This invention relates to actively-tracked medical devices. More particularly, the present invention is related to a steerable sheath used in interventional vascular procedures to deliver tools into the human body, a dilator used in conjunction with the steerable sheath and a transseptal puncture device, which can be actively visualized and/or tracked in a magnetic resonance imaging (MRI) environment.
MRI has achieved prominence as a diagnostic imaging modality, and increasingly as an interventional imaging modality. The primary benefits of MRI over other imaging modalities, such as X-ray, include superior soft tissue imaging and avoiding patient exposure to ionizing radiation produced by X-rays. MRI's superior soft tissue imaging capabilities have offered great clinical benefit with respect to diagnostic imaging. Similarly, interventional procedures, which have traditionally used X-ray imaging for guidance, stand to benefit greatly from MRI's soft tissue imaging capabilities. In addition, the significant patient exposure to ionizing radiation associated with traditional X-ray guided interventional procedures is eliminated with MRI guidance. Presently, however, due to the lack of appropriate surgical instrumentation MRI is not available to interventionalists for use during interventional therapy to accurately track and precisely guide medical devices to regions of a patient needing treatment.
By way of example, the left atrium of the heart is the most difficult cardiac chamber to access percutaneously. Although the left atrium may be reached via the left ventricle and mitral valve, manipulation of catheters requiring two 180 degree turns may be cumbersome and time consuming for the surgeon. Thus the transseptal puncture is the procedure of choice because it permits a direct route to the left atrium via the intra-atrial septum and systemic venous system. The technique has been used for mitral valvuloplasty and ablation in the left heart and with the explosion of interest in catheter ablation of atrial fibrillation, transseptal puncture is increasingly being adopted by cardiac electrophysiologists and the method of choice. However, it is critical for cardiac electrophysiologists interested in transseptal puncture techniques to be able to track sheaths for carrying dilators and transseptal puncture devices in an MR environment to know when the transseptal device has punctured the septum to avoid unintentional perforation of the opposite side of the heart.
While there are many types of sheaths, dilators and transseptal needles currently available for transseptal puncture (and other medical procedures) few are well-suited for use in an MRI environment and to the inventor's knowledge none are actively tracked. For example, deflectable (i.e., steerable) sheaths including multi-directional, bi-directional and uni-directional deflectable catheters are known. However, many of these sheaths have ferromagnetic components that pose a safety hazard to the patient in a magnetic field environment, as they can cause injury to the patient, as they may move in an undesired manner due to the magnetic field. The ferromagnetic components can also cause image distortions, thereby compromising the effectiveness of the procedure. Still further, such sheaths may include metallic components that may cause radiofrequency (RF) deposition in adjacent tissue and, in turn, tissue damage due to an extensive increase in temperature.
Similarly, dilators and transseptal needles currently available have the same problems, i.e. they either include ferromagnetic components that cause image distortions or include metallic components that cause RF deposition in tissue.
Moreover, it is difficult to track and/or visualize the location of the aforementioned sheaths, dilators and transseptal needles in an MRI environment. In general, there are two types of tracking in an MRI environment: active tracking and passive tracking. Active tracking is more robust than passive tracking but typically involves resonant RF coils that are attached to the device and directly connected to an MR receiver allowing for the determination of the three-dimensional coordinates of the resonant RF coils within the scanner. To the inventors' knowledge neither active nor passive tracking techniques are presently utilized in conventional sheaths, dilators or transseptal needles.
Thus, there is a need for sheaths, dilators and transseptal needles that can be used alone or in combination with each other that can be actively and effectively tracked and/or visualized in an MRI environment.
The shortcomings of the present steerable sheaths, dilators and transseptal needles are addressed by the actively tracked medical devices in accordance with the invention. The actively-tracked medical devices in accordance with the invention are directed to a deflectable tip sheath, a dilator and a transseptal needle that may be used alone or in combination with each other.
The actively-tracked medical device in accordance with the invention substantially obviates the deficiencies and disadvantages associated with the related art as set forth above. More specifically, the present invention is directed to a deflectable sheath, a dilator and a transseptal needle that can be actively tracked in an MRI environment, without excessive RF deposition (i.e., local tissue heating) and the other safety and procedural drawbacks associated with the prior related art.
In one aspect of the invention, a deflectable sheath that can be easily and effectively visualized and actively tracked in an MRI environment is provided.
In another aspect of the invention an actively tracked dilator that is used in conjunction with a deflectable sheath and effectively visualized and tracked in an MRI environment is provided.
In yet another aspect of the invention a deflectable sheath and/or dilator that is effective when used in an MRI environment and does not, among other things, distort the image, and does not cause local tissue damage due to excessive RF deposition along the length of the catheter is provided.
In yet another aspect of the invention, a transseptal puncture device that may be used in combination with the aforementioned actively-tracked, deflectable sheath and/or dilator is also provided.
For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:
Numerous structural variations of an MR compatible steerable sheath and dilator that can be actively tracked in accordance with the invention are contemplated and within the intended scope of the invention. Those of skill in the art will appreciate that the exemplary actively tracked sheath and/or dilator can be accomplished in a variety of ways. Those of skill in the art will also appreciate that the transseptal puncture device may comprise numerous structural variations. Therefore, for purposes of discussion and not limitation, exemplary embodiments of the actively tracked steerable sheath, dilator and transseptal puncture device will be described in detail below.
Actively tracking the medical devices in accordance with the invention may be accomplished by integrating one or more tracking coils into the sheath or the dilator. Tracking coils may include wound tracking coils or printed circuit board (PCB) tracking coils. Active tracking may also be accomplished by integrating tracking coils into the dilator and using the actively tracked dilator to track both the sheath and transseptal needle in in vivo MRI applications. In alternative embodiments, tracking coils may also be incorporated into the transseptal needle.
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Tubular shaft may include two or more lumens. One lumen may comprise the main lumen that allows for the passage of the transseptal needle as well as fluid such as contrast and saline. Additional lumens may be used to house transmission lines that connect the tracking region to the proximal hub. Tubular main shaft may also be constructed of two tubes, an inner tube that has a main lumen as well as two 180 degree opposed channels that receive the transmission lines and an outer tube that slides over the inner tube and transmission lines.
In an alternative embodiment an inner tube that has a simple circular profile may create the main lumen for the dilator and includes an outer tube that has a profile such that it slides over the inner tube, but also contains 180 degree channels that receive the transmission lines.
The main tubular shaft may also comprise a single tube that is reflowed over the transmission lines. The proximal hub could be connected to the main shaft by an over molding process or with adhesive. The main shaft could be connected to the tracking region by a reflow process or with adhesive.
Distal end 140 includes transition section 180, deflectable tip portion 200, and metal ring 220. Those of skill in the art will appreciate that metal ring 220 may comprise a metal foil. Metal ring 220 may be provided at the deflectable tip portion for spoiling the active tracking signal on a medical device (such as a dilator) inserted into sheath 100 and for identifying and/or tracking the tip 280 of the sheath. Spoiling the tracking signal from a device inserted in the sheath at a specific and limited location along the sheath provides a method for identifying that location on the sheath during active MR tracking.
Pressure relief holes 240, 260 may be formed in the tubular shaft 120 at the distal end 140. Those of skill in the art will appreciate that while only two pressure relief holes 240, 260 are shown there may any number of pressure relief holes formed and still be within the scope of the invention. When retracting an item housed by the sheath 100, such as a dilator, catheter or MR active tracking system, pressure may form at the end of the sheath thereby drawing or sucking in tissue. Pressure relief holes 240, 260 are designed to reduce this pressure thereby ameliorating the risk of tissue damage.
Transition section 180 is optionally included for purposes of manufacturability. The deflectable tip section 200 has a significantly lower durometer making it more malleable and flexible than the main body portion of tubular shaft 120 which has a higher durometer or, in other words, quite stiff. As a consequence, these two sections do not bond to one another well. Transition section 180 has a mid-range durometer allowing it to bond well to both the deflectable tip section 200 and the main body of the tubular shaft 120. Those of skill in the art will appreciate that the transition section 180 may be of any length desired so as to provide an adequate transition between the distal tip portion 200 and the main body portion 170. In one exemplary embodiment transition section may range from about 0.25 to about 0.75 inches. In addition, those of skill in the art will appreciate that transition section may be eliminated and the deflectable tip section 200 may be coupled to the main body of tubular shaft 120 by means known to those of skill in the art without departing from the spirit of the invention.
Steerable sheath 100 includes central lumen 300 therewithin. In one aspect of the invention, the inner diameter of the tubular shaft 120 is approximately 6 French or greater but those of skill in the art will appreciate that varying internal diameters may be used depending on the particular application and instrumentation required without departing from the scope of the present invention. Central lumen 300 may include one or more liners (not shown) disposed therewithin to allow for easier movement of instruments therethrough. Liners may comprise materials made from polytetrafluoroethylene (PTFE), fluorinated ethylene propylene copolymer (FEP), nylons and combinations of the foregoing. Alternatively, the lumen 300 may be coated with any such polymers. The polymer tubular shaft 120 may also include one or more passive visualization markers, such as a ferrous or magnetic marker (not shown), disposed circumferentially about the tubular shaft 120 at one or more locations along the length thereof and/or one or more active visualization markers such as an active tracking coil along the length of the tube. An active tracking coil may comprise one or more small antennas integrated into the device and include traces on a circuit board, coiled wire, and/or a dipole. If an active visualization marker is used, one or more devices may be included in the conductors to mitigate RF field heating may be included. Such devices include chokes, transformers, impedances, and other such devices known to those of skill in the art. One or more fluoroscopy markers (not shown) may also be included along the length of the polymer tubular shaft 120. Alternatively, an active tracking device may be eliminated from the sheath and instead be integrated into the dilator. The dilator may then be used to track the location of the sheath as described below.
One or more optional fluid ports (not shown) may be located on the proximal end 160 of the tubular shaft 120 to allow for homeostasis of the sheath with the patient body. The fluid port(s) allows access for the user or physician to aspirate blood from the steerable sheath lumen 300 and flush with saline. Aspirating and flushing of the sheath prevents air from entering the body before and during insertion of a dilator, tool and/or other instrumentation.
In addition, or as an alternative to active/passive tracking of the sheath, measurements taken from a dilator (or catheter) located within the sheath may be used to determine the location of the tip of the sheath. The change in the electrogram signal (in the case of a catheter) or tracking signal (for any actively tracked device) may then be used to manually or automatically mark the sheath tip on the MR image and/or an associated visualization/navigation tool. In other words, when a tracking coil on an actively tracked device exits the sheath the amplitude of the tracking signal will increase. In the case of a catheter with electrodes, the measured electrogram amplitude between of the one or more electrodes increases while impedance decreases and differs from when the catheter is inside the sheath. Variation in either electrogram or tracking signal measurements can be used for tracking of the sheath tip.
In an alternative embodiment, one or more tracking coils may be integrated into a dilator (as best seen in
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Puncture plate 614 is operably coupled to shaft 610 by connector 618. Those of skill in the art will appreciate that shaft 610 may also be integrally coupled to puncture plate 614 or removably coupled via connector 618. Shaft 610 and connector 618 may be constructed from the same or different materials. In another aspect of the invention connector 618 and shaft 610 may be integrally formed. In another aspect of the invention, connector 618 provides added strength to the interface where the shaft joins to the puncture plate 614 and functions as a strain relief.
Housing 616 is operably coupled to puncture plate 614 and houses an insertion depth sensor (not shown) that provides information to the physician about how deep the transseptal needle has been inserted into the dilator. Housing 616 may also house transformers and other electronics that provide tactile feedback to the physician about needle depth. For example, the needle handle may be structured to vibrate as the needle is about to exit the dilator tip.
The transseptal puncture device 600 may be constructed from a single material or a combination of materials. Suitable materials include rigid non-conductive materials such as carbon fiber composites, glass fiber reinforced epoxy resin, polyether ether ketones (PEEK), polyetherimides (Ultem), polycarbonates and the like. In combination, the shaft 610 and needle portion 612 may prevent MR induced heating at the needle, for example if the bulk of the transseptal needle is non-conductive and the length of the conductive section is sufficiently small.
In one aspect of the invention, as best seen in
In another aspect of the invention, and as best seen in
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Puncture tip/needle 622 may be constructed from materials selected from polyimides, long-chain aliphatic polyamides such as GRILAMID (EMS-GRIVORY), thermoplastic elastomers including polyether block amides such as PEBAX (Arkema) and polyester elastomers such as HYTREL (Dupont), and combinations of the foregoing. The puncture needle 622 may also be of conventional metal construction, such as stainless steel, titanium, nonmagnetic, nickel-cobalt-chromium-molybdenum alloys (such as MP35N), Nitinol, and other similar biocompatible metals, with an overall length of 4 inches or less, or constructed of a rigid non-conducting material as describe above. In another aspect, the needle 622 may be constructed using a metal having a polymer shaft over molded onto the needle as best seen in
After puncture tip 622 is over-molded or bonded to first cannula 624, a second cannula 626 is slidably positioned over first cannula 624. The inner diameter of second cannula 626 is greater than the outer diameter of first cannula 624 while the outer diameter of second cannula 626 is substantially equal to the outer diameter of puncture tip/needle 622 to ensure a tight bond between them and to ensure that a continuous outer surface is formed. Second cannula 626 is slidably received by first cannula 624 until the distal portion of the second cannula 626 abuts the proximal surface of the puncture tip 622 at point 628 best seen in
In other aspects of the transseptal needle, the cannula may be solid or hollow. The cannula may be made of MRI compatible materials such as PEEK, Ultem, Polycarbonate, or Glass Fiber reinforced Epoxy. If the cannula is hollow, it may be constructed to have a lumen that connects the distal puncture tip to the proximal handle. The distal puncture tip geometry could be created by a grinding process to create many different geometries. Alternatively, the distal puncture tip could be created by bonding or over molding a separate sharp component to the cannula. This bonded component could be solid or have a through hole. If the bonded component is solid, there could be flush holes proximal of the solid tip.
The transseptal needle tip in accordance with the invention could be passively tracked. The transseptal needle tip may be tracked by having a small metal component that interferes with the dilators tracking component and thereby indicates that the transseptal tip is passing through the dilator tracking region. The transseptal needle tip may also incorporate an active tracking region in a similar fashion to the dilator. (Tip coils, Flat Flex Circuit, etc . . . )
The transseptal needle may be tracked with a depth sensor that indicates the linear position of the needle in relation to the dilator. This information indicates the translational position of the needle tip in relation to the dilator, effectively tracking the needle. The depth sensor may be located proximally in the needle hub or dilator hub. Conversely, the depth sensor may be located distally in the needle tip or dilator tip.
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The transseptal puncture device may use one or more methods of MR tracking. In a first aspect, the actively tracked sheath and/or dilator described above may be utilized. In this first aspect, the transseptal puncture device is used in conjunction with the actively tracked sheath and/or dilator with lumen. A tracking coil is integrated into the dilator and the transseptal needle is inserted through a lumen in the dilator and tracked in the method described above.
In another aspect, MR tracking may consist of visualization of the needle using passive markers. In yet another aspect, a coupling between an active coil in the dilator and a metallic needle on the device may be provided. In another aspect of tracking, an electronic sensor may be integrated into proximal region of the needle shaft or needle handle to determine the needle penetration depth and the position of the needle tip relative to the location of the tracking coils in the dilator. In another aspect of tracking, an electronic sensor may be integrated in the distal region of the needle tip or dilator to determine the relative position of the needle tip in relation to the dilator tip. The transseptal puncture device in accordance with the invention may be used to puncture the septum of the heart. To determine when the septum has been crossed, and to determine the pressure applied to the septum, a pressure sensor, such a fiber optic Bragg grating, may also be placed in the distal needle portion 622 of the device 600.
Although the present invention has been described with reference to preferred embodiments, those of ordinary skill in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
Filing Document | Filing Date | Country | Kind |
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PCT/US2014/048583 | 7/29/2014 | WO | 00 |
Number | Date | Country | |
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61859528 | Jul 2013 | US | |
61974700 | Apr 2014 | US |