DOUBLE THERMOFORM CANNULA

Abstract

Systems and methods for providing a reinforced cannula for use in a blood pump assembly. The reinforced cannula comprises one or more thermoformed reinforced end portions. The thermoformed reinforced end portions may be stiffer than a medial portion of the cannula, allowing the medial portion of the cannula body to stretch and bend more readily than the cannula ends when the cannula is subject to an applied stress, reducing the stress and strain on the cannula ends.

Claims

1. An intravascular blood pump system comprising: a pump having a pump housing and a rotor, the pump being configured to be operated by a motor; an elongate catheter having a distal end, the distal end coupled to the motor or to the pump housing; a cannula having a proximal end that interfaces with a distal end of the pump housing, a distal end with at least one distal opening, the cannula having a longitudinal length and comprising: a thermoformed inner layer extending along the longitudinal length of the cannula, the inner layer comprising an inner material; a coil having a shape memory material, the coil disposed over an outer diameter of the inner layer; a thermoformed outer layer extending along the longitudinal length over the inner layer and the coil, the outer layer comprising an outer material; and a thermoformed first outer end reinforcement layer extending over the outer layer at the proximal end of the cannula, the first outer end reinforcement layer comprising a first reinforcement material and forming a first reinforced portion of the cannula, wherein the first reinforced portion of the cannula is at least two times as stiff as a medial portion, the medial portion being distal of the first reinforced portion of the cannula.

2. The system of claim 1, wherein the first reinforced portion of the cannula is at least four times as stiff as the medial portion of the cannula.

3. The system of claim 1, further comprising a thermoformed second outer end reinforcement layer disposed at the distal end of the cannula, wherein the second outer end reinforcement layer comprises a second reinforcement material and forms a second reinforced portion of the cannula, and wherein the medial portion is proximal of the second reinforcement portion of the cannula.

4. The system of claim 3, wherein the first reinforcement material is the same as the second reinforcement material.

5. The system of claim 3, wherein the distal end of the cannula interfaces with an inflow cage.

6. The system of claim 1, wherein a thickness of the first outer end reinforcement layer tapers in a distal direction.

7. The system of claim 3, wherein a thickness of the second outer end reinforcement layer tapers in a distal direction.

8. The system of claim 1, wherein the inner material is polyester polyurethane.

9. The system of claim 1, wherein at least one of the outer material or the first reinforcement material is polyether polyurethane.

10. The system of claim 1, wherein the inner material has a hardness in the range of about 45D-65D.

11. The system of claim 1, wherein the outer material has a hardness in the range of about 75A-95A.

12. The system of claim 1, wherein the first reinforcement material has a hardness in the range of about 55D-75D.

13. The system of claim 1, wherein a hardness of the inner material and a hardness of the first reinforcement material are equal or approximately equal.

14. The system of claim 1, wherein the coil is embedded in the outer layer.

15. The system of claim 1, wherein the shape memory material comprises at least one of Nitinol or a copper-aluminum alloy.

16. The system of claim 1, wherein: an outer diameter of the medial portion of the cannula is less than an outer diameter of the first reinforced portion of the cannula; the medial portion of the cannula comprises the inner layer, the coil, and the outer layer; and the first reinforced portion of the cannula comprises the inner layer, the coil, the outer layer, and the first outer end reinforcement layer.

17. The system of claim 1, wherein the cannula is configured to be positioned in a patient's heart such that it extends across an aortic valve of the patient's heart, with the distal end of the cannula being within a left ventricle of the patient's heart and the proximal end of the cannula being within an aorta of the patient's heart.

18. A method for manufacturing a cannula, the method comprising: thermoforming an inner layer of the cannula over a mandrel, the inner layer comprising an inner material and an inner diameter and outer diameter; placing a shape memory coil over the outer diameter of the inner material; thermoforming an outer layer of the cannula over the inner layer and the coil, the outer layer extending along a longitudinal length and comprising an outer material; and thermoforming a first outer end reinforcement layer to extend over the outer layer at a proximal end of the cannula to form a first reinforced portion of the cannula, the first reinforced portion of the cannula being at least two times as stiff as a medial portion of the cannula, the medial portion being distal of the first reinforced portion of the cannula.

19. The method of claim 18, further comprising bonding the cannula to a pump housing and an inflow cage of an intravascular blood pump, the pump housing being configured to at least partially enclose a rotor.

20. The method of claim 19, wherein a distal end of the cannula is bonded to the inflow cage, and a proximal end of the cannula is bonded to the pump housing.

