rate. When stimulation is desired, the stimulation circuit  32  applies electrical voltage from its internal storage capacitor across the electrodes  20  and  21 . The second electrode  21  and the first electrode when located remotely from the stimulator  16 , can be mounted on a collapsible body of the same type as the stimulator body  30 .  
         [0034]     With reference to  FIG. 3 , the components of the medical device  15  are inserted into the patient utilizing a catheter system  50  which is a meter or more long as is necessary to extend from an incision in the patient through the vascular system to the various locations where the components of the medical device  15  are to be implanted. The catheter system  50  has a proximal end that remains outside the patient to which the physician has access to manipulate the elements of the catheter system, and has a distal end that is inserted into the patient and which contains the medical device components.  
         [0035]     The distal end section of the catheter system  50  is illustrated in  FIG. 3  to which continuing reference is made. The catheter system comprises a conventional guide wire  52  over which an assembly  51  of several catheters and sheaths are coaxially inserted. Those catheters and sheaths are made of a flexible biologically compatible material commonly used for medical catheters. A first, or inner, catheter  54  has a tubular construction with a lumen  55  through which the guide wire  52  extends, see also the cross-section through this region of the catheter system  50  in  FIG. 4 . A first component, such as the second electrode  21 , of the medical device is positioned around the end of the first catheter  54  with a first inner sheath  56  around the first component to maintain it in a collapsed state. A first cavity  57  is formed between the first catheter  54  and the first inner sheath  56  within which the first component is located. The first inner sheath  56  extends longitudinally to the proximal end of the first catheter  54  which is outside the patient. Both the first catheter  54  and the first inner sheath  56  have a distal end that is spaced from the distal end  53  of catheter assembly  51 .  
         [0036]     A second, or intermediate, catheter  58  extends longitudinally over the first inner sheath  56  so that the inner components of the catheter system  50  described thus far are located within a lumen  60  of the second catheter  58 , see also the cross-section through this region in  FIG. 5 . The end of the second catheter projects beyond the end of the first catheter, but falls short of the distal end  53  of the catheter assembly  51 . The antenna  40 , which also is referred to herein as a second component of the medical device  15 , is placed around the end section of the second catheter  58  and is held in an elongated, reduced diameter state by a second inner sheath  62  that extends around the antenna  40  and along the second catheter  58  to the proximal end of the catheter system  50 . A second cavity  63  is defined between the second catheter  58  and the second inner sheath  62  within which the second medical device component is located.  
         [0037]     With reference to  FIGS. 3 and 6 , a third catheter  64  is located around and extends along the outside of the second inner sheath  62  and projects to substantially the distal end  53  of the catheter assembly  51 . A third component, in this case the stimulator  16 , is located around the third catheter  64  and is held in its collapsed state by a third, or outer, sheath  66  that forms the outermost element of the catheter system  50  extending around all of the other elements. A third cavity  65  is located between the third catheter  64  and the third sheath  66  within which the stimulator  16  is located. The electrical wire  25  extends from the stimulator  16  through the catheter system  50  to the first component, electrode  21 , and the micro-coaxial cable  34  extends from the stimulator  16  to the second component  40 . More coaxially arranged catheters and sheaths can be provided to deliver additional components of a medical device.  
         [0038]     The medical device  15  is implanted in the vascular system of the patient by first inserting the guide wire  52  as depicted in  FIG. 7 . An incision is made into large blood vessel in the patient&#39;s thigh, for example, using conventional surgical procedures for inserting catheters. The guide wire  52  is then threaded through the vasculature until its distal end reaches the location at which the stimulator  16  is to be implanted. Next, the catheter assembly  51  is inserted over the proximal end of the guide wire  52  and pushed there along to the location selected for the stimulator implantation, as shown in  FIG. 8 . With the stimulator  16  properly positioned within the blood vessel  18 , the outer, or third sheath  66  is pulled out of the patient while maintaining the remainder of the catheter system  50  in place. Once the third sheath  66  clears the stimulator  16 , the stimulator&#39;s body  30  expands diametrically against the wall of the blood vessel  18  thereby securing the stimulator  16  in place, as illustrated in  FIG. 9 . This diametric expansion of the stimulator body  30  causes a longitudinal contraction as evident from a comparison of the length of the stimulator  16  in  FIGS. 8 and 9 . It should be noted that before the third sheath  66  fully exposes the stimulator body  30 , that sheath can be pushed back into the patient over the third catheter  64  and the exposed portion of the stimulator  16 . This action re-collapses the stimulator body  30  so that it may be repositioned within the blood vessel  18 .  
