Abstract:
A medical delivery system for delivering a fluid to a desired location within a body that includes a first member having an aperture, and a second member adapted to be positioned over the first member. The fluid to be delivered is contained within a fluid storage device, formed by at least one of the first member and the second member. The medical delivery system includes means for repositioning the first member relative to the second member between a first state preventing passage of the fluid through the aperture and a second state enabling passage of the fluid outward from the fluid storage device through the aperture.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to delivering a drug to an internal body tissue, and in particular, the present invention relates to an apparatus and system that provides improved control of drug delivery to an internal body tissue.  
       BACKGROUND OF THE INVENTION  
       [0002]     Drug therapies are a primary component of an overall patient health plan. Drugs or therapeutic agents can be delivered to a patient in various ways including oral ingestion, intramuscular and/or intravenous injection or topical absorption. Most of these approaches require administration by medical professionals or regular patient compliance with the drug regimen. In addition, these drug delivery approaches, although useful, are not very effective in delivering therapeutic agents to internal body tissues or organs.  
         [0003]     Drugs and therapeutic agents can also be administered through the use of catheters. Catheters are medical devices designed for insertion into a body passageway that facilitate injection or withdrawal of fluids into a patient&#39;s body. Catheters provide an advantage of direct vascular and/or local delivery of a therapeutic agent to body tissues and organs that can include the heart, esophagus, stomach, large intestine, and other tissues which may be accessed via a catheter system. Catheters and catheter systems can deliver drugs to the sites where they are most needed, reduce the amount of medication required, and improve the control over the time for delivering the drug. However, drug deliver using current drug delivery devices can be problematic in that certain problems, such as the growth of tissue over the catheter opening, control of the fluid flow rate of the drug being administered, and resistance from other bodily fluids when introducing the drug need to be addressed.  
         [0004]     One approach to overcoming some of these drawbacks is to use an implantable infusion pump. Implanted infusion pumps usually include a pressurized drug reservoir and a form of fluid flow control. However, for some applications, implantable infusion pumps are inadequate because the amount of the therapeutic agent required for delivery and the need for additional pressure exceed the capability of most infusion pumps. Redesigning the infusion pump to address these deficiencies substantially increases the cost and size of the device.  
         [0005]     There is a need for a drug delivery system for administering drug therapies that can be used with conventional, implantable infusion pumps and catheters, and that addresses the aforementioned problems, as well as other related problems.  
       SUMMARY OF THE INVENTION  
       [0006]     Various embodiments of the present invention are directed to addressing the above and other needs in connection with vascular and/or local drug delivery arrangements that improve the performance of implantable fusion pumps, catheter systems and other drug delivery devices.  
         [0007]     According to an embodiment of the present invention, a medical delivery system for delivering a fluid to a desired location within a body includes a first member having an aperture and a second member adapted to be positioned over the first member. The fluid is contained within a fluid storage device, formed by at least one of the first member and the second member. The system includes means for repositioning the first member relative to the second member between a first state preventing passage of the fluid through the aperture and a second state enabling passage of the fluid outward from the fluid storage device through the aperture.  
         [0008]     According to another embodiment of the present invention, a medical delivery system for delivering a fluid to a desired location within a body includes a first member having an aperture and a second member adapted to be positioned over the first member. The fluid is contained within a fluid storage device, formed by at least one of the first member and the second member. The system includes means for repositioning the first member relative to the second member between a first state preventing passage of the fluid through the aperture and a second state enabling passage of the fluid outward from the fluid storage device through the aperture. A pressure sensing device is communicatively coupled to the repositioning means, and is adapted to sense pressure and generate a pressure feedback signal, wherein the repositioning means repositions the first member relative to the second member in response to the pressure feedback signal.  
         [0009]     The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures in the detailed description that follow more particularly exemplify these embodiments. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:  
         [0011]      FIG. 1A  illustrates a drug delivery arrangement according to an example embodiment of the invention;  
         [0012]      FIG. 1B  illustrates a wall portion of the drug delivery arrangement of  FIG. 1A  according to an example embodiment of the invention;  
         [0013]      FIG. 2  illustrates a drug delivery system according to another example embodiment of the invention;  
         [0014]      FIG. 3A  illustrates another drug delivery arrangement according to another example embodiment of the invention; and  
         [0015]      FIG. 3B  illustrates an exploded view of a drug delivery device of the arrangement of  FIG. 3A  according to another example embodiment of the invention. 
     
    
       [0016]     While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.  
       DETAILED DESCRIPTION  
       [0017]     The present invention is generally directed to a drug delivery arrangement that improves the performance of implantable fusion pumps, catheter systems and other drug delivery devices. In one example embodiment, the present invention prevents blood coagulation at a distal end of a drug delivery system by preventing the blood from flowing back into the tubing of the drug delivery system. In an example application, the present invention facilitates the treatment of atrial fibrillation and atrial flutter through pharmaceutical therapies, as an alternative to electrical cardioversion therapy. While the present invention is not necessarily limited to such an application, the invention will be better appreciated using a discussion of example embodiments in such a specific context.  
         [0018]     According to an embodiment of the present invention, an implantable drug delivery device includes a drug reservoir having movable surfaces or plates at a drug delivery end or wall portion. The movable plates have two surfaces overlapping each other when the drug delivery device is in an OFF state, so that, while in the OFF state, the drug remains inside the drug reservoir. However, when in an ON state, the drug is able to flow out of the reservoir in a controllable displacement or flow via apertures disposed in the movable plates that become exposed in response to relative movement of the movable surfaces. The motion of the movable plates results from elongation of the plate material upon receiving heat generated from an electrical source (current or voltage), a magnetic source or a thermal source. The plate material includes shape memory alloys responsive to various external stimuli. The shape memory alloy used is configurable to include apertures that open and close as the material elongates and contracts in response to the external stimulation, as described below.  
         [0019]      FIG. 1A  illustrates a drug delivery device according to an illustrative embodiment of the present invention. As illustrated in  FIG. 1A , a drug delivery device  100  according the present invention delivers a drug  102  stored within a drug reservoir  104  to an internal body tissue or organ  106  through apertures of a bottom side  108  of the drug delivery device  100 . The drug delivery device  100  includes a top side  105 , along with a first wall member  114  and a second wall member  116  that form the drug reservoir  104 . In particular, first wall member  114  includes a first side wall  118  integral with a first plate  110  that extends the entire length of bottom side  108  when drug delivery device is in an OFF state, illustrated in  FIG. 1A . Second wall member  116  includes a second side wall  120  integral with a second plate  112  having a length shorter than first plate  110  and slideably positioned over first plate  110 . First side wall  118  extends horizontally between an outer side  119  and an inner side  121  and second side wall  120  extends horizontally between an outer side  123  and an inner side  125 .  
         [0020]     The drug delivery device  100  is located proximate to body tissue  106  to maximize drug delivery through the bottom side  108  of drug delivery device  100 . Drug  102  is released through bottom side  108  and into body tissue  106  upon receipt of an external stimulus at wall member  114  and wall member  116 . In this example, an electrical circuit  119 , located external to or within drug delivery device  100 , such as a pump system, or within an implantable pulse generator, such as a pacemaker, cardiac defibrillator/cardioverter, provides the external stimulus to wall member  114  and wall member  116 . The external stimulus, which can either be electrical, magnetic or thermal, physically reconfigures the relative position of first plate  110  and second plate  112  forming bottom side  108  so that drug  102  is released through bottom side  108  and into body tissue or organ  106 , as described below.  
         [0021]      FIG. 1B  illustrates a detailed view of a bottom side of the drug delivery device of  FIG. 1A  according to an illustrative embodiment of the invention. As illustrated in  FIG. 1B , wall portion  108  is formed by overlapping plates  110  and  112  made of a shape memory alloy, with plate  110  extending from a first end  120 , at which a series of one or more apertures  110 A are positioned, to a second end  122 , and plate  112  extending from a first end  124 , at which a series of one or more apertures  112 A are positioned, to a second end  126 .  
         [0022]     According to the present invention, when the drug delivery device is in an OFF state, plates  110  and  112  are relatively positioned so that plate  112  is positioned over apertures  110 A so that drug is prevented from passing through bottom side  108  via apertures  110 A of plate  110 , and plate  110  is positioned over apertures  112 A so that drug is prevented from passing through bottom side  108  via apertures  112 A of plate  112 . On the other hand, apertures  110 A and  112 A of plates  110  and  112 , respectively, allow drug  102  of  FIG. 1A  to flow outward from drug reservoir  104  to body tissue  106  when plates  110  and  112  are positioned in an ON state, illustrated in  FIG. 1B . In particular, when plates  110  and  112  are positioned in the OFF state, second end  126  of plate  112  is positioned to cover apertures  110 A of plate  110  and second end  122  of plate  110  is positioned to cover apertures  112 A of plate  112  to prevent flow of drug  102  outward from drug reservoir  104 . As wall members  114  and  116  are electrically stimulated by circuit  120 , plates  110  and  112  begin to elongate and expose apertures  110 A and  112 A such that drug  102  is released through one or more of apertures  110 A and  112 A into body tissue  106  of  FIG. 1A . The relative movement of plates  110  and  112  results from elongation of the plate material upon receiving heat generated from an electrical source (current or voltage). In this example embodiment, the plates are made from a Nitinol-based shape memory alloy that is a 50/50 mix of titanium nitinol, for example.  
         [0023]     The choice of the type of shape memory alloy used in the various embodiments of bottom portion  108  depends on where the movable plate arrangement will be used and the acceptable range of electrical, thermal or magnetic parameters. The distribution and size of the apertures in the movable plates are designed according to particular parameters for the flow rate and drug dosage requirements of an individual patient or condition to be treated. The quantity of displacement of the movable plates can be controlled by the source providing the stimulus to the plates.  
         [0024]     According to an embodiment of the present invention, apertures  110 A and  112 A may be positioned so as to be offset relative to each other in such a way as to minimize the distance that plates  110  and  112  are required to advance relative to each other in order to enable drug  102  to flow outward from drug reservoir  104 .  
         [0025]     It is understood that while the drug delivery device  100  described in reference to  FIGS. 1A and 1B  includes one or more apertures  110 A and  112 A located along both plates  110  and  112 , the present invention is intended to include other combinations of apertures and movable plates. For example, according to an alternate embodiment of the present invention, one or more apertures are positioned along only one of plates  110  and  112 , and/or only one of plates  110  and  112  moves in response to the electrical stimulation from circuit  119 . According to yet another embodiment of the present invention, apertures are included only along first plate  110 , and are in direct opposition to second plate  112  when delivery device  100  is in the closed state preventing flow of drug  102  from drug reservoir  104 . The external stimulus is received at plate  110  and top side  105 , so that only top side  105  and plate  110  are physically reconfigured, while second plate  112  remains at a fixed position. When top side  105  and plate  110  expand, the apertures positioned along plate  110  move relative to fixed plate  112  to become exposed, enabling flow of drug  102  through the apertures. The magnitude of the physical reconfiguration of plate  110  is controlled via pressure feedback to meet a desired flow rate.  
         [0026]      FIG. 2  illustrates a drug delivery system according to an alternate embodiment of the present invention. As illustrated in  FIG. 2 , a drug delivery system  200  according to an alternate embodiment of the present invention includes a valve arrangement  201  for connecting to an implantable infusion pump  210 . Valve  201  includes an outer sleeve member  202  and an inner sleeve member  204 , having a diameter less than the outer sleeve member  202  so as to be insertable within the outer sleeve member  202 , with one or more apertures  206  positioned along inner sleeve member  204 . A medicinal fluid  208  flows within an interior  207  of inner sleeve  204 , in the direction of dashed arrow  208 A. When in an OFF state, inner sleeve member  204  is positioned relative to outer sleeve member  202  so that apertures  206  are covered by outer sleeve member  202 , preventing fluid  208  from exiting from inner sleeve member  204  via apertures  206 .  
         [0027]     On the other hand, when in an ON state, inner sleeve member  204  is positioned relative to outer sleeve member  202  so that apertures  206  are not covered by outer sleeve member  202 , enabling fluid  208  to exit from inner sleeve member  204  via apertures  206 . Fluid  208  exits inner sleeve  204  through apertures  206 , as indicated by directional arrow  208 B, flowing into a patient. Fluid  208  is pumped out of a drug reservoir  209  by infusion pump  210 , infusion pump  210  drawing suction from reservoir  209  and discharging into inner sleeve  204 .  
         [0028]     Medicinal fluid  208  flows to the patient after valve  201  opens as a result of stimulating inner sleeve member  204 . In one example implementation, inner sleeve member  204  is stimulated directly with an electrical current from a wire  214  disposed within sleeve member  204  provided by an electrical circuit  212 . The electrical stimulation of inner sleeve member  204  causes inner sleeve member  204  to elongate and expose apertures  206  thereby allowing medicinal fluid  208  to flow to the patient. Inner sleeve member  204  elongation results in relative motion of portions of inner sleeve member  204  with respect to outer sleeve member  202 , as indicated by directional arrow  220 . In another example implementation, an electrical current through wire  214  indirectly stimulates inner sleeve member  204 , the electrical current causing a heating element  222  to generate heat, and the heat causing member  204  to elongate, and expose apertures  206 .  
         [0029]     Medicinal fluid flow can cease before infusion pump  210  stops by closing valve  201  via a reconfiguration of inner sleeve member  204 , for example by stimulating member  204  using reverse polarity current, or by curtailing electrical current flow thereby cooling heating element  222  respectively. This approach allows better control of the flow rate of the medicinal fluid stream through the apertures. Providing movable surfaces in valve  201  for use with infusion pump  210  improves drug flow and pump efficiency. For a more detailed discussion of implantable infusion pumps, reference is made to U.S. Pat. No. 5,820,589 to Torgerson, et al., which is assigned to the assignee of the present invention and is incorporated herein by reference in its entirety.  
         [0030]     The present invention addresses certain difficulties that currently exist in known valve designs, such as controlling the flow rate of the medicinal fluid, high resistance from the surrounding blood or bodily fluids to introduction of the drug, and limited pressure generated from the infusion pump  210 . In particular, the present invention utilizes the reconfiguration properties of the shape memory alloy in inner sleeve member  204  so that the internal pressure generated by infusion pump  210  enables medicinal fluid  208  to flow outside valve  201  more easily when the valve  201  is open, and will prevent blood from refluxing into apertures  206 . System  200  has low resistance, and the pressure generated from infusion pump  210  only needs to be slightly greater than that of the blood or surrounding bodily fluid to move medicinal fluid  208  out of valve  201 . Once the fluid  208  is delivered, valve  201  is closed completely with an additional electrical stimulus. The drug flow rate from valve  201  can be more easily controlled by infusion pump  210 , circuit  212 , and the design of inner sleeve member  204  according to the present invention. The present invention improves the control of fully turning ON or OFF valve  201  to prevent drug leakage. The drug dosage and speed of delivery is also controlled more precisely.  
         [0031]     According to a further example embodiment of the present invention, fluid  208  is pumped out of a drug reservoir  209  by infusion pump  210 , pump  210  drawing suction from reservoir  209  and discharging fluid  208  into inner sleeve  204  through pressure sensor  216 . Pressure sensor  216  detects pressure of the flow of medicinal fluid  208  at a selected location between infusion pump  210  and a point at which the medicinal fluid  208  exits through apertures  206 . As discussed above, the elongation of inner member  204 , and the relative movement of portions of member  204  with respect to outer member  202 , is proportional to the amount of stimulation experienced by member  204 . Therefore, the quantity of apertures  206  exposed through which fluid can flow, the flow rate and pressure of medicinal fluid through apertures  206 , are also controlled by the amount of stimulation experienced by member  204 . As more apertures are exposed, pump  210  backpressure decreases and flow rate increases, but at a lower fluid pressure as sensed by pressure sensor  216 . The rate and pressure of fluid delivery to the patient is thereby proportional to the stimulation to inner member  204 .  
         [0032]     In order for medicinal fluid to exit apertures  206 , the pressure of fluid flow through apertures  206  must be greater than a predetermined threshold, such as the patient&#39;s blood pressure for example. If medicinal fluid pressure is too low, bodily fluid will flow into the interior of inner member through exposed apertures  206 . Unnecessarily exposing too many apertures  206  reduces medicinal fluid delivery pressure. Additionally, exposing apertures  206  to bodily fluids (e.g., blood cells and proteins) subjects the apertures to buildup of blockage elements. Conversely, an excessive medicinal fluid pressure through apertures  206  resulting from exposing too few apertures, may be detrimental to pump  210 , and/or the patient.  
         [0033]     According to one aspect, stimulation of inner member  204  is controlled to limit the quantity of exposed apertures  206 , while providing medicinal fluid flow through the apertures  206  at a pressure not to exceed a selected maximum threshold. A closed loop feedback path  218  communicatively couples pressure sensor  216  with the inner sleeve elongation control mechanism, circuit  212  for example. As pressure increases, and is detected by sensor  216 , sensor  216  electrically communicates a feedback signal to circuit  212  via feedback path  218 . Circuit  212  stimulates inner sleeve  204  responsive to the feedback signal thereby causing additional apertures  206  to be exposed and mitigating the detected pressure increase. The quantity of exposed apertures is controlled to maintain fluid pressure according to a selected flow rate, not to exceed a selected maximum pressure, 250 mm Hg for example. For example, the inner sleeve member  204  is initially stimulated to cause a limited number of apertures  206  to be exposed. If fluid pressure is subsequently sensed to be too high, a pressure feedback signal causes further stimulation of inner sleeve member  204  resulting in more of apertures  206  to be exposed.  
