Retroperfusion Balloon Catheter and Method

This invention relates to retroperfusion catheters and more particularly, to a tip construction for retroperfusion catheters. Retroperfusion catheters have heretofore been provided which have utilized auto-inflatable balloons and alternatively, non-auto-inflatable balloons. Such retroperfusion catheters exhibit too much restriction to blood flow in a forward direction and, in addition have suffered from the fact that they are often too stiff and non-resilient which inhibited placement of the catheter in the vessel. In the past when such catheters have been made more resilient or flexible they provide too little torque and inhibit directional control of the catheter. In addition, certain such catheters have generally had open ends which permitted bi-directional flow permitting undesirable mixing of venous and arterial blood. Such construction also has hindered rapid and complete deflation of the balloon. There is therefore a need for a new and improved retroperfusion balloon catheter and a method which overcomes the above-identified deficiencies.

In general, it is an object of the present invention to provide a retroperfusion balloon catheter and method which is provided with differing degrees of flexibility particularly at its distal extremity.

Another object of the invention is to provide a catheter of the above character which has a distal extremity which is relatively soft and flexible.

Another object of the invention is to provide a catheter of the above character which is provided with a flexible distal extremity.

Another object of the invention is to provide a catheter of the above character in which the shaft is provided with differing degrees of flexibility along its length.

Another object of the invention is to provide a catheter and method of the above character in which the major portion of the shaft is relatively stiff so that the catheter is torqueable.

Another object of the invention is to provide a catheter and method of the above character which has a relatively soft and flexible tip.

Another object of the invention is to provide a catheter of the above character having a tip construction with a plurality of redundant features to prevent the tip from becoming separated from the distal extremity of the catheter.

Another object of the invention is to provide a catheter of the above character in which the tip construction provides a minimum resistance to forward flow of retroperfusion blood.

Another object of the invention is to provide a catheter having tip construction of the above character which is lightly biased into a closed position so as to provide a minimum of resistance to forward flow of retroperfusion blood.

Another object of the invention is to provide a catheter of the above character in which the tip construction is of such a character that a guide wire can be introduced and retracted through the tip construction without difficulty.

Another object of the invention is to provide a catheter of the above character which can be utilized with an auto-inflatable balloon or alternatively, a non-auto-inflatable balloon.

Another object of the invention is to provide a catheter of the above character in which pressure measurements can be accurately made without substantial interference from the retroperfusion blood flow.

Additional objects and features of the invention will appear from the following description in which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings.

FIG. 1 is a plan view of a retroperfusion catheter incorporating the present invention.

FIG. 2 is a greatly enlarged cross-sectional view of the distal extremity of the catheter shown in FIG. 1.

FIG. 3 is a view looking along the line 3--3 of FIG. 2.

FIG. 4 is a greatly enlarged cross-sectional view of the proximal extremity of the catheter shown in FIG. 1.

FIG. 5 is a side elevational view of the flexible elongate double lumen member utilized in the construction of the catheter shown in FIG. 1.

FIG. 6 is an enlarged view partly in cross-section of the member shown in FIG. 5 before the forming operation.

FIG. 7 is a cross-sectional view taken along the line 7--7 of FIG. 6.

FIG. 8 is an enlarged detail view partially in cross section showing the flexible elongate member after forming.

FIG. 9 is a cross-sectional view taken along the line 9--9 of FIG. 8.

FIG. 10 is a cross-sectional view taken along the line 10--10 of FIG. 8.

FIG. 11 is a plan view of a three lumen retroperfusion catheter incorporating another embodiment of the present invention.

FIG. 12 is an enlarged detail view partially in cross section of the distal extremity of the catheter shown in FIG. 11.

FIG. 13 is a cross-sectional view taken along the line 13--13 of FIG. 11.

FIG. 14 is a cross-sectional view taken along the line 14--14 of FIG. 12.

FIG. 15 is a cross-sectional view taken along the line 15--15 of FIG. 12.

FIG. 16 is a plan view of another embodiment of a retroperfusion balloon catheter incorporating the present invention.

FIG. 17 is a enlarged plan view of the distal extremity of the catheter shown in FIG. 16.

FIG. 18 is a cross-sectional view taken along the line 18--18 of FIG. 17.

FIG. 19 is a cross-sectional view taken along the line 19--19 of FIG. 17.

FIG. 20 is a cross-sectional view taken along the line 20--20 of FIG. 17.

FIG. 21 is a end view of the catheter shown in FIG. 17.

In general, the retroperfusion catheter of the present invention is comprised of a flexible elongate element having proximal and distal extremities with first and second lumens extending therethrough. A balloon is secured to the distal extremity of the flexible elongate element. The distal extremity of the flexible elongate element has portions thereof with different degrees of flexibility with the portion having the greatest flexibility being disposed at the distal extremity. In certain embodiments, a flexible valve-like tip is provided on the distal extremity.

In the method for making a retroperfusion balloon catheter having parts comprising a proximal extremity, a distal extremity and a tip with different degrees of flexibility. The proximal extremity is formed of a first tubing material having one Shore hardness value. The tip is formed of a second tubing material having a Shore hardness value different from said one Shore hardness value. The distal extremity is formed by utilizing the first and second tubing materials having different Shore hardness values. These materials of different Shore hardness values are combined to form the distal extremity of the catheter. Pressure, heat and filler material, which preferably is the same material as the lower Shore hardness material of the two materials being joined, are applied to form the junctions between the parts of the catheter to form a continuous catheter tube. Each of the junctions has a stiffness or hardness value less than that of the proximal part or portion. A part formed of the two materials will have a stiffness which is between that provided by the material of one Shore hardness value and the other Shore hardness value. Other parts or portions of the catheter can be formed in the same manner utilizing materials having different Shore hardness values when it is desired to obtain a part with a intermediate Shore hardness value.

More specifically, the retroperfusion catheter of the present invention as shown in FIGS. 1-10 consists of a double lumen retroperfusion catheter 21. The double lumen retroperfusion catheter 21 consists of a flexible elongate tubular member 22 formed of a suitable plastic material, as for example, a material known as Pebax which is basically a modified combination of polyether and nylon. The member 22 has an enlarged conically-shaped portion 22a and an intermediate cylindrical portion 22b. It is provided with proximal and distal extremities 23 and 24. The tubular member 22 is formed in a suitable manner such as by extruding to provide at least two lumens 26 and 27 therein as shown in FIG. 9. The lumen 26 is a large lumen crescent-shaped in cross-section, whereas the lumen 27 is a small lumen circular in cross-section. As can be seen, the lumen 27 extends in from one side wall of the flexible elongate member 22 in towards the central axis lumen so as to provide the crescent-shaped lumen 26.

The flexible elongate tubular member 22 can be of a suitable size, as for example, 8 French and having an outside diameter of approximately 0.105 inches and an inside cross-sectional area corresponding diameter in a tube of approximately 0.090 inches. The distal extremity of the catheter 24 is provided with a bend 28 to facilitate positioning of the catheter.

The flexible elongate tubular member 22 has a suitable length, as for example, 24 to 48 inches. The proximal extremity 23 has an outside diameter of approximate 0.200 inches. The tubular member 22 has a wall thickness at the upper extremity of the same where the lumen 27 passes as shown in FIG. 10 of approximately 0.023 inches and a wall thickness on the lower side of approximately 0.010 inches. The inner lumen 27 also shown in FIG. 10 is formed by a wall thickness of approximately 0.010 inches with an inside diameter of 0.097 inches and an outside diameter of 0.130 inches. From the distal extremity of the flexible elongate tubular member 22, it can be seen that a taper is provided to form the tapered portion 22a which can have a length ranging from 3 to 5 inches. The cylindrical portion 22b has a suitable length as, for example, 20-48 inches to provide a total length of approximately 23 to 53 inches. The tubular portion 22b has a suitable outside diameter of approximately 0.105 inches. The necked-down portion 22c is of a smaller diameter, as shown in FIG. 8, as for example, 0.091 inches. The upper portion of the flexible tubular member adjacent the lumen 27 as shown in FIG. 8 is provided with a wall thickness of approximately 0.010 inches at the upper extremity and a wall thickness of approximately 0.008 inches at the lower extremity. The lumen 27 is formed by a wall thickness of approximately 0.006 inches. It has an outside diameter of 0.040 inches and an inside diameter of 0.027 inches. The flexible tubular member 22 is also provided with a threaded portion 22d on its distal extremity having a length of approximately 0.250 inches.

A plurality of spaced apart holes 31 are provided in the portion 22c of the elongate tubular member 22 are provided for inflation purposes as hereinafter described. The holes 31 are spaced apart by a suitable distance, as for example, 0.100 inches on centers. A suitable number of holes can be provided, as for example, four holes as shown in FIG. 8 and can have a suitable diameter as, for example, 0.039 inches. The holes can be arranged in a suitable manner in the portion 22c. For example, they can be spaced apart longitudinally of the portion 22c and also can be spaced circumferentially of the portion 22c. All of the holes 31 open into the main blood flow lumen 26. It should be appreciated that if desired a slot (not shown) can be provided in the portion 22c instead of the holes 31.

An additional hole or port 32 is formed in the threaded portion 22b and opens into the lumen 27. The lumen 27 is plugged at the distal extremity by a plug 36 having a suitable length, as for example, 0.100 inches, as shown, particularly in FIGS. 6 and 7.

Preparatory to the forming operation to provide the catheter construction which is shown in FIG. 7, a mandrel 37 of a suitable diameter such as 0.025 inches is placed in the small lumen 27 and a larger D-shaped mandrel 38 formed from a rod having a suitable diameter such as 0.074 inches which is ground down on one side to provide a depth of 0.038 inches. The mandrel 38 is placed in the lumen 26 as shown in FIGS. 6 and 7. The mandrel 37 is advanced in the lumen 27 until it is in engagement with the plug 36. The mandrel 38 is positioned so it extends through the portion 22c of the tubular member 22 where the mandrel meets the crescent-shaped portion of lumen 26 as shown in FIG. 9. A pair of additional plugs 39 of a suitable length, as for example, 0.300 inches are placed in the lumen 26 on opposite sides of the mandrel 38 as shown in FIGS. 6 and 7 to occupy additional portions of the space in the lumen 26.

The flexible elongate tubular member 22 is formed of a plastic as hereinbefore described which can be shaped upon the application of heat. The distal extremity of the tubular member 24 is placed in a mold with heat and drawn to form the threaded portion 22d and portion 22c with the mandrels 37 and 38 therein and with the plugs 36 and 39 therein. After the forming operation has been completed, the mandrels 37 and 38 can be removed. The plugs 39 are formed of plastic and melt with the application of heat and form a part of the member 22. The plug 36 can also be fastened in place by a suitable means such as by an adhesive.

A tip valve 41 is secured to the distal extremity of the flexible elongate member 22. The tip valve 41 is formed of a suitable material such as a silicone elastomer. It is generally cylindrical with a hemispherical distal extremity in which there are provided four leaflet portions 41a, 41b, 41c and 41d, each of which subtend approximately 90.degree.. The leaflet portions are formed by two slits 42 and 43 provided in the hemispherical portion of the tip valve extending at right angles to each other. During the molding of the tip valve, the tip valve is also provided with molded threads at its proximal extremity which are adapted to mate with the threaded portion 22d of the flexible elongate member 22. The threaded portions of the tip valve 41 and the threaded portion 22d of the flexible elongate member interlock to form a mechanical bond between the tip valve and the flexible elongate member 22. The threaded tip valve 41 can have a suitable length as, for example, 0.375 inches and an outside diameter of 0.094 inches and an inside diameter of 0.078 inches. The slits 42 and 43 can have a depth of approximately 0.040 inches plus or minus 0.015 inches.

The threaded interior of the tip valve 41 and the threaded portion 22d of the flexible elongate member 22 are preprimed with a suitable primer and then a silicone rubber adhesive is applied over the threaded portion 22d. The tip valve 41 is then mounted thereon to extend over the threaded portion 22d as shown in FIG. 2. In this manner it can be seen that the tip valve is permanently secured to the distal extremity of the flexible elongate member 22. Thus two means of attachment are provided. One is the use of the threads on the threaded portion 22d and on the tip valve 41 and the other is the silicone adhesive which is utilized. In other words two levels of redundancy are provided for securing the tip valve 41 to the distal extremity of the flexible elongate member 22 to ensure that the tip valve cannot accidentally become dislodged from the flexible elongate member 22.