         [0039]     With reference to  FIG. 10 , after implanting the stimulator  16 , the guide wire  52  is advanced through the vascular system until it reaching a point at which the antenna  40  is desired to be placed in blood vessel  26 . Thereafter, the remainder of the catheter assembly  51  is advanced along the guide wire  52  until the distal end  53  reaches the desired location (as seen as  FIG. 3 ). As this advancement occurs, the micro-coaxial cable  34  connecting the antenna  40  to the stimulator  16  is unfurled from catheter assembly. Next, the physician withdraws the second inner sheath  62  from the patient. When the second inner sheath  62  has been withdrawn sufficiently to expose the antenna  40 , that component contracts longitudinally and expands diametrically against the inner surface of the blood vessel  26 . That action secures the antenna  40  in place, as shown in  FIG. 11 . Before the antenna  40  has been fully exposed, the second inner sheath  62  may be pushed back into the patient to re-collapse the partially expanded antenna, if necessary.  
         [0040]     With the antenna  40  secured in place, the physician extracts the remainder of the catheter system  50 , including the guide wire  52  from the blood vessel  26  to a junction where the assembly can be directed into the other blood vessel  19  for implantation of the second electrode  21 . From that withdrawn position, the guide wire  52  alone is advanced through the vascular system until its distal end reaches the location within blood vessel  19  at which the electrode is to be implanted. Then, the remainder of the catheter assembly  51  is advanced along the guide wire  52  until its distal end  53  reaches the distal end of the guide wire, as depicted in  FIG. 12 . At this point, the first, or inner, catheter  54  and its surrounding sheath  56  are located at the distal end of the guide wire along with the second electrode  21 . With that electrode properly positioned within the blood vessel  19 , the first sheath  56  is withdrawn from the patient along the first catheter  54 . Upon being exposed, the second electrode  21  expands to engage the wall of the blood vessel  19 , thereby being secured in place as illustrated in  FIG. 13 . Other techniques for securing the electrode and the other components in the blood vessel wall may be employed. Then, the first catheter  54  and guide wire  52  are withdrawn from the vascular system of the patient leaving the components of the medical device  15  in place, as shown in  FIG. 14 .  
         [0041]     The first catheter system  50  employs a single catheter assembly  51  that comprises coaxially located catheters and sheaths to carry the components of the medical device  15 .  FIGS. 15-22  illustrate a second catheter system  70  having first and second catheter assemblies  71  and  72 , which are inserted through the vascular system of the patient. These catheter assemblies  71  and  72  are structurally each similar to the catheter assembly  51  previously described. The first catheter assembly  71  is used to deliver the stimulator  16  and the antenna  40 , and the second catheter assembly  72  delivers a pair of electrodes  87  and  90  to different locations in the patient&#39;s vasculature. The implantation procedure commences by inserting a first guide wire  74  into the patient and threading it through the vascular system until reaching a position  75  in blood vessel  26  at which the antenna  40  is to be located as shown in  FIG. 15 . A second guide wire  76  also is inserted through the vascular system to a location  77  in blood vessel  19  for one of the electrodes. Then the first catheter assembly  71  is placed over the first guide wire  74  and the second catheter assembly  72  is placed over the second guide wire  76 . The two catheter assemblies are slid in unison over their respective guide wires until the first catheter assembly  71  reaches the location  79  in blood vessel  18  for the stimulator  16  as illustrated in  FIG. 16 . The two catheter assemblies  71  and  72  have to be inserted simultaneously into the patient because the components carried by them are connected by relatively short electrical wires. Alternatively those interconnecting wires may be long enough to extend outside the patient while only some of the components have been implanted. This eliminates the need to simultaneously insert both catheter assemblies  71  and  72  and also permits testing of each component upon being finally positioned in the vascular system. For example, the antenna  40  can be tested for adequate signal reception before implanting the stimulator  16 .  
