Fluid treatment system for a driveline cable and methods of assembly and use

A fluid treatment system for a percutaneous cable and methods of assembly and use are described herein. In one aspect, the fluid treatment system includes a delivery tube comprising a distal end and a proximal end. The distal end is configured to surround at least a portion of the percutaneous cable. The percutaneous cable extends from within a patient to outside the patient through tissue at an exit site. The proximal end is connectable to a fluid source. Fluid from the fluid source is configured to be delivered to the exit site through the delivery tube. The fluid treatment system includes an anchor coupleable to the percutaneous cable to secure the percutaneous cable to the tissue at the exit site.

BACKGROUND

This application relates generally to mechanical circulatory support systems, and more specifically relates to fluid treatment systems, such as may be used for a driveline cable for an implantable blood pump.

Ventricular assist devices, known as VADs, are implantable blood pumps used for both short-term (i.e., days, months) and long-term applications (i.e., years or a lifetime) where a patient's heart is incapable of providing adequate circulation, commonly referred to as heart failure or congestive heart failure. According to the American Heart Association, more than five million Americans are living with heart failure, with about 670,000 new cases diagnosed every year. People with heart failure often have shortness of breath and fatigue. Years of living with blocked arteries or high blood pressure can leave your heart too weak to pump enough blood to your body. As symptoms worsen, advanced heart failure develops.

A patient suffering from heart failure, also called congestive heart failure, may use a VAD while awaiting a heart transplant or as a long term destination therapy. In another example, a patient may use a VAD while recovering from heart surgery. Thus, a VAD can supplement a weak heart (i.e., partial support) or can effectively replace the natural heart's function. VADs can be implanted in the patient's body and powered by an electrical power source inside or outside the patient's body.

The VAD is powered and may also be controlled by a driveline cable that extends from the VAD and through an aperture of the patient to an external power source and/or controller device. The driveline cable may terminate in a connector having a connector adapted to connect to a corresponding connector receptacle of an external power source and/or control unit worn by the patient. Because the driveline cable passes through skin or tissue of the patient, infection around an exit site following implantation of a VAD is a serious complication that may arise in patients with percutaneous driveline cables (e.g., as a result of injury to tissue or skin around the exit site due to tunneling of the driveline cable or movement after implantation). It would be desirable to provide improved systems and methods for the administration of medication or other treatments to treat or manage infections when present, or prevent or reduce the likelihood of infections occurring, associated with such percutaneous driveline cables.

BRIEF SUMMARY

The invention relates generally to mechanical circulatory support systems, and in one embodiment to a fluid treatment systems, such as may be used for a driveline cable for an implantable blood pump. Such fluid treatment systems may be suitable for percutaneous driveline cables that extend outside the body through an incision in the skin. In certain aspects, the invention provides fluid treatment systems suitable for delivering to or removing fluid from incision sites of percutaneous cables for various implantable medical devices. Fluid may be delivered to the incision sites by such fluid treatment systems for improved healing around the incision site, treating or reducing infected tissue, and/or for reducing or preventing the occurrence of infection of the tissue.

In one aspect, a fluid treatment system in accordance with embodiments of the present invention includes a delivery tube comprising a distal end and a proximal end. The distal end is configured to surround at least a portion of a percutaneous cable. The percutaneous cable extends from within a patient to outside the patient through tissue at an exit site. The proximal end is connectable to a fluid source. Fluid from the fluid source is configured to be delivered to the exit site through the delivery tube. The fluid treatment system includes an anchor coupleable to the percutaneous cable to secure the percutaneous cable to the tissue at the exit site. In some embodiments, the delivery tube extends coaxially around the percutaneous cable. The anchor may include at least one of: an outer covering, an adhesive, a sleeve, a tubular device, a filament bundle, or a skirt. Further, the anchor may be implantable subdermally within the tissue surrounding the exit site. The anchor may include a skirt with the skirt including a mesh material coupleable to the percutaneous cable and configured to extend radially away from the percutaneous cable to engage the tissue surrounding the exit site. In certain embodiments, the mesh material includes titanium or nickel titanium wires. In certain embodiments, the fluid treatment system further includes a vacuum assisted closure system configured to remove the fluid delivered to the exit site. In some embodiments, the vacuum assisted closure system is configured to apply negative pressure to the exit site. The delivery tube may be attachable to the percutaneous cable prior to implantation of the percutaneous cable. The delivery tube may be attachable to the percutaneous cable after implantation of the percutaneous cable. In some embodiments, the delivery tube is releasably slidable onto the percutaneous cable.

In another aspect, a blood pump system configured in accordance with embodiments of the present invention includes an implantable blood pump and an implantable cable coupleable to the implantable blood pump. The cable includes a percutaneous portion configured to extend through tissue of a patient at an exit site. The blood pump system further includes a delivery tube including a first end configured to be positioned proximate the exit site and a second end coupleable to a fluid source. The delivery tube is configured to deliver fluid from the fluid source to the exit site. In some embodiments, the blood pump system further includes an anchor configured to secure the cable to the tissue at the exit site. In certain embodiments, the cable comprises a porous cover. In some embodiments, the delivery tube extends coaxially around a portion of the percutaneous portion of the cable. In certain embodiments, the blood pump system further includes a vacuum assisted closure system configured to remove the fluid delivered to the exit site. In some embodiments, the vacuum assisted closure system is configured to apply negative pressure to the exit site.

In yet another aspect, a method of delivering fluid to an exit site of a percutaneous cable is provided in accordance with embodiments of the present invention. The percutaneous cable is coupleable to an implantable medical device and extends through tissue of a patient. The method reduces or prevents infection of tissue at the exit site. The method includes surrounding at least a portion of a percutaneous cable extending through tissue of a patient at an exit site with a delivery tube, positioning a first end of the delivery tube proximate the exit site, connecting a second end of the delivery tube to a fluid source, securing the percutaneous cable to tissue at the exit site, and delivering fluid from the fluid source to the exit site through the delivery tube. Delivering fluid from the fluid source to the exit site through the delivery tube may include delivering fluid between an inner surface of the delivery tube and an outer surface of the percutaneous cable. Surrounding at least a portion of the percutaneous cable with the delivery tube may include coaxially surrounding at least a portion of the percutaneous cable with the delivery tube. In some embodiments, the method further includes removing fluid delivered from the fluid source to the exit site via a vacuum assisted closure system. In some embodiments, the method may include further applying negative pressure to the exit site via a vacuum assisted closure system.

DETAILED DESCRIPTION

FIG. 1is an illustration of a mechanical circulatory support system10(e.g., a blood pump system) implanted in a patient's body12. The mechanical circulatory support system10comprises an implantable blood pump14, ventricular cuff16, outflow cannula18, system controller20, and power sources22. The implantable blood pump14may comprise a VAD that is attached to an apex of the left ventricle, as illustrated, or the right ventricle, or two or more VADS attached to both ventricles of the heart24. The VAD may comprise a centrifugal (as shown) or axial flow pump that is capable of pumping the entire output delivered to the left ventricle from the pulmonary circulation (i.e., up to 10 liters per minute). Related blood pumps applicable to the present invention are described in greater detail below and in U.S. Pat. Nos. 5,695,471, 6,071,093, 6,116,862, 6,186,665, 6,234,772, 6,264,635, 6,688,861, 7,699,586, 7,976,271, 7,997,854, 8,007,254, 8,152,493, 8,652,024, and 8,668,473 and U.S. Patent Publication Nos. 2007/0078293, 2008/0021394, 2009/0203957, 2012/0046514, 2012/0095281, 2013/0096364, 2013/0170970, 2013/0121821, and 2013/0225909, all of which are incorporated herein by reference for all purposes in their entirety. With reference toFIG. 1, the blood pump14may be attached to the heart24via the ventricular cuff16which is sewn to the heart24and coupled to the blood pump14. The other end of the blood pump14connects to the ascending aorta via the outflow cannula18so that the VAD effectively diverts blood from the weakened ventricle and propels it to the aorta for circulation to the rest of the patient's vascular system.

