Vascular Occlusion Devices

Abstract

A vaso-occlusive device comprising an elongate main portion (e.g., a braided portion) having a plurality of openings (e.g., openings between strands of the braid) along the length of the main portion. The main portion has a first bending stiffness. An atraumatic distal segment is coupled to a distal end of the braided portion and extends distally from the distal end of the braided portion. The distal segment has a second bending stiffness. A ratio of the second bending stiffness to the first bending stiffness is within a particular range, which mitigates problems with the distal segment slipping into and engaging the openings in the main portion while maintaining the deployment performance of the device.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to medical devices and intravascular medical procedures, and more particularly to devices and methods for occluding vascular defects such as aneurysms. [Background technology]

[0002] Vascular occlusion devices or implants are used for a variety of reasons, including the treatment of intravascular aneurysms. Aneurysms are dilations of vasculature, such as blood vessels, that can rupture, clot, or dissociate, posing a risk to a patient's health. For example, an aneurysm in a patient's brain may rupture, causing a stroke, leading to brain damage and death. Cerebral aneurysms may be detected in a patient, for example, after a stroke or hemorrhage, and treated by application of a vascular occlusion device.

[0003] A commonly used vaso-occlusive device comprises a soft, helically wound coil formed by winding a platinum (or platinum alloy) wire strand around a "primary" mandrel. This coil is then wound around a larger "secondary" mandrel and heat treated to impart a secondary shape. For example, U.S. Pat. No. 4,994,069 issued to Ritchart et al. (which is incorporated herein in its entirety by reference as if set forth in its entirety) describes a vaso-occlusive device that assumes a straight, helical primary shape when stretched for placement through the lumen of a delivery catheter, and a folded, complex secondary shape when released from the delivery catheter and placed in the vasculature. Complex three-dimensional secondary shapes can be imparted to the vaso-occlusive device to better frame and fill the aneurysm, and the stiffness / flexibility of the vaso-occlusive device can be altered.

[0004] To deliver a vaso-occlusive device to a desired site within the vasculature, e.g., into an aneurysmal sac, it is well known to first position a small profile delivery catheter or "microcatheter" at the site using a guidewire. Typically, the distal end of the microcatheter is provided with a selected preformed bend, e.g., 45°, 26°, "J" shaped, "S" shaped or other bend shape, by the attending physician or manufacturer depending on the patient's particular anatomy, so that when the guidewire is withdrawn, it will remain in a desired position to release one or more vaso-occlusive devices into the aneurysmal sac. A delivery or "pusher" assembly or "wire" is then threaded through the microcatheter until the vaso-occlusive device coupled to the distal end of the delivery assembly extends from the distal end opening of the microcatheter into the aneurysmal sac. Once inside the aneurysmal sac, a portion of the vaso-occlusive device can be deformed or bent to allow for more efficient and complete filling. The vaso-occlusive device is then released or "detached" from the distal end of the delivery assembly, and the delivery assembly is pulled back through the microcatheter. Depending on the particular needs of the patient, one or more additional vaso-occlusive devices can be pushed through the microcatheter and released into the same aneurysm sac.

[0005] Importantly, fluoroscopy is typically used to visualize the vaso-occlusion device during delivery into the aneurysm, while magnetic resonance imaging (MRI) is typically used to visualize the treatment site post-procedure (e.g., several weeks after initial treatment of the aneurysm) to ensure that the aneurysm sac has been adequately occluded. For this reason, it is important that the vaso-occlusion device be constructed to allow for its radiopacity during treatment of the aneurysm while minimizing visualization-impeding artifacts that arise during post-procedure MRI (i.e., MRI-compatible). It is also important that such vaso-occlusion devices be "soft" (i.e., laterally flexible or malleable) and thereby atraumatic, to prevent rupture of the delicate tissue of the aneurysm.

[0006] It is also important that such vaso-occlusion devices are retained within the aneurysm for an extended period of time. However, aneurysms with large mouths, commonly known as "wide-necked aneurysms," are difficult to place and retain within the aneurysm sac, and in particular small and relatively thin vaso-occlusion coils, no matter how skillfully placed, lack sufficient mechanical strength to maintain their position within such an aneurysm sac. This requires the deployment of stents or balloons in blood vessels adjacent to the aneurysm neck region to ensure placement of the vaso-occlusion coil within the aneurysm sac, thereby complicating the procedure. To address this issue, vaso-occlusion devices have been developed that are at least partially constructed of braided (or woven) structures. Such braided vaso-occlusion devices provide a larger neck coverage and a more effective backbone across the aneurysm neck, allowing them to be effectively retained within a wide-necked aneurysm without the need to deploy ancillary aneurysm retention devices such as balloons or stents.

[0007] Vascular occlusion devices having braided portions may also include coils at the distal and / or proximal ends that provide an atraumatic end to the vasculo-occlusive device to prevent damage to the aneurysm through which the device advances and to the fragile tissue throughout the vasculature during use. However, it has been found that the coils can undesirably interact with the braid by weaving into the openings between the strands / wires of the braid, resulting in entanglement of the braided portion of the vasculo-occlusive device with the coil. This entanglement condition is also referred to herein as "engagement" or "interlocking." Engagement between the coil and the braid can prevent proper manipulation of the vasculo-occlusive device, for example, preventing the device from being pulled back into the delivery device (e.g., delivery catheter) and / or preventing proper transition of the vasculo-occlusive device from its delivery configuration to its deployed, expanded configuration. Entanglement of the coil and braid occurs more frequently when smaller sized vasculo-occlusive devices are deployed into smaller aneurysmal cavities. This is because the limited space in the smaller aneurysms constrains the device and increases the contact between the coil segments and the braid.

[0008] Furthermore, whether coiled or braided vaso-occlusion devices are used, conventional vaso-occlusion device delivery systems require such vaso-occlusion devices to be relatively short and of limited expandability, otherwise they are difficult (if not impossible) to push into and / or remove from the microcatheter. Unfortunately, delivery of small (short) vaso-occlusion devices into the aneurysm sac may require longer and more complicated procedures, making such smaller vaso-occlusion devices less desirable. For example, a 7 mm diameter neuroaneurysm sac is typically filled with 5-7 individual spring-like coils, which may result in a longer and more complicated procedure than would be possible with a reduced number of devices.

[0009] Theoretically, the length of the vaso-occlusive device can be increased to reduce the number of vaso-occlusive devices required to treat an aneurysm. However, increasing the length of the vaso-occlusive device necessarily increases friction between such vaso-occlusive devices and the lumen of the delivery catheter. Therefore, in order to reliably deliver the vaso-occlusive device into the aneurysm, it is necessary to increase the column strength of such vaso-occlusive devices (e.g., by selecting a material with a high Young's modulus or by increasing the diameter of the wire forming the vaso-occlusive device) and / or increase the diameter of the delivery catheter. However, as mentioned above, in order to allow the aneurysm to be accessed through a very small vasculature, it is important both to make the diameter of the delivery catheter as small as possible and to make the vaso-occlusive device soft enough not to traumatize the delicate tissue of the aneurysm.

[0010] There are very few materials that allow relatively long vaso-occlusive devices to have the necessary column strength to be delivered through a relatively small diameter delivery catheter while satisfying other competing requirements, including softness, radiopacity and MRI compatibility requirements. For example, known materials with relatively high Young's modulus and relatively high radiopacity, such as platinum-tungsten (PtW) alloys commonly used in the manufacture of vaso-occlusive coils, may be used to provide the necessary column strength for relatively long vaso-occlusive devices, but the diameter of the wire used to manufacture such vaso-occlusive devices must be reduced to meet the softness requirements while allowing the vaso-occlusive device to fit within a small diameter delivery catheter. As a result, the vaso-occlusive device has a reduced radiopacity and reduced column strength, requiring the vaso-occlusive device to be shortened and / or the diameter of the delivery catheter to be increased.

[0011] Thus, a need remains to provide a vaso-occlusive device that satisfies the aforementioned demands while minimizing the problem of entanglement between the coiled and braided portions. Summary of the Invention

[0012] According to one aspect of the medical devices and endovascular medical procedures of the present disclosure, the vaso-occlusive device includes an elongated vaso-occlusive device (e.g., at least 5 cm in length) configured for implantation within an aneurysm sac. The vaso-occlusive device has a delivery configuration when constrained within a delivery catheter and a deployed configuration when released from the delivery catheter into the aneurysm sac. The vaso-occlusive device includes an elongated braided portion, the braided portion having the primary physical structure of the device. The braided portion is comprised of a plurality of elongated strands braided together such that gaps or openings exist between the strands. The braided portion has a proximal end and a distal end. The braided portion has a first bending stiffness, the first bending stiffness being a function of the material, shape and dimensions of the braid.

[0013] The vaso-occlusive device also has a distal coil segment coupled to the distal end of the braided portion. In another embodiment, the distal coil segment is typically much shorter than the braided portion and is used to provide an atraumatic end to the device to avoid damaging the delicate tissue of the aneurysm and vasculature during use of the device. The distal coil segment extends distally from the distal end of the braided portion to extend the length of the entire device. The distal coil segment has a second bending stiffness.

[0014] In another embodiment, the ratio of the second bending stiffness (the bending stiffness of the distal coil segment) to the first bending stiffness (the bending stiffness of the braided portion) is within the range of 0.5 to 1.0, alternatively within the range of 0.6 to 0.8. This ratio range has been determined to provide improved performance over previously available vaso-occlusive devices having a braided portion and a distal coil segment. This distal coil segment to braided portion bending stiffness ratio provides an unexpected combination of desirable performance while also reducing the likelihood of engagement between the distal coil segment and the braided portion. For example, outside this range, the distal coil segment may be too stiff or too soft, resulting in an increased likelihood of engagement and / or undesirable performance characteristics such as a lack of uniformity in loop distribution, more difficult deployment (e.g., requiring more manual manipulation by the clinician) and / or catheter recoil forces that cause loss of access to the aneurysm.

[0015] Alternatively, the ratio of the second bending stiffness (the bending stiffness of the distal coil segment) to the first bending stiffness (the bending stiffness of the braided portion) can be within the range of 0.5 to 1.0, or within the range of 0.55 to 0.9, or within the range of 0.65 to 0.75, or within the range of 0.6 to 0.8, or any suitable smaller range, for example within the range of 0.68 to 0.72.

[0016] In yet another embodiment, the vaso-occlusive device can further include a proximal coil segment coupled to the proximal end of the braided portion. The proximal coil segment extends proximally from the proximal end of the braided portion to extend the overall length of the device. Like the distal coil segment, the proximal coil segment can be much shorter than the braided portion, providing an atraumatic end to the device to avoid damaging the delicate tissue of the aneurysm and vasculature during use of the device. In yet another embodiment, the proximal coil segment can have a bending stiffness substantially the same as the second bending stiffness.

[0017] In yet another embodiment, the braided portion of the vaso-occlusive device can have a delivery configuration when constrained in a delivery catheter and a deployed configuration when released from the delivery catheter that is different from the delivery configuration. For example, the deployed configuration can be an expanded shape having a larger cross-sectional dimension than the constrained delivery configuration. For example, the delivery configuration can be a substantially straight shape or a helical coil. The braided portion can be formed from a self-forming / expanding material that is biased to form into the deployed configuration upon release from the delivery catheter. The braided portion can include a shape memory material or component that self-forms upon release or forms into the deployed configuration when exposed to a preset condition such as a temperature change, an electric current, etc. The deployed configuration can be any suitable shape, such as one or more helical coils, one or more loops, a complex three-dimensional shape, etc. In another embodiment, the deployed configuration is a three-dimensional shape having a cross-sectional dimension that is at least three times, or at least two times, or at least 1.5 times the cross-sectional dimension of the delivery configuration.

[0018] According to another aspect of the medical devices and endovascular medical procedures of the present disclosure, another vaso-occlusive device includes an elongated main portion having a proximal end and a distal end, and a plurality of openings along the length of the main portion. For example, the main portion may be a braid, mesh, a tube with a plurality of openings, or other suitable elongated structure. The tube may be an elongated hollow object, including, but not limited to, a flat sheet rolled into the tube. The openings are large enough for a distal tip of the atraumatic distal segment to enter the opening and engage the main portion. The vaso-occlusive device has a delivery configuration when restrained within a delivery catheter and a deployed configuration when released from the delivery catheter into the aneurysm sac. The main portion has a first bending stiffness.

[0019] The vascular occlusion device has an atraumatic distal segment coupled to a distal end of the main portion. The distal segment extends distally from the distal end of the main portion. The distal segment has a second bending stiffness. The distal segment has a distal tip and an opening large enough for the distal tip to enter the opening and engage the main portion.

[0020] The ratio of the second bending stiffness (the bending stiffness of the atraumatic distal segment) to the first bending stiffness (the bending stiffness of the main portion) is within the range of 0.5 to 1.0, or within the range of 0.6 to 0.8. This ratio range has been determined to provide improved performance over previously available vascular occlusion devices having a main portion and an atraumatic distal segment, similar to the vascular occlusion devices described above. This distal segment to main portion bending stiffness ratio provides an unexpected combination of desirable performance while also reducing the likelihood of engagement between the distal coil segment and the main portion. Outside this range, the distal segment may be too stiff or too soft, resulting in an increased likelihood of engagement and / or undesirable performance characteristics.

[0021] Alternatively, the ratio of the second bending stiffness (the bending stiffness of the distal segment) to the first bending stiffness (the bending stiffness of the main portion) may be in the range of 0.5 to 1.0, or in the range of 0.55 to 0.9, or in the range of 0.65 to 0.75, or any suitable smaller range of 0.6 to 0.8, for example in the range of 0.68 to 0.72.

[0022] In another embodiment, the distal segment may be a coil, a helical coil, a tube, and a flexible rod, or a combination thereof. The distal segment may have a rounded and / or soft tip to provide an atraumatic tip for the vaso-occlusive device that avoids damaging the delicate tissue of the aneurysm and vasculature during use of the vaso-occlusive device.

[0023] In another embodiment, the vaso-occlusive device can also have an atraumatic proximal segment coupled to and extending proximally from the proximal end of the main portion. The proximal portion can have one or more of the same or similar characteristics as the distal segment.

[0024] In additional aspects, any of the vaso-occlusive devices disclosed herein may be part of a vaso-occlusive system that includes a vaso-occlusive assembly and a delivery assembly. For example, the vaso-occlusive assembly may include any of the vaso-occlusive devices described herein and a pusher member detachably coupled to the vaso-occlusive device. The pusher member is configured to enable a clinician to advance the vaso-occlusive device along a delivery catheter through a patient's vasculature to a target site, such as an aneurysm, to be treated with the vaso-occlusive device and push the vaso-occlusive device out of the distal end of the delivery catheter to deploy the vaso-occlusive device.

[0025] In yet another aspect, the vaso-occlusive assembly can also include a detachment device that releasably couples the pusher member to the vaso-occlusive device. For example, the detachment device can include an electrolytic detachment, a mechanical connector, a thermally actuated detachment, a dissolution detachment, etc. The delivery assembly can include a delivery catheter through which the vaso-occlusive device can be introduced in its compact delivery configuration. The delivery assembly can also include a guidewire for guiding the delivery catheter to a target implantation site within the patient's vasculature, such as an aneurysm. The guidewire is then removed and the vaso-occlusive device is advanced through the delivery catheter to the target implantation site.

[0026] In yet another aspect of the present disclosure, the device is not limited to a vaso-occlusive device, but may be any medical device including an elongated main portion and a distal segment attached to a distal end of the main portion, and having other features of the vaso-occlusive device disclosed herein. For example, the medical device may be any suitable thrombus removal device, stent retriever, embolic filter, stent delivery system, other implantable device, guidewire, intravascular device, or other medical device. The medical device comprises an elongated main portion having a proximal end and a distal end, and a plurality of openings along the length of the main portion. For example, the main portion may be a braid, mesh, a tube with a plurality of openings, or other suitable elongated structure. The tube may be an elongated hollow object, including, but not limited to, a flat sheet rolled into the tube. The openings are large enough for the distal tip of the atraumatic distal segment to enter the opening and engage the main portion. Optionally, the medical device may have a delivery configuration when constrained within a delivery catheter, and a deployed configuration when released from the delivery catheter into the aneurysm sac. The main portion has a first bending stiffness.

[0027] The medical device has an atraumatic distal segment coupled to a distal end of the braided portion. The distal segment extends distally from the distal end of the main portion. The distal segment has a second bending stiffness. The distal segment has a distal tip and an opening large enough for the distal tip to enter the opening and engage the main portion.

[0028] The ratio of the second bending stiffness (the bending stiffness of the atraumatic distal segment) to the first bending stiffness (the bending stiffness of the main portion) is within a range of 0.5 to 1.0, or within a range of 0.6 to 0.8. This ratio range provides superior performance over previously available medical devices having a main portion and an atraumatic distal segment. This distal segment to main portion bending stiffness ratio provides an unexpected combination of desirable performance while also reducing the likelihood of engagement between the distal coil segment and the main portion. Outside this range, the distal segment may be too stiff or too soft, resulting in an increased likelihood of engagement and / or undesirable performance characteristics.

[0029] Alternatively, the ratio of the second bending stiffness (the bending stiffness of the distal segment) to the first bending stiffness (the bending stiffness of the main portion) may be in the range of 0.5 to 1.0, or in the range of 0.55 to 0.9, or in the range of 0.65 to 0.75, or any suitable smaller range of 0.6 to 0.8, for example in the range of 0.68 to 0.72.

[0030] In another embodiment, the distal segment may be a coil, a helical coil, a tube, and a flexible rod, or a combination thereof. The distal segment may have a rounded and / or soft tip to provide an atraumatic tip for the vaso-occlusive device that avoids damaging the delicate tissue of the aneurysm and vasculature during use of the vaso-occlusive device.

[0031] Methods of deploying any of the vascular occlusion devices and other medical devices disclosed herein within an anatomical cavity, such as an aneurysm, are also disclosed. In one method, the vascular occlusion device is inserted into a delivery catheter device in a compact delivery configuration and advanced through the delivery catheter device. The delivery catheter is first inserted into the patient's vasculature and advanced within the vasculature to position a distal end of the delivery catheter at a target insertion site. In this example, the target insertion site is an aneurysm. It should be understood that the target insertion site may be any suitable anatomical site within the vasculature where the vascular occlusion device is deployed. If a guidewire is used, the guidewire is first inserted into the patient's vasculature and advanced through the vasculature to the site of the aneurysm. A delivery catheter is then advanced along the guidewire to the aneurysm, after which the guidewire is removed.

[0032] The vaso-occlusive device is then inserted into the delivery catheter in its compact delivery configuration and advanced along the delivery catheter until the distal end of the vaso-occlusive device is located at the target insertion site. The vaso-occlusive device is then pushed distally out of the delivery catheter using a pusher member. The distal segment (e.g., the distal coil segment) is advanced through the neck of the aneurysm and into the aneurysm sac. As the vaso-occlusive device continues to advance out of the delivery catheter via the pusher member, the braided portion also advances into the aneurysm sac. Also, as the vaso-occlusive device is released from the delivery catheter, it expands to an expanded deployed configuration within the aneurysm sac. Once the entire vaso-occlusive device is inserted into the aneurysm sac, it can be detached from the pusher member, for example, by actuating or activating a detachment device. In some cases, a single vaso-occlusive device is sufficient to fill and occlude the aneurysm. If multiple vaso-occlusive devices are required, this process can be repeated to deliver a sufficient number of vaso-occlusive devices to fill and occlude the aneurysm.

[0033] Other and further aspects and features of embodiments of the disclosed invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. [Brief description of the drawings]

[0034] The drawings illustrate the design and utility of various aspects of the devices and methods disclosed herein, with similar elements being commonly numbered. It should be noted that the drawings are not drawn to scale, and elements of similar structure or function are indicated by similar numbers throughout the drawings. It should also be noted that the drawings are intended only to facilitate the description of various aspects of the disclosed technology. They are not intended as an exhaustive description of the technology or as a limitation on the scope of the technology, which is defined only by the appended claims and their equivalents. Furthermore, an exemplary embodiment of the disclosed technology need not have all aspects or advantages disclosed or described herein. An aspect or advantage described in connection with a particular embodiment of the disclosed technology is not necessarily limited to that embodiment, and may be implemented in any other embodiment, even if not so illustrated. To better understand how the above and other advantages and objects of the technology are obtained, a more particular description of the technology, briefly described above, will be made by reference to specific examples thereof illustrated in the accompanying drawings. The present technology will be explained and described with additional specificity and detail through the use of the accompanying drawings, with the understanding that the drawings and corresponding description illustrate only illustrative embodiments of the disclosed technology and therefore should not be considered as limiting its scope.

[0035] [Figure 1] FIG. 1 is a perspective view of a vaso-occlusive device showing a distal coil segment engaged with a braided portion of the vaso-occlusive device. [Diagram 2] 2A and 2B are cross-sectional side views of the vascular occlusion system of FIG. 1 with the vascular occlusion device in a constrained delivery configuration within a delivery catheter and deployed outside the delivery catheter in its expanded deployed configuration. [Diagram 3]FIG. 3 is a graph illustrating the relationship between the bending stiffness ratio of the distal segment and main portion of the vaso-occlusive device of FIG. 1 and performance characteristics and engagement issues for various ranges of bending stiffness ratios. [Figure 4] FIG. 4 is a graph of empirical data for an example vascular occlusion device constructed according to the design of FIGS. 2A and 2B, showing the relationship between the bending stiffness ratio of the distal segment and main portion of the vascular occlusion device of FIG. 1 and performance characteristics and engagement issues for various ranges of bending stiffness ratios. [Diagram 5] FIG. 5 is a table of empirical data for examples of vaso-occlusive devices constructed according to the designs of FIGS. 2A and 2B and having various bending stiffness ratios. [Figure 6] FIG. 6 is a cross-sectional side view showing a guidewire being advanced into a portion of a patient's vasculature to the location of an aneurysm. [Figure 7] FIG. 7 is a cross-sectional side view of the guidewire of FIG. 6 and a patient's vasculature with a delivery catheter advanced over the guidewire. [Figure 8] FIG. 8 is a cross-sectional side view showing the vaso-occlusive system of FIGS. 2A and 2B being advanced within the delivery catheter of FIG. 7 to deploy a vaso-occlusive device within an aneurysm. [Figure 9] FIG. 9 is a cross-sectional side view of the vaso-occlusive system of FIG. 7 with the vaso-occlusive device deployed within the aneurysm. [Figure 10] FIG. 10 is a flow chart of an exemplary method for deploying a vaso-occlusive device within an aneurysm using the vaso-occlusive system of FIGS. 2A and 2B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] FIG. 1 illustrates the issue of engagement of a vaso-occlusive device 100 including a braided portion 102 and a distal coil segment 104. The vaso-occlusive device 100 comprises a main braided portion 102 and a distal coil segment 104 attached to a distal end 106 of the braided portion 102. It has been discovered that during insertion of such a vaso-occlusive device 100 including a braided portion 102, or other portion having an opening large enough to receive the distal coil segment 104, the distal coil segment 104 may engage the braided portion 102 as the vaso-occlusive device 100 transitions from a delivery configuration within the delivery catheter to an expanded deployed configuration as the vaso-occlusive device advances out of a delivery catheter and into an anatomical cavity such as an aneurysm. This engagement is illustrated in FIG. 1, which shows the vaso-occlusive device 100 in a deployed configuration having a three-dimensional shape. The distal coil segment 104 is inserted through an opening in the braided strands of the braided portion 102 as shown in FIG. 1, resulting in the distal coil segment 104 being securely engaged with the braided portion. This engagement is a highly undesirable outcome because it prevents the vascular occlusion device 100 from being properly manipulated, for example, by preventing the device 100 from being pulled back into the delivery device (e.g., a delivery catheter) and / or by preventing the vascular occlusion device 100 from properly transitioning from its delivery configuration to its deployed, expanded configuration.

[0037] Although engagement issues and specific examples are described herein with respect to vascular occlusion devices for occluding anatomical spaces (such as aneurysms), the present disclosure is not limited to such devices, but rather is directed to any medical device that includes an elongated main portion and a distal segment attached to a distal end of the main portion. For example, the medical device may be any suitable thrombus removal device, stent retriever, embolic filter, stent delivery system, other implantable device, guidewire, intravascular device, or other medical device.

[0038] 2A and 2B, a vascular occlusion system 200 is shown having a vascular occlusion device 210 that mitigates engagement problems. The vascular occlusion device 210 also exhibits good performance characteristics during insertion and use. The vascular occlusion system 200 includes a delivery assembly 202 and a vascular occlusion assembly 204. As shown in FIGS. 6 and 7, the delivery assembly 202 can include a delivery catheter 206 and an optional guidewire 208. The vascular occlusion assembly 204 includes the vascular occlusion device 210 and a pusher member 212 that is releasably coupled to the vascular occlusion device 210 via a separation device or joint 214. FIG. 2A shows the vascular occlusion assembly 204 after it has been slidably positioned within the delivery catheter 206 such that the vascular occlusion device is in its compact delivery configuration.

[0039] The delivery catheter 206 is typically an elongated flexible tube, and may be, for example, a microcatheter or the like. The delivery catheter 206 comprises an elongated sheath body 215 having a proximal portion 216, a distal portion 218, and a lumen 220 extending from the proximal portion 216 to the distal portion 218. The proximal portion 216 of the delivery catheter 206 typically remains outside the patient's body and is accessible to a clinician when the vascular occlusion system 200 is used, while the distal portion 218 is sized and dimensioned to reach a remote location in the patient's vasculature and is configured to deliver the vascular occlusion device 210 to the aneurysm. The delivery catheter 206 may also have one or more ports 222 in fluid communication with the lumen 220 for introducing fluids into or removing fluids from the sheath body 215. The sheath body 215 may be constructed of a suitable polymeric material, metal and / or alloy, such as polyethylene, stainless steel, or other suitable biocompatible material or combinations thereof. In some cases, the proximal portion 216 can include a reinforcing layer, such as a braided or coiled layer, to enhance the pushability of the sheath body 215. The sheath body 215 can include a transition region between the proximal portion 216 and the distal portion 218.

[0040] The vaso-occlusive device 210 comprises an elongated main portion 224 having a proximal end 226 and a distal end 228. The main portion 224 may be a braided portion including multiple strands braided together to form an elastic tubular member. Alternatively, the main portion 224 may comprise a mesh, or a tube with multiple openings (the tube may be any elongated hollow object including, but not limited to, a flat sheet rolled into a tube), or other elongated structure with multiple openings along the length of the main portion 224, for example, along substantially the entire length of the main portion 224, or at least 50% of the length of the main portion 224, or at least 75% of the length of the main portion. The main portion 224 has a first bending stiffness that is a measure of the resistance of the main portion 224 to bending deformation. This is typically expressed in bending moment per unit width, such as in units of "mN / mm". For braided section 224, the first bending stiffness is determined by the braid configuration and its secondary diameter (ie, the outer diameter of braided section 224 or the outer diameter of device 210).

[0041] The vaso-occlusive device 210 also has a flexible, atraumatic distal segment 230 coupled to the distal end 228 of the main portion 224. The distal segment 230 has a proximal end 232 and a distal end 234. The distal segment 230 in the figure comprises a helical coil such that the distal segment 230 is the distal coil segment 230. The proximal end 232 of the distal coil segment 230 can be attached to the distal end 228 of the main portion 224 by any suitable means such as welding, mechanical fasteners, adhesives, etc. The distal segment 230 can also have an atraumatic tip 236 attached to the distal end 234 of the helical coil 230. The atraumatic distal segment 230 has a second bending stiffness that is lower than the first bending stiffness of the main portion 224. Distal segment 230 can be more flexible than main portion 224, i.e., have a lower bending stiffness than the first bending stiffness of the main portion, thereby providing an atraumatic distal tip for the vascular occlusion device that does not damage, rupture, or otherwise cause trauma to the delicate tissue of the aneurysm and / or vasculature as vascular occlusion device 210 advances out of delivery catheter 206 and into the patient's vasculature and aneurysm. Alternatively, distal segment 230 can be other suitable flexible structures that provide the desired atraumatic properties, such as, for example, a polymer rod or tube.

[0042] The atraumatic distal segment 230 has a second bending stiffness that is different from the first bending stiffness of the main portion 224. For the distal coil segment 230, the second bending stiffness is a function of the coil wire diameter, pitch, primary coil diameter, and secondary coil diameter (diameter of the secondary coil shape). As described herein, a particular range of the ratio of the second bending stiffness of the distal segment 230 to the first bending stiffness of the main portion 224 (referred to herein as the "bending stiffness ratio") can mitigate engagement issues while still providing desirable performance characteristics of the vaso-occlusive device 210. For a given first bending stiffness of the main portion 224, the second bending stiffness of the distal coil segment 230 can be engineered by controlling the configuration of the distal segment 230 along with the outer diameter of the distal segment 230 to target a desired range of the ratio of the second bending stiffness to the first bending stiffness.

[0043] The vaso-occlusive device 210 is sized for implantation in the aneurysmal sac 240 (see Figures 6-9) and can have any shape or geometry in cross-section. For example, in the embodiment shown in Figures 1 and 2, the vaso-occlusive device 210 takes the form of a resilient braided mesh or porous main portion 224 having a tubular shape that can be partially flattened by internal and / or external forces, and a distal segment 230 that is a helical coil.

[0044] Optionally, the vascular occlusion device 210 can have a compact delivery configuration when radially constrained within the delivery catheter 206, and can be configured to be formed into a deployed configuration having a secondary shape different from the delivery configuration when released from the delivery catheter 206, such as for release into an aneurysmal sac 240 or other anatomical cavity. FIG. 2A illustrates the vascular occlusion device 210 in a compact delivery configuration in which the vascular occlusion device 210 is retained within the delivery catheter 206 and substantially conforms to the longitudinal path (i.e., shape) of the delivery catheter 206. For example, in FIG. 2A, the vascular occlusion device 210 has a substantially straight axial shape. As shown in FIG. 8, when inserted into the delivery catheter 206, the vascular occlusion device 210 follows the longitudinal path of the delivery catheter 206 within the blood vessel 242. When released from the delivery catheter 206, the vascular occlusion device 210 is formed into its deployed configuration, which is a three-dimensional shape that includes multiple loops and / or curves that are non-overlapping, overlapping, or a combination thereof, as shown in FIG. 2B and FIG. 9. The cross-sectional dimension of vaso-occlusive device 210 in its deployed configuration may be, for example, more than 1.5 times, preferably more than 2 times, and most preferably more than 3 times the cross-sectional dimension of vaso-occlusive device 210 in its compact delivery configuration.

[0045] The deployed configuration of the vaso-occlusive device 210 can be formed or programmed into the device by any suitable method. For example, the main portion 224 (e.g., the braided main portion 224) can be formed of a shape memory material. The main portion 224, such as the braid 224, can be formed of any suitable material, including, but not limited to, platinum alloy, platinum-tungsten alloy, gold alloy, or nitinol, or any combination thereof. The main portion 224 is wound around a mandrel in the looped and / or curved shape of the deployed configuration and then heat treated to form or program the deployed configuration into the main portion 224. Alternatively, the main portion 224 can be formed of a shape memory material and programmed into the deployed configuration when the main portion 224 is exposed to a preset condition, such as a temperature change, an electric current, or other shape-forming condition.

[0046] As described herein, the main portion 224 can be formed with a braid having a desired length (e.g., greater than 5 cm, 5 cm to 45 cm, 5 cm to 30 cm, etc.). The braid can be formed from multiple wires or strands using a braiding machine and braided around a mandrel (e.g., a mandrel having a circular, oval, flat, or other shape depending on the desired final cross-sectional shape of the main portion 224). After braiding, the main portion 224 can be heat set in its delivery configuration to form the linear "primary shape" of the mesh portion 224. The completed heat set braid can then be wrapped around a second mandrel (e.g., a three-dimensional mandrel) and heat set a second time to impart a three-dimensional deployed configuration.

[0047] Referring to Figure 3, a graph illustrates an optimized combination of desired performance characteristics and minimized engagement for vascular occlusion device 210 for various ranges of bending stiffness ratios. The graph in Figure 3 plots bending stiffness ratio versus outer diameter of main portion 224 (either device outer diameter or outer diameter of secondary shape of braided portion). Performance characteristics of vascular occlusion device 210 include observable functional attributes such as uniformity of loop distribution within the aneurysm, ease of deployment, effective retention of distal segment 230 within the aneurysm (i.e., distal segment 230 remains within the aneurysm and does not advance out of the aneurysm during deployment), and catheter recoil force during deployment (i.e., the magnitude of recoil force acting on delivery catheter 206 that causes displacement of distal end 218 of delivery catheter 206).

[0048] The graph in FIG. 3 illustrates that a bending stiffness ratio greater than 1.0 will result in a high degree of engagement of the vascular occlusion device 210 and a distal segment that is too stiff, resulting in undesirable performance, such as a lack of uniformity in loop distribution within the aneurysm, difficulty in deployment requiring more user input (e.g., manipulation) to deploy the vascular occlusion device 210, inconsistent placement of the distal segment 230, and / or catheter bounce that causes the distal end 218 of the delivery catheter 206 to move away from the target insertion site.

[0049] 3, for bending stiffness ratios in the range of 0.8-1.0, the vaso-occlusive device 210 tends to eliminate engagement issues, but still exhibits undesirable performance characteristics. More specifically, vaso-occlusive devices 210 having bending stiffness ratios in the range of 0.8-1.0 result in a lack of uniformity in loop distribution, difficulty in deployment, requiring more user input (e.g., manipulation) to deploy the vaso-occlusive device 210, and / or catheter bounce that causes the distal end 218 of the delivery catheter 206 to move away from the target insertion site.

[0050] 3 shows that a bending stiffness ratio of the vaso-occlusive device 210 in the range of 0.6 to 0.8 provides the best combination of desirable performance characteristics and avoidance of engagement. A bending stiffness in the range of 0.6 to 0.8 provides a vaso-occlusive device 210 that provides uniform loop distribution, ease of deployment requiring minimal user input during deployment, consistent placement of the distal segment 230 without dislodging from the aneurysm, and minimal bounce that allows the distal end 218 of the delivery catheter 206 to remain in place at the target insertion site, such as within the neck of the aneurysm.

[0051] 3, when the vaso-occlusive device 210 has a bending stiffness ratio of less than 0.6, the vaso-occlusive device 210 will experience excessive engagement during deployment, but will exhibit other desirable performance characteristics such as good uniformity of loop distribution, ease of deployment, consistent placement, and minimal catheter bounce. However, due to excessive engagement, a vaso-occlusive device 210 having a bending stiffness ratio of less than 0.6 is undesirable.

[0052] 4 and 5 provide empirical experimental data for several examples of prototypes of vaso-occlusive device 210 constructed in accordance with device 210 described herein shown in FIG. 1 and FIG. 2. The experimental data was used to analyze the effect of bending stiffness ratio on engagement issues and performance characteristics and to determine the optimal bending stiffness range. The various prototypes are labeled P1-P6 in the graph of FIG. 4 and Table 1 of FIG. 5. Prototype P1 has a bending stiffness ratio of 1.20. Testing was performed for 15 simulated use cycles and 10 samples of each prototype design. As shown in FIG. 4 and FIG. 5, prototype P1 exhibited undesirable performance characteristics and a high incidence of engagement (40%) as described herein for bending stiffness ratios greater than 1.0.

[0053] Prototype P2 has a stiffness ratio of 0.95 and exhibited no engagement issues but undesirable performance characteristics as described herein for stiffness ratios ranging from 0.8 to 1.0. Prototype P3 has a stiffness ratio of 0.70, prototype P5 has a stiffness ratio of 0.71, and prototype P6 has a stiffness ratio of 0.67. Prototypes P3, P5, and P6 exhibited excellent performance characteristics and no engagement issues as described herein for stiffness ratios ranging from 0.6 to 0.8. Prototypes P3 (vaso-occlusive device 210 diameter OD 3 mm), P5 (vaso-occlusive device 210 diameter OD 6 mm), and P6 (vaso-occlusive device 210 diameter OD 8 mm) also demonstrate that differences in the diameter of vaso-occlusive device 210 do not significantly affect performance characteristics and / or engagement issues.

[0054] While prototype P4 had a bending stiffness ratio of 0.55 and exhibited excellent performance characteristics, prototype P4 exhibited moderate engagement issues with distal segment 230 engaging main portion 224 in 20% of simulated use cycles, as described herein for bending stiffness ratios less than 0.60.

[0055] Alternatively, the bending stiffness ratio may be in the range of 0.55 to 0.9, or in the range of 0.65 to 0.75, or in the range of 0.6 to 0.8, or any suitable smaller range, for example in the range of 0.68 to 0.72.

[0056] 2A and 2B, the vaso-occlusive assembly 204 also includes a pusher member 212. The pusher member 212 is disposed within the lumen 220 of the delivery catheter 206. The pusher member 212 has a proximal portion 250, which typically extends proximally beyond the proximal portion 216 of the delivery catheter 206, and a distal portion 252 that is detachably coupled to the proximal portion 226 of the vaso-occlusive device 210 via a detachment device 214. The pusher member 212 may be a coil, wire, tendon, conventional guidewire, torque-transmitting cable tube, hypotube, or the like, having sufficient column strength to enable the vaso-occlusive device 210 to be pushed through the distal end 218 of the delivery catheter 206 and into the aneurysmal sac 240 (see FIGS. 8 and 9).

[0057] The detachment device 214 provides a severable connection between the pusher member 212 and the vaso-occlusive device 210. The detachment device 214 may include electrolytic detachment, mechanical connectors, thermally actuated detachment, dissolution detachment, or other mechanical, thermal, and hydraulic mechanisms. For example, the detachment device 214 may be an electrolytically degradable segment for electrolytically detaching the vaso-occlusive device 210 from the pusher member 212.

[0058] 6 and 7, the optional guidewire 208 of the delivery assembly 202 has a proximal end 244 and a distal end 246. As shown in FIG. 7, after the guidewire 208 is positioned within the patient's vasculature 242 with the distal end 246 located at the target insertion site, the delivery catheter 206 is advanced over the guidewire 208 with the guidewire 208 positioned within the lumen 220 of the delivery catheter 206. In a "rapid-exchange" configuration of the delivery catheter 206 and guidewire 208, the guidewire 208 extends only through a distal portion of the delivery catheter 206, such as the rapid-exchange lumen. The guidewire 208 is typically used by first advancing the guidewire 208 through the patient's vasculature to the target insertion site (e.g., the neck of an aneurysm to be filled by the vascular occlusion device 210), and then advancing the delivery catheter 206 over the guidewire 208 to the target insertion site.

[0059] 6-10, an exemplary method 300 of deploying a vascular occlusion device 210 in an anatomical body cavity using a vascular occlusion system 200 will now be described. The method will be described in the context of deploying a vascular occlusion device 210 in an aneurysmal sac 240, by way of example. However, the method 300 is not limited to deploying a vascular occlusion device 210 in an aneurysmal sac 240, but may be used to deploy a vascular occlusion device 210, or other medical devices disclosed herein, in any suitable anatomical body cavity accessible via a patient's vasculature. As shown in the flow chart of FIG. 10, in step 302, a guidewire 208 is inserted into a patient's vasculature 242 and advanced to a target insertion site, i.e., the aneurysmal sac 240. As described herein, the use of a guidewire 208 is optional and not required in the method 300 of deploying a vascular occlusion device 210 using a vascular occlusion system 200.

[0060] In step 304, the delivery catheter 206 of the delivery assembly 202 is advanced over the guidewire 208 to a position where the open distal end 218 is adjacent to or within the aneurysm neck 248 of the aneurysm, as shown in FIG. 7. In step 306, the guidewire 208 is withdrawn from the delivery catheter 206, leaving the delivery catheter 206 in place. In step 308, the vaso-occlusive assembly 204 is inserted into and advanced through the delivery catheter 206 of the delivery assembly 202, positioning the distal end 234 of the vaso-occlusive device 210 adjacent the distal portion 218 of the delivery catheter 206. In this position, the proximal portion 250 of the pusher member 212 remains proximal and outside the proximal portion 216 of the delivery catheter 206. In one aspect of the method 300, the vascular occlusion device 210 is pre-introduced into a sheath such that the vascular occlusion device 210 is in its delivery configuration prior to insertion into the delivery catheter 206. The vascular occlusion device 210 is then inserted into the delivery catheter 206 by abutting the distal end of the sheath with the proximal end 216 of the delivery catheter 206 and pushing the vascular occlusion device 210 out of the sheath and into the delivery catheter 206, such that the vascular occlusion device 206 remains in its delivery configuration within the delivery catheter 206.

[0061] In step 310, the vaso-occlusive device 210 is pushed distally out of the delivery catheter 206 through the lumen 220 of the delivery catheter 206 by pushing the proximal portion 250 of the pusher member 212. As the vaso-occlusive device 210 is pushed out of the open distal end 218 of the delivery catheter 206, the distal segment 230 advances through the aneurysm neck 248 and into the aneurysm sac 240, thereby depositing the vaso-occlusive device 210 within the aneurysm sac 240. As the vaso-occlusive device 210 continues to advance out of the delivery catheter 206 via the pusher member 212, the main portion 224 also advances into the aneurysm sac 240. And as the vaso-occlusive device 210 is released from the delivery catheter 206, in step 312 the vaso-occlusive device 210 forms a deployed configuration within the aneurysm sac 240. Once the entire vaso-occlusive device 210 is inserted within the aneurysmal sac 240, at step 314, the detachment device 214 is actuated, activated or otherwise manipulated to separate the vaso-occlusive device 210 from the pusher member 212. At step 316, the pusher member 212 is removed from the patient's vasculature 242 by withdrawing it out through the delivery catheter 206. If a single vaso-occlusive device 210 is sufficient to fill and occlude the aneurysmal sac 240, the method 300 proceeds to step 320, where the delivery catheter 206 is removed from the patient's vasculature 242. With reference to 308-316, it is determined whether additional vaso-occlusive devices 210 should be deployed. Alternatively, if multiple vaso-occlusive devices 210 are to be implanted, the process of steps 308-318 is repeated to deliver a sufficient number of vaso-occlusive devices 210 to fill and occlude the aneurysmal sac 240. Once a sufficient number of vaso-occlusive devices 210 have been implanted into the aneurysm sac 240 , the delivery catheter 206 is removed, at step 320 .

[0062] While specific embodiments of the disclosed invention have been shown and described herein, those skilled in the art will understand that they are not intended to limit the invention. It will also be apparent to those skilled in the art that various changes and modifications (e.g., dimensions of various parts) can be made without departing from the scope of the disclosed invention, which is defined solely by the following claims and equivalents thereof. Accordingly, the specification and drawings should be regarded in an illustrative, rather than a restrictive, sense. The various embodiments of the disclosed invention shown and described herein are intended to cover alternatives, modifications and equivalents of the disclosed invention, which may fall within the scope of the appended claims.

Claims

1. A medical device, comprising: an elongated main portion having a proximal end and a distal end, the main portion having a first bending stiffness and having a plurality of openings along the length direction of the main portion; a non-invasive distal segment coupled to the distal end of the main portion and extending distally from the distal end of the main portion, the distal segment having a second bending stiffness and having a distal tip; wherein the openings of the main portion are sized such that the distal tip can enter the openings and engage with the main portion; a medical device, characterized in that, when deployed, the ratio of the second bending stiffness to the first bending stiffness is in the range of 0.6 or more and 0.8 or less so that the distal tip does not engage with the opening.

2. The medical device according to claim 1, wherein the plurality of openings extend along at least 50% of the length of the main portion.

3. The medical device according to claim 1, wherein the ratio of the second bending stiffness to the first bending stiffness is in the range of 0.65 or more and 0.75 or less.

4. The medical device according to any one of claims 1 to 3, wherein the elongated main portion includes one of a braid, a mesh, and a tube having a plurality of openings.

5. The medical device according to claim 1, wherein the distal segment is one of a coil, a helical coil, a tube, a braid, and a flexible rod.

6. The medical device according to claim 1, further comprising a non-invasive proximal portion coupled to the proximal end of the main portion and extending proximally from the proximal end of the main portion.

7. The medical device according to claim 1, wherein the medical device is a vascular occlusion device.

8. A vascular occlusion device according to claim 7, wherein the main portion has an elongated braided portion including a plurality of elongated strands braided together, the distal portion having a distal coil segment, wherein the plurality of openings include the openings of the braided portion.

9. The vascular occlusion device according to claim 8, The vascular occlusion device, wherein the plurality of openings extend along at least 50% of the length of the braided portion. **Claim 10** The vascular occlusion device according to claim 8, further comprising a proximal coil segment coupled to the proximal end of the braided portion and extending proximally from the proximal end of the braided portion. **Claim 11** The vascular occlusion device according to claim 8, wherein the braided portion has a delivery configuration when constrained within a delivery catheter and has a deployed configuration when released from the delivery catheter. **Claim 12** The vascular occlusion device according to claim 11, wherein the delivery configuration is substantially linear and the deployed configuration is a three-dimensional shape having a cross-sectional dimension that is at least three times the cross-sectional dimension of the delivery configuration. **Claim 13** The vascular occlusion device according to claim 8, wherein the braided portion is formed of a shape memory material. **Claim 14** The vascular occlusion device according to claim 8, wherein the braided portion is formed of one of platinum, a platinum alloy, and a platinum-tungsten alloy. **Claim 15** The vascular occlusion device according to claim 8, wherein the braided portion is formed of one of gold and a gold alloy. **Claim 16** The vascular occlusion device according to claim 8, wherein the braided portion is formed of one of a platinum-gold alloy and nitinol. **Claim 17** A vascular occlusion assembly, comprising: the vascular occlusion device according to claim 8; and a pusher member detachably coupled to the vascular occlusion device. **Claim 18** The vascular occlusion assembly according to claim 17, further comprising a separation device for detachably coupling the pusher member to the vascular occlusion device. **Claim 19** The vascular occlusion assembly according to claim 18, wherein the separation device includes one of electrolysis, a mechanical connector, heating, and melting.

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