Stent installation method using balloon catheter having stepped compliance curve

• US 5,980,532 A
• Filed: 09/16/1997
• Issued: 11/09/1999
• Est. Priority Date: 03/02/1995
• Status: Expired due to Term

• Current Assignee: Boston Scientific Scimed (Boston Scientific Corporation)
• Original Assignee: Scimed Life Systems Incorporated (Boston Scientific Corporation)
• Inventors: Wang, Lixiao
• Primary Examiner(s): Buiz, Michael
• Assistant Examiner(s): Ho, (Jackie) Tan-Uyen T.
• Application Number:
  US08/931,190
• Time in Patent Office: 784 Days
• Field of Search: 606/108, 606/194, 606/192, 606/198
• US Class Current: 623/1.11
• CPC Class Codes: A61F 2/958 Inflatable balloons for placing stents or stent-grafts
• CPC Class Codes: A61F 2250/0039 differing in diameter
• CPC Class Codes: A61M 2025/1059 having different inflatable sections mainly depending on the response to the inflation pressure, e.g. due to different material properties with different compartments A61M2025/1072
• CPC Class Codes: A61M 2025/1075 having a balloon composed of several layers, e.g. by coating or embedding
• CPC Class Codes: A61M 25/10 Balloon catheters A61M25/0125 takes precedence; embolectomy A61B17/22032; retractors A61B17/02; inflatable balloons for placing stents or stent-grafts A61F2/958 ; stomach balloons for treatment of obesity A61F5/0003; oesophagal tubes A61J15/00
• CPC Class Codes: A61M 25/1002 characterised by balloon shape A61M25/1006, A61M25/1009 take precedence
• CPC Class Codes: A61M 25/1029 Production methods of the balloon members, e.g. blow-moulding, extruding, deposition or by wrapping a plurality of layers of balloon material around a mandril
• CPC Class Codes: A61M 25/104 used for angioplasty

Abstract

A method for installing a stent in a vessel utilizes a single balloon catheter for both low pressure predilation at a relatively small diameter to open the lesion sufficiently to allow insertion and deployment of the stent across the lesion and for subsequent high pressure embedding of the stent in the vessel wall. The same balloon catheter may also be employed to insert and deploy the stent. The balloons utilized in the method have a stepped compliance curve which allows for predilation at a low pressure and predetermined diameter and for high pressure embedding at a substantially larger diameter. The balloons may be provided with a configuration in which only a portion of the balloon has a stepped compliance curve while a further portion has a generally linear compliance profile. With such balloons high pressure treatment of the vessel wall areas not reinforced by the stent can be avoided despite the occurence of longitudinal shrinkage of the stent during expansion thereof.

Claims

1. A method for introducing a stent into a vessel at a lesion site, the method comprising the steps of:

first, introducing into the vessel a catheter carrying a balloon on a distal end thereof so that the balloon crosses the lesion and pre-dilating the lesion by inflating the balloon to a predetermined first diameter, and then withdrawing the catheter,

second, introducing into the vessel a catheter carrying a stent and on a distal end thereof so that the stent crosses the lesion and then deploying the stent and further dilating the lesion to a second diameter greater than said first diameter;

third, introducing into the vessel a catheter carrying a low-compliance balloon on a distal end thereof so that the balloon is positioned within the deployed stent and post-dilating with the low-compliance balloon to a third diameter greater than or equal to said second diameter at a pressure substantially higher than the pressure of said further dilation, so that the stent is embedded in the vessel wall at the lesion site,

wherein;

the catheter used in said first and third steps are the same, at least a portion of the balloon carried thereon has a compliance curve which has a stepped profile characterized by a first generally linear low pressure segment of the compliance curve and a second generally linear higher pressure segment of the curve, the two regions being non-collinear so that linear extension of each segment into the pressure range of the other would diverge by at least 0.25 mm, the predetermined first diameter is on the first segment of the stepped profile compliance curve and the third diameter is on the second segment of the stepped profile compliance curve.

2. The method of claim 1, wherein said stepped compliance curve is provided on only a portion of the balloon, the remainder of the balloon having a generally linear compliance curve.

