AU2011202650A1 - Actuator for a heart assist device - Google Patents

Abstract

Abstract Actuator for a heart assist device An actuator (10) for a heart assist device. The actuator (10) includes an inflatable balloon (12) and a shroud or wrap (14). The inflatable balloon (12) has a first body portion (22), s a second body portion (26) and a flexure region joining (24) the first (22) and second (26) body portions. The shroud or wrap (14) is positioned adjacent the first body portion (24) and has a peripheral extent at least equal to the peripheral extent of the balloon flexure region (24). The balloon (12) and the shroud or wrap (14) are shaped such that the shroud or wrap (14) restrains a part of the balloon first body portion (22) at or near the flexure io region (24) against displacement towards the shroud or wrap (outward displacement) past a predetermined limit but allows unrestrained displacement away from the shroud or wrap (inward displacement).

Description

S&F Ref: 635200AUD1 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name and Address Sunshine Heart Company Pty Ltd, of 2A River Street, of Applicant: Birchgrove, New South Wales, 2041, Australia Actual Inventor(s): Scott Hugh Miller Address for Service: Spruson & Ferguson St Martins Tower Level 35 31 Market Street Sydney NSW 2000 (CCN 3710000177) Invention Title: Actuator for a heart assist device The following statement is a full description of this invention, including the best method of performing it known to me/us: 5845c(5236681_1) -1 Actuator for a heart assist device Field of the Invention The present invention relates generally to heart assist devices, systems and methods and, more particularly, to an actuator for a counter-pulsation heart assist device. 5 Background of the Invention US Patent No. 4630597 and International PCT Patent Application No. PCT/USOO/22992 (WO 01/13974) both disclose heart assist devices that utilise an inflatable balloon that is positioned within an arterial vessel of a patient. The balloons 10 replace a resected portion of the vessel and are cyclically inflated and deflated to expand into the vessel and thus assist in blood displacement during diastole and retract from within the vessel during systole. Both of the above documents disclose devices that have a relatively rigid shell with an inlet/outlet port which is connected to a fluid pump. The flexible balloon seals IS around the periphery of the shell and extends back over the shell for some or all of its exterior. Another layer of material is then placed over the balloon exterior, adjacent the shell, to secure the balloon to the shell. The Applicant's International PCT Patent Application No's. PCT/AUOO/00654, PCT/AUO1/01 187, and PCT/AU02/00974 all disclose actuators that were found to fail 20 due to fatigue in the balloon interfacing with the aorta. It is an object of the present invention to provide an improved actuator. Summary of the Invention Accordingly, the present invention provides an actuator for a heart assist device, 25 the actuator comprising: (a) a restraint component comprising a hole; and (b) a flexible balloon comprising: (i) a tubular neck portion disposed through the hole in the restraint component; 30 (ii) a first body portion coupled to the neck portion, wherein the first body portion is unattachedly disposed adjacent to the restraint component; (iii) a second body portion; and (iv) a flexure portion coupled to the first body portion and the second body portion, -2 wherein the balloon comprises a deflated configuration and an inflated configuration in which at least a portion of the first body portion is displaced inwardly away from the restraint component. Preferably, the restraint component comprises a shroud or a wrap. s Preferably, the restraint component comprises a wrap configured to be disposed around the flexible balloon and an exterior of a patient's arterial vessel. Preferably, the balloon is formed from silicone, polyurethane, or a polyurethane polysiloxane block copolymer. Preferably, the actuator further comprises a bushing disposed within and io extending from the tubular neck portion of the balloon, the bushing comprising a bore, wherein the bushing is configured to be coupleable to a fluid line. Preferably, the bore comprises at least one internal projection disposed within the bore. Preferably, the at least one internal projection comprises at least one flute, at is least one rib, or at least one secondary lumen. Preferably, the flexure portion has a radius of curvature of at least 0.1 mm in the inflated configuration. Preferably, the flexible balloon has a thickness ranging from about 150 microns to about 300 microns. 20 Preferably, the heart assist device is an extra-aortic counterpulsation heart assist device. Preferably, the restraint component is disposed against an exterior portion of the tubular neck portion of the balloon, thereby resulting in a snug sealing fit between the restraint component and the tubular neck portion. 25 Brief Description of the Drawings Preferred embodiments of the invention will now be described, by way of examples only, with reference to the accompanying drawings in which: Fig. 1 is an exploded perspective view of a first embodiment of an actuator 30 according to the invention; Fig. 2 is an assembled, partial cut away, perspective view of the actuator shown in Fig. 1; Fig. 3 is an assembled, cross sectional view of the actuator shown in Fig. 1 along the line 3-3; -3 Fig. 4 is an assembled, cross sectional view of the actuator shown in Fig. 1 along the line 4-4; Fig. 5 is a cross sectional view of the second embodiment of an actuator according to the invention along the line 5-5; s Fig. 6 is an underside view of the bushing used in the actuator shown in Fig. 5; Fig. 7 is a cut away perspective view of a balloon for a third embodiment of an actuator according to the invention; Fig. 8 is a top view of the balloon shown in Fig. 7; Fig. 9 is a cut away side view of a fourth embodiment of an actuator according to io the invention; Fig. 10 is a perspective view of the actuator shown in Fig. 9; and Fig. 11 is a front view of the actuator shown in Fig. 9. Detailed Description of the Preferred Embodiments 15 Fig. 1 shows an exploded perspective view of an actuator 10 according to a first embodiment of the present invention, which is sized for paediatric use. The actuator 10 has a flexible, inflatable balloon 12, an inelastic shroud 14, and a relatively rigid bushing 16. The balloon 12 is formed from Polyurethane or similar biocompatible and 20 biostable material by mandrel dipping. The balloon 12 has a narrower neck portion 18 which is connected by a flared part 20 to a wider first body portion 22. A flexure region 24, which extends generally around the exterior of the balloon 12 at its widest part connects a second body portion 26 (see Figs. 2 to 4) to the first body portion 22. When viewed in plan, the first and second body portions are generally elliptical 25 in shape and have a maximum width and length of about 20-35mm and 50-90mm respectively for adult sized balloons. The balloon neck portion has a diameter of approximately 10-14mm at its distal end 18a and, at its proximal end 18b, it is elliptical in shape with dimensions of approximately 30-50mm in the long axis and 15-30mm in the short axis of the balloon 12, and with a converging taper therebetween. Paediatric 30 balloons are also considered in this same application, but scaled downward appropriately. The shroud 14 is formed, by mandrel dipping, from a material substantially equivalent to the material used for the balloon, such as a Polyurethane or a Polyurethane Polysiloxane block co-polymer. The shroud 14 has a narrower neck portion 28 which is joined to a wider body portion 30 by a flared part 32. The shroud body portion 30 is also -4 generally elliptical in shape when viewed in plan and has a larger peripheral extent (ie extends further in all directions) than the balloon body portions 22 and 26 and flexure region 24. More particularly, the shroud body portion 30 has a length (along the long axis of the balloon 12) of 60-100mm and a minimum width of (across the short axis of the 5 balloon 12) of 20 mm. The shroud neck portion 28 is sized to be a snug sealing fit over the exterior of the balloon neck portion 18. The bushing 16 is formed, by injection moulding, from a flexible plastic such as Polyurethane or a similar material. The bushing 16 has a hollow bore 36 which is adapted for sealing connection with a fluid line from a motive power source such as a fluid pump to (not shown). Suitable pumps are disclosed in the Applicant's International PCT Patent Application No. PCT/AU02/00974 entitled "A fluid pressure generating means", the contents of which are hereby incorporated by cross reference. The bushing 16 also has a relatively more tapered distal part 38 and a relatively less tapered proximal part 40. The proximal part 40 is sized to be a snug sealing fit within the interior of the balloon neck 15 portion 18. Fig. 2 shows the device 10 after assembly. The assembly comprises initially stretching the neck portion 18 of the balloon 12 so that the proximal part 40 of the bushing 16 can be inserted therein. The balloon 12 is retained adjacent the bushing 16 by the shroud 14 being forced past the distal part 38 of the bushing 16 until it is a snug 20 sealing fit on the exterior of the balloon neck portion 18 as shown. The bushing proximal part 40, the balloon neck portion 18, and the shroud neck portion 28 all have a common taper angle. The components are also bonded together with a suitable adhesive in order to ensure an effective seal therebetween. The operation of the device 10 will now be described by with reference to Figs. 3 25 and 4. Fig. 3 is a cross-sectional (anterior) view along the longitudinal direction of the aorta. Fig. 4 is a partial cross-sectional view orientated at 90 degrees from that of Fig. 3. For extra-aortic heart assistance, the device 10 is placed with the balloon second portion 26 adjacent the exterior of an arterial vessel, most preferably the outer part of the ascending aorta (not shown). A flexible, relatively inelastic wrap is placed over the 30 shroud 30 and around the aorta in order to retain the device 10 in place. Wraps are well known in the art and thus will not be described in further detail. The wrap can also be used in place of the shroud. In use, fluid is cyclically driven to and from the balloon 12, via the bushing bore 36, to cyclically inflate and deflate the balloon 12. The inflated balloon 12 is shown in -5 solid line in Fig. 3. The inflated balloon 12 compresses the aorta and thus assists in blood displacement during diastole. When the balloon 12 is deflated it retracts to the position shown in phantom line, which allows the aorta to return to its natural shape during systole. 