Method of Uniform Crimping and Expansion of Medical Devices

• US 20140096357A1
• Filed: 10/04/2012
• Published: 04/10/2014
• Est. Priority Date: 10/04/2012
• Status: Active Grant

• Current Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories)
• Original Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories)
• Inventors: Wang, Yunbing
• Granted Patent: US 9,724,219 B2
• Time in Patent Office: Days
• US Class Current: 29/446
• CPC Class Codes: A61F 2/91 made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes
• CPC Class Codes: A61F 2/9522 Means for mounting a stent or stent-graft onto or into a placement instrument
• CPC Class Codes: A61F 2/958 Inflatable balloons for placing stents or stent-grafts
• 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: A61M 25/1025 Connections between catheter tubes and inflation tubes
• CPC Class Codes: B23P 11/00 Connecting or disconnecting metal parts or objects by metal-working techniques not otherwise provided for connecting sheet metal or metal tubes, rods or profiles B21D39/00; riveting B21J; soldering, unsoldering, welding B23K; hand tools for connecting wire or strip B25B25/00; connecting metal parts by adhesives F16B11/00
• CPC Class Codes: Y10T 29/49863 with prestressing of part

Abstract

A medical device-includes a scaffold crimped to a catheter having an expansion balloon. The scaffold is crimped to the balloon by a process that includes one or more balloon pressurization steps. The balloon pressurization steps are selected to enhance scaffold retention to the balloon, maintain a relatively uniform arrangement of balloon folds about the inner surface of the crimped scaffold so that the scaffold expands in a uniform manner when the balloon is inflated, and to avoid any possible over-stretching of balloon material.

Claims

1. A method for crimping a medical device to a balloon having pre-made folds forming pleats in a compact form, comprising the steps of:

fully or over inflating the balloon including maintaining the balloon in a fully or over inflated state for a period of time sufficient to remove all pre-made folds in the balloon;

placing the medical device over the balloon; and

while the balloon has the fully or over inflated state, performing a first crimping of the medical device to the balloon, wherein the medical device diameter is reduced to about 50% of the medical device'"'"'s original diameter after the first crimping step;

reducing the pressure in the balloon; and

while the balloon has a reduced pressure performing a second crimping of the medical device to the balloon, wherein the medical device diameter is reduced from its about 50% of the medical device'"'"'s original diameter to a final crimping diameter.

2. The method of claim 1, wherein the medical device is a polymeric scaffold or a stent made from a metal, metal alloy, bio-erodible metal or metal alloy or including a metal in the material used to make the stent.

3. The method of claim 2, wherein the polymeric scaffold'"'"'s original diameter is larger than the balloon diameter when the balloon has the fully or over inflated state.

4. The method of claim 3, wherein there is at least one and no more than three dwell periods during the first and second crimping steps and wherein the balloon has the fully or over inflated state for all of the first crimping step and a portion of the second crimping step.

5. The method of claim 3, wherein the polymeric scaffold inner diameter prior to crimping is between about 109-116% of the balloon diameter when the balloon has the fully or over inflated state.

6. The method of claim 1, wherein after the first crimping and prior to the second crimping, further including the step of removing the medical device from a crimping device, checking alignment, then returning the medical device to the crimping device to perform the second crimping step.

7. The method of claim 1, wherein the medical device diameter is reduced down an additional 40% after the first crimping step.

8. The method of claim 1, wherein medical device'"'"'s original diameter is about equal to, or less than the balloon diameter when the balloon has the fully or over inflated state.

9. The method of claim 1, wherein the balloon is maintained at a consistent pressure for substantially all of the combined first and second crimping steps.

10. The method of claim 9, wherein the balloon is maintained at a consistent pressure until the about 50% reduction in the medical device diameter, after which the balloon pressure is reduced to about 80% of the fully or over inflated balloon pressure or a one atmosphere (atm) pressure, followed by a reduction to about zero pressure in the balloon for a final dwell period.

11. A method for making a medical device, comprising the steps of:

providing a scaffold formed from a radially-expanded tube comprising PLLA characterized by a glass transition temperature range having a lower limit of about TG-low, the scaffold having a pre-crimp diameter that is greater than a first diameter;

placing the scaffold on a balloon;

inflating the balloon until the balloon is fully or over inflated, wherein the fully or over inflated balloon has the first diameter; and

using a crimping device, crimping the scaffold to the balloon, including

while the scaffold has a crimping temperature of between about TG-low and 15 degrees below TG-LOW and the balloon has the first diameter, reducing the scaffold inner diameter to about the first diameter,

when the scaffold has the first diameter, removing the balloon and scaffold from the crimping device to verify alignment between balloon markers,

returning the scaffold to the crimping device, and

further reducing the scaffold diameter while the balloon is fully inflated.

12. The method of claim 11, wherein the further reducing the scaffold diameter step includes the steps of reducing the scaffold diameter to about 50% of the pre-crimp diameter.

13. The method of claim 12, wherein the further reducing the crimping step includes reducing the balloon pressure for a dwell period, removing substantially all balloon pressure, then without balloon pressure reducing the scaffold diameter down to a final crimp diameter.

14. The method of claim 13, wherein the balloon is further reduced down from the about 50% of the pre-crimp diameter to about 30% of the pre-crimp diameter to arrive at a final crimp diameter.

15. The method of claim 11, wherein the scaffold diameter is reduced in diameter by about 10% when the scaffold diameter is reduced to the first diameter.

16. The method of claim 11, wherein the crimping temperature is about 48°

C.

17. The method of claim 11, wherein prior to reducing the scaffold diameter to a first diameter and a heating the scaffold to the crimping temperature,

fully or over inflating the balloon to remove pre-made folds forming pleats of the balloon so that when deflated the balloon will not re-form one or more pleats.

18. A method for crimping a medical device to a balloon, comprising the steps of:

placing the medical device over a first balloon which is in a fully or over inflated state, the medical device having a first diameter, wherein when the first balloon is in the fully or over inflated state the balloon outer diameter is the same as, or slightly greater than the first diameter; and

while the first balloon has the fully or over inflated state, performing a first crimping of the medical device to the balloon, wherein the medical device diameter is reduced to a second diameter after the first crimping step; and

performing a second crimping of the medical device, wherein the medical device diameter is reduced to a third diameter after the second crimping step.

19. The method of claim 18, wherein the second crimping of the medical device includes reducing the diameter of the medical device to the third diameter in a crimping device while the first balloon has the fully or over inflated state, followed by

reducing the pressure in the first balloon for a dwell period,

removing substantially all pressure in the first balloon, then

reducing the medical device diameter from the third diameter to a final crimp diameter.

20. The method of claim 18, wherein the medical device diameter is reduced down from the first diameter to the final crimp diameter without removing the medical device from a crimping device.

21. A method for crimping a medical device to a balloon having prearranged pleats folded into a compact form, comprising the steps of:

placing the medical device over a fully or over inflated first balloon, the medical device having a first diameter, wherein when the first balloon is in the inflated or over inflated state the balloon outer diameter is the same or slightly greater than the first diameter;

using a crimping device, crimping the medical device from the first diameter to a second diameter while the first balloon has the fully or over inflated state;

removing the medical device from the crimping device;

replacing the first balloon with a second balloon having a fully or over inflated diameter about equal to the second diameter, wherein the second balloon is a balloon of a delivery system for the medical device;

placing the medical device and second balloon into the crimping device while the second balloon has the fully or over inflated diameter; and

crimping the medical device to the second balloon.