Interventional medical systems and improved assemblies thereof and associated methods of use

A system includes a delivery catheter and a separately-packaged implantable medical device assembly. The assembly includes a relatively compact implantable medical device, a support shaft, a tether, and a snare mandrel. The tether, which extends in the support shaft, has a distal portion coupled to the device, at a distal end of the support shaft, and a proximal portion protruding from a proximal end of the support shaft, for engagement by a hook of the snare mandrel. An operator may use the engaged snare mandrel to pull the support shaft into a lumen of an inner shaft of the catheter so that the coupled device comes into engagement with a flared end of the catheter inner shaft. Then, after locking the proximal portion of the tether within the catheter, the operator may advance a receptacle of the catheter over the device.

TECHNICAL FIELD

The present invention pertains to the delivery of implantable medical devices, and more particularly to systems, improved assemblies thereof and associated methods that facilitate the securing of relatively compact implantable cardiac medical devices to delivery catheters.

BACKGROUND

The traditional implantable cardiac pacemaker includes a pulse generator device to which one or more flexible elongate lead wires are coupled. The device is typically implanted in a subcutaneous pocket, remote from the heart, and each of the one or more lead wires extends therefrom to a corresponding electrode, coupled thereto and positioned at a pacing site, either endocardial or epicardial. Mechanical complications and/or MRI compatibility issues sometimes associated with elongate lead wires are well known to those skilled in the art and have motivated the development of cardiac pacing devices that are wholly contained within a relatively compact package for implant in close proximity to the pacing site, for example, within a right ventricle RV of the heart.

FIG. 1is a schematic showing an example of an implanted relatively compact implantable medical device100.FIG. 1illustrates medical device100having been delivered through a catheter200, which an operator has maneuvered up through the inferior vena cava IVC and the right atrium RA into the right ventricle RV. Device100is shown deployed at an implant site in the right ventricular apex. Another potential cardiac implant site may be within an appendage of a right atrium RA, or within a coronary vein. Device100and catheter200may be similar to the device and tool, respectively, described in the commonly assigned United States Patent Application US 2015/0094668.

FIG. 1further illustrates device100including a hermetically sealed enclosure105containing pulse generator electronics and a power source (not shown), pace/sense electrodes111,112formed on an exterior surface of enclosure105, and a fixation member, for example, formed from a plurality of elastically deformable fingers115mounted to a distal end of enclosure105, in proximity to electrode111, in order to fix, or secure electrode111against the endocardial surface at the implant site. Enclosure105is preferably formed from a biocompatible and biostable metal such as titanium overlaid with an insulative layer, for example, medical grade polyurethane or silicone, except where electrode112is formed as an exposed portion of the metal. An hermetic feedthrough assembly, such as any suitable type known to those skilled in the art, couples electrode111to the pulse generator contained within device enclosure105.

Device100is shown fixed at the implant site by fingers115of the fixation member thereof, but still secured to catheter200by a flexible tether280, which extends out from a distal opening203of catheter200, being joined to an engaging member121of device100. Thus, the operator, via tether280, is able to test the fixation of device100at the implant site, and/or remove device100from the implant site for repositioning at a more suitable site, if necessary. Once satisfied with the implant of device100, the operator can separate tether280from device100, for example, by releasing an end of one length281of tether280, and then pulling on an end of another length282of tether280to withdraw an entirety of length282proximally through delivery catheter200so that tether length281is pulled distally and through engaging member121.

Securing device100to catheter200with tether280is typically accomplished by a process in which tether280is looped through engaging member121, after which first and second lengths281,282of tether280are threaded through one or more lumens of catheter200such that opposing ends thereof protrude out from a proximal opening201of catheter200. Because this process may be somewhat tedious, a manufacturer of device100and catheter200may secure the two together as a system, and provide the system to the operator in a single sterile package. However, due to shelf life considerations, the packaging of such a device separately from the associated catheter may be preferred, so that alternative means for securing the device to the catheter may be desired, to increase the ease by which an operator may secure the device to the catheter at the time of an implant procedure.

SUMMARY

Interventional medical systems disclosed herein include a delivery catheter and a separately-packaged implantable device assembly. According to some embodiments, the delivery catheter includes an elongate inner shaft having a flared end that surrounds a distal-most opening of a lumen of the inner shaft, and a receptacle in sliding engagement with the inner shaft; and the device assembly includes a relatively compact implantable medical device, a support shaft, and a tether that extends within the support shaft with a distal portion thereof, which protrudes from a distal end of the support shaft, coupling the device to the support shaft. The device assembly may further include an elongate snare mandrel that has a distal end formed in a hook to engage with a proximal portion of the tether, which protrudes from a proximal end of the support shaft, so that an operator may use the snare mandrel to pull the support shaft into the lumen of the inner shaft of the delivery catheter and bring the coupled device into engagement with the flared end of the inner shaft. When the coupled device is thus engaged, the operator may lock the proximal portion of the tether within the delivery catheter and then advance the receptacle of the catheter over the device so that the device is contained therein. In some embodiments, the implantable device assembly further includes a tether retainer attachable and detachable from the proximal portion of the tether.

DETAILED DESCRIPTION

The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following description provides practical examples, and those skilled in the art will recognize that some of the examples may have suitable alternatives.

FIG. 2Ais a plan view of an interventional medical system3400, according to some embodiments.FIG. 2Aillustrates a delivery catheter300of system3400including a handle310, an elongate outer shaft320, and a flushing assembly315coupled to handle310.FIG. 2B, which is a partial cross-section view through section line B-B ofFIG. 2A, shows a distal-most portion322of outer shaft320defining a receptacle321that has a distal-most opening303, wherein receptacle321is sized to contain an implantable medical device of system3400, such as device100, for delivery to an implant site.FIG. 2Billustrates an inner shaft350of catheter300extending within a lumen302of outer shaft320that is in fluid communication with receptacle321. According to the illustrated embodiment, receptacle321is in sliding engagement with inner shaft350, and may be retracted and advanced relative to inner shaft350(for the purposes described in greater detail below) by means of a first control member311of handle310(FIG. 2A), to which outer shaft320is coupled. Furthermore, lumen302of shaft320may be flushed via flushing assembly315.

According to some embodiments, outer shaft320may be constructed in a similar fashion to a deployment tube of a tool described in co-pending and commonly assigned U.S. Patent Application 2015/0094668, Ser. No. 14/039,937. For example, outer shaft320may be formed by a stainless steel braid-reinforced medical grade polymer, for example, one or more appropriate grades of polyether block amide, which are arranged for decreasing stiffness from handle310to distal-most portion322(e.g., including PEBAX® 3533, 6333, 4033, and 7233), and receptacle321may have a diameter of up to approximately 0.3 inch (7.6 mm). Distal-most portion322may have a radiopaque filler blended therein, or a radiopaque marker (e.g., Tungsten-filled Vestamid®) bonded thereto, either according to methods known to those skilled in the art.FIG. 2Afurther illustrates handle310including a second control member312which may be coupled to a pull-wire mounted in inner shaft350, wherein the pull-wire is operable, via control member312, to deflect inner and outer shafts350,320for navigation of catheter300to an implant site, for example, as described above in conjunction withFIG. 1.

FIG. 2Bfurther illustrates device100being secured to catheter300and contained within receptacle321of outer shaft320such that a proximal end11of device100is engaged with a flared end352of inner shaft350. According to the illustrated embodiment, flared end352defines a distal-most opening35into a lumen305of inner shaft350(seen inFIGS. 4A-B), which lumen305is sized to receive a support shaft450of a medical device assembly400of system3400, which is shown inFIGS. 3A-B. (Note that inner shaft350may include another lumen that extends alongside lumen305and that receives the aforementioned pull wire.) According to an exemplary embodiment, flared end352may be formed from a polyether block amide, for example, PEBAX® 7233, and the remainder of inner shaft350may be formed by a tube, for example, extruded polyether block amide, polyurethane, or silicone rubber, or a composite thereof, which includes an overlay, for example, formed of braid-reinforced polyether block amide.

FIG. 3Ais a perspective view of medical device assembly400, which is configured for securing a relatively compact medical device, such as device100, to catheter300, and is packaged separately from catheter300, according to some embodiments. Thus, as alluded to above, a shelf life of catheter300in its own package is independent of that of device100when packaged separately as part of assembly400. This may be particularly significant when electrode111of device100is manufactured with an anti-inflammatory steroid embedded therein.FIG. 3Aillustrates assembly400including device100, support shaft450, and an elongate tether480, wherein tether480is coupled to device100, and has a first length481extending within a lumen45of support shaft450, and a second length482extending alongside first length481, either within lumen45, or within another lumen of support shaft450(not shown) that extends alongside lumen45, or adjacent an outer surface of support shaft450.FIG. 3Afurther illustrates device assembly including an optional tether retainer460attached to a proximal portion484of tether480(seen inFIG. 3B) in proximity to proximal end456of support shaft450.

FIG. 3Bis a plan view of various parts of device assembly400, according to some embodiments, wherein the parts are shown separated from one another.FIG. 3Billustrates the parts of assembly400further including an elongate snare mandrel490, which has a distal end494formed in a hook. According to the illustrated embodiment, the hook of distal end494is designed to engage with proximal portion484of tether480, according to a method described below in conjunction withFIGS. 4A-C.FIG. 3Bfurther illustrates proximal and distal portions484,483of tether480each joining first and second lengths481,482of tether480together at opposite ends thereof; and, when tether480is assembled together with support shaft450, as illustrated inFIG. 3A, tether proximal portion484protrudes from proximal end456of shaft450and tether distal portion483protrudes from distal end457of shaft450. Thus, tether proximal portion484can be engaged by mandrel490, for example, as illustrated inFIG. 4A, and tether distal portion483can couple to engaging member121of device100, for example, as illustrated inFIG. 4B.