         [0042]     The first catheter assembly  71  has a first catheter  78  with a second catheter  80  extending coaxially there around. Specifically, the first catheter  78  has a lumen through which the first guide wire  74  passes and the second catheter  80  has another lumen within which the first catheter is received. A first cavity is formed between those catheters within which the antenna  40  is located. In the second catheter system  70 , there is no inner sheath between the antenna and the second catheter  80 , however such a sheath could be provided as in the previously described catheter system  50 . A first outer sheath  82  extends longitudinally along and around the second catheter  80  forming a second cavity there between within which the stimulator  16  is located adjacent the distal end of the first catheter assembly  71 .  
         [0043]     The second catheter assembly  72  has a third catheter  84  immediately surrounding the second guide wire  76 . A fourth catheter  86  extends coaxially around and along the third catheter  84  forming a cavity there between within which a first electrode  87  is located. In particular, the third catheter  84  has a lumen through which the second guide wire  76  passes and the fourth catheter  86  has another lumen within which the third catheter is received. A second outer sheath  88  extends coaxially around and along the fourth catheter  86  forming a cavity there between within which a second electrode  90  is held.  
         [0044]     With reference to  FIG. 17 , while the first catheter assembly  71  is held in place, the second catheter assembly  72  is advanced along the second guide wire  76  past the end of the first catheter assembly  71  and into the blood vessel  19 . As this advancement occurs, the electrical wires connecting the first and second electrodes  87  and  90  to the stimulator  16  are pulled along and unfurled from the distal end of the second catheter assembly  72 . The second catheter assembly  72  continues slide over the second guide wire  76  until reaching the location desired for implantation of the second electrode  90 . Then the second outer sheath  88  is withdrawn from the patient by sliding it along the remaining components of the second catheter assembly  72 . That action exposes the second electrode  90  which thereby expands diametrically to become imbedded in the inner wall of the blood vessel  19 , as shown in  FIG. 18 . Other techniques for securing the electrode in the blood vessel wall may be employed.  
         [0045]     Then the third and fourth catheters  84  and  86  are withdrawn partially from the patient carrying the first electrode  87  through the blood vessel  19  until it is located at the desired place for implantation, as depicted in  FIG. 19 . If the desired location for the first electrode  87  is not along the existing route of the second guide wire  76 , that guide wire may also be partially extracted from the patient and reinserted through a different route to the desired implantation point. In that latter case, the two catheters  84  and  86  then are slid along the second guide wire  76  until the first electrode  87  reaches that desired point of implantation. When the first electrode is properly positioned, the third catheter  84  is withdrawn from the patient so its distal end slides over the first electrode  87 . Upon being fully exposed, the first electrode  87  expands diametrically thereby engaging the walls of the blood vessel  19  becoming secured in place as illustrated in  FIG. 20 . Here too, other techniques may be used to secure this electrode in the blood vessel wall. Thereafter, the third catheter  84  and the second guide wire  76  are withdrawn from the patient leaving the two electrodes  87  and  90  in place, as shown in  FIG. 21 .  
         [0046]     Then with the first catheter assembly  71  still positioned at the location desired for the stimulator  16 , the first outer sheath  82  of the first catheter assembly  71  is withdrawn from the patient to release the stimulator. When the body  30  of the stimulator is fully exposed, it expands diametrically against the inner wall of the blood vessel  18  to secure the stimulator  16  in place, as depicted in  FIG. 22 . Next, the first and second catheters  78  and  80  are advanced along the first guide wire  74 , through the now expanded stimulator body  30 , until the collapsed antenna  40  carried by those catheters is located within the blood vessel  26  at the desired position for implantation shown in  FIG. 23 . At this time, the second catheter  80  is pulled at least partially from of the patient to expose the antenna  40  thereby allowing the antenna coil to expand against the inner wall of the blood vessel  26  as exemplified in  FIG. 24 . Then, the first catheter  78  and the first guide wire  74  are removed from the patient, either separately or in unison. This leaves the medical device  15 , comprising the stimulator  16 , antenna  40  and the first and second electrodes  87  and  90 , implanted in the patient&#39;s vasculature as shown in  FIG. 25 .  
         [0047]     The foregoing description was primarily directed to preferred embodiments of the invention. Even though some attention was given to various alternatives within the scope of the invention, it is anticipated that one skilled in the art will likely realize additional alternatives that are now apparent from disclosure of embodiments of the invention. For example, different quantities of components for the medical device can be implanted by modifying the catheter assembly with more catheters and sheaths, and the position of the components on the catheter assembly can be changed to enable a different order of implantation. Accordingly, the scope of the invention should be determined from the following claims and not limited by the above disclosure.