Sensor-bearing tip and medical device including the same

A tip for a medical device includes a hollow body having a window, a sensor positioned within the hollow body and oriented such that its active surface is pointed towards the window, and a membrane positioned within a beam path of the sensor. The membrane passes energy without preventing an outer surface of the hollow body of the tip from coming in contact with tissue, thus allowing the hollow body to deliver therapy to an adjacent tissue and/or diagnose adjacent tissue. The membrane can cover the window or the sensor. The membrane is desirably permeable to an irrigant, such that a suitable level of irrigant outflow from the window is maintained, and thin enough that it minimizes attenuation of energy passing to and/or from the sensor.

BACKGROUND

The instant disclosure relates to medical devices. In particular, the instant disclosure relates to sensor-bearing tips that can be mounted to medical devices for use in the human body, such as diagnostic and therapeutic catheters.

Catheters are used in a variety of diagnostic and therapeutic procedures, for example to diagnose and/or treat conditions such as atrial arrhythmias. For example, a catheter carrying one or more electrodes can be deployed and manipulated through a patient's vasculature and, once located at the intended site, radiofrequency (“RF”) energy can be delivered through the electrodes to ablate tissue. Alternatively, or in addition, the electrodes can be used to create a map of the electrophysiological activity of the patient's heart. Further, the electrodes can be used to localize (that is, determine the position and orientation of) the catheter as it is deployed and manipulated to the intended site.

In some catheters, an additional sensor, such as an ultrasound sensor or optical sensor, is provided in the catheter tip to provide additional information during performance of the primary diagnosis or therapy. For example, RF ablation catheters can include one or more ultrasound sensors, located within the hollow tip of the catheter, that can be used to monitor the progress of a lesion forming in the tissue being treated and/or to confirm one or more characteristics of the lesion once created.

Extant sensor-bearing tip medical devices, however, are subject to various issues, including excessive irrigant outflow, the passage of debris from the interior of the medical device into the patient's body, and distortion of signals to and/or from the sensors. Although there are known solutions to some of these problems, they very often exacerbate others (e.g., a rigid cover can be used to prevent the passage of debris, but increases signal distortion).

BRIEF SUMMARY

Disclosed herein is a tip for a medical device that includes: a hollow body including a window; a sensor including an active surface positioned within the hollow body and oriented such that the active surface is pointed towards the window; and a membrane positioned within a beam path of the sensor, wherein the membrane passes energy without preventing an outer surface of the hollow body of the tip from coming in contact with tissue. The membrane can be positioned such that it covers the window, for example by securing it to either an outer surface of the hollow body or an inner surface of the hollow body. The membrane can also have its outer edge proximate the perimeter of the window. Alternatively, the membrane can take the form of a balloon secured within the hollow tip.

In other aspects, the membrane can be positioned such that it covers the sensor. For example, the membrane can be adjacent to the sensor or adhered to the sensor, such as by chemically vapor depositing the membrane material onto the sensor.

In some embodiments, the sensor is an acoustic sensor and the membrane is an acoustically-transmissive membrane.

The sensor can sense energy coming from tissue and, in some embodiments, can transmit energy to the tissue and sense returning and/or reflected energy. The energy emitted by the sensor can be a different form of energy than the energy used by the tip to provide diagnosis and/or therapy. For example, the sensor can emit ultrasonic energy, and the tip can use radiofrequency energy to provide ablation therapy.

In some embodiments, the membrane is permeable to an irrigant. This can be accomplished, for example, by using a hydrophilic material for the membrane, by treating the membrane to be hydrophilic, by using a porous (e.g., micro- or macro-porous) material for the membrane, and/or by forming irrigation holes in the membrane (e.g., by laser drilling).

Typically, the membrane will be flexible. It can also exhibit elastomeric, viscoelastomeric, or plastic properties when deformed.

Certain advantages can be achieved by making the membrane thin, including the minimization of acoustic distortion and the attenuation of energy passing through the membrane (e.g., passing to and/or from the sensor). Thus, for example, the membrane can have a thickness of no more than 30 microns, such as between 5 microns and 25 microns or between 10 microns and 20 microns.

Also disclosed herein is a medical device including: an elongate tubular body having a distal section and including a lumen extending along its length; a hollow tip, including a window, attached to the distal end of the elongate tubular body, wherein the lumen of the elongate tubular body is in fluid communication with an interior of the hollow tip; a sensor disposed within the hollow body, wherein the sensor comprises an active surface oriented towards the window; and a membrane positioned between the active surface of the sensor and the window. The membrane can be secured to the hollow tip or, alternatively, to the elongate tubular body.

In another aspect, a tip for a medical device includes: a hollow body including a window; a sensor including an active surface positioned within the hollow body and oriented such that the active surface is pointed towards the window; a membrane deposited upon and overlying the sensor; and an irrigant dam positioned to restrict outflow of irrigant from the window. The membrane can include a chemically vapor deposited poly(p-xylylene), such as Parylene™.

DETAILED DESCRIPTION

The present disclosure provides sensor-bearing tips for use in medical devices and medical devices including the same. The tips can have a diagnostic or therapeutic function, with the sensor(s) used to monitor such function. For purposes of illustration, several exemplary embodiments will be described in detail herein in the context of a radiofrequency (“RF”) ablation catheter including an acoustic sensor (e.g., a pulse-echo transducer) that can be used to monitor the progress of the lesion being formed in an adjacent tissue. It should be understood, however, that the methods, apparatuses, and systems described herein can be utilized in other contexts (e.g., optical sensors).

FIG. 1is a schematic diagram of an ablation system100including an exemplary catheter10. As shown inFIG. 1, catheter10generally includes an elongate tubular body12having a proximal end14and a distal end16. Tubular body12defines a lumen18(not visible inFIG. 1, but shown inFIGS. 2-7). Although only a single lumen18is depicted in the figures, this is only for the sake of clarity of illustration; tubular body12can have any number of lumens18without departing from the scope of the instant teachings.

Proximal end14of tubular body12is attached to a catheter control handle20. Catheter control handle20can include, for example, an actuator (not shown) coupled to suitable structure (e.g., pull wires and/or pull rings) within tubular body12in order to effect the deflection of distal end16. It can also include connections to additional components of ablation system100as discussed in further detail below. Insofar as the construction of catheter control handle20will be familiar to those of ordinary skill in the art and a detailed understanding thereof is not necessary to make and use the teachings herein, however, no further description need be provided.

A hollow tip22is attached to distal end16of tubular body12. Tip22can be a diagnostic tip, a therapeutic tip, a hybrid diagnostic and therapeutic tip, or any other type of tip that may be desirable for a given application of catheter10.

For example, tip22can include an RF ablation element, such as a tip electrode. As such, catheter10can be connected with an ablation energy source120, such as an RF generator.

FIG. 2is a close-up and partial cross-section of hollow tip22(and a portion of tubular body12proximate distal end16) against a tissue surface24. As shown inFIG. 2, lumen18of tubular body12is in fluid communication with the interior26of hollow tip22, which is defined by a wall28of hollow tip22. An irrigant (e.g., saline) or other fluid can be delivered from fluid source124(shown inFIG. 1), through lumen18, and into hollow tip22, for example for cooling purposes, for energy transmission purposes, and/or for acoustic matching purposes.

Wall28of hollow tip22further includes a window or (“beam hole”)30(e.g., a break in wall28). Window30allows for the passage of energy to and/or from a sensor32, which, in some embodiments, is an ultrasound transducer, disposed within interior26of hollow tip22along a beam path34. It is therefore desirable for window30to be larger than the active surface36of sensor32, which is oriented towards window30, to minimize or eliminate diffraction and/or attenuation of energy passing to and/or from sensor32by reducing the likelihood that incoming and/or outgoing energy will pass through or otherwise impinge the edges of wall28defining window30.

As illustrated, sensor32is mounted to an acoustic backer38, but any suitable structure to secure sensor32within hollow tip22can be employed. Backer38can be acoustically attenuative, such that any acoustic energy that propagates backwards from sensor32towards backer38, rather than towards tissue24, is attenuated. This also allows acoustic sensor32to have a short acoustic ring-down time, making it suitable for the transmission of short pulses for pulse-echo lesion sensing.

Window30also allows for irrigant to pass out of interior26of hollow tip22, for example for tissue cooling purposes, energy transmission purposes, and/or for energy coupling to adjacent tissue. The irrigant, such as saline, can benefit the coupling and transmission of both RF ablation energy and pulse-echo acoustic energy to (and, in the case of pulse-echo energy, from) tissue24. Tissue24may naturally distend into window30.

A transducer pinger128(seeFIG. 1), which might have more than one channel, supplies pinging energy, such as electrical energy pulses, to sensor32(e.g., an ultrasound transducer). A control unit130(also shown inFIG. 1) is provided for controlling the ablation and the acoustic pinging during ablation. For instance, control unit130can be configured to carry out duty cycling or synchronization for both ablation and pinging. An acoustic pinger echo analyzer or acoustic receiver132is provided to condition and analyze the data collected by sensor32to provide one or more of lesion feedback, tissue thickness or proximity measurement, tip contact force monitoring, and pre-pop detection. The information can be presented to a practitioner (e.g., using a graphical user interface) to provide real-time assessment of the ablation. The information may additionally or alternatively be utilized by the system itself without operator intervention, for example as input to a feedback control loop to avoid steam pops and/or to achieve a desired lesion depth.

Thus, one aspect disclosed herein is directed to an RF ablation catheter with one or more acoustic transducers therein or thereon, wherein the acoustic transducer is capable of at least one of acoustic lesion feedback, catheter tip-force monitoring, tissue thickness or proximity measurement, or pre-pop warning. The catheter is capable of delivering an RF ablating tip to a patient's tissue to be ablated. These aspects and others are described in U.S. patent application publication no. 2012/0265069, which is hereby incorporated by reference as though fully set forth herein.

A fully-open window30, however, has certain attendant disadvantages. For example, it allows for a very substantial volume of irrigant outflow, which can starve smaller irrigation passageways (e.g., apertures that are not also intended to pass energy to and/or from a sensor) of irrigant. This results in decreased irrigant backpressure in hollow tip22, which can in turn lead to increased bubble formation due to a reduced boiling point, particularly when the temperature of hollow tip22increases during use (e.g., where hollow tip22functions as a radiofrequency (“RF”) ablation electrode). Similarly, a fully-open window30presents no obstacles to the passage of potentially harmful debris into the patient's body if, for example, a portion of sensor32were to break off.

Though extant devices mitigate some of these concerns (e.g., a rigid polymeric acoustic covering over window30reduces the risk of debris passing into the patient's body), they do so at the expense of other desirable aspects (e.g., a rigid polymeric acoustic covering over window30can defocus and attenuate ultrasonic energy passing therethrough and/or limit the outflow of irrigant to such an extent that blood coagulates at window30or the tissue becomes dewetted). The embodiments disclosed herein advantageously allow the simultaneous achievement of multiple desirable attributes—including, without limitation, an appropriate volume of irrigant outflow, the prevention of debris escape, avoidance of beam distortion, and the minimization of window-edge diffraction and/or attenuation of energy passing to and/or from sensor32—by placing a membrane within beam path34of sensor32(that is, between active surface36of sensor32and tissue24).

A first embodiment of a sensor-bearing hollow tip300is depicted inFIG. 3. As shown inFIG. 3, a membrane310covers window30. In particular, membrane310is secured to the inner surface311of wall28, for example by thermoforming an outer periphery313of membrane310to wall28under heat and pressure or by securing the outer periphery313of membrane310to wall28with a suitable adhesive. Outer periphery313of membrane310is proximate the perimeter of window30; that is, membrane310is roughly the same size and shape (e.g., round, oval, or other shape) as window30.

A second embodiment of a sensor-bearing hollow tip400is depicted inFIG. 4. The embodiment ofFIG. 4is similar to that ofFIG. 3, except that membrane410is secured to the outer surface411of wall28, for example by thermoforming an outer periphery413of membrane410to wall28under heat and pressure or by securing outer periphery413of membrane410to wall28with a suitable adhesive. Outer periphery413of membrane412is proximate the perimeter of window30; that is, membrane410is roughly the same size and shape as window30.

A third embodiment of a sensor-bearing hollow tip500is depicted inFIG. 5. As shown inFIG. 5, a membrane510is secured proximate sensor32, for example to acoustic backer38. To inflate membrane510, there is an inlet (e.g., passageway511) to deliver irrigant (or another suitable inflation fluid) to the space513between membrane510and sensor32/acoustic backer38).

FIG. 6depicts another embodiment of a hollow tip600. In the embodiment ofFIG. 6, membrane610comprises a balloon (or bladder) that is inflated against the inner surface of wall28, for example under pressure of an irrigant or other suitable inflation fluid, when in use. Membrane610can be secured to elongate tubular body12, for example by thermoforming membrane610to elongate tubular body12under heat and pressure at one or more locations interior to hollow tip600.