A flexible balloon or bladder 46 is provided which is formed of a suitable material such as a heat shrinkable polyethylene. The outside diameter of the balloon can range from approximately 3 millimeters to 20 millimeters depending upon the use for the same. The length of the balloon can range from 1/2 inch to approximately one inch. The distal extremity 47 of the balloon 46 is secured to the distal extremity of the flexible elongate member 22 over the threaded portion of the tip valve 41 and is secured thereto. This is accomplished by applying a suitable adhesive such as a cyanoacrylate adhesive over the exterior of the threaded tip valve 41. The distal extremity 47 of the balloon 46 is then positioned over the threaded portion of the tip valve 41 and is shrunk onto the threaded portion of the tip valve 41 by the application of heat. This results in a further mechanical attachment for the tip valve because of the compression forces applied by the shrink tubing utilized for the balloon 46 as well as the adhesive which is applied between the distal extremity 47 of the balloon 46 and the threaded portion of the tip valve 41. Thus there are provided at least three independent means for redundantly attaching the tip valve 41 to the distal extremity of the flexible elongate member 22. The proximal extremity 48 of the balloon 46 is secured to the portion 22c of the flexible elongate member so that the openings 31 in the flexible elongate element 22 open into the balloon 46 and so that the proximal extremity 48 terminates in a region immediately prior to the portion 22b of the flexible elongate member 22 as shown in FIG. 2.

The port 32 which has been formed in the distal extremity of the flexible elongate member 22 as shown in FIG. 2, also extends through the tip valve 41 and the distal extremity 47 of the balloon 46 so that it is open to ambient.

A fitting assembly 51 is provided on the proximal extremity 23 of the flexible elongate member 22 and consists of first and second female and male Luer-type fittings 52 and 53 respectively mounted upon extension tube assemblies 54 and 56. The tubular assemblies 54 and 56 are comprised of an inner tube 57 and an outer reinforcing shrink tube 58. The extension assemblies 54 and 56 are inserted into the lumens 27 and 26 in the proximal extremity 23 of the flexible elongate member 22 and are secured therein by suitable means such as an adhesive or potting compound 61 as shown particularly in FIG. 4. Alternatively, the extension assemblies can be secured by insert molding using heat fusion.

Operation and use of the double lumen retroperfusion catheter 21 may now be briefly described as follows. The catheter is introduced into a venous vessel of a patient in a manner conventionally used in retroperfusion procedures. During the procedure, blood will flow through and into the male Luer-type fitting 53 and into the large lumen 26 and through the holes 31 to automatically inflate the balloon 46 to its maximum diameter. Blood at the same time will flow through the tip valve 41 and into the vessel of the patient. Pressure monitoring can occur by measuring the pressure of the blood appearing in the port 32 and extending through the lumen 27 to the female Luer-type fitting 52 which can be connected to a suitable pressure gauge.

From the foregoing description it can be seen that a large lumen 26 is used for retroperfusion and that the balloon 46 is automatically inflated during blood flow. The secondary lumen 27 terminates in the side port 32 which is used for pressure monitoring. The positioning of the side port prevents a pressure wave from the forward flow of retroperfusion blood from interfering with the pressure measurement. With the side port 32 arranged in a side position, the forward flow of blood through the tip valve 41 has very little, if any, effect upon the pressure measurement to make it possible to obtain relatively clean pressure signals.

The tip valve 41 of the present invention has construction features which are particularly advantageous. The four leaflets which are provided have a relatively low preload to maintain and yieldably urge the leaflets into a closed position. There is therefore very little pressure drop in a fluid such as blood passing through the tip valve to thereby provide the minimum of forward flow resistance. Upon reverse flow, the leaflets will readily move to a closed position to stop reverse flow. In addition, the soft walls of the tip valve will collapse and form a liquid-tight seal to further ensure that there is no reverse flow. This facilitates the rapid and complete deflation of the balloon 46. It also inhibits mixing of venous blood with arterial blood and to prevent venous blood from flowing into and through the catheter. The tip valve helps to prevent the auto-inflatable balloon from being accidentally inflated by hemostatic pressures which may occur in the blood vessel.

In addition, the construction of the tip valve is advantageous in that it permits the use of a guide wire to aid in the positioning of the retroperfusion catheter during its insertion into the venous vessel of the patient. The leaflets permit the guide wire to be advanced and retracted therethrough without damaging the valve.

The tip valve 41 has a rounded distal extremity which is quite soft so that there is reduced danger of penetrating a vessel wall as the retroperfusion catheter is being advanced into the vessel of the patient. The softness of the tip valve permits the tip valve to act as a shock absorber or bumper as the catheter is being advanced.

Another embodiment of the retroperfusion catheter of the present invention is a triple lumen retroperfusion catheter 71 shown in FIGS. 11 through 15. The catheter 71 is of the type which utilizes a non-auto-inflatable balloon in which the inflation of the balloon is controlled completely independently of the retroperfusion flow. The retroperfusion catheter 71 consists of a flexible elongate tubular member or element 72 which is extruded from a suitable material such as Pebax to provide a large lumen 73 and two small lumens 74 and 76 as shown in FIGS. 13 and 14. As shown in FIG. 13, the lumen 73 is substantially circular in cross section at the proximal end 77 of the tubular element 72 and is substantially D-shaped cross-section near the distal extremity 78 of the tubular element 72. Note that other shapes, such as an ellipse which is not shown, could be used for this lumen to increase flow area.

Extension tube assemblies 81, 82 and 83 are provided which are mounted in the lumens 73, 74 and 76 respectively in a suitable manner such as by use of a potting compound 84 or by heat fusion as hereinbefore described in connection with the previous embodiment. The flexible elongate member 72 is provided with an enlarged portion 72a in much the same manner as the flexible elongate element 22 was provided with an enlarged portion 22a in the previous embodiment so as to accommodate the extension tube assemblies 81, 82 and 83. Each of the extension tube assemblies 81, 82 and 83 is provided with a suitable fitting, as for example, a female or male Luer-type fitting 85 or 86. Thus a female fitting 85 is provided which is in communication with the lumen 76. Male fittings 86 are provided which are in communication with the lumens 74 and 73.

A balloon 87 formed of the same polyethylene material as hereinbefore described is provided which has proximal and distal extremities 88 and 89. The balloon 87 can be secured to the distal extremity of the tubular member 72 by suitable means such as a silicone adhesive, and in addition, or alternatively, by utilizing a heat shrinkable material with or without cyanoacrylate adhesive. It can be shrunk onto the tubular member 72 to provide a fluid-tight seal between the balloon 87 and the tubular member 72. An elongate slot 91 of a suitable length as, for example, 0.150 inches and a suitable width of 0.020 inches is provided in the tubular member 72 and opens into the balloon lumen 74 and into the interior of the balloon 87. Another slot 92 is provided in the tubular member 72 near the distal extremity 89 of the balloon and has a suitable width as, for example, 0.020 inches and a length of approximately 0.075 inches and opens into the pressure lumen 76.

A relatively soft tip or bumper 96 has been provided and is mounted on the distal extremity of the tubular member 72. It can be mounted in a manner very similar to the manner in which the tip valve 41 has been mounted. It also can be formed of a similar material. However, the leaflet portions 41a, 41b, 41c and 42d are not provided so that there is formed a large open passage 97 which is in communication with the large lumen 73 used for retroperfusion blood flow.

Operation and use of a triple lumen retroperfusion catheter 71 may now be briefly described as follows. The catheter 71 can be introduced into the venous vessel with or without the use of a guide wire. As can be appreciated, the guide wire can extend through the large lumen 73 provided for retroperfusion blood flow. The balloon 87 can be inflated through the slot 91 with a suitable gas such as carbon dioxide or helium through the balloon inflation and deflation lumen 74 to provide the desired amount of inflation. Retroperfusion blood can flow through the lumen 73 from a pump cassette which is provided for the retroperfusion blood flow. Pressure measurements can be readily made by attaching a suitable pressure gauge to the appropriate extension tube assembly 83 and monitored through the port 92.

The construction of the retroperfusion catheter 71 with its very soft bumper or tip 96 makes it possible to position the catheter 71 with reduced danger of damaging or penetrating the side wall of the vessel into which the catheter 71 is being introduced. The very flexible tip also aids in steering the catheter as it is introduced into the vessel.

Another embodiment of the retroperfusion balloon catheter incorporating the present invention is shown in FIGS. 16 through 21 and is in the form of a triple lumen retroperfusion catheter 101. It consists of a flexible tubular member 102 formed of the Pebax material hereinbefore described. It is formed of a suitable diameter as, for example, an outside diameter of 0.114 inches. The tubular member is provided with three lumens 103, 104 and 106 Lumen 103 is the infusion lumen and is D-shaped in cross-section. Lumens 104 and 106 are circular in cross-section and are the inflation lumen and pressure lumen respectively. The tubular member 101 is provided with a tapered conical portion 101a at the proximal extremity 107 and a cylindrical portion 101b intermediate the ends of the tubular member. The tubular member is provided with a distal extremity 108 which as hereinafter described is provided with differing degrees of stiffness or flexibility.

The intermediate portion or part 101b of the catheter can have various diameters, as for example, 0.078 inches for a 6 French device, 0.092 inches for a 7 French device, 0.104 inches for an 8 French device and 0.112 inches for an 8.5 French device. As shown, the distal extremity of the catheter 101 is provided with a bend 109. The flexible elongate tubular member 102 can have a suitable length as, for example, 24 to 48 inches. As hereinafter described, the tubular member in accordance with the present invention can be formed of materials providing differing degrees of stiffness or flexibility.

A fitting assembly 111 is mounted on the proximal extremity 107 of the tubular member 102. The fitting assembly consists of flexible tubing 112, 113 and 114 which carry Luer-type fittings 116, 117 and 118 that are in communication respectively with lumens 103, 104 and 106. Shrink fit tubing 119 is provided for masking the attachment of the fitting assembly 117 to the flexible extremity 107 of the tubular member 102.

The distal extremity 108 of the catheter 101 is provided with a very soft flexible tip 121 which has a suitable length as, for example, 5 to 25 millimeters. This tip can be formed of the same material as the main shaft for the catheter 101 but of a lesser hardness to provide a shaft with additional rigidity to permit steering of the catheter, but with a soft flexible tip so that it can be introduced without the use of a guide wire. Thus by way of example, the main or shaft portion 102a of the tubular member 102 can be formed of a Pebax having a hardness of 63 Shore D whereas, on the other hand, the soft tip 121 can be formed of the same material having a hardness of 25 Shore D. The soft tip 121 can be formed by the use of a mold using heat, pressure and filler material of the same material and hardness value as the softer material being added, and by the use of mandrels to provide the desired flow passages. By the application of heat, pressure and filler material to the mold, a good bond can be obtained between the harder material and the softer material to form a relatively short transition region or junction which serves to form the two parts for the flexible elongate member. The tip 121 is formed so that there is provided a convex outer surface 124 which has a large radius that terminates in a generally flat surface 123 extending at right angles to the axis of the tubular member 102.

The tubular member 102 is provided with a balloon inflation port 126 extending through the side wall of the same which is in communication with the balloon inflation lumen 104. A pressure port 127 is also provided in the tubular member 102 adjacent or within the tip 121 and is in communication with the pressure lumen 106. The distal extremity of the pressure lumen 106 is closed off by a flat piece 128 which serves as a plug and which can be formed during the molding of the tip 121. A plug (not shown) of similar material can be added to accomplish this purpose prior to molding. The infusion lumen 103 extends through the tip 121 as shown in FIG. 21.

A balloon 131 is provided as a part of the catheter and is mounted on the distal extremity of the tubular member 102. The balloon 131 has proximal and distal extremities 132 and 33. The balloon 131 can be formed of a suitable material such as heat shrinkable polyethylene. The distal extremity 133 can be secured to the distal extremity of the tubular member 102 so that it overlies the proximal portion of the tip 121. Suitable sealing means such as an adhesive (not shown), can be utilized for securing the distal extremity 133 to the distal extremity of the tubular member 102. The proximal extremity 132 of the balloon 131 is also secured to the flexible tubular member 102 by suitable means such as by heat shrinking to provide mechanical attachment forces and, or with, an adhesive. With the proximal and distal extremities 132 and 133 secured to the tubular member 102, the collapsible balloon 131 is in registration with the inflation port 126 which can be utilized for inflating and deflating the balloon with a fluid. The distal extremity of the balloon 131 overlies the pressure port 127 which extends therethrough.

The catheter 101 can be utilized in the manner hereinbefore described with respect to the previous embodiments. Because substantially the entire length of the tubular member 102 is formed of the relatively stiff material, the catheter itself can be utilized for positioning the same in the vessel of the patient. Since the tip 121 is very soft, there is no danger of penetrating the side wall of the vessel. The tip in effect serves as a bumper. Infusate can be introduced through the large infusion lumen 103. The balloon 131 can be inflated and deflated through the inflation lumen 104 and pressure measurements can be made through the pressure lumen 106.

In the event it is desirable to provide a catheter which is more flexible at its distal extremity and which can be utilized with a guide wire, the tubular member 102 can be provided with an intermediate portion (not shown) which can be of a suitable length as, for example, 5 to 15 centimeters. This intermediate portion or part can adjoin the soft tip 121 and extend through the balloon to where it makes a junction with the portion formed of a harder material. Thus the intermediate portion can be formed of a material having an intermediate Shore hardness or softness. This can be accomplished by mixing a 40 Shore D Pebax material with a 55 Shore D Pebax material in a 50:50 ratio to provide a material for the intermediate portion having a hardness of approximately 48 Shore D. The mixed materials can then be extruded to form a tube with dimensions that match the tubular member 102 with the desired lumens extending therethrough by the use of mandrels in the manner hereinbefore described. This tube is cut to a suitable length, as for example, 5 to 15 centimeters and then introduced into a mold to which heat, pressure and filler material is applied to form the appropriate junctions. Thus there is provided a catheter with two transitions or junctions with the first transition or junction being between the very soft material forming the tip 21 and the portion generally within the balloon and/or the curve of intermediate hardness as, for example, 48 Shore D. The second transition or junction is formed between the intermediate hardness material of approximately 48 Shore D and the remainder of the tubular member 102 formed of 63 Shore D material. The two transitions or junctions are made in two separate molding operations.

With the catheter utilizing the two transitions, it is possible to utilize the catheter with a guide wire. The guide wire extends through the infusion lumen 103 and can be utilized for positioning the catheter. Because the distal extremity of the catheter is relatively flexible, it is possible for the catheter to readily follow the guide wire and accommodate the tortuosities in the vessels which have been navigated by the guide wire. The catheter can be utilized for retroperfusion in the manner hereinbefore described with respect to the previous embodiments. The construction which is utilized also ensures that the tip is not separated from the shaft of the catheter.

It is apparent from the foregoing that there has been provided a retroperfusion catheter which has distinct advantages over retroperfusion catheters heretofore provided. The tip of the catheters of the various embodiments is very soft and pliable or flexible so that it will not cause damage to the venous vessel or penetrate the vessel as the catheter is being introduced. The tip construction which has been utilized in certain embodiments is provided with a triple redundancy to ensure that the tip will not become separated from the distal extremity of the catheter. In one embodiment, the tip is constructed in such a manner so as to provide leaflets and flexible collapsible walls which readily prevent reverse flow but which provide very little resistance to forward flow of blood through the leaflets. The leaflets also permit the use of a guide wire for introducing the catheter when desired by permitting easy insertion and removal of the guide wire through the tip valve.

As shown from the various embodiments the very soft tip of the catheter can be provided in different ways. In one of the embodiments, the soft tip is provided by utilizing the soft material and molding the same to the harder material by the use of heat and pressure. When additional flexibility is desired, an intermediate portion can be provided adjacent the tip portion of an intermediate hardness which is intermediate that of the shaft portion of the catheter and the tip portion of the catheter to provide a catheter with two transitions and with a relatively soft tip which can be readily guided through the vessel by the use of a guide wire.

Although the catheter of the present invention has been described for use with retroperfusion, it should be appreciated that the catheter and tip construction can also be used for retroinfusion for the administration of pharmacological agents.