Patent Description:
The severity of a stenosis or lesion in a blood vessel may be assessed by obtaining proximal and distal pressure measurements relative to the given stenosis and using those measurements for calculating a value of the Fractional Flow Reserve (FFR). FFR is defined as the ratio of a first pressure measurement (Pd) taken on the distal side of the lesion and to a second pressure measurement taken on the proximal side of the lesion usually within the aorta (Pa). Conventionally, a sensor is placed on the distal portion of a guidewire or FFR wire to obtain the first pressure measurement Pd, while an external pressure transducer is fluidly connected via tubing to a guide catheter for obtaining the second or aortic (AO) pressure measurement Pa. Calculation of the FFR value provides a lesion specific index of the functional severity of the stenosis in order to determine whether the blockage limits blood flow within the vessel to an extent that treatment is needed. An optimal or normal value of FFR in a healthy vessel is <NUM>, while values less than about <NUM> are generally deemed significant and in need of an interventional treatment. Common interventional treatment options include balloon angioplasty and/or stent implantation.

If an interventional treatment is required, the interventional device, such as a balloon catheter, is tracked over a guide wire to the site of the lesion. Conventional FFR wires generally are not desired by clinicians to be used as guide wires for such interventional devices. Accordingly, if an intervention treatment is required, the clinician generally removes the FFR wire, inserts a conventional guide wire, and tracks the interventional device to the treatment site over the conventional guide wire.

The mounting of a pressure sensor on the distal end of a catheter, such as a microcatheter makes it difficult to isolate the pressure sensor from bending stresses experienced as a result of interaction between the pressure sensor and the housing of the catheter. Due to the high sensitivity and size of the pressure sensor used in this application, any stress placed on the pressure sensor can cause a distortion of the sensor resulting in an incorrect pressure reading or bend error. Accordingly, there remains a need for a microcatheter to obtain pressure measurements suitable for use in calculating an FFR value for a given stenosis, whereby the clinician may use a conventional or preferential guidewire instead of a FFR guidewire. In addition, there remains a need for a FFR microcatheter to minimize both the profile of the catheter and the bending stresses experienced by the pressure sensor. Various devices measuring the pressure inside a blood vessel are known from documents <CIT>, <CIT>, and in <CIT>.

Embodiments hereof relate to a catheter, such as a pressure measurement catheter, including an elongate shaft having a proximal end optionally coupled to a handle or luer fitting and a distal end having a distal opening. The elongate shaft further includes a proximal portion, an intermediate portion, and a distal portion having a distal tip. In the proximal portion of the elongated shaft, a shaft wall may define two separate lumens: a guide wire lumen and a second or pressure sensor wire lumen, extending parallel to each other or side-by-side along the proximal portion. The distal portion of the elongate shaft is configured to receive a guidewire in a distal portion of guidewire lumen thereof. The pressure sensing wire may extend to the distal portion of the elongate shaft to be coupled to a pressure sensor mounted to a deformable member on the distal tip for measuring a pressure of a fluid within lumen of vessel. The deformable member has adhesive properties and is disposed between the pressure sensor and the catheter. The deformable member reduces the amount of stress and strain transferred to the pressure sensor, thereby reducing distortion of the sensor that may result in an incorrect pressure reading.