21. The method of claim 20, wherein bonding the distal end of the cannula to the inflow cage comprises: applying an epoxy to the interface between the distal end of the cannula and the inflow cage; and heat curing the epoxy.

22. The method of claim 20, wherein bonding the proximal end of the cannula to the pump housing comprises: applying an epoxy to the interface between the proximal end of the cannula and the pump housing; and heat curing the epoxy.

23. The method of claim 18, wherein thermoforming the inner layer comprises: placing an inner extruded sleeve comprising the inner material on the mandrel; placing a first heat shrink tube around the inner extruded sleeve; heating the inner extruded sleeve and the heat shrink tube to soften the sleeve and cause the heat shrink to apply force on the sleeve towards the mandrel; and removing the first heat shrink tube.

24. The method of claim 18, wherein thermoforming the outer layer comprises: placing an outer extruded sleeve comprising the outer material over the inner layer and the coil; placing a second heat shrink tube around the outer extruded sleeve; heating the sleeve and the heat shrink tube to soften the sleeve and cause the heat shrink to apply force on the sleeve towards the inner layer and coil, embedding the coil in the outer material; and removing the second heat shrink tube.

25. The method of claim 18, wherein the first reinforced portion of the cannula is at least four times as stiff as the medial portion of the cannula.

26. The method of claim 18, further comprising thermoforming a second outer end reinforcement layer to extend over the outer layer at the distal end of the cannula to form a second reinforced portion of the cannula, and wherein the medial portion is proximal of the second reinforced portion of the cannula.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The foregoing and other objects and advantages will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which:

[0027] FIG. 1 shows an illustrative blood pump assembly having a thermoformed outer end reinforcement layer at its proximal end in accordance with aspects of the disclosure;

[0028] FIG. 2 shows an illustrative cross-section of a cannula for use in a blood pump assembly having a thermoformed outer end reinforcement layer in accordance with aspects of the disclosure;

[0029] FIG. 3 shows an illustrative blood pump assembly having two thermoformed outer end reinforcement layers in accordance with aspects of the disclosure; and

[0030] FIG. 4 shows an illustrative method for manufacturing a reinforced cannula in accordance with aspects of the disclosure.

DETAILED DESCRIPTION

[0031] To provide an overall understanding of the systems, methods, and devices disclosed herein, certain illustrative implementations will be described. Although the implementations and features described herein are specifically described for use in connection with a blood pump assembly, it will be understood that the teaching may be adapted and applied to other pumps and other types of medical devices.

[0032] FIG. 1 shows an illustrative blood pump assembly 100 having a pump 102 comprising a motor 106 and a rotor 104, a pump housing 108, a catheter 110 having a distal end 112, a cannula 114 having a proximal end 116, a distal end 118, a medial portion 120, a length 124, a thermoformed inner layer 126, a coil 128, an inner layer outer diameter 130, a thermoformed outer layer 132, and a thermoformed outer end reinforcement layer 134, and an atraumatic extension 136. Rotor 104 of pump 102 comprises at least one blade (not shown) for conveying fluid through pump 102. Pump housing 108 surrounds the at least one blade of rotor 104. Proximal end 116 of cannula 114 is coupled to pump housing 108, and distal end 118 of cannula 114 is coupled to a blood inflow cage 122 which itself is coupled to the flexible, atraumatic extension 136. Extension 136 may help to stabilize pump 102 when pump 102 is deployed within the patient by serving as a flow-straightening region. In some implementations, extension 136 is a pigtail.

[0033] Cannula 114 may have the same structure as shown below with respect to FIG. 2. In that regard, the cannula 114 of FIG. 1 comprises a thermoformed inner layer 126 extending along length 124 of cannula 114, inner layer 126 comprising an inner material. Additionally, cannula 114 comprises a coil 128 disposed over the thermoformed inner layer 126 and comprising a shape memory material. Cannula 114 further comprises a thermoformed outer layer 132 extending along length 124. The outer layer comprises an outer material. Thermoformed outer end reinforcement layer 134 extends over the outer layer of cannula 114 at proximal end 116 of cannula 114. Thermoformed outer end reinforcement layer 134 comprises a reinforcement material. Further, thermoformed outer end reinforcement layer 134 provides added stability to the joint between cannula 114 and pump housing 108.

[0034] In some implementations, thermoformed outer end reinforcement layer 134 is at least two times as stiff as medial portion 120 of cannula 114. In other implementations, thermoformed outer end reinforcement layer 134 is between about 1.5 times and 5.5 times as stiff as medial portion 120 of cannula 114. In other implementations, thermoformed outer end reinforcement layer 134 is between about 2 times and about 5 times as stiff as medial portion 120 of cannula 114. In further implementations, thermoformed outer end reinforcement layer 134 is between about 3 times and about 4 times as stiff as medial portion 120 of cannula 114. In certain implementations, thermoformed outer end reinforcement layer 134 is about 3.5 times as stiff as medial portion 120 of cannula 114.

[0035] As discussed previously, in certain implementations, the inner material has a hardness between about 45D and about 65 D. In other implementations, the inner material has a hardness between about 50D and about 60D. In further implementations, the inner material has a hardness of about 55D. In some implementations, the outer material has a hardness between about 75A and about 95A. In other implementations, the outer material has a hardness between about 80A and about 90A. In further implementations, the outer material has a hardness of about 85A. In certain implementations, the reinforcement material has a hardness between about 45D and about 65D. In other implementations, the reinforcement material has a hardness between about 50D and about 60D. In further implementations, the reinforcement material has a hardness of about 55D. In certain implementations, the hardness of the inner material and the reinforcement material are equal or approximately equal.

[0036] The relative stiffnesses of the reinforced portion of the cannula and the medial portion of the cannula can be adjusted to yield a desired stiffness profile along the length of the cannula. The relative stiffnesses can be adjusted by the incorporation of one or more thermoformed outer end reinforcement layers of varying stiffnesses. The thermoformed outer end reinforcement layers may comprise a material with a higher stiffness than the medial portion of the cannula. The relative stiffness can be further adjusted by the incorporation of materials having varying rigidities encompassed by the above ranges. Additionally, the geometry of the thermoformed outer end reinforcement layer can be adjusted to attain the desired relative stiffnesses. For example, the thermoformed outer end reinforcement layer 134 may have a radial thickness between about 0.05 mm and about 0.15 mm. In certain implementations, the radial thickness of the thermoformed outer end reinforcement layer 134 is less than about 0.1 mm. Additionally, the thermoformed outer end reinforcement layer 134 may have a varying length. In certain implementations, the length of the thermoformed outer end reinforcement layer 134 is between about 1 centimeter and about 3 centimeters. In other implementations, the length of the thermoformed outer end reinforcement layer 134 is about 2 centimeters. In some implementations, the length of the thermoformed outer end reinforcement layer 134 is between about 3 mm and about 9 mm. In certain implementations, the length of the thermoformed outer end reinforcement layer 134 is between about 5 mm and 7 mm. In other implementations, the length of the thermoformed outer end reinforcement layer 134 is about 6 mm. In general, different procedures requiring different insertion methods and angles may call for cannulas having a specific stiffness profile along the length of the cannula. For example, some femoral insertions of blood pump assemblies into obese patients suffer from kinking because the blood vessel is deeper with respect to the insertion point than in a patient of a lower bodyweight. In such cases, it may be desirable to increase the reinforcement on the distal end and the proximal end of a cannula that is inserted in procedures for obese patients.

[0037] FIG. 2 shows an illustrative partial longitudinal cross-section of a cannula 200 for use in a blood pump assembly having a thermoformed outer end reinforcement layer, such as the cannula 114 of FIG. 1. Cannula 200 of FIG. 2 has an inner layer 202, a coil 204, an outer layer 206, a thermoformed outer end reinforcement layer 208, a proximal end 210, a medial portion 212, and a distal end 214. Inner layer 202 has outer diameter 216. Inner layer 202 comprises an inner material. Similarly, outer layer 206 comprises an outer material. In some implementations, the inner material is polyurethane. In some implementations, the outer material is polyurethane. In such cases, the polyurethane of the inner and/or outer materials may comprise polyether or polyester. Coil 204 comprises a shape memory material, and coil 204 is disposed over inner layer 202. The shape memory material may be Nitinol or a copper-aluminum alloy. Thermoformed outer end reinforcement layer 208 extends over outer layer 206 at proximal end 210 of cannula 200. Thermoformed outer end reinforcement layer 208 comprises a reinforcement material and forms a reinforced section at or near where cannula 200 is coupled to, for example, a pump housing (e.g., pump housing 108 of FIG. 1).

[0038] In some implementations, thermoformed outer end reinforcement layer 208 is between about 1.5 times and 5.5 times as stiff as medial portion 212 of cannula 200. In other implementations, thermoformed outer end reinforcement layer 208 is between about 2 times and 5 times as stiff as medial portion 212 of cannula 200. In further implementations, thermoformed outer end reinforcement layer 208 is between about 3 times and about 4 times as stiff as medial portion 212 of cannula 200. In certain implementations, thermoformed outer end reinforcement layer 208 is about 3.5 times as stiff as medial portion 212 of cannula 200. At least one advantage of the varying relative stiffnesses of thermoformed outer end reinforcement layer 208 and medial portion 212 is that a cannula having a specific rigidity profile can be selected for a procedure depending on the tortuosity of the vasculature that will be traversed by the cannula during the procedure.

[0039] The relative stiffnesses of thermoformed outer end reinforcement layer 208 and medial portion 212 of cannula 200 can be adjusted by varying the geometry of one or both of these elements in order to yield a desired stiffness profile along the length of cannula 200. For example, thermoformed outer end reinforcement layer 208 can be made stiffer by increasing the radial thickness of thermoformed outer end reinforcement layer 208. Additionally, medial portion 212 can be made less stiff than thermoformed outer end reinforcement layer 208 by decreasing the radius of medial portion 212. Further, the relative stiffnesses of medial portion 212 and thermoformed outer end reinforcement layer 208 can be adjusted by changing outer diameter 216 of inner layer 202. For example, increasing outer diameter 216 of inner layer 202 while keeping the same thickness of the inner layer 202 and the same outer diameter of outer layer 206 results in a lower stiffness of medial portion 212 as there is less material within medial portion 212 to bend. Conversely, decreasing outer diameter 216 of inner layer 202 while keeping the same thickness of the inner layer 202 and the same outer diameter of outer layer 206 results in a larger stiffness of medial portion 212 as there is a larger amount of material within medial portion 212 to bend. Additionally, the relative stiffnesses between medial portion 212 and thermoformed outer end reinforcement layer 208 can be adjusted by the incorporation of materials having varying stiffnesses. At least one advantage of being able to adjust the relative stiffnesses between medial portion 212 of cannula 200 and thermoformed outer end reinforcement layer 208 is that a desired stiffness profile that is particularly suitable for a given procedure can be implemented along the length of cannula 200.

[0040] FIG. 3 shows an illustrative blood pump assembly 300 having a pump 302, pump 302 comprising a motor 306 and a rotor 304, a pump housing 308, a catheter 310 having a distal end 312, a cannula 314 having a proximal end 316, a distal end 318, a medial portion 320, a distal opening 340, a length 324, a thermoformed inner layer 326, a coil 328, an inner layer outer diameter 330, a thermoformed outer layer 332, a proximal thermoformed outer end reinforcement layer 334, a distal thermoformed outer end reinforcement layer 336, an atraumatic extension 338, and an inflow cage 322. Similar to thermoformed outer end reinforcement layer 134 of FIG. 1, proximal thermoformed outer end reinforcement layer 334 extends over the outer layer of cannula 314 at proximal end 316 of cannula 314, and comprises a reinforcement material. The proximal thermoformed outer end reinforcement layer 334 may provide added stability to the cannula 314 at or near the interface between cannula 314 and pump housing 308. Likewise, distal thermoformed outer end reinforcement layer 336 extends over the outer layer of cannula 314 at distal end 318 of cannula 314, and comprises a reinforcement material which may be the same or different than the reinforcement material used for proximal thermoformed outer end reinforcement layer 334. The distal thermoformed outer end reinforcement layer 336 may provide added stability to the cannula 314 at or near the interface between cannula 314 and inflow cage 322.

[0041] Proximal thermoformed outer end reinforcement layer 334 has outer diameter 342, and medial portion 320 has outer diameter 344. In some implementations, outer diameter 344 of medial portion 320 is less than outer diameter 342 of proximal thermoformed outer end reinforcement layer 334. Similarly, distal thermoformed outer end reinforcement layer 336 has outer diameter 346. In some implementations, outer diameter 344 of medial portion 320 is less than outer diameter 346 of distal thermoformed outer end reinforcement layer 334.

[0042] In some implementations, at least one of proximal thermoformed outer end reinforcement layer 334 and distal thermoformed outer end reinforcement layer 336 is between about 1.5 times and 5.5 times as stiff as medial portion 320 of cannula 314. In other implementations, at least one of proximal thermoformed outer end reinforcement layer 334 and distal thermoformed outer end reinforcement layer 336 is between about 2 times and 5 times as stiff as medial portion 320 of cannula 314. In further implementations, at least one of proximal thermoformed outer end reinforcement layer 334 and distal thermoformed outer end reinforcement layer 336 is between about 3 times and 4 times as stiff as medial portion 320 of cannula 314. In certain implementations, at least one of proximal thermoformed outer end reinforcement layer 334 and distal thermoformed outer end reinforcement layer 336 is about 3.5 times as stiff as medial portion 320 of cannula 314. As previously discussed, the relative stiffnesses of the reinforced portion of the cannula and the medial portion of the cannula can be adjusted to yield a desired stiffness profile along the length of the cannula by varying the geometry and the materials of the reinforced and the medial portions of the cannula. As already noted, different procedures requiring different insertion methods and angles may call for cannulas with different stiffness profiles.

[0043] FIG. 4 shows an illustrative method 400 of manufacturing a cannula. The cannula may be, for example, any of the cannulas described above in relation to FIGS. 1-3. Method 400 first comprises step 402, in which an inner layer is thermoformed over a mandrel, and wherein the inner layer comprises an inner material, an inner diameter, and an outer diameter. Step 404 subsequently comprises placing a shape memory coil over the outer diameter of the inner material. Step 406 then comprises thermoforming an outer layer over the coil and the inner layer, wherein the outer layer is configured to extend along the length of the cannula. The outer layer comprises an outer material.

[0044] Step 408 comprises thermoforming an outer end reinforcement layer to extend over the outer layer at an end of the cannula. The outer end reinforcement layer comprises a reinforcement material and forms a reinforced section of the cannula. For example, the reinforced material may be applied to the proximal end of the cannula as shown in FIGS. 1 and 2, and be configured to increase the stiffness of the cannula at or near an interface between the cannula and the portion of the pump to which the proximal end of the cannula is bonded (e.g., between the cannula and the pump housing). In such cases, the method may further comprise bonding the thermoformed outer end reinforcement layer to the pump housing of the blood pump assembly. Likewise, the reinforcement material may be applied to the distal end of the cannula as shown in FIG. 3, and be configured to increase the stiffness of the cannula at or near an interface between the cannula and the portion of the pump to which the distal end of the cannula is bonded (e.g., between the cannula and the inflow cage). In such cases, the method may further comprise bonding the thermoformed outer end reinforcement layer to the inflow cage of the blood pump assembly.

[0045] In some implementations, the thermoformed outer end reinforcement layer is between about 1.5 times and about 5.5 times as stiff as the medial section of the cannula of the blood pump assembly. In other implementations, the thermoformed outer end reinforcement layer is between about 2 times and about 5 times as stiff as the medial section of the cannula of the blood pump assembly. In certain implementations, the thermoformed outer end reinforcement layer is between about 3 times and about 4 times as stiff as the medial section of the cannula of the blood pump assembly. In further implementations, the thermoformed outer end reinforcement layer is between about 3.5 times as stiff as the medial section of the cannula of the blood pump assembly. The thermoformed outer end reinforcement layer may be bonded to the pump housing or to the inflow cage by the application of an epoxy which is cured.

[0046] As previously discussed, the thermoforming of the inner layer comprises placing an inner extruded sleeve, the inner extruded sleeve comprising the inner material, on a mandrel and subsequently placing a first heat shrink tube around the inner extruded sleeve. The heat shrink tube and the inner extruded sleeve are then heated so as to soften the sleeve and to cause the heat shrink tube to apply a compressive force on the sleeve in the direction of the mandrel. The first heat shrink tube is then removed. Similarly, the thermoforming of the outer layer comprises placing an outer extruded sleeve, the outer extruded sleeve comprising the outer material, over the inner layer and the coil, and subsequently placing a second heat shrink tube around the outer extruded sleeve. The heat shrink tube and the outer extruded sleeve are then heated so as to soften the sleeve and to cause the heat shrink tube to apply a compressive force on the sleeve in the direction of the inner layer and the coil, causing the coil to be embedded in the outer material. The second heat shrink tube is subsequently removed.

[0047] The foregoing description is merely intended to be illustrative of the principles of the technology. As such, the devices and methods described herein can be practiced by other than the described implementations, which are presented for purposes of illustration and not of limitation.

[0048] In addition, the disclosed features may be implemented in any combination or subcombination (including multiple dependent combinations and subcombinations) with one or more other features described herein. The various features described or illustrated above, including any components thereof, may also be combined or integrated into other systems. Moreover, certain features may be omitted or not implemented without departing from the spirit of the technology.