Methods for Crimping a Polymeric Scaffold to a Delivery Balloon and Achieving Stable Mechanical Properties in the Scaffold After Crimping
First Claim
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1. A method for crimping a balloon-expanded scaffold to a balloon, comprising the steps of:
- providing a tube comprising PLLA characterized by a glass transition temperature range having a lower limit of about TG-low;
radially expanding the tube to increase its radial stiffness;
forming the scaffold from the radially-expanded tube; and
crimping the scaffold to the balloon while the scaffold has a crimping temperature of between about TG-low to about 5 degrees Celsius above TG-low including maintaining a pressure in the balloon as the scaffold diameter is being reduced in size.
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Abstract
A medical device-includes a polymer scaffold crimped to a catheter having an expansion balloon. The scaffold is crimped to the balloon by a process that includes inflating the delivery balloon during a diameter reduction to improve scaffold retention. A crimping temperature is maintained at about the onset of glass transition of the polymer material to facilitate more rapid stabilization of mechanical properties in the scaffold following crimping.
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Citations
21 Claims
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1. A method for crimping a balloon-expanded scaffold to a balloon, comprising the steps of:
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providing a tube comprising PLLA characterized by a glass transition temperature range having a lower limit of about TG-low; radially expanding the tube to increase its radial stiffness; forming the scaffold from the radially-expanded tube; and crimping the scaffold to the balloon while the scaffold has a crimping temperature of between about TG-low to about 5 degrees Celsius above TG-low including maintaining a pressure in the balloon as the scaffold diameter is being reduced in size. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for securing a scaffold to a balloon, comprising the steps of:
crimping the scaffold to the balloon while the scaffold has a temperature of between about TG-low to about 5 degrees Celsius above TG-low, the scaffold being made from a polymer comprising PLLA or PLGA, the crimping step including the steps of (a) reducing the scaffold diameter from a starting size to a first size while the balloon has a first pressure, (b) maintaining the first size for a first dwell period to allow for stress relaxation in the polymer while the balloon has the first pressure, (c) reducing the scaffold diameter from the first size to a second size while the balloon has the first pressure, (d) maintaining the second size for a second dwell period to allow for stress relaxation in the polymer while the balloon has the first pressure, and (e) reducing the scaffold diameter from the second size to a third size, wherein the balloon has a second pressure while the scaffold diameter is being reduced from the second size to the third size. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A method of making a balloon-expanded scaffold, comprising the steps of:
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forming the scaffold from a polymer; crimping the scaffold to the balloon, including selecting a crimping temperature of between about a TG-low for the polymer and about 5 degrees centigrade above TG-low to accelerate stress relaxation throughout the crimped scaffold and thereby reduce the period of time it takes for radial strength, recoil and other important scaffold properties to stabilize. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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Specification