Embodiments hereof also relate to a catheter, such as a measurement catheter, including an elongate shaft having a proximal end optionally coupled to a handle or luer fitting and a distal end having a distal opening. The elongate shaft further includes a proximal portion, an intermediate portion, and a distal portion having a distal tip. In the proximal portion of elongated shaft, shaft wall may define two separate lumens: a guide wire lumen and a second or pressure sensor wire lumen, extending parallel to each other or side-by-side along the proximal portion. The distal portion of the elongate shaft is configured to receive a guidewire in a distal portion of the guidewire lumen thereof. The pressure sensing wire lumen may extend to the distal portion of the elongate shaft to be coupled to a pressure sensor mounted to an intermediate member on the distal tip for measuring a pressure of a fluid within lumen of vessel. The intermediate member is disposed between the pressure sensor and the catheter. The intermediate member has a first portion, which is coupled to pressure sensor and a second portion, which is coupled to the catheter. The intermediate member also has a hinge disposed between the first and second portions. When the distal portion of the catheter bends away from the pressure sensor, the catheter does not contact the intermediate member or the pressure sensor because the intermediate member maintains the pressure sensor is a substantially straight configuration relative to the bending catheter. When the distal portion of the catheter bends towards the pressure sensor, the catheter applies a force on the intermediate member. As a result of this force, the first portion of the intermediate member rotates about the hinge in the same direction as the applied force. Since the intermediate member moves the pressure sensor away from the bending catheter, the amount of stress and strain transferred to the pressure sensor is reduced, thereby reducing distortion of the sensor that may result in an incorrect pressure reading.

Embodiments hereof also relate to a catheter, such as a measurement catheter, including an elongate shaft having a proximal end optionally coupled to a handle or luer fitting and a distal end having a distal opening. The elongate shaft further includes a proximal portion, an intermediate portion, and a distal portion having a distal tip. In the proximal portion of elongated shaft, shaft wall may define two separate lumens: a guide wire lumen and a second or pressure sensor wire lumen, extending parallel to each other or side-by-side along the proximal portion. The distal portion of the elongate shaft is configured to receive a guidewire in a distal portion of the guidewire lumen thereof. The pressure sensing wire lumen may extend to the distal portion of the elongate shaft to be coupled to a pressure sensor on the distal tip for measuring a pressure of a fluid within lumen of vessel. Although the pressure sensor is coupled to the distal tip of the catheter, the pressure sensor is suspended above the shaft wall of the catheter by a step extending from the shaft wall. An electrical interconnect (or other wiring) is mounted on the step such that a distal end of the electrical interconnect extends past the step and is disposed within a pocket on the distal tip of the catheter. The pressure sensor is coupled to the distal end of the electrical interconnect and is thereby disposed within the pocket without contacting the shaft wall or the side walls of the pocket. Since the pressure sensor has no contact with the catheter, the amount of stress and strain transferred to the pressure sensor is reduced or even eliminated, thereby reducing distortion of the sensor that may result in an incorrect pressure reading.

Specific embodiments of the present invention are now described with reference to the figures, wherein like reference numbers indicate identical or functionally similar elements. While the disclosure refers to illustrative embodiments for particular applications, it should be understood that the disclosure is not limited thereto. Modifications can be made to the embodiments described herein without departing from the scope of the present disclosure. Those skilled in the art with access to this disclosure will recognize additional modifications, applications, and embodiments within the scope of this disclosure and additional fields in which the disclosed examples could be applied. Therefore, the following detailed description is not meant to be limiting. Further, it is understood that the systems and methods described below can be implemented in many different embodiments of hardware. Any actual hardware described is not meant to be limiting. The operation and behavior of the systems and methods presented are described with the understanding that modifications and variations of the embodiments are possible given the level of detail presented.

References to "an example," "one embodiment," "an embodiment," "in certain embodiments," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic.

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" and "distally" are positions distant from or in a direction away from the clinician. "Proximal" and "proximally" are positions near or in a direction toward the clinician.

With reference to <FIG>, a pressure measurement catheter <NUM> is shown with a proximal portion thereof outside of a patient and a distal portion thereof positioned in situ within a lumen <NUM> of a patient vessel <NUM> having a stenosis or lesion <NUM>. In an embodiment hereof, the vessel <NUM> is a blood vessel such as but not limited to a coronary artery. Lesion <NUM> is generally representative of any blockage or other structural arrangement that results in a restriction to the flow of fluid through lumen <NUM> of vessel <NUM>. Lesion <NUM> may be a result of plaque buildup, including without limitation plaque components such as fibrous, fibro-lipidic (fibro fatty), necrotic core, calcified (dense calcium), blood, fresh thrombus, and mature thrombus. Generally, the composition of lesion will depend on the type of vessel being evaluated. In that regard, it is understood that embodiments hereof are applicable to various types of blockage or other narrowing of a vessel that results in decreased fluid flow.

Measurement catheter <NUM> is shown in <FIG> with a distal portion thereof in longitudinal cross-section. Measurement catheter <NUM> includes an elongate shaft <NUM> having a proximal end <NUM> that may be coupled to a handle or luer fitting <NUM> and a distal end <NUM> having a distal opening <NUM>. Elongate shaft <NUM> further includes a proximal portion <NUM>, an intermediate portion <NUM>, and a distal portion <NUM> having a distal tip <NUM>. Although proximal portion <NUM>, intermediate portion <NUM>, and distal portion <NUM> of elongate shaft <NUM> have been described separately, they are described in such a manner for convenience and elongate shaft <NUM> may be constructed unitarily such that the portions described are part of a unitary shaft. However, different portions of elongate shaft <NUM> may also be constructed separately and joined together.

In embodiments hereof, elongate shaft <NUM> or component and/or segments thereof may be formed of polymeric materials, non-exhaustive examples of which include polyethylene terephthalate (PET), polypropylene, polyethylene, polyether block amide copolymer (PEBA), polyamide, fluoropolymers, and/or combinations thereof, either laminated, blended or coextruded. Optionally, the catheter shaft or some portion thereof may be formed as a composite having a reinforcement material incorporated within a polymeric body in order to enhance strength and/or flexibility. Suitable reinforcement layers include braiding, wire mesh layers, embedded axial wires, embedded helical or circumferential wires, and the like. In one embodiment, for example, at least a proximal portion of elongate shaft <NUM> may be formed from a reinforced polymeric tube. In other embodiments of an elongate tubular shaft or component in accordance herewith, a proximal segment thereof may be a hypotube of a medical grade stainless steel with outer and inner tubes of a distal segment thereof being formed from any of the polymeric materials listed above.

As shown in <FIG>, elongate shaft <NUM> has a shaft wall <NUM> defining a guide wire lumen <NUM> extending therethrough. Guide wire lumen <NUM> extends through proximal portion <NUM>, intermediate portion <NUM>, and distal portion <NUM>. However, instead of the over-the-wire configuration shown in <FIG>, catheter <NUM> may have a rapid exchange configuration wherein guide wire lumen <NUM> extends through distal portion <NUM> and intermediate portion <NUM>, and the guidewire exits shaft <NUM> through a rapid exchange port (not shown) in proximal portion <NUM>, as would be understood by those skilled in the art. In one embodiment, with reference to the cross-sectional view of <FIG> (taken along line <NUM>-<NUM> of <FIG>), in proximal portion <NUM> of elongated shaft <NUM>, shaft wall <NUM> defines two separate lumens, guide wire lumen <NUM> and a second or pressure sensor wire lumen <NUM>, extending parallel to each other or side-by-side along proximal portion <NUM>. Communication wires <NUM> are omitted in <FIG> for clarity. Although depicted as circular in cross-section, one or more lumen(s) of elongated shaft <NUM> may have any suitable cross-section including for example circular, elliptical, rectangular or crescent-shaped. As explained in more detail below, pressure sensing wire lumen <NUM> may extend to distal portion <NUM> of elongate shaft <NUM> to be coupled to a pressure sensor <NUM>, as shown in <FIG>. In one embodiment, pressure sensor wire lumen <NUM> may be eliminated wherein a signal from pressure sensor <NUM> is sent to a computing device <NUM> other than via a wire <NUM> in a dedicated pressure sensor wire lumen <NUM>, such as, but not limited to, wireless transmission or integration of wire <NUM> into the wall of elongate shaft <NUM>. In other embodiments of an elongate shaft or tubular component in accordance herewith, pressure sensor wire lumen <NUM> may be eliminated wherein the shaft or a portion thereof may be formed by a tubular polymeric inner liner overlaid with a power lead layer and a polymeric outer jacket. In such an embodiment, the power leads for the respective pressure sensor of the inner shaft may be wrapped around the respective shaft for all or at least a portion of the shaft and secured in position by the polymeric outer jacket so as to be embedded within the shaft. In another such embodiment, the power lead for the respective pressure sensor of the inner shaft may be straight for a section or for the entire length of the shaft, and secured in position against the inner liner by the polymeric outer jacket so as to be embedded within the shaft.

