Patent Application
20130035636
The invention relates to delivery and deployment systems for implantable medical devices.
Various implantable medical devices have been clinically implanted or proposed for therapeutically treating or monitoring one or more physiological conditions of a patient. Such devices may be adapted to monitor or treat conditions or functions relating to heart, blood vessels, muscle, nerve, brain, stomach, endocrine organs or other organs and their related functions. Advances in design and manufacture of miniaturized medical devices have resulted in devices capable of therapeutic as well as diagnostic functions such as pacemakers, cardioverters, defibrillators, biochemical sensors, pressure sensors, various endovascular devices and the like. Such devices may have electronic functions and may be associated with electrical leads or may be wireless, with the ability to transmit data electronically either to another device implanted in the patient or to another device located externally of the patient, or both. Such devices also may include purely mechanical functions
Although implantation of some devices requires a surgical procedure (e.g., pacemakers, defibrillators, etc.) other devices may be small enough to be delivered and placed at an intended deployment site in a relatively noninvasive manner, such as by a delivery catheter introduced percutaneously. Delivery also may be accomplished by advancing a catheter intravascularly through an exposed vessel during a surgical procedure. Depending on the nature, function and intended deployment site of the device, the manner in which the device is fixed in place and oriented in the body may affect the operation and accuracy of the device. Consequently, the accuracy of means by which the device is fixed in place in the body can be a significant factor in the performance and utility of the device.
For those devices intended for placement by a delivery catheter, the ability to reliably place the medical device in the desired position and orientation may present some difficulty, depending on variables such as the intended placement site, the patient's anatomy and the device design. During advancement of the catheter, its positioning and deployment of the device is monitored fluoroscopically while the distal end of the catheter is navigated and manipulated from its proximal end. Typically, the device is carried at the distal end of the catheter in a low profile, radially compressed configuration to facilitate navigation of the catheter. When the catheter has been navigated to the target site and is operated to release and deploy the device, the device expands or is expanded to its larger profile into engagement with the vessel.
It is not uncommon, however, for self-expanding devices, when released from the delivery catheter, to shift position or orientation from that intended by the clinician. This may result from a number of causes as will be recognized by those familiar with the art. For example, in the case of a stent or spring-like support for a sensor or the like, the springy nature of the device may cause it to jump out of position before it has engaged the vessel wall sufficiently to assume a secure placement in the vessel. In such circumstances it would be desirable to recapture the device in the catheter to enable it to be repositioned and redeployed. Delivery catheters have been described to permit recapture of the medical device for that purpose.
It is among the general objects of the invention to provide an improved delivery catheter adapted to engage a medical device in a manner that allows for a controlled release of the device and allows the device to be recaptured, repositioned and redeployed at the intended site.
In accordance with the invention the delivery catheter is arranged to engage and contain the medical device within the distal end of a sheath in a low profile delivery configuration. The catheter also includes a retention mechanism that releasably engages the medical device at a single point of connection by which the medical device may be securely held during and after its expansion at the deployment site. The retention mechanism enables the clinician to release the connection to the device only after it is determined that the location and orientation of the deployed device is satisfactory. If not, it enables the clinician to maintain the position of the medical device while recapturing the device in the sheath either for repositioning or removal from the patient.
The delivery catheter is suited particularly for use with implantable devices that have a loop at the proximal end to which the retention mechanism may attach at a single connection point. The loop may be formed in one unitary piece with the medical device or may be separately attached to form an integrated unit. For example the device may be of the types described in U.S. patent applications No. 13/109,409 filed May 17, 2011 and No. 13/090,854 filed Apr. 20, 2011 in which the device has a sensor or the like attached to a fixation member that has a loop extending proximally from the proximal end of the fixation member. The disclosures of those applications are incorporated by reference herein, in their entireties. As described in those applications the implantable device preferably has a configuration at its proximal region that facilitates its progressive radial contraction as the sheath is progressively advanced distally over the device to effect recapture.