It is desirable for membranes310,410,510,610to be wettable by irrigant (e.g., saline), for example by using a material that is either naturally hydrophilic to the irrigant or has been treated to be hydrophilic to the irrigant.

It is also desirable for membranes310,410,510,610to be permeable to the irrigant (that is, membranes310,410,510,610should permit the irrigant to pass through its thickness). For example, a microporous, micropermeable, or foamlike material can be used for membrane310,410,510,610. Alternatively or additionally, a plurality of irrigation holes312,412,512,612can be provided in membranes310,410,510,610respectively, for example by laser-drilling or punching. Because irrigant flow out of windows30will be limited, however, by the presence of permeable membranes310,410,510,610there remains net positive irrigant pressure inside hollow tip300,400,500,600, which in turn suppresses bubble formation, boil-over, and thrombus formation.

Membranes310,410,510,610are flexible, in order to attain a curvilinear shape in window30, for example under pressure of an irrigant. In addition to being flexible, membranes310,410,510,610can be elastomeric (e.g., deforming elastically under irrigant pressure), viscoelastomeric (e.g., deforming elastically under irrigant pressure, but returning to its relaxed state after a time delay), plastic (e.g., deforming plastically under irrigant pressure), or may exhibit a combination of the foregoing properties.

According to certain aspects, membranes310,410,510,610have a thickness of no more than about 30 microns. For example, membranes310,410,510,610can each have a thickness between about 5 microns and about 25 microns, or between about 10 microns and about 20 microns. At these dimensions, acoustic distortion and attenuation of energy passing to and/or from sensor32are minimized, but the membrane itself remains able to withstand the irrigant pressure.

The embodiments discussed above offer the advantages of simultaneously allowing a desirable volume of irrigant outflow, preventing debris escape, avoiding beam distortion, providing excellent acoustic coupling to wetted tissue, and minimizing diffraction and attenuation of energy passing to and/or from sensor32. Each embodiment also offers additional advantages beyond those discussed above. For example, in hollow tips300and600, the bond between membrane310,610and wall28or elongate tubular body12is protected from abrasion against tissue24when catheter10is in use.

As another exemplary advantage of the embodiment illustrated inFIG. 3, because membrane310is only slightly larger than window30, there is less interference with the ability of an irrigant delivered to hollow tip300to cool the interior of wall28before flowing out of hollow tip300(e.g., through irrigant holes312or additional irrigation passageways (not shown) in wall28).

Hollow tips400,500, and600offer the additional exemplary advantage of easier installation of membrane410,510,610resulting from the ability to see the point(s) at which the membrane is bonded during assembly. That is, unlike membrane310, membranes410,510, and610are not attached to wall28at a blind point.

Still another embodiment of hollow tip700is shown inFIG. 7. As shown inFIG. 7, a membrane710is placed closely around sensor32and acoustic backer38. Indeed, membrane710can be directly deposited upon sensor32and acoustic backer38. Membrane710can be used in conjunction with a ring-shaped dam712, formed, for example, of a compressible rubber or foam material, at or near window30to control the flow of irrigant out of hollow tip700. As shown inFIG. 8, ring-shaped dam712can include a plurality of flow passageways714designed to promote a suitable volume of irrigant outflow from window30.

Membrane710can be a chemically vapor-deposited layer of a poly-para-xylylene, such as Parylene™, and, in particular, Parylene™ C. Such materials are desirably pin-hole free and can be precisely deposited over irregular surfaces substantially conformally. Membrane710can have a thickness of between about 10 microns and 15 microns.

Additional exemplary advantages (e.g., beyond the prevention of debris escape and the other advantages discussed above) of membrane710include increased mechanical capture of sensor32in the event of breakage, increased high voltage leakage protection, and ease of assembly.

Although several embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention.

For example, although the exemplary embodiments are discussed and illustrated in connection with a single sensor, the teachings herein are equally applicable to devices including additional sensors and/or more than a single window. Indeed, certain aspects disclosed herein are particularly advantageous in medical devices including several sensors (e.g., three radially-looking sensors arranged circumferentially about the hollow tip at about 120° intervals and a fourth forward-looking sensor).

All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other.