Distal portion <NUM> of elongate shaft <NUM> is configured to receive a guidewire <NUM> in a distal portion of guidewire lumen <NUM> thereof. Further, as shown in <FIG>, distal portion <NUM> is sized to extend from a proximal side <NUM> of lesion <NUM>, through lesion <NUM>, and to a distal side <NUM> of lesion <NUM> such that distal tip <NUM> is disposed on distal side <NUM> of lesion <NUM>. Accordingly, in an embodiment, distal portion <NUM> has a length LD in the range of <NUM>-<NUM>. However, length LD may be any length suitable such that distal portion <NUM> may extend from proximal side <NUM> to distal side <NUM>. Further, because distal portion <NUM> is configured to extend through lesion <NUM>, the cross-sectional dimension or profile of distal portion <NUM> is minimized such as to minimize the disruption of blood flow through lesion <NUM> in order to obtain an accurate FFR measurement.

Distal tip <NUM> is disposed on distal portion <NUM> of elongate shaft <NUM>. In an optional embodiment (not shown), distal tip <NUM> is disposed on intermediate portion <NUM> of elongate shaft <NUM> and is located proximally of distal portion <NUM>. Distal tip <NUM> includes pressure sensor <NUM> for measuring a pressure of a fluid within lumen <NUM> of vessel <NUM>, as shown in <FIG>. In the embodiment shown in <FIG>, pressure sensor <NUM> is disposed in a pocket <NUM> of a thickened portion <NUM> of distal tip <NUM>. As shown in <FIG>, pocket <NUM> may be defined by at least one substantially vertical sidewall <NUM> and substantially horizontal shaft wall <NUM>. In another embodiment, pocket <NUM> has at least one sidewall with a curvilinear shape. Pressure sensor <NUM> may be a piezo-resistive pressure sensor, a piezo-electric pressure sensor, a capacitive pressure sensor, an electromagnetic pressure sensor, an optical pressure sensor, and/or combinations thereof. In one non-limiting example, pressure sensor <NUM> is a micro electromechanical sensor (MEMS) based pressure die measuring about <NUM> microns by <NUM> microns by <NUM> microns in size. However, other sized pressure sensors may be used. As shown in <FIG>, thickened portion <NUM> needs to accommodate pressure sensor <NUM>. Accordingly, thickened portion <NUM> of elongate shaft <NUM> causes tip portion <NUM> to have an outer diameter OD<NUM> (shown in <FIG>) which is larger than the outer diameter OD<NUM> of distal portion <NUM> of elongate shaft <NUM>. However, depending on the size of pressure sensor <NUM>, the outer diameters OD<NUM> and OD<NUM> of the elongate shaft <NUM> could have substantially the same diameter. In one embodiment, outer diameter OD<NUM> of tip portion <NUM> is in the range of <NUM> inch - <NUM> inch in order to accommodate pressure sensor <NUM>. However, outer diameter OD<NUM> may vary depending on the size of pressure sensor <NUM>, thickness of elongate shaft <NUM>, and other factors used to determine the diameter or profile of shafts. In an optional embodiment, a cover (not shown) could extend substantially over pocket <NUM> to protect pressure sensor <NUM> from contacting the vessel wall while still allowing blood flow to surround pressure sensor <NUM>.

