Abstract:
An assembly of a pulmonary venting catheter and a pacing wire disposed therethrough whereby the pacing wire is extended from the distal end of the catheter tube during pacing mode, eliminating the need for exchanging the venting catheter with a pacing catheter to begin pacing after venting. The pacing wire includes a flexible distal end for a first conductor to conductively engage heart tissue after the pacing wire is extended from the catheter distal end; a second conductor, also exposed outside the catheter distal end, completes the circuit. The pacing wire is lockable in unextended and extended positions at the proximal end portion of the assembly. A method for venting and pacing a patient&#39;s heart during cardiac surgery is described, which includes retracting the catheter distal end from the pulmonary artery after venting mode, into the right ventricle during pacing mode, whereafter the pacing wire is extended for pacing.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/470,779 filed Apr. 1, 2011, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of cardiac surgery, and more particularly, to a catheter used for minimally invasive cardiac surgery and cardiac pacing during and after the surgery, and a method of using same for treatment of a patient undergoing cardiopulmonary bypass surgery. 
       BACKGROUND OF THE INVENTION 
       [0003]    Minimally invasive cardiac surgery entails the performance of heart surgery through very small incisions. Due to the limited size of the incisions, the patient&#39;s heart is not completely exposed. To assure a good or stable heart rhythm during and or after heart surgery, temporary pacing wires, which electrically stimulate the heart, are often sewn to the heart surface, and are used until patient self-pacing is achieved. This can be very difficult to do in some types of minimally invasive cardiac surgery cases without increasing the amount of heart dissection that is done, or increasing the risk of bleeding due to wire placement. 
         [0004]    Minimally invasive cardiac surgery is known to utilize catheters that are placed into and along the patient&#39;s vasculature to allow safe initiation of cardiopulmonary bypass through catheters via small incisions. During cardiopulmonary bypass, blood is removed from the patient&#39;s pulmonary artery and the heart is stopped. The aspirated blood is then oxygenated by a medical apparatus and is then returned to the patient&#39;s arterial system at an appropriate location spaced from the heart, such as into a peripheral artery. Once the patient&#39;s heart function is undertaken by the cardiopulmonary bypass machine, the surgery can be safely performed through small incisions. The bypass procedure generally utilizes, along with several other catheters, a pulmonary venting (draining) catheter that is placed into and through the vasculature, preferably the jugular vein and superior vena cava, into and through the heart&#39;s right atrium and right ventricle, and into the pulmonary artery. The catheter distal end is then left in the pulmonary artery so that drainage of blood is by way of the distally open intake lumen of the catheter. One such pulmonary venting catheter is the ENDOVENT® catheter manufactured by Edwards Lifesciences Corp. (Irvine, Calif.). 
         [0005]    It is known to provide a pacing wire into a patient where the distal wire end does not require sewing the tip to heart tissue. By use of a Swan-Ganz PACEPORT® pacing wire manufactured by Edwards Lifesciences Corp., a bipolar pacing wire is introduced into the patient&#39;s vasculature and the distal pacing wire end enters into the heart&#39;s right ventricle until it becomes engaged against the inner surface of the ventricle, termed intracardiac pacing. This catheter is utilized after pulmonary venting has been performed and after the venting catheter has been withdrawn from the patient. The bipolar pacing wire includes two conductive electrodes that are insulated from each other, one of which extends to the distal wire end, while the other concludes proximally of the distal wire end and is exposed to engage nearby right ventricle tissue. The distal wire end portion is so made to be extremely flexible so as not to damage the heart (or other) tissue of the patient, whereby a length of the distal end portion lies along and against the heart surface for best results. Such intracardiac pacing is performed during weaning from cardiopulmonary bypass, and also for post-operative management to improve cardiac output. 
         [0006]    Generally, in the course of performing minimally invasive cardiac surgery without the use of pacing wires sewn to the patient&#39;s heart, the pulmonary vent must be exchanged with a pacing catheter that contains the pacing wire through the use of an introducing catheter. This requires a sterile technique with limited access to the head and neck of the patient during the procedure. Additionally, the heart may not have adequate flow or any native activity, making it a challenge to advance the pacing catheter into the right ventricle, and further out into the pulmonary artery. This may lead to numerous problems, including: the catheter being positioned in an incorrect location; the introducing catheter may become bent during the exchange, trapping the pacing catheter; or, the pacing catheter may loop, knot, perforate the heart, damage the heart valves, or become entangled in the chordae tendinae, etc. 
         [0007]    It would be desirable to have a catheter assembly and a method of use of same that simplifies the minimally invasive cardiac surgery procedure, reduces the total time needed therefor in patients, and eliminates the need for additional heart surface stitches, among other desirable features, as described herein. 
       SUMMARY OF THE INVENTION 
       [0008]    In one aspect, the present invention is directed in part to a medical apparatus for use during cardiopulmonary bypass surgery of a patient. The medical apparatus includes a venting catheter having a flexible elongate shaft with a distal end, a proximal end, and an inner venting lumen. The inner venting lumen extends from the proximal end of the shaft to an inlet port at the distal end of the shaft. The inlet port is configured to withdraw blood from a pulmonary artery of the patient. The shaft has a length that allows the distal end to be positioned in the pulmonary artery with the proximal end extending transluminally to a central vein and out of the patient through a puncture in the central vein. The medical apparatus also includes a pacing wire disposed within the shaft, and in certain embodiments, the pacing wire may be disposed within the inner venting lumen. The pacing wire is movable axially along the shaft between a first, retracted position and a second, extended position. 
         [0009]    The medical apparatus is insertable into the vasculature and heart of a patient for pulmonary venting in a venting mode. During venting mode, the entire pacing wire is within the venting lumen of the catheter tube at the first position. The medical apparatus is also used for pacing of the heart in a pacing mode subsequent to the venting mode. During pacing mode, the pacing wire is extended from the venting lumen of the catheter tube to the second position to engage intracardial tissue of the heart for pacing thereof. 
         [0010]    The medical apparatus of the present invention may further include an inflatable balloon having an interior mounted at the distal end of the shaft. The venting catheter may further have an inflation lumen extending from the proximal end to an opening near the distal end in communication with the interior of the balloon. 
         [0011]    The pacing wire may include a distal end portion that is flexible and resilient along its length. This distal end portion may include a flexible electrode that is exposed when the pacing wire is in the second position whereby current can be passed between said electrode and the heart. The distal end portion may further include a flexible region located adjacent to and proximally of the flexible electrode. The flexibility of this region tapers as the region extends proximally. The pacing wire may also include a section being wound into a coil to form the flexible region and at least a part of the flexible electrode. The axial spacing between the turns of the coil at the flexible region may increase as the flexible region extends proximally. Additionally, the wire may have a progressively increasing cross-sectional area as the wire extends proximally in the flexible region. The pacing wire can also include at last one marking to indicate the axial position of the pacing wire within the shaft. The pacing wire may further include a proximal electrode spaced proximally from the flexible electrode. This proximal electrode may be formed from a region of a conductive wire having a plurality of coils. 
         [0012]    In another aspect, the present invention is directed in part to a method for treatment of a patient undergoing cardiopulmonary bypass surgery. The method includes the steps of: (1) providing an apparatus having a venting catheter assembly including a flexible catheter tube having a distal end, a proximal end, and an inner venting lumen extending from the proximal end to an inlet port at the distal end configured to withdraw blood from a pulmonary artery, and further including a pacing wire within the catheter tube extending to a distal wire end, the pacing wire being movable axially within and along the catheter tube between first and second positions; (2) inserting a distal portion of the catheter tube into the vasculature and into the heart of a patient such that the catheter tube distal end accesses the pulmonary artery; (3) venting the pulmonary artery during cardiopulmonary bypass; (4) closing the venting lumen at a vent port at the catheter tube proximal end; (5) partially retracting the catheter tube distal end from the pulmonary artery and into the heart; (6) extending the distal wire end distally from the catheter tube distal end until a conductive end of the pacing wire enters into conductive engagement with an inner surface of the heart; and (7) pacing the heart. 
         [0013]    The apparatus and method of the present invention eliminates the need to utilize a dedicated catheter for delivery of the pacing wire to the heart, thus substantially hastening the initiation of pacing, greatly simplifying the cardiac surgery procedure, reducing the total time, and also reducing risk to the patient. It also permits the surgeon to initiate pacing when the surgeon is unable to exchange catheters due to unusual problems. The present invention eliminates the need for exchanging the venting catheter for the pacing catheter near or at the end of surgery, and eliminates the risk of problems commonly encountered during catheter exchange, such as inadequate blood flow that challenges proper advancement of the pacing catheter into the right ventricle, cardiac perforation or laceration, or post-operative bleeding related to wire placement or removal. It also eliminates, with respect to the pacing catheter, encountering the risks involved during insertion of any catheter through a catheter introducer or into and along the vasculature to and into the heart. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention. 
           [0015]      FIG. 1  is a plan view of a pulmonary venting catheter assembly containing a pacing wire, in accordance with the present invention; 
           [0016]      FIG. 2  is a side elevational view partially in section of a pacing wire of the assembly of  FIG. 1 ; 
           [0017]      FIG. 3  is an isometric view of the distal pacing wire end extending from the distal end of the venting catheter assembly of  FIG. 1 ; and 
           [0018]      FIG. 4  is a diagrammatic view of the distal portion of the venting catheter illustrating the pacing wire extending from the catheter distal end and in engagement with the inner surface of the right ventricle, with a previous pulmonary venting position shown in dashed lines. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    In the drawings, like numerals indicate like elements throughout. Certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. The terms “proximal” and “distal” refer, respectively, to directions closer to and away from the operator of the apparatus of the present invention. The terminology includes the words specifically mentioned, derivatives thereof, and words of similar import. The terms and expressions used herein, and the embodiments illustrated below, are not intended to be exhaustive or to limit the invention to the precise form disclosed. These terms, expressions and embodiments are chosen and described to best explain the principle of the invention and its application and practical use and to enable others skilled in the art to best utilize the invention. 
         [0020]      FIG. 1  illustrates a pulmonary venting catheter assembly  10 , including a catheter tube  12  having inserted therethrough a pacing wire  14 , in accordance with the present invention. The catheter tube  12  includes a distal end  16  and a proximal end  18 . The pacing wire  14  similarly includes a highly flexible distal end portion  20  and a proximal end  22 . The illustrated embodiment shows a bipolar catheter setup. The catheter of the present invention may also employ a monopolar scheme, which requires that the patient is appropriately grounded. 
         [0021]    As shown in  FIG. 1 , the catheter assembly  10  is preferably provided with an inflatable/deflatable balloon  26  at the distal end  16  of the catheter tube  12 . An inflation/deflation lumen (not shown) extends through catheter tube  12  from balloon  26  to the proximal end  18  of the catheter tube  12 , where an inflation/deflation port  28  is provided, joining the catheter tube  12  at a hub  30 . The balloon  26  is inflated by injecting air through the inflation port  28 , which communicates with the inflation lumen. 
         [0022]    Additionally, a controllable vent port  32  is attached to the proximal catheter portion  18  for aspirating blood from the pulmonary artery during cardiopulmonary bypass. A three-way stopcock  34  is placed in the proximal end proximally of hub  30 , which serves as a T-piece for both venting and the entry of the pacing wire  14  into the catheter tube  12 . Proximally of the stopcock  34  is a pressure tubing  36  that can connect to a pressure sensing line, by which blood pressure in the pulmonary artery is monitored. Just proximally of the connection of the pressure tubing  36  to the catheter assembly  10  is provided a valve  38  that serves to occlusively seal around the pacing wire  14  when the valve  38  is tightened, and also to lock and unlock the axial positioning of the pacing wire  14  with respect to the catheter tube  12 . Sterile sheathing may be used around the pacing wire and the catheter tube. 
         [0023]    Referring now to  FIG. 2 , the bipolar pacing wire  14  is shown in greater detail in which the highly flexible distal end portion  20  is shown to include a first conductor  40 . The first conductor  40  may have a circular cross-section, and is in the form of an elongated wire having a first section  66  extending from a housing  58  axially through a body  60 , a transition section  46  and a distal-most portion  44 . As best shown in  FIG. 2 , the first section  66  is straight and is covered by an insulation cover  43 . The transition section  46  comprises a plurality of coils  47  which are spaced apart axially, with the axial spacing between adjacent coils  47  progressively reducing as the transition section  46  extends distally. This progressive reduction is preferred, but not essential. The distal most portion  44  comprises a plurality of contiguous coils  45  and terminates at the distal end  20  of the pacing wire  14 . The coils  45 ,  47  are wound about an insulative core  42 . These coils  45 ,  47  can be tightly or loosely wound to further control the flexibility of the pacing wire  14 . 
         [0024]    A second conductor  52  concludes at the proximal end  50  of the transition section  46  and extends proximally thereof, being preferably flat and ribbon-shaped in cross-section and being wound about an insulative core section  48  to the proximal end  22  of the pacing wire  14  in the form of contiguous coils  55 , being exposed in a coaxial section  54  of the pacing wire  14 . This exposed coaxial section  54  forms a proximal electrode. Proximally of the coaxial section  54 , the pacing wire  14  is sheathed in an insulative covering  56  until concluding in a housing  58 , wherein the first and second conductors  40 ,  52  are exposed at the end of the pacing wire  14  to be connected to respective leads  60 ,  62  of a pulse generating apparatus  64 . 
         [0025]    In the illustrated embodiment, a non-conductive elastomer fills the central space within the coils  55 ,  47 ,  45 , forming the insulative core sections  42 ,  48  about which the first and second conductors  40 ,  52  are wound about, and helping insulate the first conductor  40  from the second conductor  52 . In this embodiment, the presence of the elastomer does not alter the flexibility characteristics of the pacing wire  14 . In addition to forming the insulative core sections  42 ,  48 , the elastomer encases the coils  47  of the transition section  46  so that only the coils  45  of the distal-most portion  44  of the first conductor are exposed to define a distal electrode. In embodiments where an elastomer is not used, it is preferred to encase the coils  47  of the transition section  46  in a suitable insulation jacket. 
         [0026]    The coaxial section  54 , the transition section  46 , and the distal most portion  44  comprise that portion of the pacing wire  14 , as shown in  FIG. 4 , that extends from the distal end  16  of the catheter tube  12  when the medical apparatus of the present invention is being used in pacing mode. Specifically, it is the exposed area of the distal most portion  44  that forms the electrode that engages the inner surface of the right ventricle  80  and pace the heart  82 . 
         [0027]    When the assembly is in venting mode, the distal end  20  of the pacing wire  14  is preferably flush or coterminus with the distal end  16  of the catheter tube  12 .  FIG. 3  illustrates the highly flexible distal end  20  of the pacing wire  14  being projected to some extent beyond the distal end  16  of catheter tube  12  (shown with the balloon  26  deflated and transparent to reveal detail). It is seen that the pacing wire  14  would not interfere with venting through the catheter tube  12  were it in venting mode (which is shown in dashed lines in  FIG. 4 ). Also seen are a plurality of side ports  70  provided at the distal end  16  of the catheter tube  12  that communicate with the venting lumen  72  there within. 
