Patent Application
20190336675
The present disclosure relates to the field of arteriovenous fistulas, and more particularly, to a device that controls the flow rate of an arteriovenous fistula.
Arteriovenous (AV) fistulas remain the preferred modality for providing blood access for hemodialysis. The surgical creation of an AV fistula involves connecting a long vein segment to an arterial source. The vein dilates from the increased blood pressure and begins to remodel on a cellular level. The vein is then left to “mature” for about one to three months. To be successful, the mature fistula needs a blood flow of about 600 milliliters/minute, be 5-6 mm in diameter, and be able to be cannulated three times per week for dialysis access. Vascular grafts may also serve as an AV fistula.
Some fistulas can reach pathologically high flows, or high flow rates, for example, 2-3 liters/minute, for a variety of reasons. Fistulas (particularly vascular grafts) that are fed by the brachial artery are most susceptible. Flow reduction methods generally reduce fistula flow from over 2 liters/minute to about 1 liter/minute.
An AV fistula can be a 6 mm diameter vessel flowing directly from a medium size artery into a medium size vein. The fistula generally becomes the preferred route for most of the feeding arterial blood rather than the higher resistance distal arteries. Retrograde flow in the distal artery, physiologic steal, is common and generally asymptomatic, stealing some blood from the hand. In some patients, high-flow fistulas create serious ischemia. Ischemic symptoms range from tingling, numbness, and extreme cold, to rest pain and tissue necrosis. Dialysis access associated ischemia (DAAS) is the primary rationale for intervention to reduce fistula flow. While the incidence of DAAS is low, the morbidity can be significant. Flow reduction provides near immediate symptom relief.
The creation of an AV fistula also has immediate and universal negative cardiac effects including an increase in cardiac output (CO), heart rate, and stroke volume. If fistula flow increases to over about 1.5 liters/minute, the decreased peripheral resistance, increased right atrial and pulmonary artery pressure, and increased left ventricular end-diastolic pressure causes the myocardium to decompensate. At that point, the patient has symptoms of heart failure. Reducing AV fistula flow (with increased peripheral resistance) can provide near immediate cardiac benefits.
Current methods to reduce fistula flow include vessel surgeries and banding procedures. In practice, each surgeon typically has a preferred flow reduction technique—generally following how one is trained. Vessel surgeries reroute some of the arterial inlet blood to the fistula, thereby reducing fistula flow and increasing distal perfusion. The most common surgeries are distal revascularization with interval ligation (DRIL) and revision using distal inflow (RUDI).
Surgical procedures provide only approximate control of blood flow, based on surgical experience. Requiring general sedation, the amount of flow reduction is considered appropriate, just based on observations of the return of color and a radial pulse. These procedures do not allow blood flow to be individually titrated for each patient. Surgeries are also significant procedures for most patients, being expensive and having associated morbidity.
A primary physiologic deficiency of surgical flow reduction methods is that it does not increase peripheral resistance. As a result, surgically-based flow reductions do not provide any cardiac benefit. Since vessel surgeries do not restrict the fistula itself, their only specific advantage is a slightly lower thrombosis rate compared with surgical banding.
Surgical banding reduces flow by directly constricting the fistula. Banding has the important physiologic advantage (vs. vessel surgeries) of increasing peripheral resistance. Fistula banding therefore provides relief from both cardiac and ischemic symptoms.
With surgical plication (surgical banding), the anastomosis region of the fistula is narrowed using a row of stitches to form a pleat. This is a poorly-controlled procedure which is frequently performed two or three times on the same individual. Plication has shown variable clinical results—with a wide range of fistula thrombosis rates. While not requiring general sedation, plication is irreversible, poorly-controlled, and has thrombosis possibilities.
Clinical reports also describe using a single loop of suture to serve as a flow reduction band around a fistula. The term “suture-banding” is used to distinguish this method from plication-type surgical banding. These reports represent the most similar methodologies to the current invention.
The use of a suture was first reported in 2006. See N. Goel, et al., Minimally Invasive Limited Ligation Endoluminal-assisted Revision (MILLER) for Treatment of Dialysis Access-associated Steal Syndrome, 70 K
The primary drawbacks of suture-banding are the approximate nature of its flow reduction and the high wall stress induced by a single wrap of suture. Flow reduction is dictated by the semi-subjective selection of balloon diameter. The method also has the potential for thrombosis of the fistula. However, acceptable thrombosis rates have been reported by different groups using suture-based methods. See Pratik A. Shukla, et al., The MILLER Banding Procedure as a Treatment Alternative for Dialysis Access Steal Syndrome: A Single Institutional Experience, 40 C
A number of vessel flow reduction devices have been reported in the patent literature. Some are applied to vessels in general, and some are specific to AV fistula. The AV fistula devices are mainly designed to reduce fistula flow between dialysis sessions when high flow is not needed. Many are elaborate and inherently impractical for a commercial medical device.