The delivery device has an elongate multi-component shaft that includes an outer sheath, an inner sheath telescopically contained in the outer sheath and an elongate inner core extending through the inner sheath, all of which are moveable longitudinally relative to each other. The retention mechanism includes a retainer mounted to the distal region of the inner sheath. The retainer is configured to normally engage the loop at the proximal end of the implantable device to secure the position of the device with respect to the inner sheath until the retainer is triggered to release the loop of the implantable device. The retainer is maintained in latched engagement with the loop as the outer sheath is retracted proximally to enable expansion of the device from its low profile configuration to its deployed configuration in engagement with the wall of the vessel. The retainer thus serves to maintain a tether to the device during deployment to prevent the device from shifting position during the deployment. While the tether is maintained the device can be recaptured by advancing the sheath distally. Only after the clinician is satisfied that the device has been placed properly in the vessel is the retainer triggered to release its connection to the device. The release is triggered in response to longitudinal movement of the inner core relative to the inner sheath that causes a cam on the core to engage the retainer in a manner that releases its connection to the loop of the device.
The various objects and advantages of the invention will be appreciated further from the following detailed description with reference to the accompanying drawings in which:
Specific embodiments of the present invention are now described with reference to the figures, wherein like reference numbers indicate identical or functionally similar elements. The terms “distal” and “proximal” are used in the following description with respect to a position or direction relative to the treating clinician. “Distal” or “distally” are a position distant from or in a direction away from the clinician. “Proximal” and “proximally” are a position near or in a direction toward the clinician.
The delivery catheter is adapted to be used with an implantable device having a loop-defining structure at its proximal end by which it may be tethered to the catheter. Although the invention is described as being used with devices such as those described in U.S. patent application Ser. Nos. 13/109,409 and 13/090,854, it also may be used to deliver other types of devices such as stents that have at least one loop-defining apex or crown or other member that includes at least a U-shaped portion. As described in those applications the implantable device includes an expandable fixation member to which a sensor may be mounted, in which the fixation member has a proximally extending loop by which it can be engaged by a tether at a single location.
As shown in the drawings, the delivery system or catheter comprises an elongate, flexible multi-component shaft 10 having proximal and distal ends 12, 14, respectively. A handle 16 is attached at the proximal end of shaft 10 and the catheter distal end terminates in a generally tapered or conical tip 18. The multi-component shaft 10 includes an elongate outer sheath 20 that contains an inner sheath 22 that, in turn, contains a tubular core member 24, longer than either of the sheaths. Tip 18 is attached to the distal end of core 24. Each of outer sheath 20, inner sheath 22 and core member 24 is moveable longitudinally with respect to the others.
Outer sheath 20 has a lumen 34 extending therethrough and a distal end terminating in a distal opening 26 that mates with a proximally facing shoulder 28 formed on distal tip 18 to form a smooth transition of the outer surfaces of sheath 20 and tip 18 when the two are mated in the delivery configuration of
Inner sheath 22 may have inner and outer diameters of about 0.050 inch and 0.070 inch, respectively, and may be formed from 70D durometer PEBA sold under the trademark PEBAX 7033. When the catheter is in its delivery configuration the implantable device is contained within the distal end of outer sheath 20 and the distal end 30 of inner sheath 22 is located proximally of the implantable device 32 except for where the proximal loop or tip of the device is in engagement with the inner sheath. The distal region 33 of inner sheath 22 is enlarged in diameter and wall thickness. For example, in the illustrative embodiment region 33 may have an inner diameter of about 0.100 inch and an outer diameter of about 0.150 inch. The enlarged diameter region may be of the order of about one centimeter long. It may be formed as a separate piece that is joined to the distal end of the smaller diameter proximal section.