5 As Figs. 3 and 4 show, when the balloon 12 is inflated the shroud 14 restrains the balloon first portion 22, up to and including the part adjacent the flexure region 24, against outward displacement past a predetermined limit. That limit being defined by the shape of the shroud body portion 30. However, the shroud 14 does not restrain the inward displacement of the balloon first portion 22, particularly that part at or near the 10 flexure region 24, during deflation. This allows the balloon 12 to always retain a relatively large radius of curvature (e.g. 1.0mm) adjacent the flexure region 24, which is the part of the balloon 12 that undergoes the most deformation. This advantageously minimises stress and strain concentration in the flexure region 24, which results in a much more reliable and longer lasting balloon 18. is This is in contrast to the balloons shown in the two prior art documents mentioned previously which are restrained at a region equivalent to the flexure region for both inward and outward displacement. These balloons undergo a movement akin to pivoting or bending at their free edge. This results in high levels of stress concentration, and associated higher risk of failure, in those balloons. 20 Further, cycle testing of a group of actuators configured for use with sheep (and corresponding to the actuator 10 described above) were terminated after the equivalent of two years cycling without any failures. In addition, cycle testing of similar actuators configured for use with humans has achieved the equivalent of 18 months use without any failures. 25 The actuator 10 is also simpler, and thus cheaper, to assemble and manufacture than the prior art devices as the bushing 16 only engages with the balloon 12 in the region of their respective neck portions 40, 18, as opposed to positioning the bushing (or shell) more fully within the body portions of the balloon. It should also be noted that the actuator 10 is designed to be applied to the 30 outside of a blood vessel and is thus advantageously non-blood contacting as compared to the prior art devices discussed in the Background of the Invention, which are positioned within the wall of a blood vessel. It should also be noted that the inward concavity of the balloon (when deflated) is designed to fit the arcuate ascending aorta particularly, to allow a conformal wrapping -6 of the assembled actuator around the ascending aorta. With balloon inflation, the aortic wall is displaced in a "thumbprinting" manner, which has been shown by finite element analysis to cause minimal strain concentration in the aortic wall and also to provide maximal blood volume displacement. 5 In a more preferred embodiment, the balloon has in its longitudinal plane, a gentle arc of the order of radius of 150-300mm, to accommodate the slight spiral nature of the ascending aorta, to allow further conformal fitting of the assembled device. Figs. 5 and 6 show a second embodiment of actuator 50 according to the invention. The device 50 is similar to the first embodiment and like reference numerals 1o are used to indicate like features. The major difference between the two embodiments is that the bushing 16 in the device 50 includes a series of internal projections 52 which serve to stop the balloon 18 being sucked into the bore 36 of the bushing during large amounts of suction/deflation. Such large amounts of suction/deflation can occur during the calibration cycle of some of is the pumps suitable for use with the blood displacing device 50. Figs. 7 and 8 show a balloon 60 for a third embodiment of actuator according to the invention. The balloon 60 is sized for adult use is but is otherwise similar to the first embodiment and like reference numerals are used to indicate like features. When viewed in plan, the first and second body portions 24 and 26 are generally elliptical in shape and 20 have a maximum width and length of 35mm and 80mm respectively. The balloon neck portion has a diameter of approximately 10mm at its distal end 18a and approximately 26 44mm (oval in cross-section) at its proximal end 18b and a conical converging taper therebetween. Figs. 8 to 10 show a fourth embodiment of actuator 70 according to the 25 invention. Like features to earlier embodiments are indicated with like reference numerals. The actuator 70 utilises the balloon 60 shown in Figs. 7 and 8. The bushing 16 of the actuator 70 differs from earlier embodiments in that it is substantially hollow with a central cylindrical part 16a attached at one end to an outer flared conical part 16b. A series of radial webs 16c are provided between the central cylindrical part 16a and the 30 flared conical part 16b. A flexible, relatively inelastic wrap 72 is provided over the balloon 60, which has an opening 72a through which the bushing 16 protrudes. It will be appreciated by the persons skilled in the art that numerous variations and/or modifications can be made to the invention as shown in the specific embodiment without departing from the spirit or scope of the invention as broadly defined. For -7 example, the blood displacing devices are described above in relation to extra-aortic counter-pulsation but also suitable for intra aortic counter-pulsation. In the latter the second portion of the balloon replaces a resected portion of arterial vessel, with the opening made in the resected arterial vessel being sealingly connected to the balloon 5 adjacent the flexure region.

Claims (11)

1. An actuator for a heart assist device, the actuator comprising: (a) a restraint component comprising a hole; and 5 (b) a flexible balloon comprising: (i) a tubular neck portion disposed through the hole in the restraint component; (ii) a first body portion coupled to the neck portion, wherein the first body portion is unattachedly disposed adjacent to the restraint component; 1o (iii) a second body portion; and (iv) a flexure portion coupled to the first body portion and the second body portion, wherein the balloon comprises a deflated configuration and an inflated configuration in which at least a portion of the first body portion is displaced inwardly is away from the restraint component.

2. The actuator of claim 1, wherein the restraint component comprises a shroud or a wrap. 20

3. The actuator of claim 1, wherein the restraint component comprises a wrap configured to be disposed around the flexible balloon and an exterior of a patient's arterial vessel.

4. The actuator of claim 1, wherein the balloon is formed from silicone, 25 polyurethane, or a polyurethane-polysiloxane block copolymer.

5. The actuator of claim 1, further comprising a bushing disposed within and extending from the tubular neck portion of the balloon, the bushing comprising a bore, wherein the bushing is configured to be coupleable to a fluid line. 30

6. The actuator of claim 5, wherein the bore comprises at least one internal projection disposed within the bore. -9

7. The actuator of claim 6, wherein the at least one internal projection comprises at least one flute, at least one rib, or at least one secondary lumen. s

8. The actuator of claim 1, wherein the flexure portion has a radius of curvature of at least 0.1 mm in the inflated configuration.

9. The actuator of claim 1, wherein the flexible balloon has a thickness ranging from about 150 microns to about 300 microns. 10

10. The actuator of claim 1, wherein the heart assist device is an extra-aortic counterpulsation heart assist device.

11. The actuator of claim 1, wherein the restraint component is disposed against 15 an exterior portion of the tubular neck portion of the balloon, thereby resulting in a snug sealing fit between the restraint component and the tubular neck portion. Dated 3 June, 2011 Sunshine Heart Company Pty Ltd Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON