Abstract:
Devices and methods for performing myocardial revascularization using fluid jets. Devices can include a pressurized fluid source coupled through fluid supply lumens to a distal-most nozzle disposed on the distal end of the catheter. Some devices have separate myocardial revascularization catheters disposed within guide catheters, while other devices have unitary devices including a generally steerable myocardial revascularization catheter shaft. Preferred embodiments include a distally disposed control valve. One valve is controlled using an electrically actuated device, another valve is controlled using a low-pressure control fluid, while yet another device valve is controlled using an axially slidable activation wire. The fluid valve can include a biasing spring to shut the valve and preclude fluid flow, with the bias opposed by a user-applied fluid, mechanical, or electrical force. One device includes a radially expandable distal catheter portion, which expands under pressure to present a significantly larger distal profile. The inflated distal region may be forced against a heart chamber wall, and can provide a larger surface area and improved seal. One catheter includes an intermediate expandable tubular anchor portion. Fluid used in the devices can include saline, revascularization enhancing therapeutic substances, angiogenic promoting substances, and radiopaque contrast media, all of which can be injected at the same time.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention is related generally to medical devices. More specifically, the present invention includes devices for performing myovascular revascularization including percutaneous myocardial revascularization (PMR).  
         BACKGROUND OF THE INVENTION  
         [0002]    A number of techniques are available for treating cardiovascular disease, such as cardiovascular bypass surgery, coronary angioplasty, laser angioplasty and atherectomy. These techniques are generally applied to bypass or open lesions in coronary vessels to restore and increase blood flow to the heart muscle. In some patients, the number of lesions is so great, or the location so remote in the patient vasculature, that restoring blood flow to the heart muscle is difficult. Percutaneous myocardial revascularization (PMR) has been developed as an alternative to these techniques which are directed at bypassing or removing lesions. PMR is performed by boring holes directly into the myocardium of the heart.  
           [0003]    PMR was inspired in part by observations that reptilian heart muscle is supplied primarily by blood perfusing directly from within heart chambers to the heart muscle. This contrasts with the human heart which is supplied by coronary vessels receiving blood from the aorta. Positive results have been demonstrated in some human patients receiving PMR treatments. These results are believed to be caused in part by blood flowing from within a heart chamber through patent holes formed by PMR to the myocardial tissue. Suitable PMR holes have been proposed to be burned by laser, cut by mechanical means, and burned by radio frequency devices. Increased blood flow to the myocardium is also believed to be caused in part by the healing response to wound formation, specifically, the formation of new blood vessels in response to the newly created wound.  
           [0004]    What would be desirable are improved methods and devices for performing myocardial revascularization. In particular, methods allowing simultaneous hole formation in the myocardium and injection of contrast media would be advantageous. Improved methods for stabilizing myocardial revascularization catheters during use would also be desirable.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention includes catheters for forming holes in the myocardium of a heart chamber wall. One catheter has a distal region, a proximal region, and an elongate tubular shaft having a lumen therethrough. A distal nozzle in fluid communication with the lumen can be disposed at the distal-most region of the catheter shaft. A fluid control valve can be disposed somewhere along the catheter shaft length for controlling fluid flow through the fluid lumen. The fluid flow through the valve can be controlled using varying devices in the various catheters.  
           [0006]    One device includes electrical means for actuating the fluid control valve. In another device, the valve includes a biasing spring to bias the valve in a closed position, with the opening force being provided by an electrically actuated member acting to oppose the biasing spring. In one device, the electronic actuating member is a Nitinol member heated by current passing from one end to the other end through the member. In this embodiment, heating a Nitinol wire shortens the wire, which opens the valve to fluid flow. In another embodiment, a flow or control pressure lumen is provided through the catheter, with the control pressure used to open and shut the valve, thereby allowing the high pressured jet fluid to flow through the valve. In one embodiment, a needle valve is used which includes a valve stem seated within a valve seat, where the valve stem can be retracted proximally to allow flow through the valve seat. In yet another embodiment, a mechanical actuating wire is used to open the control valve. In one embodiment, an elongate control wire is operably coupled to a distal valve stem. The valve stem can have a first position for occluding flow through a valve seat, and a second position for allowing flow through the valve seat. In one device, the actuation wire is proximally retracted to allow flow, and distally extended to preclude flow. In another embodiment, a biasing spring is included within the distal region, acting to shut the valve in the absence of any applied mechanical force. In this embodiment, the actuation wire can be retracted to open the valve to fluid flow. In one embodiment, the retractable activation wire may be sufficiently strong under tension, but not compression, to open the valve.  
           [0007]    The control valve can be located at any position along the catheter shaft length, with a preferred embodiment having a distally disposed control valve. The distally disposed control valve can allow for a relatively large inside diameter distal accumulator and orifice, while having a substantially smaller cross-section supply lumen extending the length of the catheter. This allows for a slow pressure buildup in the distal region of the catheter, followed by rapid injection of high pressure fluid into the heart wall.  
           [0008]    One catheter includes preferentially expandable regions which expand more readily than other regions under pressure. In one example, a far distal region of a catheter device is formed of a more pliant, more easily expandable tube wall material. The more readily expanded material may inflate and expand radially under pressure. In one device, the distal-most region of the catheter is formed of a readily inflatable material. In use, the catheter formed of the more readily inflated material may be inflated to significantly increase the distal cross-sectional area of the catheter, whereupon the increased cross-sectional distal tip is forced against the heart chamber wall, for improving the seal against the heart wall. One catheter according to the present invention includes an intermediate region which is also more readily expandable than the immediate more proximal and distal regions. The expandable intermediate region can serve to anchor the fluid jet catheter within an enclosing guide catheter. The anchored catheter can more easily withstand pressures or forces which could otherwise act to shift the position of the fluid jet catheter.  
           [0009]    Fluids which are used in the present invention can include relatively inert fluids such as saline, suitable therapeutic substances, angiogenic enhancing substances, as well as radiopaque contrast media. Adhesive agents can also be included for enhancing the retention of therapeutic substances within the heart wall. The inclusion of radiopaque contrast media allows holes to be formed and contrast media to be injected in a single step. The contrast media allows the already treated regions to be visualized under fluoroscopy by the treating physician. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a perspective, cut-away view of a fluid jet PMR catheter disposed within a guide catheter, forming holes in the left ventricle myocardium;  
         [0011]    [0011]FIG. 2A is a highly diagrammatic plan view of a fluid jet PMR system;  
         [0012]    [0012]FIG. 2B is a transverse, cross-sectional view of the fluid jet PMR catheter of FIG. 2A;  
         [0013]    [0013]FIG. 3 is a fragmentary, cut-away, longitudinal, cross-sectional view of a fluid jet PMR catheter distal region having a biasing spring and an electrically activated opening mechanism;  
         [0014]    [0014]FIG. 4 is a fragmentary, longitudinal, cross-sectional view of a fluid jet PMR catheter distal region having a fluid controlled valve;  
         [0015]    [0015]FIG. 5 is a highly diagrammatic, plan view of a fluid jet PMR catheter system having a wire-activated distal valve;  
         [0016]    [0016]FIG. 6 is a fragmentary, longitudinal, cross-sectional view of a fluid jet PMR catheter distal region having a spherical valve stem seated against a valve seat portion of a nozzle and controlled by an elongate wire valve control member;  
         [0017]    [0017]FIG. 7 is a fragmentary, longitudinal, cross-sectional view of the catheter of FIG. 6, shown in an expanded state;  
         [0018]    [0018]FIG. 8 is an end view of the catheter of FIG. 7, in the expanded state; and  
         [0019]    [0019]FIG. 9 is a highly diagrammatic, side view of a fluid jet PMR catheter having an expandable intermediate portion for stabilizing the catheter within a guide catheter. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    [0020]FIG. 1 illustrates a heart  20  having a guide catheter  22  disposed within an aorta  24  and extending into a left ventricle  26 . Guide catheter  22  is preferably a steerable catheter and can serve to contain a fluid jet PMR catheter  28  having a distal tip  29  disposed within. Fluid jet PMR distal tip  29  is shown after a plurality of channels  30  have been formed within myocardium  32 . In a preferred system and method of using the present invention, fluid jet PMR catheter  28  is disposed within a guide-in-guide catheter, or tube-within-steerable-tube, catheter. For example, see U.S. Pat. No. 5,968,059 to Ellis et al., entitled TRANSMYOCARDIAL REVASCULARIZATION CATHETER AND METHOD; and U.S. Pat. No. 6,056,743 to Ellis et al., entitled PERCUTANEOUS MYOCARDIAL REVASCULARIZATION DEVICE AND METHOD, herein incorporated by reference.  