FIG. 1illustrates the mechanical circulatory support system10during battery22powered operation. A driveline cable25(e.g., a percutaneous cable or lead) connects the implanted blood pump14to the system controller20, which monitors system10operation. The driveline cable25may include a percutaneous portion26that exits the patient through an exit site29(e.g., abdominal aperture) and terminates at in-line connector28that connects the percutaneous portion26with a modular external cable27, the other end of the modular external cable27being protected within the system controller20. In some embodiments, prior to the connection of the percutaneous cable portion26and the modular cable27being made in the operating room, a fluid delivery tube132of fluid treatment system131in accordance with the present invention (e.g., as described in more detail below with respect toFIGS. 3A-3C) may be installed over a free end of the percutaneous portion26and/or the modular cable27. In other embodiments, the fluid delivery tube132may be installed to or over the driveline cable25after connection of the percutaneous cable portion26and the modular cable27. Further, in other embodiments, the fluid delivery tube132may be installed prior to or after implantation of the driveline cable25.

Implantable medical pumps (e.g., blood pumps) are used to provide mechanical assistance or augmentation to pumping performed by the left and/or right ventricles of the heart. Due to the pumping volume and constant operation required in such applications, such pumps typically have substantial power requirements, often necessitating a remotely located power source, usually an external power source worn outside the body, such as shown inFIG. 1. Such pumps are typically powered through a driveline cable (e.g., the driveline cable25), which extends percutaneously through the patient. Because the driveline cable25passes through skin or tissue of the patient and may be subject to frequent movement and flexure, infection of tissue at or around the exit site may occur or arise. A fluid treatment system in accordance with the present invention may be installed over the driveline cable25to deliver fluid to treat, reduce, or prevent infection of tissue at the exit site29of the driveline cable25. It is further appreciated that a fluid treatment system in accordance with aspects of the invention may be used in various other applications apart from implantable heart pumps. For example, the fluid treatment system131may be used to deliver fluid to exit sites of percutaneous cables for any number of implantable medical devices and provide the advantages described herein.

The system controller20monitors system operations. Related controller systems applicable to the present invention are described in greater detail below and in U.S. Pat. Nos. 5,888,242, 6,991,595, 8,323,174, 8,449,444, 8,506,471, 8,597,350, and 8,657,733 and U.S. Patent Publication Nos. 2005/0071001 and 2013/0314047, all of which are incorporated herein by reference for all purposes in their entirety. The system may be powered by either one, two, or more batteries22. It will be appreciated that although the system controller20and power source22are illustrated outside/external to the patient body, the driveline cable25, system controller20and/or power source22may be partially or fully implantable within the patient, as separate components or integrated with the blood pump14. Examples of such modifications are further described in U.S. Pat. No. 8,562,508 and U.S. Patent Publication No. 2013/0127253, all of which are incorporated herein by reference for all purposes in their entirety.

In the example embodiment shown inFIG. 2, the driveline cable25includes a central core1around which insulated conductors2are wound, each conductor comprising uninsulated wire strands that are loosely packed. Related driveline or percutaneous cables applicable to the present invention are described in greater detail below and in U.S. Patent Publication Nos. 2012/0046515 and 2016/0064117, all of which are incorporated herein by reference for all purposes in their entirety. The exemplary cable25may include a redundant set of wires, and accordingly, may include a total of six insulated conductors2. The insulated conductors may be formed of copper alloy or other suitable material. The central core1may be a polyethylene strength member and the conductors2may be wound at a 1.00 inch pitch or less, preferably a 0.75 pitch or less, such as at a 0.6 inch pitch. Advantageously, the configuration of the conductors allows for tighter wrapping at smaller, tighter pitches that creates a spring-like effect which considerably reduces strain forces and further improves durability. The wound conductors2may be surrounded by a polytetrafluoroetheylene (PTFE) layer3, followed by a polymer layer with moisture ingress resistance properties4, such as a Bionate® or a PCU (e.g., a thermoplastic polycarbonate-urethane) layer, followed by an aramid armor layer5, and an outer cover6. The outer cover6may be a silicone jacket or other material permeable to fluids, porous and configured to allow ingrowth of the patient's biological tissue that contacts the outer cover6. Providing a permeable and porous outer cover6may provide improved distribution of fluid delivered to the exit site29and/or vacuum assisted treatments about the exit site29(e.g., as described in more detail below with respect toFIG. 5).