         [0034]      FIG. 3A  illustrates a drug delivery system  300  that includes a drug delivery device  308  according to another example embodiment of the invention. In particular, drug delivery system  300  includes a catheter  301  having a catheter body  302  and a catheter tip  304  with a pair of tines  306  for anchoring catheter  301  to body tissue. Drug delivery system  300  further includes drug delivery device  308  that is mounted between catheter body  302  and catheter tip  304  for local delivery of medication. The medication can be in the form of a fluid or a solid that can travel within catheter  301 .  
         [0035]      FIG. 3B  illustrates an exploded view of drug delivery device  308  of  FIG. 3A  according to another example embodiment of the invention. Drug delivery device  308  includes an outer sleeve member  310  and an inner sleeve member  312  having a plurality of apertures  314 . A drug  316  elutes out of inner sleeve member  312  via apertures  314  once drug delivery device  308  is in an ON position in response to an electrical stimulation of inner sleeve member  312 . In the ON state, the electrical stimulation of inner sleeve member  312  causes inner sleeve member  312  to elongate and expose apertures  314 , thereby allowing drug  316  to elute or flow into the patient in a controlled manner. In an OFF state, drug flow is cease by closing apertures  314  via a reconfiguration of sleeve member  312  upon receiving the electrical stimulus so that apertures  314  are covered by outer sleeve member  310 . This approach allows better control of the flow rate of a drug, with or without a particulate substance, to the patient.  
         [0036]     In another embodiment, drug delivery arrangement  300  is incorporated into a pacing/sensing electrode lead head member that is implantable in a patient&#39;s heart. In this embodiment, drug delivery device  308  is disposed within the electrode lead head member and opens via an electrical stimulus received from the electrode lead body. This approach to drug delivery can replace a monolithic controlled release (MCR) device normally incorporated into electrode leads. MCR devices typically include a small sponge disposed at the end of the electrode lead that elutes a steroid to inhibit implant rejection. The use of drug delivery device  308  provides the capability of inhibiting tissue inflammation, thereby delaying or preventing the onset of implant rejection, by controlling the elution rate, quantity and release time of the steroid. Device  308  can be intermittently stimulated to open and close, thereby locally releasing the desired drug in a controlled manner.  
         [0037]     In related embodiment, the electrode lead head member of drug delivery arrangement  300  can be similarly formed from a shape memory alloy with a series of apertures. Similar to the embodiment illustrated in  FIGS. 3A and 3B , the electrode lead head member would include outer sleeve member  310  and an inner sleeve member  312  having apertures  314 . Drug  316  elutes out of inner sleeve member  312  via apertures  314  once drug delivery device  308  is in an ON position in response to an electrical stimulation of inner sleeve member  312 . In the ON state, the electrical stimulation of inner sleeve member  312  causes inner sleeve member  312  to elongate and expose apertures  314 , thereby allowing drug  316  to elute or flow into the patient in a controlled manner. In an OFF state, drug flow is cease by closing apertures  314  via a reconfiguration of sleeve member  312  upon receiving the electrical stimulus so that apertures  314  are covered by outer sleeve member  310 . According to an alternate embodiment, both inner sleeve member  312  and outer sleeve member  310  include apertures not directly opposed. When in the ON state, outer sleeve member  310  is physically reconfigured by the stimulus so that the apertures positioned along inner sleeve member  312  become aligned with the apertures positioned along outer sleeve member  310 , enabling flow of the drug outward from the electrode head member. When in the OFF state, the apertures positioned along outer sleeve member  310  are covered by a portion of inner sleeve member  312  not having apertures and the apertures positioned along inner sleeve member  312  are covered by a portion of outer sleeve member  310  not having apertures, preventing flow of the drug outward from the electrode head member. Upon stimulating the electrode head member, the head member elongates and exposes the apertures, thereby releasing the drug stored within the head member. This approach prevents the formation of fibrosis around the apertures by intermittently releasing a steroid that inhibits tissue inflammation. The electrode head member can be easily placed against the surface of an internal body tissue, such as the myocardium of the heart, to increase the penetration of drug delivery to the body tissue. With this approach the drug is not diluted by local bodily fluids, because the drug is delivered directly to the body tissue or organ.  
         [0038]     According to an embodiment of the present invention, the drug delivery system may include more than one valve arrangement as described above, so that two or more sets of apertures are positioned along various portions of the inner and outer sleeve members, longitudinally displaced relative to one another along a length of the inner and outer sleeve members, to form multiple sleeve valves that may act as surrogate valves in the case a primary valve becomes occluded.  
         [0039]     Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the present specification. The claims are intended to cover such modifications and devices.