         [0021]    [0021]FIG. 2A illustrates a fluid jet PMR system  40  having a steerable catheter  42 , which can be a guide catheter, coupled to a pressure source  44 , and having a fluid jet PMR catheter  46  disposed within. Fluid jet PMR catheter  46  can terminate in a distal nozzle  47 . Fluid jet system  40  includes a pressure regulator  48  for regulating pressure from pressure source or canister  44 , and is coupled to a pressure supply line  50 , which is in turn coupled to a pressure manifold port  52 . Pressure manifold port  52  is in fluid communication with fluid jet distal nozzle  47 . In the embodiment illustrated in FIG. 2A, fluid jet catheter system  40  includes a proximal region  54  and a distal region  56  on steerable catheter  42 . In the embodiment shown, proximal region  54  is coupled to a proximal control assembly  58  which, in the embodiment shown, is an electrical control assembly. Proximal control assembly  58  can include an activation button  60 , a safety button  62 , a steering handle  64 , a power supply cord  66 , and a electrical plug  67 . Also illustrated is a battery  68 , coupled through a power cord  70 , to an electrical plug  72 , for joining to plug  67 . Proximal control assembly  58 , in the embodiment illustrated in FIG. 2A, provides electrical control signals for controlling a distal valve coupled to distal nozzle  47 .  
         [0022]    Referring now to FIG. 2B, catheter  42  is shown in a transverse cross-section. Catheter  42  can include a shaft or body  43  including a steering pull wire  78  slidably disposed therein. A pair of electrode wires  80  can also be disposed within shaft  43  to provide electrical signals to distal nozzle  47 . A pressure fluid lumen  76  is also illustrated, being defined within a pressure tube  74  in the illustrated embodiment. In one device, pressure lumen  76  is defined within a metal tube, which can be formed of Nitinol. In another embodiment, lumen  76  is defined within shaft  43 , not requiring a separate tube. In another embodiment, not requiring illustration, electrical wire pair  80  can be replaced or supplanted by a fluid control lumen which can be defined by a fluid control tube. In one embodiment, steerable catheter  42  includes a catheter shaft disposed within a steerable guide catheter such as a guide-in-guide catheter. In this embodiment, a steering pull wire can be provided within the guide catheter, rather than within the fluid jet PMR catheter shaft itself.  
         [0023]    Referring now to FIG. 3, a pressure jet PMR catheter  100  is illustrated, having an intermediate region  106 , a distal region  102 , and a distal tip  104 . Pressure jet device  100  includes an outer sleeve or guide catheter portion  103 , a pull wire  101 , and a pressure supply lumen  108  disposed therein. A valve assembly  110  is disposed in distal region  102 , and includes a fixed block  112 , coupled to a spring or biasing mechanism  114 , also coupled to an electrically actuated control element  116 . Biasing spring  114  and control element  116  can both be coupled to a needle valve body  118  which rests in a fixed Block  120  having a lumen  121  therethrough for receiving the needle valve body. Needle valve body  118  can extend distally into a valve stem portion  122  which is illustrated lying within a fluid reservoir portion  129  and also residing within and against a valve seat portion  124 , with valve stem  122  occluding a fluid flow lumen  125  disposed within valve assembly  110 . A nozzle portion  126  is illustrated, extending distally to a distal-most orifice  132  within distal tip  104 . Fluid, under pressure, may be seen to flow through pressure lumen  108 , through a pressure fluid intermediate region  128 , and into fluid reservoir  129 . When valve stem  122  is disposed sufficiently proximal of valve seat  124 , fluid flows through lumen  125 , and out of orifice  132  as a fluid jet  130 .  