Pocket <NUM> is in communication with pressure sensor wire lumen <NUM> such that any communication wire(s) <NUM> from pressure sensor <NUM> may extend from pocket <NUM> proximally through pressure sensor wire lumen <NUM>, through a corresponding lumen in luer fitting <NUM> exiting through proximal port <NUM> to a computing device <NUM> coupled to proximal end <NUM> of communication wire <NUM>. Proximal end <NUM> of communication wire <NUM> may be coupled to computing device <NUM> via various communication pathways, including but not limited to one or more physical connections including electrical, optical, and/or fluid connections, a wireless connection, and/or combinations thereof. Accordingly, it is understood that additional components (e.g., cables, connectors, antennas, routers, switches, etc.) not illustrated in <FIG> may be included to facilitate communication between the proximal end <NUM> of communication wire <NUM> and computing device <NUM>. In an optional embodiment, computing device <NUM> is incorporated into catheter <NUM> or for example, in proximal portion <NUM>.

<FIG> is a cross-sectional view of distal tip <NUM>. Therein, sensor <NUM> has a first surface <NUM>, second surface <NUM>, first end <NUM> and a second end <NUM>. A diaphragm <NUM> of sensor <NUM> is disposed on first surface <NUM> but in other embodiments, diaphragm <NUM> cold be disposed anywhere on sensor <NUM>. Communication wires <NUM> (for example, <NUM> inch coated copper wire in a trifilar configuration) extending from lumen <NUM> are coupled to an electrical interface, such as an interposer <NUM> which has first and second surfaces <NUM>, <NUM>. In this embodiment, communication wires form an "S-shape", such that one end of the communication wires <NUM> is raised up to the elevated level of first surface <NUM> of interposer <NUM>. Second sensor surface <NUM> is coupled to first surface <NUM> of interposer <NUM> (for example, by an adhesive <NUM>), thereby disposing interposer <NUM> between shaft wall <NUM> of elongate shaft <NUM> and sensor <NUM>.

Sensor wires <NUM> (for example, <NUM> inch gold wires) have a first end coupled to first surface <NUM> of interposer <NUM> and a second end coupled to first surface <NUM> of sensor <NUM> adjacent to first end <NUM>. Similarly to the communication wires, sensor wires may also make an S-shape, such that one end of the sensor wires <NUM> is raised up to the elevated level of first surface <NUM> of sensor <NUM>. Interposer <NUM> has second surface <NUM> coupled to shaft wall <NUM> of elongate shaft <NUM>. In one embodiment, interposer <NUM> is coupled to shaft wall <NUM> by an adhesive <NUM> having a layer depth of about <NUM> microns. Sensor <NUM> may be elevated above shaft wall <NUM> by the thickness of interposer <NUM> and to some degree by the thickness of the adhesive layers <NUM> and <NUM>.

<FIG> is a cross-sectional view of another embodiment of distal tip <NUM>. Instead of sensor <NUM> being mounted on interposer <NUM> as in <FIG>, sensor <NUM> is elevated above shaft wall <NUM> by a deformable member <NUM> disposed between sensor <NUM> and shaft wall <NUM>. Deformable member <NUM> has a first surface <NUM> and a second surface <NUM>. First surface <NUM> of deformable member <NUM> is coupled to sensor <NUM> along second surface <NUM> and second surface <NUM> is coupled to shaft wall <NUM>. In one embodiment, deformable member <NUM> is any material having a lower durometer than shaft wall <NUM> in order to minimize the transfer of stress and strain being experienced by shaft wall. In one embodiment, deformable member <NUM> is coupled to sensor <NUM> and shaft wall <NUM> by, for example, an adhesive. However, in another embodiment, deformable member <NUM> comprises silicone with adhesive properties.

Deformable member <NUM> elevates sensor <NUM> above shaft wall <NUM> by a distance, for example, of about <NUM>-<NUM> microns. In another example, the amount of distance between the sensor <NUM> and shaft wall <NUM> is about <NUM>-<NUM> microns. As shown in <FIG>, sensor <NUM> is coupled to deformable member <NUM> at a location that is adjacent first end <NUM> of sensor <NUM>. Placement of deformable member <NUM> at this location with respect to sensor <NUM> creates a pocket <NUM> under first end <NUM> of sensor <NUM>, such that first end <NUM> of sensor <NUM> is spaced apart from shaft wall <NUM>. In another embodiment, deformable member <NUM> can extend along any length of second surface <NUM> of sensor <NUM>. For example, deformable member <NUM> can extend along substantially the entire length of second surface <NUM> of sensor <NUM> such that second end <NUM> of sensor is not suspended above shaft wall <NUM>. In yet another embodiment, deformable member <NUM> has a recess (not shown) formed in first surface <NUM> which is sized to receive sensor <NUM> therein.

<FIG> is a cross-sectional view of another embodiment of distal tip <NUM>. Instead of sensor <NUM> being mounted on interposer <NUM> as in <FIG>, sensor <NUM> is elevated above shaft wall <NUM> by an intermediate member <NUM> disposed between sensor <NUM> and shaft wall <NUM>. Intermediate member <NUM> has a first surface <NUM> and a second surface <NUM>. First surface <NUM> of intermediate member <NUM> is coupled to sensor <NUM> along second surface <NUM> and second surface <NUM> is coupled to shaft wall <NUM> by, for example, an adhesive <NUM>. More specifically, as shown in <FIG>, intermediate member <NUM> has a first portion <NUM> and a second portion <NUM>. First portion <NUM> is coupled to shaft wall <NUM> via adhesive <NUM>, while sensor <NUM> is coupled to second portion <NUM> along first surface <NUM>. Although <FIG> shows first end <NUM> of sensor <NUM> coupled to intermediate member <NUM> with intermediate member <NUM> extending approximately halfway across second surface <NUM>, intermediate member <NUM> could extend along any length of second surface <NUM> of sensor <NUM>.

With first portion <NUM> of intermediate member <NUM> coupled to shaft wall <NUM> by, for example, adhesive <NUM>, intermediate member <NUM> is elevated above shaft wall forming a second pocket <NUM>. Thus, sensor <NUM> would be spaced apart from shaft wall <NUM> by pocket <NUM>, and intermediate member <NUM> would be spaced apart from shaft wall by second pocket <NUM>, thereby further isolating sensor <NUM> from the bending stresses and strains of shaft wall <NUM>. In another embodiment, second pocket <NUM> is eliminated, and instead, second surface <NUM> of intermediate member <NUM> extends along shaft wall <NUM>. In the same embodiment, first surface <NUM> of intermediate member <NUM> extends along any length of second surface <NUM> of sensor <NUM>, such as, for example, intermediate member <NUM> extending approximately halfway across second surface <NUM> or intermediate member <NUM> extending along the entire length of second surface <NUM>.

Intermediate member <NUM> has a hinge <NUM> on first portion <NUM>. In one embodiment, hinge <NUM> is a channel on first or second surfaces <NUM>, <NUM> (or on both first and second surfaces <NUM>, <NUM>) extending transverse to a longitudinal axis of intermediate member <NUM>. In this embodiment, hinge <NUM> can have a plurality of cross sectional profile shapes, such as rectangular, arcuate or triangular. In other embodiments, hinge <NUM> can be a living hinge or any type of hinge that allows two portions of intermediate member <NUM> to rotate relative to each other about a fixed axis of rotation.

<FIG> are exemplary illustrations of shaft wall <NUM> under bending stress and strain. <FIG> are exaggerated to better show the functionality of hinge <NUM>. <FIG> shows shaft wall <NUM> bending or flexing in the direction of arrow A. As can be seen in <FIG>, intermediate member <NUM> remains substantially straight despite shaft wall <NUM> bending away from intermediate member <NUM>. As a result, sensor <NUM> also remains substantially straight and is not affected by the bending of shaft wall <NUM> in the direction of arrow A. In one embodiment, intermediate member <NUM> is at least as rigid as shaft wall <NUM>. In another embodiment, intermediate member <NUM> is less rigid that shaft wall <NUM>. However, in either embodiment, intermediate member <NUM> must be at least rigid enough to maintain sensor in a substantially straight position relative to shaft wall <NUM>.

As shown in <FIG>, shaft wall <NUM> is bending or flexing in the direction of arrow B causing second portion <NUM> of intermediate member <NUM> to move in a direction away from shaft wall <NUM>. Specifically, second portion <NUM> rotates about an axis of rotation provided by hinge <NUM>, wherein the axis of rotation is substantially perpendicular to the longitudinal axis of intermediate member <NUM>. As second portion <NUM> is rotating about hinge <NUM>, first portion <NUM> of intermediate member <NUM> remains coupled to shaft wall <NUM>. Since sensor <NUM> is coupled to second portion <NUM> of intermediate member <NUM>, sensor <NUM> also is rotated about hinge <NUM>. In this way, sensor will maintain being spaced apart from shaft wall <NUM> thereby preventing stress and strain from being transmitted to sensor <NUM>.

<FIG> is a cross-sectional view of another embodiment of distal tip <NUM>. <FIG> is a top view of distal tip <NUM> of <FIG>. In the embodiment of <FIG>, sensor is not mounted to shaft wall <NUM> but is instead suspended above shaft wall <NUM> by a step <NUM>. Step <NUM> extends from shaft wall <NUM> and has a top surface <NUM>. Communication wiring <NUM> (or other electrical wiring) or an electrical interconnect <NUM> is disposed on top surface <NUM> of step <NUM>. As shown in <FIG>, second surface <NUM> of sensor <NUM> is coupled to electrical interconnect <NUM>. Specifically, electrical interconnect <NUM> has a first portion <NUM> and a second portion <NUM>. First portion <NUM> of electrical interconnect <NUM> is coupled to step <NUM> while second portion <NUM> is disposed within pocket <NUM> without contacting shaft wall <NUM> or sidewalls <NUM>. As shown in <FIG>, sensor <NUM> is coupled to second portion <NUM> of electrical interconnect <NUM>. In this configuration, sensor <NUM> is suspended within pocket <NUM> and therefore does not contact shaft wall <NUM> or sidewalls <NUM>. The suspended sensor <NUM> being spaced apart from shaft wall <NUM> defines a first pocket <NUM>. As shown in <FIG>, first end <NUM> of sensor <NUM> is spaced apart from step <NUM> to form a second pocket <NUM> between sensor <NUM> and step <NUM>. As shown in <FIG>, sensor <NUM> is spaced apart from side walls <NUM> to define a third pocket <NUM> between sensor <NUM> and side walls <NUM>. Thus, third pocket extends around the outer periphery of sensor <NUM> as shown in <FIG>.

In order to suspend sensor <NUM> within pocket <NUM>, electrical interconnect <NUM> needs to be rigid enough to support the weight of sensor <NUM> and maintain the sensor <NUM> in a substantially straight configuration relative to shaft wall <NUM>, so as to prevent sensor <NUM> from contacting shaft wall <NUM>. This is especially the case when shaft wall <NUM> experiences bending or flexing forces. To better maintain the stability of suspended sensor <NUM> during bending or flexing, in an optional embodiment, step <NUM> has grooves or channels (not shown) formed into top surface <NUM> to receive electrical interconnect <NUM> (or other electrical or communication wires).

A method of measuring FFR using measurement catheter <NUM> will now be described with reference to <FIG>. As would be understood by those skilled in the art, when measuring FFR a guide catheter (not shown) may be advanced through the vasculature such that the guide catheter is disposed within the aorta with a distal end thereof disposed within the aorta at an ostium of the aorta adjacent the branch vessel <NUM> within which lesion <NUM> is located. As shown in <FIG>, guidewire <NUM> can be advanced intraluminally through the guide catheter, into vessel <NUM> within lumen <NUM> to the site of lesion <NUM>. In the embodiment shown, guidewire <NUM> is advanced from proximal side <NUM> of lesion <NUM> to distal side <NUM> of lesion <NUM>, which is also consistent with the direction of the blood flow BF, as indicated by the arrow BF in <FIG>. In an embodiment, vessel <NUM> is a coronary artery, but vessel <NUM> may be other vessels in which it may be desirable to measure pressure, and in particular, to measure FFR.

Thereafter, as shown in <FIG>, measurement catheter <NUM> can be tracked or advanced over indwelling guidewire <NUM> to the target site such that distal end <NUM> of elongate shaft <NUM> is positioned distal of lesion <NUM>. As can be seen in <FIG>, distal tip <NUM> including pressure sensor <NUM> can be disposed distally of lesion <NUM> such that elongate shaft <NUM> is disposed through lesion <NUM>.

With measurement catheter <NUM> in place, pressure sensor <NUM> measures the pressure of blood distal of the lesion within lumen <NUM>. Accordingly, the pressure measured by pressure sensor <NUM> is the distal pressure measurement, or Pd, used in calculating FFR. In one embodiment, adenosine is administered either intracoronary at the site, bolus, or intravenously by continuous infusion for providing an accurate distal pressure measurement (Pd) for an FFR value. A proximal pressure measurement Pa, which is taken in the aorta by an external AO pressure transducer associated with the guide catheter, and a simultaneous pressure measurement Pa taken with pressure sensor <NUM> of measurement catheter <NUM> are then obtained to provide the FFR value, i.e., Pd/Pa, for the lesion. The proximal pressure measurement Pa and distal pressure measurement Pd can be communicated to computing device <NUM>. Computing device <NUM>, shown schematically in <FIG> and <FIG>, may include such components as a CPU, a display device, an amplification and filtering device, an analog-to-digital converter, and various other components. Computing device <NUM> may receive the proximal pressure measurement Pa and distal pressure measurement Pd, and may process them to provide a continuous display of FFR measurement.

When the FFR measurement is completed, measurement catheter <NUM> may then be completely withdrawn from the patient or repositioned in vivo at another lesion and the process repeated. Pressure-sensing catheters in accordance with embodiments hereof may be used for other than providing proximal and distal pressure measurements (Pa, Pd) for calculating an FFR value. For instance, pressure-sensing catheters in accordance with embodiments hereof may be used to provide an in vivo pressure measurement anywhere along the vasculature, or a particular lesion therein. As well, embodiments hereof may be used to provide in vivo pressure measurements, across a heart valve, venous valve or other valvular location within the body where it may be deemed useful.

The detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Although the description of the invention is in the context of treatment of blood vessels such as the coronary arteries, the invention may also be used in any other body passageways where it is deemed useful such as but not limited to peripheral arteries, carotid arteries, renal arteries, and/or venous applications. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the detailed description.

Claim 1:
A catheter (<NUM>) comprising:
an elongate shaft (<NUM>) including a proximal portion (<NUM>) and a distal portion (<NUM>), the elongate shaft (<NUM>) having a shaft wall (<NUM>), the shaft wall having an outer and inner surface, the shaft wall inner surface defining a guidewire lumen (<NUM>);
a deformable member (<NUM>) coupled to the shaft wall outer surface at the distal end (<NUM>) of the elongate shaft (<NUM>), wherein the deformable member (<NUM>) is a material having a lower durometer than the shaft wall (<NUM>); and
a pressure sensor (<NUM>) coupled to the deformable member (<NUM>), wherein the sensor has first and second surfaces (<NUM>, <NUM>) and the sensor is coupled to the deformable member (<NUM>) along the second surface (<NUM>).