         [0028]    In venting mode, the catheter tube  12  is introduced into a central vein by a percutaneous technique such as the Seldinger technique. The catheter tube  12  is advanced through the central vein and through a vena cava  88  into the right atrium  86  of the heart  82 . The balloon  26  on the distal end  16  of the catheter tube  12  is then expanded. As the operator pushes distally on the proximal end of the venting catheter, the flow of blood through the right side of the heart  82  will tend to guide the distal end  16  and the expanded balloon  26  from the right atrium  86  through the tricuspid valve into the right ventricle  80 , and from the right ventricle  80  through the pulmonary valve  90  into the pulmonary artery  84 . The catheter tube  12  is advanced until the distal end  16  and the inlet ports  70  are positioned in the pulmonary artery  84  downstream of the pulmonary valve  90 . Pressure monitoring through pressure ports (not shown) located at the distal end  16  of the catheter tube  12  in communication with the pressure tubing  36  facilitates proper positioning of the distal end  16  in the pulmonary artery  84 . Accurate placement may be verified by fluoroscopy or by transesophageal echocardiography. The balloon  26  may then be deflated. Generally, the balloon  26  is used only to help the catheter tube  12  migrate into the pulmonary artery with direction provided by the patient&#39;s native blood flow. The balloon  26  should not remain inflated or continue to occlude the pulmonary artery. Leaving the balloon  26  inflated could risk causing pulmonary artery or branch rupture, or lung infarction. 
         [0029]    Once in position, and upon starting cardiopulmonary bypass, the blood present in the pulmonary trunk may be vented through the venting lumen  70  of the catheter tube  12  where it is discharged through the proximal end  18  of the catheter tube  12 , which extends outside of the patient. The blood withdrawn through the venting catheter tube  12  then travels through the vent port  32  and may be routed to a cardiopulmonary bypass unit for oxygenation and return to the patient&#39;s arterial system through an arterial return catheter (not shown). 
         [0030]      FIG. 4  illustrates the distal end  16  of the pulmonary venting catheter assembly  10  of the present invention in position within the right ventricle  80  of heart  82  and in pacing mode after venting mode is completed. The catheter tube  12  is shown having been retracted from its position when in venting mode, which is shown in dashed lines extending through the right ventricle  80  and into the pulmonary artery  84  where the balloon  26  had been inflated to occlude the artery. After retraction, the position of the distal end  16  of the catheter tube  12  is about one to three centimeters into the right ventricle  80  from the right atrium  86 . The distal end  20  of the pacing wire  14  is shown deployed into its extended position, protruding from the distal end  16  of the catheter tube  12  until it is in engagement with the inner surface of the right ventricle  80  so that the distal electrode located at the distal most portion  44  of the pacing wire  14  of the first conductor  40  can convey a pacing pulse directly to the heart tissue. Proximally of the distal electrode is the proximal electrode formed by the exposed second conductor  52 , by which the circuit is completed via heart tissue and bodily fluids. The catheter tube  12  is seen extending proximally through the right atrium  86  and the superior vena cava  88  into the patient&#39;s vasculature. 
         [0031]    It is preferable that the catheter tube  12  be marked on its exposed proximal end portion  18  such that the operator may determine the precise distance between the distal end  16  of the catheter tube  12  when in position for venting mode and when in position for pacing mode, so that retraction is quickly attained during the surgical procedure. This may easily be determined by ultrasound guidance prior to venting mode. When the catheter assembly  10  is in venting mode, the axial position of the pacing wire  14  within the catheter tube  12  is locked such that the distal end  40  of the pacing wire is approximately coterminus with the distal end  16  of catheter tube  12 . It is likewise preferable that the exposed portion of the proximal end of the pacing wire  14  be marked to indicate the amount by which the pacing wire  14  is to be extended from the distal end  16  of the catheter tube  12  to engagement with the inner surface of the right ventricle  80 , after which the pacing wire  14  will again be locked, for pacing mode. Axial positioning of the pacing wire  14  is attained at valve/lock  38  in the proximal end of the catheter assembly  10 , as provided hereinabove with respect to  FIG. 1 . 
         [0032]    Tests have shown that the venting/pacing catheter assembly of the present invention is easily operable by the operator to convert from venting mode to pacing mode, which can be performed within two minutes, because exchange of catheters is eliminated. 
         [0033]    It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.