CA2185920A1 - Intra-aortic balloon catheters - Google Patents

Abstract

An intra-aortic balloon pump catheter includes an inner lumen (14) formed by a thin walled super-elastic metal alloy tube, namely of nitinol, with an inside diameter sufficient for a guide wire (28) and a small outside diameter which allows reduction of the outer lumen and related components by at least one size French while providing gas shuttle capacity between the lumens for conventional intra-aortic balloon pump operation. The outer lumen (12) is a tube formed of co-extruded plastics to enhance the size reduction and capacity goals, with an inner nylon portion (12b) for strength and relatively thin polyurethane outer portion (12a) for bio-compatibility, flexibility and compatibility for bonding to a thin polyurethane balloon (18). The proximal end sleeve of the balloon is stretched and then stress relieved by heating with an internal heater on a mounting mandrel (70) to effect a desired small diameter sizing. A radiopaque metal marker ring (94) of nitinol also is provided to improve imaging capabilities while being compatible with the lumen materials.

Description

~ WO95/25560 2 ~ Q r~ 7~,~

INTRA "' lC BALLOON ~'7~'1'~'r~70~
- This application is a continuation-in-part of co-pending application Serial No. 08/170,513 filed December 20, 1993.
FTP rn OF Tl~17. INVE~TION
This invention relates to intra-aortic balloon pumps and particularly to improved intra-aortic balloon pump catheters .
BACKGROUND OF THE INVENTION
Intra-aortic balloon pumps (IABP) are used to provide counter pulsation within the aorta of ailing hearts over substantial periods of time, e.g. to provide ventricular assistance during cardiogenic shock, low cardiac output in post-operative care, weaning from car~ p~ ry bypass, treatment for refractory unstable angina, and other circumstances of sub-normal cardiac function. Such pumps of the type involved in this invention include a flexible intra-aortic balloon (IAB) which is readily in~latable under low pressure to substantial size and displ~ ~~ L. The balloon is mounted on a catheter device used for insertion of the balloon into a remote artery, typically a femoral artery, and through the intervening vascular system of the patient to the aortic pumping site while the balloon is def lated and furled . This requires insertion of the furled large capacity balloon through a small insertion passage, e.g., a small puncture opening or through an introducer cannula into the selected artery, and then sliding-threading of the catheter and furled balloon through tortuous lumen passageways of the patient's vascular system over a guidewire to the pumping site, e.g. from insertion into an artery in the groin area to the patient's ~cc~ntlin~ aorta. At the pumping site, the W095/25560 21 ~g2.0 PcrluS95/03464 ~
balloon is unfurled and then successively and rapidly inflated and deflated in synchronism with the patient's cardiac pulsation rates over extended periods of time in t a known counterpulsation technique to enhance cardiac 5 output. Thus, use of an IABP requires forceful sliding insertion of a relatively large balloon through a small insertion opening and tortuous arterial lumens, which may be randomly narrowed by arteriosclerotic deposits of plaque, and sllhceq~l~nt unfurling and reliable pulsation 10 operation at heart-beat rates over substantial periods of time, e . g . f or several days .
It will be appreciated that the circumstances and requirements of insertion and use of intra-aortic balloon pumps provide numerous conf licting parameters .
15 Significant aspects of these conflicting parameters are related to the fact that the inf lated but unstretched diameter of the balloon is much larger than the ~l;Ar ~ F~r of the insertion site, which may be percutaneous, and larger than at least portions of the lumen of the 20 vascular system through which it is to be threaded. This requires that the balloons be furled for insertion through passa~_.. y~ which are of very small inside diameter lID) relative to the size of the ~alloon when opened. The related catheter equipment typically must include dual col,ce.,~L ic lumens, including an inner lumen passageway to serve functions such as ~n~ i n~ over a guidewire, sensing values in the aorta, e.g. arterial . ~S_UL~:I and/or administration of - 'l rAr~ntS. A
~UL r vull-ling annular passageway between the inner and outer lumens must be of a size adequate to shuttle an operating gas such as helium at rates to obtain the rapid repetitious expansion and collapse of the balloon n~r~qC ~ry for the pumping function in counterpulsation to the patient's heart.
The aforenoted parameters for intra-aortic balloon catheters have resulted in these catheters being of significant complexity of CU-~ LU- Lion and attendant ~ Wo95/2ss60 2 ~ ~59~ r~~ o I 1 6ubstantial size, i.e. substantial effective diameter of the catheter structure during insertion as well as during the periods of pumping operation within the patient ' s vasculature. A significant potential complication during 5 use is associated with limb; ~ h~mi ;I due to size mismatch between the overall size (diameter) of the counter pulsation catheter and the effective lumen size of the patient's vasculature through which the catheter must pass and in which it must remain during the period of 10 pumping assistance. Heretofore, the full featured IAB
catheter systems available on the market have been of nominal 9 French (Fr) size or larger. The Fr size designation of an IABC refers to the approximate size of the outer lumen. Thus, for example, while 9 Fr literally is about 0.118" diameter, catheters designated as 9 Fr may have outer lumens which slightly exceed that dimension, e.g., up to about .122". Further, such catheters may include balloons which originally were furled to about .126" outer t~i~r t,~r and in which the 20 furling has relaxed to about .144" outer diameter in their packaging sheaths. In any event, reduction in size of intra-aortic balloon catheters and introducer systems would improve systemic f low to limbs at risk .
However, as indicated above the insertion of an IAB
25 catheter intrinsically involves pushing the device along a tortuous path through the patient's vasculature. This requires applying and transmitting compressive forces through the very slender "column" ~LU~:LU't: of the catheter, which requires a significant degree of 30 stiffness in the catheter. The catheter also must flex or bend to follow the desired path through the patient's vasculature without undue lateral reactive force which could cause trauma to the vessels. Thus IAB cathet ld h e a high degree of stiffneSs over a wide range 35 of bending angles, while providing flexibility to follow tortuous paths along which the IAB catheter is being pushed. These characteristics are measures of the W0 95/25560 2 ~ .D J ~
~pllchAhi1ity~ and ~tri~rk~hi1ity" of the catheter, e.g., to follow a guide wire when pushed therealong over a tortuous path without UVt!~C ing the guiding fitiffness of that wire and/or otherwise impinging on the vasculature 5 walls with potentially injurious forces.
IAB catheters also must resist kinking , i . e ., sharp bending collapse of either or both of the lumen tubes with attendant loss of smooth ~.:UL Vi' ~U' a and closing or drastic reduction of the respective internal passageway.
lo Resistance to kinking is nPcPc~ Iry to maintain pushability of the catheter assembly and to avoid binding on the guide wire. Avoiding kinking also m; n~mi zp~s risks of cracking of the lumens during insertion and attendant risks of later leakage during operation, as well as 15 minimi7in~ risks of kink-blockage of the gas shuttle capacity between the lumens or blockage of medication or ssnsing operations through the inner lumen during pumping operation .
It is an object of this invention to provide 20 i ~Jv~=d intra-aortic balloon pump catheters.
It is a more specific object of this invention to provide such catheters wherein adequate gas shuttling capacity can be obtained with conventional pump controllers through cathsters of significantly reduced 25 size.
Similarly, it is an object of this invention to provide such; uv~d catheters wherein substantially higher gas f low rates and attendant higher shuttle speeds Day be obtained in catheters of sizes used heretofore, 30 thereby permitting tracking of heart rhythms not trackable with conventional previous catheters.
It is a further object to provide; uvt:d IAB
catheters which attain some or all of the aforegoing object6 and which maintain high degrees of fl~Y;h; l ity, 35 torquability, pushability and trackability for safe and easy insertion, with minimal risk of trauma to the patient .

~ wo 95/25560 ~ 1 8 5 ~ 2 ~ I ~ 11 ~,~ 1A7 1~ 1 It has been found that IAB catheters using very small metal lumen tubes having high degrees of elasticity and particularly shape restorative elasticity will 5 satisfy the aforementioned parameters. This will allow flexibility with stiffness over a wide range of bending angles of IAB catheters, down to quite severe bends and other temporary deformations which may occur in the course of insertion or operation. More particularly, it has been found that by fabricating IAB catheters with at least the inner lumen being a superelastic thin walled metal tube such as of nitinol, the inner lumen can have a very thin wall with an inside diameter (ID) sufficient for a guidewire and a small outside diameter (OD) which allows reduction of the outer lumen and related ts by at least one size Fr while providing gas shuttle capacity between the lumens for conventional IAB
pump oper2tion. This design also attains excellent flexibility and stiffness of the catheters for ease of insertion and assurance of functionality while reducing the outside ~l i; Pr to signif icantly reduce the risks of vascular and i c~h~m; ;~ complications.
As used herein, the terms "superelastic alloy" or "superelastic alloys" and "superelasticity" refer to those materials, specifically those metal alloys, which return to their original shape upon unloading after a substantial deformation. In most if not all instances superelasticity is related to shape memory. It is understood that a shape memory alloy is one which displays a th-:L ~l~ctic martensitic transformation and is able to absorb several percent shear strain by preferential orientation of martensite variants, and then can reverse that shear strain upon being heated, as the martensite transforms back to the parent (austenite) phase. Similarly, it is understood that a superelastic alloy is the same as a shape memory alloy except that it absorbs strain above the transformation temperature by W095/~5s6!) 2 i 35~2~ PCTIUS95/03464 1--the creation of stress-induced martensite variants of preferential orientation, and then reverts to the parent phase at the same temperature as reduced stress reverses the strain. Superelastic alloys can be strained up to 5 ten times more than ordinary spring materials without 6ubstantial permanent deformation, i.e., less than 0.5%.
They provide nearly constant stress f orces over a wide range of elastic deformation, as repre6ented by typically "flag shaped" stress-strain curves, without significant 10 change of temperature.
Nitinol (nickel-titanium alloys) is perhaps the best known of these materials. Its tranformational superelasticity is about ten times higher than elasticity in ordinary materials. Further, various nitinol alloys 15 are known which are superelastic within the t ~ Lu~ ~
ranges of the living human body. One further description of the superelasticity characteristic and of nitenol alloys which provide this characteristic at human body t~ eLLuLe8 appears in a publication of Raychem 20 Corporation entitled "Su~erelasticitY - Su~erelastic Tinel~ Allovs", which is incorporated herein by this reference and a copy of which is being filed with this application .
Further, it has been found that improved forms of 25 the outer lumen may be provided of co-extruded plastics to complement and enhance the size reduction and capacity goals noted above. In the preferred PTnhOr i-- L this in,ll-rZP~ a relatively thin major inner nylon portion for strength and a polyurethane outer portion for 30 biocompatability, flexibility and compatibility for bonding to the balloon.
T ~ve d techniques f or production of appropriate balloons and for joining the respective components also are provided, particularly for joining of each balloon to 35 the distal end of the outer lumen and to the distal end of the inner lumen while avoiding or minimizing buildup of ~Ziz LL~1 dimensions. ~JLC:UVe~, it has been found ~ ____ _ W095/25560 21~5~0 r~ /r7lc~
that intra-aortic balloons may be made with thinner walls than heretofore to further complement the aforenoted results without C~ ing the integrity of the system.
A radiopaque metal marker ring also has been provided 5 which is compatible with the size reduction goal while providing;, ov~d imaging capabilities.
Brief De6cri~tion of the Drawinas Fig. 1 is a simplified top view of an intra-aortic 10 balloon catheter employing this invention.
Fig. 2 is an enlarged ~;~oss-s~ctional view taken along line 2-2 of Fig. 1.
Fig. 3 is an enlarged cross-sectional view taken along line 3-3 of Fig. 1, on a lesser scale than Fig. 2.
Fig. 4 is an enlarged side elevation view of the balloon portion of the catheter with the balloon furled, such as f or insertion .
Fig. 5 is an enlarged sectional view of a portion of the catheter assembly at the distal end of the balloon, taken along an axial ~ir 1~1 plane.
Fig. 6 is an enlarged side view of the outer lumen and adjacent proximal end portion of the balloon of the catheter of Fig. 1.
Fig. 7 is an end view of a radiopaque tracer ring included in~ the catheter of Fig. 1.
Figs. 7A and 7B illustrate alternative conf igurations of the tracer ring .
Fig. 8 is a side view of a stylet used in forming the guidewire of the catheter of Fig. 1.
Fig. 9 is an enlarged side view of the outer end of the guidewire used in the catheter of Fig. 1.
Figs lOA and lOB schematically illustrate the stripping of intra-aortic h;~l lor~ns: from mandrels on which they have been formed by dip casting.
Figs. llA-E are schematic illustrations of steps for reforming the proximal end sleeve portions of such balloons .
, . . _ . . = . _ . _ _ _ . _ _ _ _ _ _ _ W09~/2556/) 2~ ~9~D r~ 5~
Fig. 12 is a schematic side view of one preferred apparatus used in the process illustrated by Figs. llA-E.
Fig. 13 is a left-end view of the balloon clamp of Fig. 12.
Fig. 14 is a right-end view of the apparatus of Fig.
12 .
Fig . 15 illustrates the shape of the cavity def ined by the balloon clamp, as seen generally along line 15-15 of Fig. 13.
While the invention will be further described in connection with certain pref erred pmho~l i r ~s, it is not intended to limit the invention to those ~ Ls. On the contrary, it is intended to cover all alternatives, modif ications and equivalents as may be included within the spirit and scope of the invention.
Detailed DesOEiption of Pref erred Embo-l i r- c As illustrated in Fig . 1, one ~nho~ i - t of an intra-aortic balloon pump catheter device 10 includes a flexible outer lumen tube 12 and a co-axial flexible inner lumen tube 14 which are attached to a wye ~r~nnr~ct~ r 16. The inner lumen tube 14 extends through the outer lumen 16 and through a single chamber intra-aortic balloon 18 to the distal tip end of the catheter. The proximal end of the balloon la is attached to the distal end of the outer lumen tube 12. The distal end of the balloon 18 is attached to a compatible tip element 20 on the distal end of the inner lumen tube 14. Each of these balloon-lumen att~` ~~ Ls is a gas-tight solvent bond connection between an end sleeve section 21,22 of the balloon and the outer surfaces of the outer lumen 12 and the tip 20, respectively. As seen in the drawings, these end atte.~ -nt sleeves are of substantially lesser diameter than the main disp~ Al- L body section 23 of the balloon and are joined thereto by short tapered sections 24, 25.

