Stent delivery system using shape memory retraction

• US 20010012944A1
• Filed: 03/27/2001
• Published: 08/09/2001
• Est. Priority Date: 10/01/1997
• Status: Active Grant

• Current Assignee: Boston Scientific Scimed (Boston Scientific Corporation)
• Original Assignee: Andrew D. Bicek, Anthony C. Vrba, Lance A. Monroe, Steven E. Walak
• Inventors: Walak, Steven E., Vrba, Anthony C., Monroe, Lance A., Bicek, Andrew D.
• Granted Patent: US 6,579,297 B2
• Time in Patent Office: Days
• US Class Current: 606/108
• CPC Class Codes: A61F 2/95 Instruments specially adapted for placement or removal of stents or stent-grafts
• CPC Class Codes: A61F 2/966 with relative longitudinal movement between outer sleeve and prosthesis, e.g. using a push rod
• CPC Class Codes: A61F 2002/9583 Means for holding the stent on the balloon, e.g. using protrusions, adhesives or an outer sleeve
• CPC Class Codes: A61F 2210/0023 operated at different temperatures whilst inside or touching the human body, heated or cooled by external energy source or cold supply

Abstract

The inventive stent delivery system includes a catheter having a retractable outer sheath near its distal end. A shape memory contraction member having a memorized contracted shape is connected to the retractable outer sheath. A heat generating device connected to the shape memory contraction member causes the shape memory contraction member to heat up to its transition temperature and assume its contracted position, retracting the retractable outer sheath. Another embodiment utilizes 2 springs, a “normal” spring and a shape memory alloy (SMA) spring, the two springs selected and designed so that the “normal” has an expansion force which is less than SMA spring when the SMA spring is austenitic, but greater than the SMA spring when the SMA spring is martensitic. Yet another embodiment utilizes a shape memory latch which in its martensitic state abuts a stop to prevent a spring from moving the sheath proximally, but in its austenitic state releases the stop, allowing the spring to retract the sheath to release the stent for deployment.

Claims

1. A catheter comprising:

a catheter body having proximal and distal ends and including a retractable outer sheath near the distal end of the catheter body;

a shape memory retraction device having a first state above a predetermined temperature and a second state below the predetermined temperature, the shape memory retraction device operatively connected to the retractable outer sheath and being constructed and arranged so that in the first state the retractable outer sheath is in an undeployed state and in the second state the retractable outer sheath is in a deployed state.

2. The catheter of

claim 1

wherein the first state of the shape memory retraction device is austenitic.

3. The catheter of

claim 1

wherein the first state of the shape memory retraction device is martensitic.

4. The catheter of

claim 2

wherein the shape memory retraction device comprises a first “

normal”

spring portion connected to the retractable outer sheath to provide a proximal retraction force, and a second shape memory alloy spring portion connected to the retractable outer sheath to provide a distal opposing force, the first and second spring portions being selected and designed so that the proximal retraction force is less than the distal opposing force when the second shape memory alloy spring portion is in its austenitic state, but where the proximal retraction force is greater than the distal opposing force when the second shape memory alloy spring portion is in its martensitic state.

5. The catheter of

claim 3

wherein the shape memory retraction device comprises a first “

normal”

spring portion connected to the retractable outer sheath to provide a distal opposing force, and a second shape memory alloy spring portion connected to the retractable outer sheath to provide a proximal retraction force, the first and second spring portions being selected and designed so that the proximal retraction force is less than the distal opposing force when the second shape memory alloy spring portion is in its martensitic state, but where the proximal retraction force is greater than the distal opposing force when the second shape memory alloy spring portion is in its austenitic state.

6. The catheter of

claim 1

wherein the shape memory retraction device is comprised of a spring connected to the retractable outer sheath to provide a proximal retraction force and a second shape memory device connected to the catheter body and having first and second states, the second shape memory device in its first state being operatively connected to the retractable outer sheath to prevent the retraction of the outer sheath, and in its second state releases the retractable outer sheath so that the spring may retract the sheath to its deployed state.

7. The catheter of

claim 1

wherein the second shape memory device is comprised of a latch connected to the catheter body, the shape memory latch in its first state being operatively connected to the retractable outer sheath to prevent the retraction of the outer sheath, and in its second state releases the retractable outer sheath so that the spring may retract the sheath to its deployed state.

8. The catheter of

claim 7

wherein the first state of the shape memory latch is martensitic.

9. The catheter of

claim 8

wherein the retractable outer sheath includes a stop which extends proximally to abut the shape memory latch when it is in its martensitic state.

10. The catheter of

claim 7

wherein the shape memory latch is softened in its second state to release the retractable outer sheath.