Stent for biliary, urinary or vascular system

• US 5,466,242 A
• Filed: 02/02/1994
• Issued: 11/14/1995
• Est. Priority Date: 02/02/1994
• Status: Expired due to Fees

• Current Assignee: Field Point Partners Sbic, L.P.
• Original Assignee: Katsushi Mori
• Inventors: Mori, Katsushi
• Primary Examiner(s): Pellegrino, Stephen C.
• Assistant Examiner(s): MULCARE, NANCY C
• Application Number:
  US08/190,303
• Time in Patent Office: 650 Days
• Field of Search: 606/198, 606/200, 606/191, 623/1, 623/12
• US Class Current: 606/198
• CPC Class Codes: A61F 2/88 the wire-like elements formed as helical or spiral coils forming a net-like or mesh-like structure A61F2/90
• CPC Class Codes: A61F 2002/041 Bile ducts
• CPC Class Codes: A61F 2210/0019 operated at only one temperature whilst inside or touching the human body, e.g. constrained in a non-operative shape during surgery, another temperature only occurring before the operation
• CPC Class Codes: A61F 2230/0067 conical

Abstract

A stent is made of shape memory alloy which has an Austenite finished temperature ranging from 41° C. to 43° C. The stent is capable of adopting a first configuration at a temperature below the Af and a second expanded configuration at or above the Af. In the first configuration, the stent comprises a proximal cylindrical portion, a distal cylindrical portion. The two portion are connected with an interspace therebetween. At the Af temperature the stent is reoriented, and at and above the Af temperature the proximal portion flares into a funnel conical shape expanding in maximum diameter and decreasing in diameter toward the distal portion. The distal cylindrical portion also expands in diameter, and the two portions directly connect with each other without the interspace. A method of placing the stent in position comprises inserting the stent in the first configuration into a system and subsequently raising the temperature of the stent to or above its Af temperature so that the stent assumes the second expanded configuration.

Claims

1. A stent for a biliary, urinary or vascular system, the stent being made of a shape memory alloy having an Austenite finished temperature ranging from 41°

to 43°

C. and having a first configuration at a temperature below the Austenite finished temperature and a second expanded configuration at or above the Austenite finished temperature and wherein in the first configuration, a proximal cylindrical portion (1), a distal cylindrical portion (2) and an interspace (3) connecting the two portions (1 ,2) therebetween, through which a portion of a catheter is bulged out to facilitate positioning of the stent in the system, and in the second configuration, the distal portion (2) expands in diameter, the proximal portion (1) is flared away from the expanded distal portion (2), and the interspace (3) is reduced to be absorbed into a shape directly combining the portions (1,

     2) so that the stent becomes funnel-shaped to be reliably anchored by the flared proximal portion (1) after the positioning.

2. A stent according to claim 1 wherein the proximal portion (1) and the distal portion (2) are both in a coiled shape.

3. A stent according to claim 1 wherein the proximal portion (1) and the distal portion (2) are made of mesh.

4. A stent according to claim 1 wherein in the first configuration the cross section of the cylindrical portion (1, 2) is ellipsoidal or circular.

5. A stent according to claim 1, wherein in the first configuration the length of the distal portion (2) is longer than that of the proximal portion (1).

6. A stent according to claim 1 wherein in the first configuration the cross section of the cylindrical portion is circular.

7. A stent according to claim 1, wherein in the first configuration the interspace (3) includes a straight wire portion (4) by which the proximal cylindrical portion (1) and the distal cylindrical portion (2) are connected together.

8. A method of locating a stent in a desired position in a biliary, urinary or vascular system, the method comprising:

mounting a stent on an inflatable catheter, said stent being made of a shape memory alloy having an Austenite finished temperature ranging from 41°

C. to 43°

C. and having a first configuration at a temperature below the Austenite finished temperature and a second expanded configuration at or above the Austenite finished temperature, said stent further having in the first configuration a proximal portion, a distal portion and an interspace therebetween;

inserting the catheter carrying the stent into the system;

inflating the catheter at least at or near the interspace of the stent so that a portion of the inflated catheter is bulged out through the interspace to facilitate accurate positioning of the stent; and

raising the temperature of the stent so that the stent assumes its second expanded funnel-shaped configuration to be reliably retained after the positioning.

9. A method according to claim 8 wherein the catheter carrying the stent is inserted into the system in a way that the proximal portion and the interspace of the stent are passed over a narrow segment, and the inflated catheter is accurately positioned by being pulled outwardly until the inflated portion thereof comes to abut against the narrow segment.