The universal shortcoming of all current surgical and banding flow reduction methods is the inability to individually titrate the flow to clinical symptoms. There is a need for a convenient atraumatic, controllable method to band a vessel for the purposes of providing controlled flow reduction.
Thus, there is a long felt need for an implantable device that provides controlled restriction of a blood conduit.
According to aspects illustrated herein, there is provided a flow controller arranged to provide controlled constriction of a hollow body conduit, comprising a catheter including a first end and a second end, a strap slidably arranged within the catheter, the strap including a third end and a fourth end, the third end arranged to be connected to the catheter to form a loop, and a tensioning means connected to the second end and the fourth end, wherein the tensioning means is operatively arranged to axially displace the strap relative to the catheter to increase and decrease a diameter of the loop.
According to aspects illustrated herein, there is provided a flow controller arranged to provide controlled constriction of a hollow body conduit, comprising a catheter including a first end and a second end, a strap slidably arranged within the catheter, the strap including a third end and a fourth end, the third end operatively arranged to be removably connected to the catheter to form a loop, wherein the loop is arranged around the hollow body conduit, and a tensioning means, including a housing connected to the second end, and a threaded rod slidably arranged in the housing, wherein the threaded rod is connected to the fourth end and is axially displaced relative to the housing to increase and decrease a diameter of the loop.
According to aspects illustrated herein, there is provided a flow controller device designed to overcome the recognized deficiencies of prior art fistula flow control methods. The device provides an atraumatic band that may be placed around the fistula. The diameter of the band may be finely controlled using an integrated and disposable controller or tensioning means. Band diameter, and thereby fistula flow, may be changed in response to observed clinical symptoms and measurements. When finished, a stainless-steel ring is pinched to fix the band diameter and the controller or tensioning means is removed, leaving only the vessel band in place.
The device comprises an adjustable strap (or band) that may be installed by leading it around a blood conduit. The strap itself typically has a cylindrical cross-section. The strap material may be a bead made of a flexible polymer such as TEFLON® polytetrafluoroethylene (PTFE). The diameter of the bead material or strap may be approximately 1.5 mm. The loop formed by the band may have a maximum inside diameter of approximately 8-12 mm and a minimum inside diameter of 3-5 mm.
The strap is considered to have a free end and a moveable end. The free end is fed around the vessel and attached to a fixed collar component or connector. Once secured to the collar or connector, the strap forms a ring or loop, and is in its fully untightened position (i.e., having a maximum diameter). There is generally a separate component or connector attached to the free end of the strap (strap tail) to facilitate proper attachment of the strap to the collar. The moveable end of the strap may pass through a catheter that is connected to a central hole in the collar component or connector.
The catheter and band may lead from the collar component to a controller or tensioning means. The controller or tensioning means provides fine and controlled movement of the strap inside the catheter to effect controlled changes in the loop diameter. This allows the loop diameter to be changed to reflect clinical symptoms for an individual patient.
In some embodiments, the controller or tensioning means uses a threaded element that is fitted with an anti-rotation means to provide linear motion when activated by a nut. The strap may be attached to the threaded element which then provides controlled movement of the strap.
When flow control is complete, a short stainless-steel sleeve is cinched over the catheter to lock the strap to the catheter, thereby fixing the loop diameter. The catheter and strap may then be cut and the controller or tensioning means removed, leaving the strap in place.
The controller or tensioning means may include the means to indicate the diameter of the strap loop. In some embodiments, the controller or tensioning means comprises transparent or translucent material which allows the internal screw to be visualized and used to indicate loop diameter. The controller or tensioning means may also indicate the rotation direction for opening and closing the strap (i.e., which circumferential direction tightens and untightens the loop). The controller or tensioning means may be fitted with a means to limit the displacement of the threaded rod in both axial directions.
These and other objects, features, and advantages of the present disclosure will become readily apparent upon a review of the following detailed description of the disclosure, in view of the drawings and appended claims.
Various embodiments are disclosed, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, in which:
At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements. It is to be understood that the claims are not limited to the disclosed aspects.
Furthermore, it is understood that this disclosure is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the claims.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure pertains. It should be understood that any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the example embodiments. The assembly of the present disclosure could be driven by hydraulics, electronics, pneumatics, and/or springs.
It should be appreciated that the term “substantially” is synonymous with terms such as “nearly,” “very nearly,” “about,” “approximately,” “around,” “bordering on,” “close to,” “essentially,” “in the neighborhood of,” “in the vicinity of,” etc., and such terms may be used interchangeably as appearing in the specification and claims. It should be appreciated that the term “proximate” is synonymous with terms such as “nearby,” “close,” “adjacent,” “neighboring,” “immediate,” “adjoining,” etc., and such terms may be used interchangeably as appearing in the specification and claims.
Referring now to the figures,
Securing means 12 comprises strap 20, female connector 30, male connector 50, and catheter 60. Securing means 12 may further comprise suture 42 and/or tube 44.
Strap 20 generally comprises a flexible material and includes end 22 and end 24. In some embodiments, strap 20 comprises a cylindrical cross-section having a diameter of approximately 1.5-3 mm. In some embodiments, strap 20 comprises a cylindrical cross-section having a diameter of approximately 1-5 mm. It should be appreciated that strap 20 may comprise any geometry cross-section (e.g., ovular, rectangular, etc.) suitable for forming a loop and tightening around a vessel (e.g., vein, gastrointestinal (GI) tract, urethra, genitourinary, vascular graft, blood vessel, artery, lungs, etc.). In some embodiments, strap 20 comprises TEFLON® PTFE, or another biocompatible polymer. In some embodiments, end 22 of strap 20 is etched to provide a surface for bonding or fixing to female component 30.
Female connector 30 is generally partially tubular in shape and comprises radially inward facing surface 32, notches 34, annular groove 36, and hole 38. End 22 is operatively arranged to engage hole 38 to fixedly secure strap 20 to female connector 30. Female connector 30 may further comprise bushing 40 to aid in fixedly securing end 22 in hole 38. For example, bushing 40 may be bonded to etched end 22 using a heat-cured epoxy, and bushing 40 is then bonded within hole 38. In some embodiments, bushing 40 comprises stainless steel. Bushing 40 may further act as a radiopaque marker. Female connector 30 is operatively arranged to connect to male connector 50 such that strap 20 forms loop 26, as will be discussed in greater detail below. In some embodiments, female connector 30 comprises PEBAX® polyether block amide (PEBA). Female connector 30 may also form part of the vein or vessel contact surface, as shown in
Male connector 50 is generally tubular and comprises radially outward facing surface 52, protrusions 54, annular groove 56, through-bore 58, and surface 59. Protrusions 54 are arranged on radially outward facing surface 52. Radially outward facing surface 52 is operatively arranged to engage radially inward facing surface 32 to connect male connector 50 and female connector 30. Protrusions 54 are operatively arranged to engage notches 34 to aid in the proper connection of female connector 30 to male connector 50 and to properly align annular groove 36 with annular groove 56. The diameter of radially inward facing surface 32 may be of a certain dimension such that it “snaps” together with radially outward facing surface 52, such that female connector 30 is removably secured to male connector 50. When female connector 30 is connected to male connector 50, annular groove 36 is aligned with annular groove 56. Suture 42 may be secured in annular grooves 36 and 56 to fixedly secure female connector 30 to male connector 50. Suture 42 may comprise any material suitable to hold female connector 30 to male connector 50. Through-bore 58 extends through male connector 50 and is arranged to be slidably engaged with strap 20 and fixedly secured with catheter 60, as will be discussed in greater detail below. The arrangement of female connector 30 and male connector 50 provides a means for connecting end 22 of strap 20 to catheter 60 to form loop 26 that helps maintain a circular loop geometry as the diameter of loop 26 changes and prevents pinching. As shown in
Catheter 60 is generally a tube comprising end 62 and end 64. In some embodiments, catheter 60 is a tube that allows sliding engagement with strap 20. In some embodiments, catheter 60 is a collar that allows sliding engagement with strap 20 and replaces, for example, male collar 50. In some embodiments, catheter 60 is any annular connecting means suitable for sliding engagement with strap 20. In some embodiments, end 62 is arranged to be connected to male connector 50. In some embodiments, end 62 is fixedly secured to surface 59 and concentrically aligned with through-bore 58. In some embodiments, end 62 engages through-bore 58 and is fixedly secured therein. End 64 is arranged to be connected to housing 70. In some embodiments, end 64 is fixedly secured to end 72 and concentrically aligned with hole 80. In some embodiments, end 64 engages hole 80 and is fixedly secured therein. Strap 20 is slideably engaged within catheter 60. Specifically, end 24 of strap 20 is fed through male connector 50, catheter 60, and hole 80, housing 70, and threaded rod 90 and is connected to end 94 of threaded rod. It should be appreciated that strap 20 is slidable with respect to male connector 50, catheter 60, and housing 70. As such, as tensioning means 14 is tightened, thereby displacing threaded rod 90 with respect to housing 70, the diameter of loop 26 is reduced, as will be described in greater detail below. Catheter 60 may further comprise tube 44 slidably arranged thereon. When loop 26 is set at a sufficient diameter, tube 44 may be crimped in order to fixedly secure strap 20 and catheter 60 together, thereby locking in the diameter of loop 26. The locking function of tube 44 allows tensioning means 14 to be removed from securing means 12 while loop 26 remains secured at the set diameter around vein or vessel 2. In some embodiments, tube 44 comprises stainless steel. Tube 44 may further act as a radiopaque marker. In some embodiments, catheter 60 comprises PEBAX® PEBA. It should be appreciated, that in some embodiments, tensioning means 14, specifically housing 70 could be fixedly secured to male collar 50. In such embodiments, there is no need for catheter 60.
Housing 70 generally comprises end 72, end 74, measuring surface 76, and fork portions 78A-B. Housing 70 further comprises hole 80 proximate end 72, which terminates at surface 82, and hole 84, which extends from surface 82 to end 74 (best seen in
Threaded rod 90 generally comprises end 92, end 94, radially outward facing surface 96, threading 98, and through-bore 100. Threaded rod 90 is slidably arranged in hole 84. End 24 of strap 20 is fixedly secured to threaded rod 90 such that, when threaded rod 90 is displaced in axial direction AD1, end 22 is pulled in axial direction AD1 and the diameter of loop 26 decreases, thus further restricting the flow through vein 2. When threaded rod 90 is displaced in axial direction AD2, end 22 is pushed in axial direction AD2 and the diameter of loop 26 increases, thus reducing the restriction on the flow through vein 2. When flow controller 10 is in a fully untightened state, as shown in
Nut 110 comprises grip 112 and hole 114. Nut 110 is axially arranged between housing cap 120 and housing 70, specifically end 74. Hole 114 comprises threading that engages with threading 98. Housing cap 120 is secured to housing 70. Specifically, clip portions 124A and 124B engage fork portions 78A and 78B. Clip portions 124A-B may comprise protrusions that engage slots in fork portions 78A-B. It should be appreciated that any suitable means for connecting housing cap 120 to housing 70 may be used, for example, adhesives, bolts, screws, rivets, soldering, welding, etc. With nut 110 engaged with threaded rod 90 and axially arranged between end 74 and housing cap 120, nut 110 can be rotated in circumferential direction CD1 or CD2 to tighten/loosen flow controller 10. For example, a user may use grip 112 to rotate nut 110 in circumferential direction CD1 to tighten loop 26 (i.e., displace threaded rod 90 in axial direction AD1) and circumferential direction CD2 to loosen loop 26 (i.e., displace threaded rod 90 in axial direction AD2). In some embodiments, a user may use grip 112 to rotate nut 110 in circumferential direction CD2 to tighten loop 26 (i.e., displace threaded rod 90 in axial direction AD1) and circumferential direction CD1 to loosen loop 26 (i.e., displace threaded rod 90 in axial direction AD2). In some embodiments, threaded rod 90 comprises a #10-32 screw. For a 32-pitch screw, four rotations of nut 110 corresponds to a 1 mm change in the diameter of loop 26. It should be appreciated that due to the engagement of nut 110 with threading 98, threaded rod 90 and thus strap 20 is prevented from axial displacement except when nut 110 is rotated, thus preventing unwanted loosening of loop 26.
Flow controller 10 may further comprise washers 106 and 108 arranged on opposite axial sides of nut 110 to aid in the reduction of friction between nut 110 and housing 70 and housing cap 120 during tightening and untightening (i.e., loosening). For example, washer 106 may be axially arranged between nut 110 and end 74 and washer 108 may be axially arranged between nut 110 and housing cap 120.
Flow controller 10 can have more than one configuration for different clinical applications. For example, for an existing high flow fistula or following kidney transplantation, securing means 12 comes attached to tensioning means ready for use. After adjusting flow (i.e., setting the diameter of loop 26), tensioning means 14 may be removed. As a precaution, when creating a potential high-flow fistula, securing means 12 may be installed and left in an untightened position. In this case, end 64 of catheter 60 (arranged subcutaneously) is fitted with a connector and capped. If, subsequently, flow control is needed, the catheter end connector may be exposed and connected to a manual tensioning means with a mating connector.
Some examples of applications for which flow controller 10 may be used are AV fistula flow reduction for ischemic symptoms, AV fistula partial flow reduction following kidney transplantation, AV fistula flow reduction to prevent or treat cardiac symptoms, reduction of portal vein flow following liver transplantation, any body conduit requiring restriction or controlled flow reduction (may be in GI tract, genito-urinary system, or lungs). Flow controller 10 allows blood flow to be individually titrated to clinical symptoms for each patient. Flow controller 10 lowers stress on the vessel wall since band diameter is significantly larger (greater than 5 times) than 2-0 suture, there is no need to puncture the fistula, and there is no vessel damage from a tight suture. Flow controller 10 utilizes a TEFLON® PTFE strap, which minimizes adhesions. Flow controller 10 comes ready to use and does not require individual sizing.
It will be appreciated that various aspects of the disclosure above and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 62/762,465, filed May 7, 2018, which application is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62762465 | May 2018 | US |