         [0024]    As can be seen from inspection of FIG. 3, spring  114  acts to bias valve stem  122  in the distal and closed position. Electronic control member or element  116 , when activated, can act to retract valve stem  122  from valve seat  124 . In one embodiment, control element  116  includes a temperature sensitive, shape memory member. Electrical control element  116  can be supplied by a pair of electrodes  134 , with one embodiment having an electrode electrically coupled to opposite ends of the control element. In one embodiment, when electrical potential is applied across the electrical control member, current flows through the control element, thereby raising the temperature, thereby changing the shape of the control element. In one example of the invention, electrical current is passed through a Nitinol wire, which heats and shortens the wire, thereby retracting or shortening control element  116  and retracting valve stem  122 . When current is removed, control element  116  can lengthen, thereby shutting valve assembly  110  and precluding fluid flow through the valve. While one embodiment of the invention uses a temperature sensitive element which changes dimensions upon application of electrical potential, other electrically activated devices would be apparent to those skilled in the art. In another embodiment of the invention, not requiring illustration, the biasing spring can bias the valve in the open position, with the control member acting to stop flow through the valve.  
         [0025]    In some embodiments, a high pressure fluid within pressure lumen  108  can act to force valve stem  122  proximally out of valve seat  124 . In these embodiments, a sufficiently strong biasing spring is used so as to counteract this force. Needle valve  118  can also be dimensioned suitably to provide a small surface area upon which the high pressure can act, thereby reducing the tendency of the pressure fluid to unseat the valve stem until such time as fluid flow is desired by the treating physician.  
         [0026]    Referring now to FIG. 4, another fluid jet PMR device  200  is illustrated. Fluid jet device  200  includes and shares many features of fluid jet device  100  illustrated in FIG. 3. Like numbered elements of FIG. 3 that are repeated in FIG. 4 are so identified and need not be discussed further. Fluid jet PMR device  200  includes generally a catheter shaft  200  having a lower pressure fluid lumen  204  disposed within. Lower pressure lumen  204  is in fluid communication with a fluid accumulator portion  206  within the valve body. Fluid accumulator portion  206  is in communication with, and brings pressure to bear upon, a valve body face region  208 .  
         [0027]    When sufficiently high control pressure is introduced into lower pressure lumen  204 , pressure is brought to bear on valve body  118 , acting to force valve stem  122  into valve seat  124 . When pressure is sufficiently reduced within pressure lumen  204 , valve stem  122  retracts proximally from valve seat  124 , thereby allowing high pressure fluid in reservoir  129  and high pressure lumen  108  to extend through nozzle  126 , exiting orifice  132  as jet  130 . In one embodiment, not requiring additional illustration, a spring, similar to spring  114  of FIG. 3, is disposed within accumulator region  206 , thereby acting to bias valve body  118  in a closed, distal position. In another embodiment, fluid must be supplied through lower pressure lumen  204  to maintain valve stem  122  against valve seat  124 . In this embodiment, pressure may be substantially reduced so as to allow high pressure flow through nozzle  126 .  
         [0028]    In yet another embodiment, needle valve body  118  and block  120  are cooperatively sized such that valve stem  122  is at least partially urged from valve seat  124  by high pressure fluid within high pressure lumen  108 . In this embodiment, less pressure reduction is required to open the valve to high pressure fluid flow. In one embodiment, negative pressure or vacuum must be applied to lower pressure lumen  204  in order to maintain valve stem  122  in a proximal position clear of valve seat  124 . In another example of the invention, lower pressure lumen  204  and high pressure lumen  108  are both provided within separate lumens of a single shaft. In another embodiment, lower pressure lumen  204  and high pressure lumen  108  are defined by separate, metallic, tubes. A preferred metallic tube includes Nitinol. The lower pressure control fluid can be provided from the catheter proximal end and can be controlled using a lower pressure control valve.  
         [0029]    Referring now to FIG. 5, another fluid jet PMR system  300  is illustrated, having a catheter  302  including a proximal region  308 , a distal region  304 , and a distal end  306 . An inflation device such as an Endoflator  316  is illustrated including a pressure gauge  320 , and a highly diagrammatic pressure source  318 . Catheter  302  includes a proximal manifold  310  having a control port  312 , illustrated having an activation wire  314  extending therethrough. Activation wire  314  may be seen to extend the length of catheter  302 , terminating within distal region  304 . In various embodiments of the invention, activation wire  314  may be either retracted or extended to release fluid pressure from within catheter  302 , thereby forcing pressurized fluid out distal end  306 . In one embodiment, activation wire  314  is slidably disposed within a lumen within catheter shaft  302 .  
         [0030]    Referring now to FIG. 6, distal region  304  of catheter  302  is illustrated. Catheter  302  includes a catheter tube wall  330 , having a high pressure lumen  332  defined therein. Catheter  302  terminates distally with a distal valve  334 , having a distal-most orifice  336  therein. A valve seat  337  is illustrated having a shoulder region  338  for receiving a valve stem  340 . In the embodiment illustrated in FIG. 6, valve seat  337  receives valve stem  340  which prevents fluid from exiting through valve  334 . In the illustrated embodiment, valve stem  334  is a substantially spherical element, coupled to an activation wire  314 . In one embodiment, activation wire  314  is formed of Nitinol, and valve stem  340  is integrally formed with wire  314  by heating wire  314 , thereby causing the wire to melt and form a ball at the distal-most end. In a preferred embodiment, activation wire  314  has sufficient column strength to allow valve stem  340  to be forced against valve seat  337 , thereby closing the valve. In another embodiment, not requiring separate illustration a biasing spring, similar to spring  114  of FIG. 3, is provided within lumen  332  and can be held by a fixed block similar to that illustrated in FIG. 3. In an embodiment having sufficient biasing means, activation wire  314  need only be strong enough to open valve  334 , with the closing being accomplished by the biasing spring.  
         [0031]    Catheter  302  may also be seen to have a tube wall distal region  348  and a far distal region  350 . In one embodiment, far distal region  350  is formed of a more pliant material than distal region  348  disposed proximal of distal region  350 . In particular, far distal region  350  can be expanded under pressure so as to substantially increase the distal profile of catheter  302 . Catheter wall  330  may also include a bonding region  342  where tube wall  330  is strongly bonded to valve  334 .  
         [0032]    Referring now to FIG. 7, catheter  302  is illustrated in an expanded configuration. In FIG. 7, far distal region  350  has been expanded to have a substantially greater distal cross-sectional profile than the more proximal distal region  348 . In one embodiment, far distal region  350  has a unexpanded length of about one-half inch (½″). Inspection of FIG. 7 indicates that distal region  348  has not expanded nearly as far as distal region  350 , due to the difference of materials between the two regions. In one example, far distal region  350  is formed of an elastomeric substance which recovers the initial dimension upon the reduction of pressure. In another embodiment, far distal region  350  is formed of a material which undergoes plastic deformation under high pressure. As can be seen from inspection of FIG. 7, catheter far distal region  350  can significantly expand under pressure. Catheter distal region  350  can be forced against the heart chamber wall, there providing a better seal about distal nozzle  334  and distal orifice  336 . This can significantly improve the seal against the heart wall and around the holes formed in the heart wall. In one embodiment, silicone rubber is included in the walls of far distal region  350 . In another embodiment, PEBAX is used in both distal region  314  and far distal region  350 , with the far distal region having lower cross-linking PEBAX material than distal region  314 . The lower cross-linking can provide a more easily expanded material.  
         [0033]    Referring now to FIG. 8, catheter  302  is shown from an end view in an expanded state, illustrating central orifice  336  within nozzle  334 . Far distal region  350  may be seen to have expanded a distal profile significantly. By providing increased surface area for contact of the catheter distal region against the heart wall, the seal may be improved, and the amount of fluid under pressure that will enter the myocardium can be increased.  
         [0034]    Referring now to FIG. 9, a PMR catheter  400  is illustrated, having a proximal region  410 , an intermediate region  406 , a distal region  412 , a far distal region  404 , and a distal end  402 . Device  400  may include differing materials of construction as discussed with respect to FIG. 7. Device  400  includes intermediate region  406  formed of a more pliant material, as well as far distal region  404  being formed of a more pliant material. A more rigid material may be found in proximal region  410 , as well as distal region  412 . The more pliant material may be seen to be employed in regions  406  and  404 . Catheter  400  is illustrated in an inflated position. Intermediate, inflatable portion  406  can be disposed about six inches proximal of distal end  402  in one embodiment. In one embodiment, the expandable regions are formed of PEBAX, as are non-expandable regions, with the expandable regions having a significantly lower degree of cross-linking. Expanded intermediate region  406  can serve to expand a catheter until the catheter is expanded against the walls of a containing guide catheter. Expanded region  406  can thus stabilize the distal region of the fluid jet PMR device. With the distal region thus stabilized, fluid being injected from distal end  402  may be counteracted by the secured intermediate region. In particular, the reactionary force from the injecting fluid may be counteracted by the expanded balloon within the guide catheter. In this way, higher pressures, and, in some instance, greater flow rates, may be employed in forming the myocardial holes.  
         [0035]    Various fluids may be employed in using the present invention. In one embodiment, saline is used as the high pressure fluid. In another embodiment, saline is combined with therapeutic substances to promote healing and/or angiogenesis within the myocardium. Examples of therapeutic substances include small molecular drugs, proteins, genes and cells which could promote angiogenesis, protect tissues (i.e., cardiac protection), or promote tissue regeneration. Vascular Endothelial Growth Factor (VEGF) and Fibroblast Growth Factors (FGFs) are believed suitable for use with the present invention. Carriers for the therapeutic agents of the present invention can include polymers, angiopoietins, biodegradable and biostable hydrogels, and dissoluble polymers. Adhesives suitable for binding the present invention include fibrin glues and cyanoacrylates which may also be included with the therapeutic substance to improve the desired response. Drug injection catheters referred to in the remainder of the present patent application, and drugs similarly referenced, may include the injection and use of the aforementioned therapeutic substances.  
         [0036]    In one embodiment, contrast media is included with the cutting fluid, to provide an indication under fluoroscopy of regions of the heart chamber wall that have been already visited by the fluid jet PMR tip. The contrast media can be injected into holes within the heart wall, which may show up under fluoroscopy.  
         [0037]    In an embodiment, a high pressure fluid pressure of at least about 10 atmospheres is used. In some embodiments of the invention, fluid pressure is built up slowly in the distal region of the catheter, and released quickly by use of a distally disposed control valve, as previously discussed. In one example, a distal reservoir region, as indicated in FIGS. 3 and 4, is included to provide a substantial volume of fluid for injecting, even though, in steady state, the high pressure lumen is not sufficiently large to maintain a high flow rate over a long time. The fluid jet PMR fluid may thus be supplied slowly, built up under pressure, and released quickly in jets by a control valve disposed within the catheter. The distal control valve can also have a larger cross-section distal-most orifice than would be possible if this orifice diameter required and maintained the entire length of the catheter. The distal control valve can also provide means for ensuring that the fluid is not injected into the heart chamber until the distal tip is properly positioned.  
         [0038]    Numerous advantages of the invention covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts without exceeding the scope of the invention. The invention&#39;s scope is, of course, defined in the language in which the appended claims are expressed.