With reference to the embodiments illustrated inFIGS. 3A-3C, the fluid treatment system131incudes a delivery tube132(e.g., a sleeve, conduit, lumen) and a fluid source134. The delivery tube132may be constructed of polymers (e.g., silicone or polyurethane blends) and/or plastic (e.g., acetal, acrylic). In some embodiments, different portions of the delivery tube132may include different materials. For example, a skin interfacing portion may be constructed of a polymer and a fluid delivery portion may be made from harder plastic materials. The delivery tube132includes a distal end, a proximal end, and a length therebetween. The distal end of the delivery tube132surrounds at least a portion of the driveline cable25(e.g., the percutaneous portion26) when the fluid treatment system131is installed. In some embodiments, the delivery tube132extends coaxially around a portion of the driveline cable25(e.g., the percutaneous portion26). As illustrated, the percutaneous portion26of the driveline cable25extends from within a patient to outside the patient through tissue130at the exit site29for connecting an external controller20or power source22to the blood pump14as described in more detail above. The proximal end of the delivery tube132is connected or configured to be connected to a fluid source134(e.g., a fluid or solution bag). Fluid (e.g., antibiotic, saline, tissue medium containing protein growth factors such as FGF, cleaning solution, or other solutions) from the fluid source134may be delivered to the exit site29for improved healing around the exit site29, treating or reducing infected tissue, and/or for reducing or preventing the occurrence of infection of the tissue. The fluid source134may include a mechanism for delivering fluid to the exit site29including, for example, a syringe or other needle assembly, a pump, or gravity drip assembly. Further, the fluid treatment system131may include an anchor140or other securement device (e.g., sutures, adhesives) coupleable to the driveline cable25to secure the driveline cable25to the tissue130at the exit site29(e.g., as described in more detail below with respect toFIGS. 3B-3C). The anchor140may also provide a seal to the driveline cable25at the exit site29to reflect or direct delivered fluid outward away from the exit site29. In this manner, the anchor140may provide both sealing and securing features.

As illustrated inFIG. 3C, fluid inflow to and outflow from the exit site29are identified by arrows I and O, respectively. For example, fluid may be delivered from the fluid source134to the exit site29between an inner surface of the delivery tube132and an outer surface of the driveline cable25. After reaching the exit site29, the delivered fluid may be reflected or otherwise directed outward away from exit site29by, for example, the anchor140or other sealing device. The delivered fluid may be drained or removed passively or actively. For example, the delivered fluid may be drained via gravity and evacuated to or by pouches, bags, gauze pads or other dressings to collect the outflow of fluid. In other embodiments, the delivered fluid and other debris may be removed via a vacuum assisted closure system166(e.g., as described in more detail below with respect toFIG. 5) or other suitable suction or drainage system.

The fluid treatment system131(e.g., the delivery tube132, vacuum assisted closure system166, or other components) may be installed prior to, during, and/or after implantation of the mechanical circulatory system10, and more specifically, the driveline cable25. For example, in some embodiments, the fluid treatment system131is installed as part of a manufacturing process (e.g., at a factory) prior to implantation of the system10by a clinician or other medical personnel. In other embodiments, the fluid treatment system131is installed by a clinician or other medical personnel during and/or after an implantation procedure of the mechanical circulatory system10. The delivery tube132may be slidably installed onto and/or translatable axially relative to at least a portion of the driveline cable25(e.g., to be moved into a desired position relative the driveline cable25at the exit site29). In some embodiments, the delivery tube132may be threaded onto the driveline cable25. In other embodiments, the delivery tube132may be secured in position (e.g., to the driveline cable25) with an adhesive or other mechanical attachment. In some embodiments, the delivery tube132may be configured to be installed permanently onto the driveline cable25(e.g., configured to remain installed while the driveline cable25is implanted within a patient). In other embodiments, the fluid treatment system131may be configured to be installed temporarily (e.g., to provide treatment by delivering fluid and then removable once treatment, a treatment session, or healing is completed).

Fluid delivered to the exit site29may promote healing. For example, the fluid may include antibiotics or other medication delivered to the exit site29. The fluid may also flush the exit site29to remove undesirable fluid, discharge, bacteria, or other debris. Therefore, the fluid treatment system131may deliver fluid to treat or reduce infection when present at the exit site29. The fluid treatment system131may also deliver fluid to prevent or reduce the occurrence of infection at the exit site29. In some embodiments, fluid is configured to be delivered and removed continuously or permanently (e.g., while the driveline cable25is implanted in the patient). Fluid may be delivered and removed at a relatively slow flow rate (e.g., on the order of milliliters per day). For example, a continuous drip-type fluid delivery assembly may be provided. In other embodiments, fluid is delivered and removed semi-continuously or over a set period of time (e.g., minutes, hours, days, etc). For example, fluid may be delivered and removed as part of a prescribed treatment cycle or cycles over set periods of time. A specific period of time or flow rate of fluid delivery and removal may be configured by the patient or medical personnel. For example, the fluid source134may include a valve that may be opened or closed as desired to release fluid to the delivery site29. In certain embodiments, two or more fluids may be delivered. For example, a saline or other cleaning solution may be delivered to flush the exit site29prior to delivering fluid containing antibiotics or other medication to the exit site29. Fluid to flush the exit site may be for a discrete period of time (e.g., seconds, minutes) and at a relatively faster flow rate (e.g., on the order of milliliters per sec) relative to delivering an antibiotic or other fluid with medication.

With reference toFIGS. 3B-3C, the anchor140may be a subdermal anchor coupled to the percutaneous driveline cable25. The subdermal anchor140may be configured for implantation within the tissue130surrounding the exit site29. The subdermal anchor140is attached to and extends radially away from the percutaneous cable25, and is configured for coupling to one or more subdermal layers under the skin136of a patient. In some embodiments, the subdermal anchor140is a porous device configured to allow ingrowth138of the tissue130surrounding or in the vicinity of the exit site29. In other embodiments, the subdermal anchor140is substantially non-porous and comprises barbs or hooks configured to engage the surrounding tissue130. In some embodiments, a subdermal anchor140, such as a skirt (FIG. 4), may be implanted in a subdermal pocket133(e.g., below the skin surface136) made in advance by an incision into the tissue130surrounding the exit site29. In other embodiments, a subdermal pocket133is not made ahead of time and a subdermal anchor, such as a filament bundle or barbed filament, is sutured against the surrounding tissue130using a needle. Related anchors and other securement devices applicable to the present invention are described in greater detail below (e.g., with respect toFIG. 4) and in U.S. Patent Publication No. 2012/0046515, which has been incorporated by reference above. For example, other securement devices may include one or more of: an adhesive, a tubular securement device, a sleeve, or, a filament bundle. Such securement devices may also provide sealing to reflect or direct delivered fluid from the fluid treatment system131outward away from the exit site29.

As illustrated, in some embodiments, the subdermal anchor140may be in the form of a porous skirt attached to and extending radially away from the driveline cable25(for example, extending radially away from the longitudinal length or axis of the cable). The skirt comprises an inner edge142attached to the cable25and an outer edge144opposite the inner edge142. The skirt may be a thin, flexible, and substantially flat material. Suitable materials include without limitation a mesh of titanium or nickel titanium wires and a mesh of synthetic polymer monofilament, such as polypropylene filament. Conventional mesh material used for hernia repair may also be used for the skirt. The skirt may have one or more radial slits146to facilitate placing the skirt in a folded or collapsed configuration. The gaps within the mesh and the slits146allow for better blood supply to the epidermis than if the skirt146were non-porous and had no slits. For example, the porosity of the skirt allows for tissue ingrowth138. Tissue ingrowth includes tissue adhesion to and encapsulation of the skirt140.

The inner edge142of the skirt may be moveable so that after the percutaneous driveline cable25is fed through the exit site29, the inner edge142may be moved axially on the cable25until the skirt is at or near the exit site29. Referring toFIG. 4, to allow such movement, the inner edge142of the skirt may be attached to a holding device, such as a split ring148, which may be slidable on or removable from the cable25. A cut150through the split ring148corresponds in position to the single slit146in the skirt. The cut150forms opposite ends on the split ring148which are spaced apart from each other by a distance that is smaller than the outer diameter of the cable25. In use, the split ring148may be bent to temporarily spread apart the split ring ends and thereby allow the split ring to be mounted around the cable25at any axial position on the cable and at any time, before or after the cable has been fed through the exit site29. The split ring148may clamp tightly around the percutaneous driveline cable25. In some embodiments, as shown inFIG. 4, the split ring148comprises a plurality of teeth170that face radially inward. The teeth170are configured to clamp down onto the percutaneous driveline cable25and prevent axial movement of the split ring148.

As illustrated inFIG. 5, a vacuum assisted closure system160may be provided for use with the fluid treatment system131or as a stand-alone system (FIG. 5) according to certain embodiments described herein. The vacuum assisted closure system160may be configured to treat infection or promote wound healing by providing fluid delivery, vacuum assisted fluid or wound drainage, and/or vacuum assisted wound closure (e.g., via negative pressure wound therapy). For example, in some embodiments, the vacuum assisted closure system160may include one or more Tegaderm™ patches or other suitable wound dressings162adhered or otherwise attached to skin136of a patient. When used in combination with the fluid treatment system131, the wound dressings162may be attached or secured to form a seal around the delivery tube132(not illustrated) rather than directly to the percutaneous portion26of the driveline cable25as illustrated inFIG. 5and described in more detail below. In some embodiments, the vacuum assisted closure system160may also include additional foam or other suitable dressings positioned at or within the exit site29to aid in wound healing with the system160.

In certain embodiments, two or more wound dressings162may be attached to the skin136of a patient and around (e.g., on opposing sides of) the driveline cable25. In this manner, the dressings162and vacuum assisted closure system160may be attached after implantation of the driveline cable25without having to disconnect the driveline cable25. In other embodiments, a single dressing162may be attached to the skin136of a patient with an aperture to allow the driveline cable25to extend therethrough rather than using two or more dressings attached together around the cable25. As described in more detail above, the driveline cable25may include a porous cover to induce tissue ingrowth and allow improved fluid dispersion or distribution around the exit site29. The two or more dressings162may include a vacuum assist port164. The vacuum assist port164may extend circumferentially through the dressing(s)162around the driveline cable25. The vacuum assist port164is connected to a vacuum source or other suction device167. As illustrated, the vacuum source167may provide suction or negative pressure for wound, fluid, or discharge drainage or removal and/or wound closure. The one or more dressings162may also include a valve or fluid port166. The fluid port166may also be connected to the vacuum source167or a separate fluid source (e.g., fluid source134) configured to deliver fluid for flushing or treating the exit site29. Therefore, vacuum assisted wound therapy (closure or drainage) and fluid delivery, drainage, or removal may be provided by the vacuum assisted closure system160either alone or in combination with the fluid treatment system131.

Although the invention is described in terms of a fluid treatment system for a VAD, one will appreciate that the invention may be applied equally to other implantable medical devices with percutaneous cables.