3. The method of claim 1 wherein the balloon portion having said stepped compliance curve is a central portion located between two side portions, each said side portion having a generally linear compliance curve.

4. The method as set forth in claim 1 wherein the balloon having said stepped compliance curve is made of a thermoplastic polymer selected from the group consisting of high strength polyester, nylons, thermoplastic polyimides and high strength engineering thermoplastic polyurethanes.

5. A method as set forth in claim 4 wherein the balloon having said stepped compliance curve is made of a polyester selected from poly(ethylene terephthalate) and poly(ethylene napthalenedicarboxylate).

6. A method as in claim 1 wherein the high pressure segment of said stepped compliance curve provides an expansion rate of no more than 0.1 mm/atm from 15 atm to burst.

7. A method as in claim 6 wherein the high pressure segment of said stepped compliance curve provides an expansion rate of no more than 0.06 mm/atm from 15 atm to burst.

8. A method as set forth in claim 1 wherein the balloon having said stepped compliance curves has a wall strength of at least 18,000 psi.

9. A method as in claim 8 wherein said wall strength is greater than 20,000 psi.

10. A method as in claim 1 wherein said balloon is a single tubular element mounted on said catheter.

11. A method as in claim 1 wherein said balloon comprises two coextensive tubular elements of different nominal diameter mounted coaxially on said catheter.

12. A method for introducing a stent into a vessel at a lesion site, the method comprising the steps of:

first, introducing into the vessel a catheter carrying a balloon on a distal end thereof so that the balloon crosses the lesion and pre-dilating the lesion by inflating the balloon to a predetermined first diameter, and then withdrawing the catheter,

second, mounting a stent on said catheter over said balloon and reintroducing the catheter into said vessel and on a distal end thereof so that the stent crosses the lesion and then deploying the stent and further dilating the lesion by inflating said balloon to a second diameter greater than said first diameter and pressurizing the balloon to a pressure sufficient to embedded the stent in the vessel wall at the lesion site, the method further characterized in that

at least a portion of said balloon has a compliance curve which has a stepped profile characterized by a first generally linear low pressure segment of the compliance curve and a second generally linear higher pressure segment of the curve, the two regions being non-collinear so that linear extensions of each segment into the pressure range of the other would diverge by at least 0.25 mm, the predetermined first diameter is on the first segment of the stepped profile compliance curve and the second diameter is on the second segment of the stepped profile compliance curve.

13. The method of claim 12 wherein said stepped compliance curve is provided on only a portion of the balloon, the remainder of the balloon having a generally linear compliance curve.

14. The method of claim 12 wherein the balloon portion having said stepped compliance curve is a central portion located between two side portions, each said side portion having a generally linear compliance curve.

15. The method as set forth in claim 12 wherein the balloon having said stepped compliance curve is made of a thermoplastic polymer selected from the group consisting of high strength polyesters, nylons, thermoplastic polyimides and high strength engineering thermoplastic polyurethanes.

16. A method as set forth in claim 15 wherein the balloon having said stepped compliance curve is made of a polyester selected from poly(ethylene terephthalate) and poly(ethylene napthalenedicarboxylate).

17. A method as in claim 12 wherein the high pressure segment of said stepped compliance curve provides an expansion rate of no more than 0.1 mm/atm from 15 atm to burst.

18. A method as in claim 17 wherein the high pressure segment of said stepped compliance curve provides an expansion rate of no more than 0.06 mm/atm from 15 atm to burst.

19. A method as set forth in claim 12 wherein the balloon having said stepped compliance curve has a wall strength of at least 18,000 psi.

20. A method as in claim 19 wherein said wall strength is greater than 20,000 psi.

21. A method as in claim 12 wherein said balloon is a single tubular element mounted on said catheter.

22. A method as in claim 12 wherein said balloon comprises two coextensive tubular elements of different nominal diameter mounted coaxially on said catheter.

23. A method for using a balloon attached to a catheter to place and implant a stent in a bodily vessel, the balloon including a portion having a low pressure diameter and a non-linear compliance curve having a compliant range and a higher pressure non-compliant range, the stent surrounding the balloon, comprising the steps of

pressurizing the balloon to a first inflation pressure to inflate the balloon portion beyond its low pressure diameter, the balloon portion increasing in diameter to a first predetermined diameter in the compliant range along the compliance curve corresponding to the first inflation pressure, and in so doing expanding the stent to a first stent diameter in which the stent is placed in the bodily vessel;

and

increasing the pressure applied to the balloon to a second inflation pressure sufficient to cause the balloon portion to increase further in diameter to a second predetermined diameter in the higher pressure non-compliant range corresponding to the second inflation pressure, whereby the diameter of the stent is expanded post-placement to implant the stent in the bodily vessel.

24. A method for placing and implanting a stent in a bodily vessel using a balloon catheter with the stent mounted on the catheter over balloon in uninflated state, the stent having an initial stent diameter, the balloon including a body portion having a low pressure diameter and a non-linear compliance curve defined by the expansion of said balloon portion from said low pressure diameter to burst as the inflation pressure is increased, the compliance curve including a first pressure range in which said balloon body portion expands a first expansion rate and a second pressure range in which said balloon body portion expands at a second expansion rate lower the first rate, the second pressure range defining a segment of the compliance curve of higher pressures than the first pressure range, the method comprising the steps of

inserting the catheter into the body vessel and manipulating the catheter to locate the balloon and stent at a site for stent placement;

pressurizing the balloon to inflate the balloon portion beyond its low pressure diameter at a high rate of expansion per atmosphere of pressure until a predetermined placement pressure is achieved whereby the stent is expanded to a second stent diameter; and

pressurizing the balloon to a third pressure, higher than the placement pressure, within the second pressure range and below the balloon burst pressure, whereby the diameter of the stent is expanded to a third stent diameter.

25. A process as in claim 24 wherein the second inflation pressure is above 12 atm.

26. A process as in claim 25 wherein the second inflation pressure is about 15 atm or higher.

27. A process as in claim 24 wherien the balloon is capable of inflation to at least 20 atm.

28. An assembly comprising

a) a catheter having a distal end,

b) an unexpanded inflatable balloon mounted near the distal end of the catheter and

c) a stent having an initial diameter mounted on the catheter over the balloon

wherein

the balloon has a wall strength of at least 18,000 psi,

the balloon includes a body portion having a low pressure diameter and a non-linear compliance curve defined by the expansion of said balloon portion from said low pressure diameter to burst as the inflation pressure is increased, the compliance curve including a first pressure range in which said balloon body portion expands at a first expansion rate and a second pressure range in which said balloon body portion expands at a second expansion rate lower the first rate, the second pressure range defining a segment of the compliance curve of higher pressures than the first pressure range,

the balloon has a strength effective to expand the stent to a second stent diameter at a first expansion rate as balloon pressure is increased through the first pressure range until a predetermined placement pressure corresponding to said second stent diameter is achieved, and

the balloon second pressure range encompasses a range of pressures which allows the stent to be further expanded at a second expansion rate, which is lower than the first expansion rate, to a third stent diameter larger than the second stent diameter.

29. An assembly as in claim 28 wherein the balloon is capable of inflation to a pressure of at least 20 atm.

30. An assembly as in claim 28 wherein the balloon has a wall strength of at least 20,000 psi.

31. An assembly comprising

a) a catheter having a distal end;

b) an unexpanded inflatable balloon mounted near the distal end of the catheter; and

c) a hollow expandable stent having an initial stent diameter, an initial stent length and a pair of ends, the stent being mounted on the catheter over the balloon, the stent being expandable by the balloon to a second stent diameter larger than the initial diameter,

wherein

the balloon has a portion which, when pressurized at a predetermined inflation pressure, expands the stent to said second stent diameter, and said balloon portion when pressurized at said predetermined inflation pressure has a length and position such that it does not extend beyond the ends of the stent at said second stent diameter.

32. An assembly as in claim 31 wherein the stent initial length shortens during expansion so that at said second stent diameter the stent has a second stent length shorter than said first stent length.