With further reference toFIG. 3B, optional tether retainer460is shown in an opened position with first and second parts460A,460B thereof separated from one another.FIG. 3Billustrates second part460B including a pair of grooves468, to receive first and second lengths481,482therein, and a receptacle462to receive a protrusion463of first part460A in interlocking engagement therewith when retainer460is in a closed position, for example, as illustrated inFIG. 3A. According to an exemplary embodiment, retainer460is formed from any suitable medical grade plastic that has living hinge properties (e.g., Polypropylene Pro-Fax™ 6523) so that first and second parts460A,460B may be joined together by such a hinge466.

FIGS. 4A-Dare various plan views of system3400outlining some methods for securing device100within receptacle321of catheter300.

With reference toFIG. 4A, an operator has inserted snare mandrel490into lumen305of inner shaft350of catheter300, so that the hook formed in distal end494of snare mandrel490protrudes from distal-most opening35of inner shaft350.FIG. 4Aillustrates distal-most opening35having been exposed at, or distal to, distal-most opening303of receptacle321by retracting receptacle321relative to inner shaft350, for example, by moving first control member311per arrow R (FIG. 2A). With reference back toFIG. 3B, a length Lmof snare mandrel490is sufficiently greater than a length of catheter inner shaft350, so that a proximal end of mandrel490protrudes from a proximal end of catheter300, for example, from a proximal port opening301shown inFIG. 2A.FIG. 4Afurther illustrates device assembly400oriented so that tether proximal portion484, protruding from support shaft proximal end456, is directed toward distal-most opening35of inner shaft350of catheter300. Thus, the operator can engage the hook at distal end494of snare mandrel490with tether proximal portion484, as shown inFIG. 4A, and then apply a pull force to the proximal end of the inserted snare mandrel490to pull support shaft450, per arrow P, into lumen305of catheter inner shaft350, as illustrated inFIG. 4B.

When, in some embodiments, lumen305of catheter inner shaft has a diameter of approximately 1.6 mm, a maximum outer diameter of each of snare mandrel490and support shaft450may be no greater than approximately 1.14 mm, so that each may be received in sliding engagement within lumen305. According to an exemplary embodiment, snare mandrel490is formed from a medical grade stainless steel, tether480is formed from a polyester fiber having a fluoropolymer coating such as PTFE, and support shaft450is formed from an extruded polyether block amide, polyurethane, or silicone rubber, or a composite thereof.

With reference toFIG. 4C, the operator may continue to pull, per arrow P, until tether proximal portion484protrudes from proximal port opening301of catheter300and the coupled medical device100comes into engagement with flared end352of catheter inner shaft350. According to some methods, before advancing receptacle321of catheter300relative to inner shaft350, per arrow A, so that device100is contained in receptacle321, as shown inFIG. 2B, the operator may lock tether480within catheter300, for example, via a locking member318mounted in handle310. Locking member318is described below in conjunction withFIG. 5. Finally, in those embodiments of device assembly400that include tether retainer460, the operator, having detached retainer460from tether proximal portion484prior to engaging mandrel490therewith, re-attaches retainer460to tether proximal portion484, as illustrated inFIG. 4D, prior to navigating system3400to an implant site. Once the operator has navigated distal-most opening303into proximity with a target implant site, the operator may retract outer shaft320relative to inner shaft350and the contained device100, for example, by moving control member311per arrow R (FIG. 2A), in order to engage fixation member fingers115of device100with tissue at the site. Once fixation member fingers115are engaged, in addition to evaluating an electrical performance of device100at the site, the operator may test the fixation of device100by grasping retainer460and applying a pull force to tether480. If the operator determines that device100needs to be repositioned to a more suitable site, the operator, again grasping retainer460, may apply a pull force sufficient to disengage fingers115. But, if the operator is satisfied with the implant, the operator may detach retainer460, unlock tether480, cut tether proximal portion484, and pull on one of tether lengths481,482to withdraw an entirety of the length proximally through delivery catheter200so that the other length is pulled distally out through device engaging member121.

FIG. 5is a plan view of an internal configuration of catheter handle310, according to some embodiments, wherein a first portion of an outer surface, or shell510A of handle310is removed, being separated from a second portion of the shell510B.FIG. 5illustrates tether lengths481,482extending within locking member318and tether proximal portion484protruding from proximal port opening301. Locking member318may be a stopcock type valve, known to those skilled in the art, wherein a lever thereof, when rotated per arrow S1, closes valve to clamp around, and secure tether lengths481,482in handle310. According to the illustrated embodiment, the lever of locking member318may extend through a corresponding aperture518formed in a recessed surface of handle shell first portion510A, when handle shell portions510A,510B are secured together.FIG. 5further illustrates proximal end456of support shaft450extending within handle310, according to some embodiments.

In the foregoing detailed description, the invention has been described with reference to specific embodiments. However, it may be appreciated that various modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims.