# Patent

## Title
A-V dialysis graft

## Abstract

An improvement to an A-V dialysis graft construction that includes an elongated length of polymer tubing having an inlet end and an outlet end adapted to be attached to access needles. The improvement comprises a normally reduced diameter intermediate portion, providing a pressure drop from the inlet end of the length of polymer tubing to the outlet end for the purpose of improving flow to the extremity, not utilizing excess cardiac output and minimizing venous stenosis. A first embodiment comprises a gradual converging portion of the lumen followed by a gradual diverging portion. A second embodiment comprises an inflatable, annular stenosis balloon, providing a variable stenosis.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a Divisional of U.S. Ser. No. 11/860,053, filed Sep. 24, 2007, entitled A-V Dialysis Graft Construction, now U.S. Pat. No. 7,833,186, issued Nov. 16, 2010; which is a Continuation-in-Part of Ser. No. 11/457,885, filed Jul. 17, 2006, entitled A-V Dialysis Graft, now U.S. Pat. No. 7,566,317, issued Jul. 28, 2009; which is a Continuation-in-Part of U.S. Ser. No. 10/614,450, filed Jul. 7, 2003, entitled A-V Dialysis Graft Construction, now U.S. Pat. No. 7,108,673, issued Sep. 19, 2006, which are incorporated by reference herein in their entirety.


STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to the field of hemo-dialysis apparatus in general and in particular to an arterial-venous graft having an intra-graft stenosis formed therein.
Description of Related Art
As can be seen by reference to the following U.S. Pat. Nos. 3,826,257; 4,549,879; 4,753,640; 5,713,859; 6,146,414; 6,461,321 and 6,585,762, the prior art is replete with myriad and diverse graft constructions employed for hemo-dialysis procedures.
While all of the aforementioned prior art constructions are more or less adequate for the basic purpose and function for which they have been specifically designed, they are uniformly deficient with respect to their failure to provide a simple, efficient, and practical means of forming an artificial intra-graft stenosis to provide increased blood flow resistance, and the associated pressure drop, during those periods when the higher blood flow rates required by hemo-dialysis are not present.
As virtually all physicians and health care specialists are aware, the process of hemo-dialysis requires large volumes of blood to be circulated through a filtration device. However, with prior art A-V graft designs having a uniform bore, the continued high velocity and high pressure blood flow into veins creates venous irritation and scarring leading to stenosis and eventual occlusion as well as causing increased cardiac demands.
Additionally, current dialysis shunts provide a continuous high flow which bypasses the patient's normal tissues and directs high pressure blood flow into the normally low pressure veins. This shunt creates what is called in medicine a “steal.” The blood flowing through the shunt bypasses tissues and then returns to the heart. This creates undue, continued stress on the heart and can invoke a situation in which the blood flow to the hand and/or arm is compromised.
Stanish, in U.S. Pat. No. 6,585,762 discloses a graft comprising, in the streamwise direction, a diverging portion followed by a lumen of substantially constant diameter, followed by a converging portion. Because the constant diameter lumen portion of the graft has a diameter greater than the ends, the pressure drop across the Stanish graft is minimized.
Buselmeier, in U.S. Pat. No. 3,826,257 discloses a converging portion followed by a lumen having a substantially constant diameter, followed by a diverging portion. The hemo-dialysis machine access tubes are located between the converging and diverging portions, in the constant diameter lumen. This arrangement, however, defeats the purpose of the flow restrictions as almost no pressure drop exists between the two ports of the access tubes. Blood will flow through the constant diameter lumen instead of, or in opposing direction to, the dialysis machine. The flow restriction must reside between the dialysis machine's access tubes to effect the needed pressure drop.
As a consequence of the foregoing situation, there has existed a longstanding need among medical personnel for a new and improved A-V stent graft construction having a reduced diameter portion, either of fixed diameter or variable diameter, and the provision of such a construction is the stated objective of the present invention.
BRIEF SUMMARY OF THE INVENTION
Briefly stated, the improved A-V graft construction that forms the basis of the present invention comprises an elongated flexible tubular member having a generally uniform inside diameter with the notable exception of a portion having a reduced diameter intermediate to the dialysis machine access ports, which forms the crux of the present invention.
As will be explained in greater detail, in a first preferred embodiment, the reduced diameter intermediate portion comprises a gently tapered segment having a cross sectional area that is gradually converging and gradually diverging sections, integral with the tubular member. In a second preferred embodiment, the reduced diameter portion comprises a constricted section being of selectable diameter.
In order to provide for a variable diameter flow restriction, a manufactured stenosis or a balloon can be disposed about the inner circumference of the lumen. When deflated, the balloon lies flat against the inner lumen wall. When inflated, the balloon restricts the flow by narrowing the diameter of the lumen.



BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
These and other attributes of the invention will become more clear upon a thorough study of the following description of the best mode for carrying out the invention, particularly when reviewed in conjunction with the drawings, wherein:
FIG. 1 is a perspective view of the prior art uniform inside diameter A-V graft construction currently employed in hemo-dialysis procedures;
FIG. 2 is a representative perspective view of the A-V graft construction that forms the basis of the present invention;
FIG. 2A is an enlarged detail view of the gradually constricted version of the invention;
FIG. 2B is an enlarged detail view of an abruptly constricted, then gradually expanded version of the invention;
FIG. 2C is an enlarged detail view of a graft using an annular stenosis balloon to provide the stenosis between the dialysis machine access needles;
FIG. 3A is an enlarged detail view of the second embodiment of the invention, showing the annular stenosis balloon used to provide a variable diameter stenosis in a deflated mode;
FIG. 3B is an enlarged detail view of the second embodiment of the invention, showing the annular stenosis balloon used to provide a variable diameter stenosis in an inflated mode;
FIG. 4 is a perspective view of an injection reservoir for inflating and deflating the annular stenosis balloon;
FIG. 5 is a side elevation view of the second embodiment with the annular stenosis balloon in its inflated mode;
FIG. 6A is a first view of a syringe being used to inflate the balloon;
FIG. 6B is a second view of a syringe being used to inflate the balloon; and
FIG. 6C is a third view of a syringe being used to inflate the balloon.



DETAILED DESCRIPTION OF THE INVENTION
As can be seen by reference to the drawings, and in particular to FIG. 2, the improved A-V graft construction that forms the basis of the present invention is designated generally by the reference number 10. Prior to embarking on a detailed description of the improved graft construction 10, it would first be advisable to describe the conventional graft construction 11, currently used as standard equipment in virtually all modern hemo-dialysis procedures.
As shown in FIG. 1, the prior art graft construction 11 includes an elongated length of hollow polymer tubing 12 having a uniform inside diameter extending from the inlet end 13 to the outlet end 14 wherein, the inlet end 13 defines the arterial anastomosis.
In addition, the conventional graft construction 11, as well as the improved graft construction 10, are commonly surgically placed within a patient's upper arm or forearm and connected via access needles 15 to a hemo-dialysis machine that withdraws blood from the arterial end 13 and removes impurities from the blood prior to re-introducing the cleansed blood through the venous end 14.
As was mentioned previously, the hemo-dialysis procedure, requiring abnormally high blood flow rates through the conventional uniform internal diameter graft construction 11, and the presence of the conventional graft construction 11, allows the elevated blood flow rates to continue unsubsided during those periods when the access needles 15 are not connected to the hemo-dialysis machine 100.
As a direct consequence of these elevated blood flow rates, increased cardiac demands are imposed on the heart as blood bypasses the distal circulation. Further, the high flow rates result in venous irritation leading to stenosis and occlusion which typically occur at the venous anastomosis.
As a consequence of the foregoing situation, and as shown in FIG. 2, the improved graft construction 10 of the present invention includes an elongated length of polymer tubing 12 having an inlet end 13, and an outlet end 14, and a reduced diameter intermediate portion 16 (see FIGS. 2A-2C) which forms the heart of this invention.
In the first preferred embodiment, depicted in FIG. 2A, the intermediate portion 16 includes a gradually converging segment 16A and a gradually diverging segment 16B wherein, the minimum inside diameter of the intermediate portion 16 is equal to or less than 2⁄3 of the generally uniform inside diameter of the remainder of the length of polymer tubing 12. The intermediate stenosis 16 necessarily resides between the hemo-dialysis machine access needles 15.
Further, as depicted in FIG. 2B, this invention also contemplates a version that includes an abruptly crimped segment 210, selectively disposed upstream or downstream of a gradually diverging or converging segment 16A, 16B.
In FIG. 2C, the second embodiment of the improved graft construction 10 is detailed. Here, the polymer tubing 12 is constructed to have a substantially constant diameter throughout. The stenosis 16 is provided by an annular balloon 230 disposed about the inner circumference of the polymer tubing 12. The annular balloon 230 provides an opportunity to vary the stenosis 16. It is to be understood that structures other than an annular balloon could be used to provide a variable stenosis.
The configuration of the annular stenosis balloon 230 may range from abrupt to smoothly tapering. As with the first embodiment of the improved graft construction 10, the annular balloon 230 stenosis is positioned between both access needles 15 of the graft as clearly seen in FIG. 5. The design intentionally maintains high pressure on the arterial end 13 and lower pressure for the incoming returning blood from the hemo-dialysis machine 100 to the patient at the venous end 14.
The design of the second embodiment of the improved dialysis graft construction 10 is shown in FIGS. 2C-6C and utilizes the annular stenosis balloon 230 for adjusting and maintaining the intermediate stenosis 16. This embodiment of the improved dialysis graft construction 10 comprises four main components: the polymer tubing 12, the annular stenosis balloon 230, the injection reservoir 410, and the catheter 420 connecting the reservoir 410 to the annular stenosis balloon 230. The injection reservoir 410 and the catheter 420 are detailed in FIG. 4. The entire assembly, shown in FIG. 5, is placed surgically and remains under a patient's skin for the life of the device which is the standard of care for current, standard A-V dialysis grafts 11.
As shown in FIGS. 4 and 6A-6C, the injection reservoir 410 communicates with the stenosis balloon 230 by way of a small caliber catheter 420. The reservoir 410 comprises a puncture resistant outer wall 430 and bottom (not shown), with a puncturable, self-sealing, pressure resistant top 440 as is common with many access ports used today in the healthcare field, as those of ordinary skill know. The reservoir 410 is accessed using a needle 610 and syringe 620 through the reservoir top 440. The syringe 620 is used to inject fluid into the reservoir 410, which then travels through the small catheter 420 and under pressure inflates the annular stenosis balloon 230. FIGS. 6A-6C chronicle the inflation procedure. The amount of stenosis created is directly related to a volume of fluid injected. Once the desired stenosis is achieved, the needle 610 is removed from the reservoir top 440, and the pressure within the reservoir 410, catheter 420, and annular stenosis balloon 230 remains, thus maintaining the degree of stenosis.
Advantages of the adjustable annular stenosis balloon graft construction 10 are many. A primary advantage is seen when attempting to maintain patency of the graft 10. For example, if there is intimal hyperplasia (fibrous growth on the walls of the balloon 230) the stenosis can become more restrictive, possibly below an optimal range. This problem is evaluated using one or more of several known techniques. The stenosis can then be corrected to again be within the optional range by varying the inflation of the stenosis balloon 230. Additionally, if an occlusion occurs within the graft 10 for any reason, the annular stenosis balloon 230 can be deflated, as shown in FIG. 3A, thereby removing the stenosis, and the graft 10 cleared using standard medical techniques. This design feature significantly improves the ability to maintain the graft 10. Another advantage is: many times following surgical placement of an A-V graft 10, it is found to have too much of a steal with its associated decreased perfusion to the hand and fingers. When this is detected, the annular balloon 230 can be inflated, as shown in FIGS. 3B and 6B, until a balance between the flow through the A-V graft 10 and to the hand and fingers is obtained. This may also be important if the patient has a change in cardiac output or blood pressure, changing the overall pressure and flow to the graft 10 and hand.
Although only an exemplary embodiment of the invention has been described in detail above, those skilled in the art will readily appreciate that many modifications are possible without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims.
Having thereby described the subject matter of the present invention, it should be apparent that many substitutions, modifications, and variations of the invention are possible in light of the above teachings. It is therefore to be understood that the invention as taught and described herein is only to be limited to the extent of the breadth and scope of the appended claims.

## Claims

1. An improved A-V dialysis graft comprising:
an elongated length of dialysis graft tubing having an inlet end and an outlet end, a direction from the inlet end to the outlet end comprising the streamwise direction, the length of tubing between the inlet end and the outlet end in the streamwise direction comprising:
a first section having a first end and a second end, the first end connected to the inlet end, the first section made from material capable of being repeatedly accessed by a first dialysis machine needle when the graft is located within a patient;
a single reduced diameter section, having a reduced diameter as compared to the first section and a second section, the reduced diameter section connected to the second end of the first section, and the reduced diameter section is intermediate the inlet end and the outlet end; and
a second section having a first end and a second end, the first end connected to the reduced diameter section and the second end connected to the outlet end, the second section made from material capable of being repeatedly accessed by a second dialysis machine needle when the graft is located within a patient.

2. The graft of claim 1 wherein the first section has a diameter that is generally the same as the second section.

3. The graft of claim 1 wherein the construction of the graft, when located in a patient, creates a blood pressure in the first section that is higher than a blood pressure in the second section.

4. An improved A-V dialysis graft comprising:
an elongated length of dialysis graft tubing having an inlet end and an outlet end, a direction from the inlet end to the outlet end comprising the streamwise direction, the length of tubing between the inlet end and the outlet end in the streamwise direction comprising:
a first section having a first end and a second end, the first end connected to the inlet end, the first section made from material capable of being repeatedly accessed by a first dialysis machine needle when the graft is located within a patient;
a single reduced diameter section, having a reduced diameter as compared to the first section and a second section, connected to the second end of the first section; and
a second section having a first end and a second end, the first end connected to the reduced diameter section and the second end connected to the outlet end, the second section made from material capable of being repeatedly accessed by a second dialysis machine needle when the graft is located within a patient, wherein the first section and the second section are of generally equal length.

5. The graft of claim 4 wherein the reduced diameter section comprises a gradually diverging cross sectional area.

6. An improved A-V dialysis graft configured to conduct blood in a steamwise direction comprising:
an A-V dialysis graft comprising a length of tubing defining a hollow interior, the graft comprising:
an inlet end configured to connect to an artery;
an outlet end configured to connect to a vein;
a stenosis generally in the middle between the inlet end and the outlet end;
a first needle access portion configured for dialysis needle access between the inlet end and the stenosis; and
a second needle access portion configured for dialysis needle access between the stenosis and the outlet end.

7. The graft of claim 6 wherein the graft, when conducting blood in the streamwise direction, is configured such that the blood in the first needle access graft portion is at a higher pressure than the blood in the second needle access portion.

8. The graft of claim 6 wherein the inlet end comprises an arterial end and the outlet end comprises a venous end.

9. The graft of claim 8 wherein the stenosis being physically located between the first needle access portion and the second needle access portion creates a pressure differential in a blood pressure in the first needle access portion and a blood pressure in the second needle access portion.

10. The graft of claim 6 wherein the first needle access portion and the second needle access portion are of generally uniform diameter.

11. The graft of claim 6 wherein the stenosis, from the streamwise direction, comprises a gradually diminishing segment and a gradually expanding segment.

12. The graft of claim 6 wherein the stenosis is generally in the middle of the graft thereby establishing the first needle access portion the second needle access portion of a generally similar length.

13. The graft of claim 6 wherein the first needle access portion the second needle access portion comprise graft portions configured to accept a needle connected to a hemo-dialysis machine.

14. The graft of claim 6, wherein the first needle access portion and the second needle access portion are configured for repeated needle access.

15. The graft of claim 6, wherein a length of each of the first needle access portion and the second needle access portion are at least two times a length of the stenosis.

16. A dialysis graft configured to conduct blood flow in a steamwise direction from a first vessel to a second vessel comprising:
a dialysis graft comprising a length of tubing defining a hollow interior, the graft comprising:
an inlet end configured to accept blood flow from the first vessel at a first pressure;
an outlet end configured to present blood flow out of the graft to the second vessel at a second pressure;
a first section having a first end and a second end, the first end connected to the inlet end and configured to conduct blood flow at the first pressure and the first section physically configured to be punctured by a dialysis needle configured to withdraw blood from the first section;
a second section having a first end and a second end, the second end connected to the outlet end and configured to conduct blood flow at the second pressure and the first section physically configured to be punctured by a dialysis needle configured to present blood into the second section; and
a restriction connected to a second end of the first section and the first end of the second section the restriction having a smaller diameter than the first section and the second section to thereby physically establish the first pressure greater than the second pressure, and the restriction is generally in the middle of the graft.

17. The graft of claim 16, wherein the first section and the second section are physically configured to be repeatedly punctured by a dialysis needle as part of dialysis treatment.

18. The graft of claim 16, wherein, in the streamwise direction, the first section is at least twice as long as a length of the restriction and, in the streamwise direction, the second section is at least twice as long as the length of the restriction.

19. The graft of claim 16 wherein the first vessel comprises an artery and the second vessel comprises a vein.

20. The graft of claim 16 wherein the first section and the second section are of generally uniform diameter.

21. The graft of claim 16 wherein the restriction from the streamwise direction, comprises a gradually diminishing segment and a gradually expanding segment.