Tubular core 24 has a lumen 31 receptive to a medical guidewire as suggested at 35 in the drawings. The tubular core may be formed from polyimide reinforced with stainless steel braiding and may have an outer diameter of about 0.031 inch and an inner diameter of about 0.021 inch for use with a 0.018 inch diameter guidewire. For a guidewire having a diameter of 0.035 inch, core 24 may have an inner diameter of about 0.038 inch and an outer diameter of about 0.046 inch. Distal tip 18 is attached to the distal end of core 24 and may be formed from 35D durometer PEBA or a blend of 40D durometer PEBA and barium sulfate. Tip 18 has a lumen 31 that is a continuation of core lumen 34. In the illustrative example the outer diameter of distal tip 18 may be 0.184 inch to match the outer diameter of outer sheath 20. As described in further detail below, an actuating cam 36 is mounted to core 24 in a position to enable it to trigger release of the implantable device from the retaining mechanism. Cam 36 may be formed as an integral part of distal tip 18 or may be formed separately and attached to core 24.
The delivery catheter includes a retention mechanism, indicated generally at 38, by which the implantable device 32 can be tethered to the catheter until the clinician desires to release it from the delivery catheter (see also
As shown in more detail in
Operation of the catheter may be controlled from the handle 16 at the system proximal end 12. The proximal end of inner sheath 22 extends into the handle and is attached, as by bonding, at its proximal end to a two-port luer fitting 60 that is securely mounted in the proximal end of the housing 17 that forms the handle. The proximal end of outer sheath 20 extends into the handle and is attached to a slide 62. Slide 62 is movably mounted about and guided along inner sheath 22 within handle 16. Slide 62 is operated by a thumb button 64 that extends out of the side of housing 17 through a longitudinal slot 63. Moving button 64 proximally or distally, as described in more detail below, controls the relative longitudinal positions of inner and outer sheaths 20, 22. The respective lengths of the sheaths and slide control enable a range of movement in which the distal end of outer sheath 20 can be moved between an extended distal position and a retracted proximal position that are distally beyond the distal end of inner sheath 22 and proximally of the retention mechanism, respectively.
Inner core 24 extends through inner sheath 22 and through the straight-through port of two-port luer fitting 60. Side port 61 of the luer fitting enables fluid communication with the patient's vessel through inner sheath 22. A cap 66 is removably attached to the proximal protruding end of core 24 and may be used to manipulate the longitudinal position of the core relative to the other shaft components.
The device may be loaded over guidewire 35 and advanced into the patient's entry vessel, such as the femoral artery, and then manipulated and navigated through the patient's vasculature until the medical device is positioned at the target site where it is to be deployed. Once positioned, the deployment procedure may be initiated by extending core 24 distally so that distal tip 18 will be clear of the deployment operation (
The clinician then may observe the position and orientation of medical device 32, e.g. fluoroscopically, to determine if it has been placed properly. If so, it can be released from retention mechanism 38 and the delivery system then may be withdrawn from the patient. With outer sheath 20 maintained in its retracted position, device 32 is released by retracting core 24 proximally within inner sheath 22. As cam 36 on core 24 engages follower 44 of retainer 40 it will resiliently bend the retainer radially outwardly to disengage finger 50 from its socket 52 and release loop 57 of medical device 32. With the device so deployed, the multi-component shaft 10 then can be removed.
In the event that the position or placement of medical device 32 is unsatisfactory, the clinician can recapture the medical device by maintaining retainer mechanism 38 in engagement with loop 57 of the device and advancing outer sheath 20 distally over the device by operating thumb button 64. When the device has been recaptured in the outer sheath, core 24 is retracted proximally to engage shoulder 28 of tip 18 to abut distal opening 26 of outer sheath 20. The delivery system then can be manipulated to reposition implant device 32 as desired, followed by the deployment procedure described above. Alternatively, the recaptured device may be removed from the patient together with the delivery catheter.
Thus, the invention provides a simple, easily operated system for deploying a medical device in a body lumen that reduces the risk of the device shifting out of position during deployment by maintaining a firm, mechanical tether at a single point of connection to the device until it is confirmed that it has been deployed as desired. It should be understood, however, that the foregoing description of the invention is intended merely to be illustrative and that other modifications, embodiments and equivalents that incorporate the principles of the invention may be apparent to those skilled in the art.
