Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
2003-01-17
2004-03-09
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
C029S517000, C029S282000
Reexamination Certificate
active
06702845
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to medical devices that are delivered into patients by catheters using minimally invasive procedures and methods of compacting such devices.
2. Description of Related Art
Arteriosclerosis affects a significant portion of the population. The progressive nature of the disease can result in severe vessel stenosis (narrowing) and ischemic conditions distal to the stenosis. Although conventional surgical interventions have proven highly effective at treating such conditions, in many cases associated procedural morbidity and mortality has driven the development of alternate “minimally invasive” therapies. These therapies are particularly useful when a lesion to be treated is deep within the body, such as in aortic and cardiac vessels or within the skull base (such as, a carotid artery or deep neuro-vasculature). These minimally invasive techniques have enjoyed increasing success and acceptance in the treatment of several vascular diseases including aneurysmal and occlusive disease.
In a typical minimally invasive procedure, upon gaining percutaneous access to the patient's vascular system, a guidewire is introduced and guided under fluoroscopic visualization to the intended site of therapy. The guidewire then serves as “rail” onto which other subsequent devices are guided through the vessels to the site. A typical occlusive lesion may require pre-dilation (e.g., PTA or PTCA) and the placement of an endovascular device (such as a stent or stent-graft). This device may then permanently reside within the lumen of the vessel. All components for these procedures are delivered within the vessel (i.e., “endoluminally”) and actuated remotely from outside of the body. Since open surgery is not required, these procedures are considered “minimally invasive.”
For the purposes of the following description, endovascular devices may be classified in two general categories: (1) plastically deformable (e.g., balloon expandable); and (2) self-expanding.
Plastically deformable devices are generally deployed by deforming the device at the site of therapy, usually by internal pressure such as inflation of an angioplasty balloon. Devices of this type are generally made of a ductile bio-acceptable material that provides little recoil after dilation. A major advantage of the plastically deformable device is obviating the need for incorporating a restraining device into the delivery system since balloon inflation is all that is needed for proper deployment.
Self-expanding devices, in contrast, are designed to spontaneously deploy in situ once they are released from a constrained profile. They are generally made from some type of elastic, super-elastic, and/or shape memory metal or polymer. Advantages of this type of device are: 1) self-deployment obviates the need for high pressure ballooning at the therapy site; 2) clinical application of self-expanding devices has demonstrated a significant increase in minimum lumen diameter as compared to balloon expandable devices; and 3) super-elastic, pseudo-elastic, and shape memory alloys provide a high degree of compliance and will maintain their expanded profiles despite subsequent mechanical deformation (such as forces that might be encountered in an accident or other pressure applied through a patient's skin).
Both device categories share a common requirement that they must be introduced to the body from an access site remote to the actual therapy site. As a result, they must be inserted in a first small “introductory” configuration, guided at this introductory profile through a patient's vasculature, and deployed through an actuation mechanism to achieve a second “functional” configuration.
Many techniques have been developed to configure endovascular devices at a small introductory profile in preparation for insertion to the body. These techniques vary depending upon the category of the individual device.
In the instance of plastically deformable devices, the device may only need to be mechanically crimped onto a balloon prior to insertion to the body. Since this device is made of substantially non-recoiling material, the device, once crimped onto the balloon, will be readily retained on the balloon while being guided to the lesion site.
Although crimping may be done by hand, manual techniques are often unsatisfactory due to non-uniform pressure applied to the crimped device. This can lead to non-uniform device expansion and increased variability in clinical performance. As a result, a number of devices and processes have been developed to reliably and consistently crimp plastically deformable devices onto, or into, a delivery system.
U.S. Pat. No. 5,920,975 to Morales describes a tool that winds a spring-like element around a plastically deformable device while it is mounted upon a delivery balloon. As the spring is tightened, pressure is applied to the device intending to crimp it onto the balloon.
EP Patent Application 630,623 to Williams et al. describes two methods to reduce the cross section of a device. In one embodiment, a plastically deformable device is mounted upon a delivery balloon and placed between reciprocating flat plates. The flat plates act to roll the device while reducing its cross sectional profile. The additions of force and size gauges, as well as inherent consistency of the machine, make this an improvement over the manual crimping technique of rolling the device between fingers.
In another embodiment of Williams et al., a plastically deformable device is mounted on a delivery balloon and then inserted into a chamber. This chamber is lined with a sealed, distensible bladder that, upon inflation, applies a circumferential crushing force to the device. This crushing force is intended to reduce the device profile and securely mount the device on the balloon.
U.S. Pat. No. 6,309,383 to Campbell et al. describes a crimping tool that resembles a hand-held nutcracker or set of pliers. A plastically deformable device is mounted on a delivery balloon and inserted into an orifice in the apparatus. The crimping tool is squeezed to apply pressure to the outside of the device to radially compact the device onto the balloon.
EP Patent Application 903,122 to Morales describes a crimping tool that uses a set of jaws to radially constrict a plastically deformable device onto a delivery balloon. The segmented jaws are hinged on one end to allow them to open and accept a device and its balloon delivery system. Once the device is inside, a collar is slid over the outer surface of the jaws. Pressure applied against the jaws by the collar causes them to close, thereby crushing the device onto the balloon.
In the instance of self-expanding devices, the diametrical size of the device needs to be reduced to an “introductory” profile and held in place by some constraint. This is generally a more complex procedure than compacting a plastically deformable device since a steady constraint must be applied to the compacted device from its initial compaction to its ultimate deployment. This is typically accomplished using a tool or machine to reduce the device profile, and then the device is transferred in its compacted state to a restraining sheath, catheter, or other constraining means. The constraining means is kept actively engaged up to the time of deployment at the treatment site.
U.S. Pat. No. 6,096,027 to Layne describes an apparatus for crushing and loading a self-expanding device. This device utilizes a bag surrounding the device that is pulled through a tapered die (funnel). As the device moves through the funnel its cross sectional profile is reduced. Upon exiting the die, the bag is removed and the device is captured in a restraining tube or sheath.
U.S. Pat. No. 5,928,258 to Kahn et al. describes an apparatus for crushing and loading a self-expanding device that utilizes a cylindrical cartridge for receiving the device and another implement for transferring the device into a delivery sheath. The device is pulled into the first cartridge, and then a plunge
Cully Edward H.
Flury Keith M.
Gore Enterprise Holdings Inc.
Johns David J.
McDermott Corrine
Sweet Thomas J
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