Wo 95l25560 2 1 8 ~ ~ ;2 0 'J ~ ,n ~ I r I
The wye ro~n~rt~r 16 provides access through the lateral branch 26 to an appropriate gas supply pump and control device (not shown) for inflating and deflating the balloon 20 by sl~r~esively injecting and withdrawing a gas such as helium through the annular space between the lumens 12 and 14. As indicated above, this is sometimes referred to as "6huttling" the inflation gas to and from the balloon. The controller responds to signals corrPcprn~lin~ to the pulsing of the heart and effects inflation and deflation of the balloon in timed counterpulsation to the pumping action of the heart in a known manner. The axial section 27 of the wye provides axial access to the inner lumen for reception of a guide wire 28 as well as for sensing of arterial ~Le2~uLc:
and/or the injection of medicaments through the inner lumen. Tie downs 32 are included for affixation to the skin of the patient by suturing and/or taping for securing the catheter in its inserted operative pumping position .
The balloon 18 is a large flexible thin-film balloon of conventional ~ iate size, i.e., on the order of about 0 . 5" to about 1. 0" in diameter when in an inflated but unstretched condition and about 8" to 12" in length.
Typical sizes are of 30cc, 40cc and 50cc displ;lc L.
The balloon may be formed of any 5uitable material, with polyurethane presently being preferred. A hydrophilic coating 36 preferably covers the balloon and forms a lubricous outer surface which is very slippery when wetted by an aqueous fluid, such as blood, while permitting processing and furling of the balloon and hAnrll;n~ of the balloon and related pump chAn;r~ in a normal manner when dry. Presently preferred coatings and appropriate modes of applying such coatings are 1; CClOfiPd in co-pending application No. 08/170,513, filed December 20, 1993, the disclosure of which is incorporated herein by this reference.
_ W095/2556~) 2 The balloon 18 i5 furled, as illustrated schematically at 18f in Fig. 4. This min;mi~es its effective outer diameter during insertion into a patient's arterial system. The furling may be S accomplished in a conventional manner. This includes applying a solution of silicone and freon on the outer surface such as by spraying to deposit ~i 1 ;rorlP thereon, then evacuating the air from the balloon thereby causing the balloon to collapse into flat generally radially extending "wings", then rolling those wings tightly about the inner lumen 14 in mutually interleaved relation with one another. This winds the collapsed balloon "wings"
into tightly packed spirals as viewed in cross-section, to minimi ~P the effective outer diameter of the balloon during h In~l in~ and during the insertion process. The ~i l i c~n~ avoids surface-to-surface sticking of the furled layers. A thin tubular packaging sheath typically is placed over each furled balloon to maintain its furled compaction to a minimum effective outside diameter during shipping and h~n~ll ing~ up to the place and time of insertion into the patient. Further, the furled balloons typically are heated, e.g., to a t _La~U~c: on the order of about 135F for about 12-16 hours, to assist in setting and thereby sustaining the furling during insertion following removal from the packaging sheath by the user. Balloons with the noted hydrophilic coatings also become very slippery promptly upon being wetted, with attendant benefits of ease of insertion and placement as well as reduction of trauma.
The wye connector 16 and related _-nPnts and equipment may be of any suitable structure and size.
The inner lumen 14 is a very thin-walled tube formed of a tough and superelastic metal, namely nitinol. For example, it has been f ound that an inner lumen tube 14 of such materials having a wall thirknPC~ of only about 0035'l will function satisfactorily in providing a small IAB catheter, e.g., 8 Fr size. The inner lumen tube 14 WO95/25560 7 ~ ~59;2~ r~ /O~IC~
m;n;mi 5!~C the outside diameter of the inner lumen while maintaining the n~CF~cs ~ry f-ln~ti-~n 11 in6ide diameter as - well as providing desirable characteristics of f 1~Y; h; l; ty and strength throughout the length of the 5 catheter.
An exemplary such inner lumen tube 14 has about . 0276" ID and . 0345" OD. By comparison, the inner lumen currently used in the 9 Fr IAB catheters being m-rk~t~
by the Cardiac Assist Division of St. Jude Medical , Inc ., 10 under the trademark RediGuardn', consi6t of a polyurethane tube of about .008" wall th;rkn~cc ~ULL~Ullded by a coiled stainless steel wire of .003" diameter generally as in the arrangement disclosed in US Patent No. 4,646,717, resulting in an effective overall thickness of the inner lumen wall of .011" and an attendant OD o~ .054" to provide an inner lumen ID of . 032" .
The outer lumen tube 12 is formed by coextrusion of a thin outer polyurethane layer around a thicker nylon inner layer 12b. The nylon layer provides high compressive ~LL~I-y~h relative to the ~h;~-kn~,c,c, and it is believed that the polyurethane layer provides flexibility as well biocompatability and compatibility for ready bonding of the polyurethane balloon. One advantageous combination has been found to be a .002" outer layer of polyurethane coextruded with a . 006" inner layer of nylon, with the total wall th;rkn~cc being about .008".
Thus the outer lumen 12 also is a relatively thin-walled tube, as compared to current commercial polyurethane outer lumens which are on the order of 0. 010" thick.
3 0 By ut; l; ~; n~ inner and outer lumens 12 and 14 as described, the annular space therebetween is of ade~uate 1L ~ss -scction to ~ te the gas shuttle capacity required for normal IABP operations using a conventional controller while minimizing the outside ~ r of the catheter, e.g., reduction of the catheter by one full size Fr, and meeting the other desirable parameters for IAB catheters. Concomitantly, IAB catheters using this Wo gs/25560 ~ ¦ 8 5 q 7 ~ P ~ ~ c ~ --construction and of the same nominal size as prior ou,.aLLu~ions would be capable of higher gas shuttle rates than those prior devices and thus capable of tracking higher heart pulsation rates.
The outer lumen also could be f ormed of a thin walled metal tube having superelasticity, for example also being formed of nitinol. This alternative would permit further reduction of the outer diameter of the outer lumen while maintaining equivalent or even better operational capabilities, but would add significantly to the costs at the present price of nitinol tubing.
Ref erring particularly to Figs . 8 and 9, the guidewire 28 is of a stylet-type with a "floppy J" tip, similar to some guidewires utilized heretofore in other applications, e.g. in cholangiography (catheterization of bile ducts). The stylet 40 is a slim rod or wire which inrl~ a main body portion 42 normally of uniform circular cross-section and a distal end portion 44 of modified configuration for forming the "J" tip. For example, the distal end portion is significantly reduced in diameter along the second portion 44, with an annular ~h~ Pr 46 between portions 42 and 44. Sequentially outward of the section 44 is a third portion 48 which is tapered to a lesser ~iAr ~r, and an end portion 50 which is flattened in cross-section. As represented in Fig. 9, the proximal end of a f ine wire 52 is brazed or welded to the stylet shaft adjacent the shoulder 46. The wire extends in closely wound coil fashion about the distal portion 44, with the distal end being brazed or welded to the distal tip of the stylet body 42. The distal end portion 50a is bent approximately 180, preferably being bent normal to the flattening planes, to form the bight of the "J" tip, generally as illustrated.
By way of further example, one guidewire 28 for use in one specif ic '~ L of this invention as described herein included a stylet 40 formed of 302/304 stainless 6teel, about 150cm in length and with the shoulder 46

2 ~ ~92~
W095/25560 r~l~-JL ~71C1 being about 30cm from the distal end. The main body portion 42 was about .025" in 1;A- Dr, Second portion - 44 was about .013" in diameter and extended for about 23cm from the shr~ Pr 46. Portion 48 was tapered from the .013" diameter to about .0055~ r over a length of about 6cm, and the di6tal end 3cm portion was flattened to about .0035" thickness. The wire 52 was about .005" ~li; Pr, also being of 302/304 StAinlPC~
6teel. The distal 3cm was bent to form the bight and remote leg of the "J" tip. The entire assembly was coated with Teflon, providing a guidewire with a diameter not PYrPPflin~ .025" for use through the inner lumen described above.
As noted above, the balloon 18 may be of the same material, configuration and size as balloons currently in use in intra-aortic balloon pumps. An example of a preferred A ~ -'ir ~ includes a thin-walled polyether based polyurethane balloon of about 0 . 003"-0. 004" wall thickness formed by dip molding on an appropriately shaped mandrel, with a hydrophilic coating as referred to above. This is a reduction of about . 001 thicknes6 from balloons currently in commercial use. Such balloons have satisfactory flexibility and strength, with high elasticity, e.g., about 525% stretchability without rupture. One specific commercially available polyurethane which has proven satisfactory in such balloons, including those used in practicing this invention, is sold by B. F. Goodrich under the designation "Estane 58810".
Referring particularly to Fig. 5 an end tip 20 is affixed over the outer end of the inner lumen tube 14, as by being molded thereonto. For this purpose, the outer surface of the end portion of the tube may be sAn~lhlA~ted as a preparatory step. The tip 20 preferably is of a plastic which is compatible with the material of the balloon, e.g., polyurethane. The outer end surface 62 of the tip is rounded in a bullet-nose shape to facilitate wogs/2s~60 ;~ ~59~ r~". 'I!~lc~ --passage through the patient ' s vasculature . The outer end portion has a central axial passage 64 which provides a smooth continuation of the central axial passage of the lumen tube 14 and preferably tapers or flares toward the 5 distal end of the tip, as illustrated in Fig. 5. This pas6age section 64 may be formed by a core pin being po6itioned in the outer end of the lumen tube 12 prior to the molding of the tip 20.
Referring now to Figs. 1, 5 and 6, the cylindrical 10 proximal sleeve portion 21 of the balloon 18 is bonded to the outer surface of the distal portion of the outer lumen 12 and the cylindrical distal sleeve portion 22 of the balloon is bonded to the outer surface of the tip 20.
These bonds must be airtight and effected in a manner to 15 minimi7e the t9i~- L~ll dimension build-up of the catheter assembly . Such bonding is f acilitated by f orming the tip 20 and at least the outer surface of the outer lumen 12 and the balloon 18 of the same types of materials, namely polyurethane in the illustrated preferred ~ L. In 20 this: ' -'i L, the sleeve portions 21 and 22 are bonded to the respective elements by a solvent and ~,L~S~Ur~
bonding technique. It is believed that ~es~,uL~ bonding with radiofrequency heating to a temperature approximating the melting temperature of the materials 25 will further enhance this bond and provide even greater control and minimizing of the final outer dimensions in these bonding areas. The intervening portion of the balloon 18, ~ nr~ i n~ the larger body section 23, is tightly furled about the inner lumen tube 14 between the 30 distal end of the inner lumen 12 and the tip 20. With the thin-walled balloon referred to above, this multi-layered furled portion will have an outer diameter which only slightly exceeds the outer diameter of the sleeve attA,~ L sections. This is an added factor in 35 maintaining the minimal profile of the entire catheter assembly during insertion.

Wo gs/25560 2 ~ 5 2 0 F.~ c Referring to Figs. lOA and lOB, the bi~llonn~ 18 are made by dip casting on a mandrel 66 having a 6hape - corresponding to the inf lated unstretched shape of the balloon 18, including the end sleeve section6 21,22, 5 generally as seen in profile in Fig. 1 and lOA. The dipping speed and time are adjusted to produce thin-walled balloons as referred to above. Each of the balloon blanks as thus formed also includes an end section S which extends from the sleeve 21 over the lO mandrel hanger generally as illustrated, and which subsequently is trimmed from the blank. The formed balloons are stripped from the respective mandrels by axial ~ t toward the distal end, whereby the proximal sleeve 21 and adjacent tapered portion 24, as 15 well as section 5, are stretched in ~ Pr as they slide over the much larger central portion of the mandrel on which the main balloon body portion 23 was formed, as illustrated schematically in Fig. lO~. This stretching of the proximal ends results in proximal end sleeves that 20 are not reliably of a sufficiently small inner ~l;i Pr to provide the desired snug fit of the balloon on the small outer lumen tubes 12 for facile formation of the nPCPF~ ry air-tight joint at this interface.
Accordingly, the production of the balloons preferably 25 includes reduction of the size of the proximal end sleeves after removal of the biil l onn~ from the casting mandrels .
Referring to Figs. llA-llE and 12, the section 5 and sleeve portion 21 of each balloon blank are mounted over 30 an internal mandrel 70 and secured in place by a collet 72. The balloon is stretched to a predetPrm;nPd length of the proximal sleeve section 21, as indicated by the arrow A in Fig. llA. The balloon then is held in the stretched state to maintain the desired sleeve length, as 35 by a hinged clamp 74 which engages the cone section 24 of the balloon, as in Fig. llB. The stretching causes the intervening sleeve to neck down to the desired reduced Wo 95/2~s60 2 diameter, as indicated in Figs. llA and llB. At this point the neck is in a stre6sed state. At least the sleeve section of the balloon is heated, as by an internal heater 76, 78 which i6 positioned with the 5 mandrel 70 (see Fig. llC), to an ~yLu~Llate temperature over an appropriate dwell time thereby relaxing the necked-down balloon material in its reduced size conf iguration . That is, the stress induced by the stretching is relieved. The balloon then i5 permitted to 10 cool to a normalizing temperature while in the reduced, n~,n c.~Ltssed configuration, as by turning off the power to the heater; see Fig. llD. This precludes subsequent elastic return of the sleeve portion 21 to its previous oversize ~ LLO~1 dimension. The balloon with the 15 reduced diameter proximal end sleeve 21 then is removed from the clamp and mandrel, and the end section S is trimmed off as in Fig. llE.
One ---h;~ni F'n for effecting the foregoing is illustrated in somewhat greater detail in Figs. 12-15. A
20 mandrel 70 is mounted in a support block 82 which is pivotally mounted to a fixed support 84 as by an appropriate pivot pin 86 located adjacent one end of the block 82, with the pivot pin offset from the mandrel 70.
The heating cable 78 extends through the mandrel 70 to a 25 pin shaped heating element 76. An intervening portion of the mandrel 70 has a bulbous section 88, with an annular outer surface 89 which tapers to smaller diameters toward the support block 82. The collet 72 is of an annular or washer" shape, having an internal surface which conforms 30 to the tapered surface of the mandrel. The clamp 74 compri6es two hinged mating halves def ining therebetween a truncated conical open section 90 i c~ting with a short small cylindrical section 92, which COLLta~ d generally to the configuration of the transitional 35 section 24 and desired sleeve section 21 of the balloons being processed.

2 7 ~?3~7~
Woss/2~6o P~IIIJ~3rIO~1CI

In operation, to practice the aforedescribed method, the clamp 74 is opened in preparation for receiving a balloon to be processed. The collet 72 is retracted toward the heater cable base block 82. The block 82 is 5 pivoted to an upper position (about 90 counterclockwise) in Fig. 14, to raise the mandrel/heater further from a support surface on which the - ^nts are mounted and thereby providing greater space for the following described r-nir~ tions. The distal end portion of a 10 balloon then is slid onto the mandrel unit 70, from the left end in Fig. 12, with the distal end portion of the sleeve section S over the enlarged section 88 and onto the tapered section 89. The collet 72 is then moved towards the enlarged section 88, to provide friction 15 clamping of the balloon end S between the inner surface of the collet and the outer tapered surface of the mandrel. The balloon is then stretched, e.g. manually by the operator, to the point where the tapered end section 24 will match up with the cavity defined by the sections 20 90 of the clamp halves, thereby suitably reducing the diameter of the neck or sleeve section 21. The heater cable base block 82 is closed, and the balloon is positioned with the tapered end section 24 mating into the cavity defined by the sections 90 of the clamp 25 halve6, with the sleeve section 6tretched over the intervening internal mandrel and heater 76. The clamp 74 then also is closed to retain the sleeve section of the balloon in the resulting 6tretched state. Internal to the balloon at this point is the heater coil 76, which

3 0 extends the entire length of the sleeve area and slightly into the balloon body area, as seen in Fig. 12.
Sl]hceq~l~ntly~ the heater is activated to thereby relax the necked down balloon material as described above.
Following heating and subsequent cooling, the clamp 74 is 35 opened and the collet 72 released, and the balloon is removed. The section S then is cut off. A distal end portion of the stretched sleeve al60 may be trimmed to _ _ _ _ , . _ . _ _ . _,,, Woss/2~s60 ~ ~ ~5~.~D P~l/U~ ~71C1 attain the desired length of sleeve 21 which now has the desired reduced inner diameter. The internal mandrel/heater may be utilized as the form ~or setting the size of the reformed sleeve section 21. By way of 5 more specific example, in a typical operation the sleeve portion 21 has been stretched to about 150% of its original length in this process, e.g., stretched from 0.5" to 0.75," to effect the desired reduction of the diameter of the neck in polyurethene bA 11 o~nC as 10 described hereinabove.
It will be appreciated that other gripping and stretching r- ' An;~mC may be utilized to effect the sleeve sizing method. For example, one and/or the other of the clamping r-~hAni~c 74 and 72,88 m2y be movable 15 toward and away from the other whereby the balloon blank may be clamped therein prior to stretching and then may be stretched by lateral movement of one or both of the clamping r - -hAn i ~ relative to the other .
Referring to Figs. 6 and 7, radiopaque marker 20 material is applied to the outer lumen 12 in a position to be adjacent the proximal end of the balloon in the final assembly. This permits the user to readily determine the location of the balloon by fluoroscopy or X-ray, as nP~cc~ry to attain maximum therapeutic 25 benefit. In a preferred ~ this marker is a thin short ring 94 of highly elastic metal such as nitinol, being the same material as the inner lumen. Use of the same metal for the marker and the lumen avoids any problems of ir- _tibility of rli~cimilAr metals, such as 30 electrokinetic corrosion of either element, while providing a highly radiopaque and therefore highly visible marker for the positioning of the IAB during use.
By using a thin short ring 94 of nitinol, e.g. .003"
thick and .075" long, the marker may be press-fit in 35 place in the outer lumen 12 and the compression of the lumen will hold the ring in place. The balloon is bonded over the outer lumen 12, preferably with the sleeve 21 of WO 95/25560 2 ~ 8 ~

the balloon over the marker ring 94, and is furled tightly over the inner lumen tube 14 as noted above. The high degree of elasticity of the ring permits the marker to deform in the process of packaging and insertion while assuring return to its nominal desired shape and size in use. Splitting the ring longitll~lin~l ~y so that it is discontinuous circumferentially, with the ends either spaced or overlapping as illustrated at 94a and 94b in Figs. 7A and 7B respectively, will enhance its hoop ~ ~ssibility by a resilient spring action and thus further complement the size reduction as well as flexibility of the catheter unit.
In a specific example of the preferred Rmho~ -nt of this invention, a nominal 8 Fr IAB catheter 10 was fabricated with an inner lumen tube 14 formed of a nitinol alloy tubing of Raychem Corporation designated Tinel Alloy BB formed of only nickel and titanium and only those trace elements naturally occurring in commercially available grades of those constituents. The tube 14 had a nominal inner r~ of . 0276", a nominal outer diameter of .0345", and a length of 32.775". The outer tube 12 was a coextrusion of 2363-55D Pellethane polyurethane (Dow 'h~mici~ Company, Nidland, MI) .002"
thick over Nylon 11 Besno (Elf Atochem, ph;l~d~rhi~, PA) . 006" thick, as described above, with a nominal inner diameter of .090" and a nominal outer diameter of .108".
The tip and guide wire used in the catheter were as described above, and the balloon was of . 003 " nominal thickness. The balloon was furled to a diameter of .118"
and could relax to about .124" diameter in its packaging sheath .
Testinq Rink tests and stiffness tests were conducted on inner and outer lumens and the combination of the two as described above, with only slightly different ~ n~:.
The nitinol inner lumens tested had an inner diameter of , _ _ _ _ _ _ _ .. , . . . _ . _ ... .. ... .. . _ wo 9sl25560 2 1 ~ ~ 92 0 PCTIUS95/03464 .0283" + .0003" and an outer diameter of .0347" + .0003.
The coextruded outer lumens had a nominal inside diameter of . 090" and a nominal outside diameter of .106" . Crush tests also were cl~n~ rted on various outer lumens.
The kink tests utilized a template having multiple circles imprinted thereon, all with a common tangent point. The circles were 2", 1~", 13~", 1%", 1", %" and 3~"
in diameter. An appropriate length of each tubing being tested was formed into a larger loop and held against the template with the ends crossing and tangent to the circles at the af orenoted common tangent point . While maintaining this relationship to the template, one end of the looped tube was pulled to gradually reduce the loop diameter until the sample kinked. The diameter, also in inches, at which kinking occurred was recorded. When the tubing kinked between two circles, the average of those two circles was used as the kink diameter for calculations. In the case of outer lumen tubes, notes also were made of whether the kinking oc- uLl~d guickly, moderately or slowly.
After ~Y~m;n;n~ a variety of potential 8 Fr outer lumens, seven coextrusions of polyurethane over nylon were tested, along with one 9 Fr outer lumen as described above for comparison ~uL~oses, using five samples of each. The following table reflects the average diameter, in inche6, at which kinking oc~ ull.:d in each of these seven prospective outer lumens, the nature of the kinking action, and the average diameter, also in inches, at which the combination of the respective outer lumen tube 3 0 and a nitinol inner lumen as described above kinked:

WO9S125~60 2185920 r~"~ 161 OUTEF~ LUIEN ONLY CO~18INED
Lumen-Coextruslon Material~ Diameter Notes Diameter a. .003" nylon, .005" polyurethi~ne 1.38 ~soderilte 1.5 b. .005" nylon, 003 n polyureth~ne l.53 Quickly l.6 5c. .004" nylon, .004" polyurethime 1.65 Quickly 1.75 d. .001" nylon, .007" polyureth~ne 1.0 Quickly 1.15 . .002" nylon, 006n polyurethAne 1.05 Slowly 1.3 . 004" nylon, 004" polyurethane 1.73 Quickly 1.33 (wLth b~rium ~ulf~te) g. .006 nylon, .002" polyurethime 1.18 Quickly 1.33 The 9 Fr outer lumen tubes were of the af oredescribed current commercial design, being polyurethane tubes with an inner rlii ~Pr of about .101" and an outer fi;; Pr of 15 about .122". The average first kinking ~i;, Pr for the 9 Fr outer lumen tubes was 1", and they kinked "slowly".
The three outer lumens with the best kink test results, namely coextrusions d, e and g, also were tested for crush resistance in hemovalves. The ~ue~LLusion g 20 provided the best re5istance to crushing by the valves.
Further samples of- the construction g, namely coa~,..sion tubes of .002" polyurethane around .006"
nylon, were subjected to further comparative tests with samples of the aforedescribed 9 Fr catheter lumen tubes, 25 singly and in combination of the respective inner and outer lumen tubes. The average kink diameters in inches were as follows:
New 8 Fr Current 9 Fr Inner Lumen Tube* Less than 0 . 5 Less than 0 . 5 30 Outer Lumen Tube 1. 35 1.15 Combination of the Above 1.19 1.15 * The nitinol tubes tested ; nrl~ ed both extruded tubes and drawn and r~l~h;nPd tubes, with the results being substantially the same.

Thirty samples each of the new inner and outer lumen tubes and ten each of the inner and outer tubes of the current design were subjected to stiffne55 tests, bûth Wo ss/2ss60 2 ~ ~ 9 2 ~ C 1 individually and with the respective inner and outer tubes assembled together, using a Tinius Olsen stiffness tester. The bending moments were calculated and used for comparisons. Since the areas of the 8 Fr and 9 Fr parts 5 were different, the values were normalized by multiplying the 9 Fr results by the ratios of their areas. Selected comparison angles were chosen within the following parameters~ All samples achieved the angle; and (2) the test data had not started to decline, i.e., no 10 indication of a kink forming in the sample. The average values in inch-pounds were as follows:
Bending Moment Inner Lumen at 57 Degrees 15New Inner Lumen o . 265 Current Inner Lumen 0. 014 Bending Meoment Outer Lumen at 2 7 Degrees 20New Outer Lumen 0.168 Current Outer Lumen 0 . 075 Bending Moment Bending Moment Combined Lumen at 69 Degrees at 57 Degrees 25New Outer/Inner Lumen 0 . 433 0 . 413 Current OutertInner Lumen 0.115 0.144 It will be seen that the constructions in accordance 30 with this invention attained the desired size reduction, while providing good kink resistance and attendant ihi 1 ity and increased stiffness.
Thin-walled balloons as alluded to above also were tested for operational strength, using thirty sample 35 uncoated balloons with an average measured thickness of .0033" (range of .003" to .004") and thirty such blllonn~
with a hydrophilic coating and therefor having an average measured thickness of .0037" (range of .003" to .004").

Claims (36)

WHAT IS CLAIMED IS:

1. An intra-aortic balloon pump catheter device including a vascular catheter and a large flexible pump balloon mounted on said catheter for insertion by said catheter into and through the vascular system of a patient and into the patient's aorta for repetitious pulse-rate inflation of said balloon over an extended time-span to assist the blood-pumping function of that patient's heart; said catheter including an inner lumen, and an outer lumen formed of an annular nylon portion and an outer annular portion of polyurethane, and the wall thickness of said outer lumen tube being about .006" or less and said outer lumen surrounding said inner lumen and communicating with said balloon for shuttling gas to and from said balloon in the annular space between said inner and outer lumens to inflate and deflate said balloon at said pulse-rate.

2. The invention as in claim 1 wherein said inner lumen is a thin-walled superelastic metal alloy tube.

3. The invention as in claim 1 wherein said inner lumen is a thin-walled nitinol tube.

4. The invention as in any preceding claim wherein said metal tube is about .0035" or less.

5. Cancelled

6. Cancelled

7. The invention as in claim 6 wherein said balloon is furled and said catheter is of a nominal 8 French size or smaller.

8. The invention as in claim 1 wherein said balloon is furled and said catheter is of a nominal 8 French size or smaller.

9. The invention as in claim 1 wherein said balloon is furled and no part of said catheter and furled balloon to be inserted into the vascular system of a patient has a cross-sectional dimension greater that about 0.124 inches.

10. The invention as in claim 1 wherein said inner lumen extends through said balloon generally along the longitudinal axis of said balloon; a plastic ferrule affixed to said inner lumen at the distal end of said balloon; and the distal end of said balloon being heat welded to the external surface of said plastic ferrule.

11. The invention as in claim 10 wherein the proximal end of said balloon is heat welded to the external surface of said outer lumen.

12. The invention as in claim 11 wherein said balloon, said ferrule and at least the outer surface portion of said inner lumen are formed of materials having substantially the same melting points.

13. The invention as in claim 12 wherein each of said ferrule, outer surface portion of said outer lumen and said balloon is formed of a polyurethane.

14. The invention as in claim 1 wherein said outer lumen is formed of an annular nylon portion and an outer annular portion of polyurethane.

15. The invention as in claim 1 wherein said inner lumen is a thin-walled nitinol tube, and including a ring of nitinol affixed to said outer lumen near the proximal end of said balloon.

16. The invention as in claim 15 wherein said ring is press fit within said outer lumen.

17. The invention as in claim 15 wherein said ring is discontinuous circumferentially.

18. An intra-aortic balloon pump catheter device including a vascular catheter and a large flexible pump balloon mounted on said catheter for insertion by said catheter into and through the vascular system of a patient and into the patient's aorta for repetitious pulse-rate inflation of said balloon over an extended time-span to assist the blood-pumping function of that patient's heart; said catheter including an inner lumen formed by a highly elastic thin-walled metal tube defined by a continuous metal wall; and an outer lumen surrounding said inner lumen and communicating with said balloon for shuttling gas to and from said balloon in the annular space between said inner and outer lumens to inflate and deflate said balloon at said pulse-rate, said outer lumen being a tube formed of at least two coextruded layers of different plastic materials.

19. The invention as in claim 18 wherein the inner layer of said outer lumen tube is a plastic having a high compressive strength and the outer layer thereof is a biocompatible plastic.

20. The invention as in claim 18 wherein said outer lumen includes at least one annular layer formed of nylon.

21. The invention as in claim 18 wherein said outer lumen is formed of an annular nylon layer and an outer layer of polyurethane over said nylon layer.

22. The invention as in claim 21 wherein said nylon layer is of substantially greater radial thickness than said polyurethane layer.

23. The invention as in claim 22 wherein said nylon layer is at least twice as thick as said polyurethane layer.

24. The invention as in claim 21 wherein said inner lumen is a thin-walled nitinol tube.

25. A method of forming intra-aortic balloons for assembly in vascular catheter systems comprising the steps of forming a balloon from a balloon blank such that a sleeve section remains at one end following formation of the balloon, stretching such sleeve section longitudinally to reduce the diameter thereof, heating said stretched sleeve section to relieve the stress in said sleeve section while so stretched, and cooling said sleeve section, thereby to preserve said sleeve section in its reduced diameter state.

26. The invention as in claim 25 wherein said balloon blank is formed of plastic by dip casting on a mandrel.

27. The invention as in claim 25 including the steps of forming said balloon blank by dip casting a plastic material on a mandrel with said sleeve section being formed on said mandrel at one end of said blank, and removing said blank from said mandrel by axial sliding over said mandrel in a direction wherein said sleeve section is stretched over said mandrel in the course of such removal.

28. The invention as in claim 25 wherein said stretching step is carried out by gripping a first portion of said balloon blank at the distal end of said sleeve section, gripping a second portion of said balloon blank at the opposite end of said sleeve section, and moving at least one of said gripped portions away from the other.

29. The invention as in claim 28 wherein said first portion is gripped between an internal mandrel and a surrounding clamp, and said second portion of said balloon is gripped in a clamp.

30. The invention as in claim 29 wherein stretching step is carried out prior to engagement of said second portion in said clamp.

31. The invention as in claim 29 wherein said stretching step is carried out by moving one of said mandrel and said clamp away from the other after said balloon portions are gripped therein.

32. The invention as in claim 28 and including positioning a heating element within said sleeve portion, and wherein said heating step is effected by said heating element from within said sleeve portion.

33. The invention as in claim 25 and wherein said heating step is effected by a heating element disposed interiorly of said sleeve portion.

34. Apparatus for reforming a sleeve section of a plastic balloon having a fully formed balloon section, comprising a mandrel for insertion into such a sleeve section portion of a balloon, a first clamp for gripping an end portion of such a sleeve section against the external surface of said mandrel, a second clamp spaced from said first clamp for gripping a portion of such a balloon spaced from said end portion and retaining said section in a stretched, unexpanded condition between said first and second clamps to elastically reform said section, and at least one heating component disposed to heat said sleeve section of said balloon while so stretched to relieve the stress therein while said balloon section remains unstretched whereby said sleeve section will retain the reformed configuration following release from said apparatus.

35. The invention as in claim 34 wherein said first clamp is a collet.

36. The invention as in claim 34 wherein said mandrel includes a heating element therein disposed to traverse such section of a balloon while so stretched in said apparatus, for heating said balloon portion.