Patent Publication Number: US-2007123750-A1

Title: Catheter apparatus and methods of using same

Description:
BACKGROUND OF THE INVENTION  
      This invention relates generally to medical devices, and more particularly to methods and apparatus for catheter devices that demand less skill for their manipulation inside a body.  
      Human vasculature possesses a highly branched structure. To place an ultrasound intracardiac probe into position within the heart, the imaging transducer is placed into a catheter and inserted into the vasculature, commonly through the leg or arm. Directing a catheter through the body&#39;s vascular network and into the heart necessitates having both the ability to visualize the vascular structure in real time and also the ability to steer the catheter tip in a desired direction. Careful steering of the cardiac tip is needed to avoid puncturing vascular walls.  
      A catheter contains a complex series of strings or wires attached to its tip at one end and to knobs on a handle at the other, opposite end. Careful turning of the knobs can pull the catheter tip in a desired direction, thereby allowing the catheter to be steered in that direction. A physician responsible for inserting the catheter must simultaneously insert and steer the catheter while monitoring the location of the catheter tip fluoroscopically.  
      An ultrasound intracardiac catheter probe must be directed through vasculature and into a heart to be placed in the appropriate location for imaging. The placement is accomplished by steering the catheter tip as the catheter is inserted within the vascular system. This steering is generally done using a series of wires or cords attached to the catheter tip and controlled manually from the catheter handle as the catheter is inserted into (for example) an artery or vein in a leg of a patient. The location of the catheter during insertion is followed fluoroscopically. A physician requires much skill to move the catheter tip into position without damaging the vasculature or heart walls.  
     BRIEF DESCRIPTION OF THE INVENTION  
      In one aspect, the present invention therefore provides a catheter apparatus. The catheter apparatus includes a catheter having an electroactive polymer inside. The electroactive polymer is configured to control either or both shape and/or direction of the catheter in a vessel as the electroactive polymer is electrically activated. The apparatus further includes a computer which may be denoted as a “control computer.” The computer includes a memory and a processor configured to store vascular information and determine voltages to be applied to activate the electroactive polymer to steer the catheter to a desired site after it is inserted into a body. Also included is an electrical source responsive to the computer and configured to apply the determined voltages to the electroactive polymer.  
      In another aspect, the present invention provides a method for imaging an organ of a body. The method includes imaging a vascular system of the body, digitizing and storing vascular information obtained from the imaging in a control computer, and using the control computer to apply voltages to an electroactive polymer in a catheter in accordance with the stored vascular information to steer the catheter to a desired site after it is inserted into the body. (Fluoroscopy and digital fluoroscopy are examples of vascular imaging systems.)  
      In yet another aspect, the present invention provides a catheter apparatus that includes a catheter having an electroactive polymer inside. The electroactive polymer is configured to control either shape and/or direction of the catheter in a vessel as the electroactive polymer is electrically activated. The apparatus further includes a contact sensor configured to sense contact with a vessel wall or an organ wall. Also included is a control computer responsive to the contact sensor and configured to utilize an electrical source to immediately electrically activate the electroactive polymer to change shape or direction of the catheter upon the contact sensor sensing contact with a vessel wall or an organ wall.  
      It will be appreciated that various configurations of the present invention provide methods and apparatus having or using catheters with very small, if any, width beyond those of prior art catheters. Catheters are easily controlled and can be automatically controlled by computer in some configurations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic pictorial view of a catheter apparatus configuration of the present invention, with a portion of the catheter itself cut away for viewing of internal electroactive polymer bundles.  
       FIG. 2  is a schematic pictorial view of the catheter of  FIG. 1  being manipulated in a body.  
       FIG. 3  is a partial cut away view of the catheter of  FIG. 1  showing the internal electroactive polymer bundles in somewhat greater clarity.  
       FIG. 4  is a flow chart of a method configuration of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      In some configurations of the present invention, a catheter tip is steered using a plurality of electroactive polymer bundles along a length of the catheter. Electroactive polymers change their size in response to an electrical voltage and are sometimes referred to as “artificial muscles.” A series of electroactive polymers formed as cords and attached to electrical leads along the catheter can be made to independently stretch or shrink in response to an applied voltages, resulting in bending or steering of the catheter in a desired direction. For example, in some configurations of the present invention, the vascular system is imaged using a contrast agent fluoroscopic method. The vascular information obtained is digitized and stored in a control computer. The computer then applies voltages to a catheter tip in accordance with the stored vascular information to steer the catheter to a desired site after it is inserted into the body. Thus, the skill and dexterity required to steer the catheter is substantially reduced, as the steering is entirely, or at partially, performed under automatic electronic control.  
      Also in some configurations, a series of cords that are formed from or that comprise electroactive polymers plus appropriate electrical connectors is placed within an intravascular catheter. A voltage is applied to individual electrical connections to individual cords using, for example, a touch panel or any other suitable electronic control and/or pointing device. As voltages are varied, the cords change shape accordingly. By varying the voltages applied to individual cords, the shape of the cords change shape, thereby steering a tip of the catheter in a desired direction.  
      Some configurations of the present invention have more than one set of electroactive polymer sets and controls along the length of the catheter. In these configurations, the shape of the catheter can be varied more than in those configurations in which guide wires are attached to the catheter tip.  
      Also, in some configurations, the shape of a vascular network through which the catheter is to be inserted is accurately ascertained using digitized x-ray fluoroscopic methods and contrast agents. Coordinates representing the shape of the vascular network are digitized and used by a “control computer” to generate electrical signals that control the location of the catheter during insertion. Thus, much of the skill required in known catheterization techniques can be supplied by the computer rather than the physician. Also, some configurations include a location sensor at the tip of the catheter to aid a computer in steering the catheter tip.  
      A contact sensor is provided in some configurations of the present invention for sensing contact with walls of the heart or vasculature. Upon contact, the contact sensor generates an electrical signal that is detected by the control computer. Once contact with the vasculature is detected, the computer or other control device causes a voltage change on an electroactive polymer cord that results in the catheter tip immediately changing shape slightly to avoid or prevent damage to cardiac or vessel walls.  
      In some configurations and referring to  FIGS. 1 and 2 , a catheter apparatus  10  comprising a catheter  12  has an electroactive polymer  14  therein. Electroactive polymer  14  is configured to control the shape and/or direction of catheter  12  in a vessel  16  as electroactive polymer  14  is electrically activated. (The term “and/or” is intended to encompass configurations in which only one of shape or direction is controlled, as well as configurations in which both can be controlled.) A computer  18  (which need not be a general purpose computer or PC in all configurations) including a memory  20  and a processor  22  configured to store vascular information and determine voltages to be applied to activate electroactive polymer  14  to steer catheter  12  to a desired site  26  after it is inserted into a body  28 . An electrical source  30  is responsive to computer  18  and is configured to apply the determined voltages to electroactive polymer  14 . An electric cable  23  from catheter  12  includes wires  24  carrying one or more electrical voltages from electrical source  30  to electroactive polymer  14 , and wires  25  carrying one or more sensing signals output by catheter  12 .  
      Also in some configurations, catheter  12  further comprises a contact sensor  32  configured to sense contact with a wall  34  of a vessel  16  wall or wall  36  of an organ  38 . Computer  18  is responsive to contact sensor  32  and is configured to utilize electrical source  30  to immediately electrically activate electroactive polymer  14  to change the shape and/or direction of catheter  12  upon contact sensor  32  sensing contact with a vessel wall  34  or an organ wall  36 .  
      Referring to  FIG. 2 , electroactive polymer  14  in some configurations comprises a plurality of cords  40 , wherein each cord  40  is electrically controllable to adjust the shape and/or direction of catheter  12 . In some configurations, the plurality of cords  40  are arranged in bundles  42 .  
      In some configurations and referring to  FIG. 3 , apparatus  10  also includes a touch panel  44  (i.e., a panel comprising push buttons, a keyboard, capacitive sensors, pressure-sensitive areas, or other types of switches  46  that are touch and/or pressure sensitive) configured to control a voltage applied to each cord  40 . For example, computer  18  is responsive to switches  46  on touch panel  44  to control a voltage supplied by electrical source  30  to each cord  40 , so that manual control of the direction and/or shape of catheter  12  can be accomplished easily.  
      Some configurations of apparatus  10  have a plurality of separately controllable cords  40  along all or a portion of the length of catheter  12 .  
      In many configurations, a contrast enhanced tip (“location sensor”)  48  is provided at tip  50  of catheter  12 . This tip is imagable with fluorscopy during catheter insertion into the vasculature and aids the control computer in determining correct catheter placement.  
      To provide images inside body  28 , catheter  12 , in some configurations, includes an ultrasound imaging transducer  52  and/or an optical imaging transducer  54 .  
      In some configurations and referring to flow chart  100  of  FIG. 3 , a configuration of a method to image an organ of a body includes imaging  102  a vascular system  56  of body  28 . The vascular information obtained from this imaging is digitized and stored  104  in a control computer  18 . Control computer  18  is then utilized to apply  106  voltages to electroactive polymer  14  in a catheter  12  in accordance with the stored vascular information to steer catheter  12  to a desired site  26  after it is inserted into body  28 .  
      In some configurations, to image  102  a vascular system  56  of body  28  , a contrast agent is used to fluoroscopically image vascular system  56 .  
      Electroactive polymer  14  is, in some configurations, configured to change at least one of shape or direction of catheter  12  when electrically activated, and catheter  12  further comprises a contact sensor  32  configured to sense contact with a vessel wall  34  or an organ wall  36 . For example, contact sensor  32  generates a signal that is sent to control computer  18  whenever contact is made. Control computer  18  is used to immediately activate electroactive polymer  14  to change shape or direction of catheter  12  upon contact sensor  32  sensing contact with a vessel wall  34  or an organ wall  36 . More than one contact sensor  32  can be used to determine the orientation of tip  50  with respect to vessel wall  34  or organ wall  36 .  
      In some configurations, catheter  12  has a plurality of cords  40  therein that are comprised of electroactive polymer  14 , and the method further includes electrically controlling each cord  40  to adjust the shape and/or direction of catheter  12 .  
      In some configurations, a touch panel  44  is utilized to control a voltage applied to each cord  40  to manually steer catheter  12 .  
      Catheter  12  has a plurality of separately controllable cords  40  along its length in some configurations, so that some method configurations further comprise separately controlling each controllable cord  40 .  
      An ultrasound imaging transducer  54  or an optical imaging transducer  56  located at a tip  50  of catheter  12  is used in some method configurations of the present invention to produce an image.  
      In some configurations of the present invention and again referring to  FIGS. 1 and 2 , a catheter apparatus  10  is provided that includes a catheter  12  having an electroactive polymer  14  therein. Electroactive polymer  14  is configured to control at least one of shape or direction of catheter  12  in a vessel  16  as electroactive polymer  14  is electrically activated. The apparatus also includes a contact sensor  32  figured to sense contact with a vessel wall  34  an organ wall  36  and a control computer  18  responsive to contact sensor  32 . Control computer  18  is configured to utilize an electrical source  30  to immediately electrically activate electroactive polymer  14  to change shape or direction of catheter  12  upon contact sensor  32  sensing contact with a vessel wall  34  or an organ wall  36 . Additionally, some of these configurations also include at least one of an ultrasound imaging transducer  52  or an optical imaging transducer  56 .  
      It thus be appreciated that various configurations of the present invention can be provide with very small, if any, width beyond those of prior art catheters. Moreover, configurations of the present invention are easily controlled and can be automatically controlled by computer in some configurations.  
      While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.