Patent Publication Number: US-2022218215-A1

Title: Devices and methods for measuring portal pressure

Description:
PRIORITY CLAIM 
     The present application is a Continuation of U.S. patent application Ser. No. 16/548,047 filed on Aug. 22, 2019, which claims priority to U.S. Provisional Patent Application Ser. No. 62/728,528 filed Sep. 7, 2018; the disclosure of which is incorporated herewith by reference. 
    
    
     BACKGROUND 
     Portal pressure is used to understand and manage hypertension, for example, in patients with liver cirrhosis. Currently, a measure for portal pressure is extrapolated by calculating a patient&#39;s hepatic venous pressure gradient (HVPG). A balloon catheter with sensing capabilities is used to measure a free hepatic venous pressure and a wedged hepatic venous pressure. The HVPG is calculated by taking a difference between the free and wedged hepatic venous pressures. The procedure for placing the balloon catheter, however, is an invasive trans-jugular approach, which provides only an approximated value for the portal pressure. 
     SUMMARY 
     The present embodiments are directed to a system for measuring a pressure in a vein, comprising a needle sized and shaped to be inserted through a working channel of an endoscope, the needle extending longitudinally and including a channel extending longitudinally therethrough, and a pressure sensing device including a longitudinally extending body sized and shaped to be slidably inserted through the channel of the needle and a sensor mounted on a distal portion of the body and connected to a proximal portion of the pressure sensing device via a connection cable, the sensor configured to detect information corresponding to a pressure of a flow of blood through a vein. 
     In an embodiment, the pressure sensing device may be longitudinally movable relative to the needle between an insertion configuration, in which the sensor is covered via a portion of the needle, and a pressure sensing configuration, in which a distal end of the body of the pressure sensing device extends distally past a distal end of the needle to expose the sensor to a flow of fluid within the vein. 
     In an embodiment, the distal end of the needle may include a sharp tip for piercing a wall of the portal vein and the distal end of the body of the pressure sensing device may include a blunted end so that, in the insertion configuration, the distal end of the body is positioned relative to the sharp tip of the needle to prevent the sharp tip from damaging the working channel of the endoscope. 
     In an embodiment, the pressure sensing device may be proximally movable relative to the needle so that the sharp tip is exposed to pierce a wall of the vein. 
     In an embodiment, the distal end of the body of the pressure sensing device may include a sharp tip and the distal end of the needle may be blunted so that, in the insertion configuration, the sharp tip of the pressure sensing device is housed within the channel of the needle, and, in the pressure sensing configuration, the pressure sensing device is moved distally relative the needle, exposing the sharp tip of the body to pierce a wall of the portal vein. 
     In an embodiment, in the pressure sensing configuration, the distal end of the body may be moved distally past the distal end of the needle via a predetermined distance. The pressure sensing device may include fins coupled to the body so that the fins are movable between a first configuration, in which the fins are constrained toward an exterior surface of the body in the insertion configuration, and a second configuration, in which the fins are moved radially outward to engage a portion of the needle in the pressure sensing configuration. 
     In an embodiment, the system may further comprise a stylet sized and shaped to be inserted through the channel of the needle, the stylet being longitudinally movable relative to the needle between an insertion configuration and a piercing configuration. 
     In an embodiment, a distal end of the stylet may include a sharp tip and a distal end of the needle may be blunted so that, in the insertion configuration, the sharp tip of the stylet is housed within the channel of the needle and, in the piercing configuration, the sharp tip of the stylet is moved distally past the distal end of the needle. 
     In an embodiment, a distal end of the needle may include a sharp tip and a distal end of the stylet may be blunted so that, in the insertion configuration, the distal end of the stylet is positioned relative to the distal end of the needle to prevent the sharp tip of the needle from damaging the working channel of the endoscope and, in the piercing configuration, the stylet is drawn proximally relative to the needle to expose the sharp tip of the needle for piercing a wall of the vein. 
     In an embodiment, the sensor may be mounted within a recess extending laterally into the body of the pressure sensing device along the distal portion thereof. 
     In an embodiment, the body of the pressure sensing device may include a through hole extending laterally through the distal portion of the body so that a distal face of the sensor is exposed to a flow of fluid passing through the through hole. 
     The present embodiments are also directed to a device for measuring a pressure within a vein, comprising a body extending longitudinally from a proximal end to a distal, the body sized and shaped to be inserted through one of a working channel of an endoscope and a channel of an endoscopic needle, and a sensor is positioned on a distal portion of the body, the sensor connected to a proximal portion of the device via a cable connection, the sensor configured to detect information corresponding to a pressure of a flow of blood through a vein. 
     In an embodiment, the device may further comprise a working channel extending longitudinally through the body. 
     In an embodiment, the sensor may be movable relative to the body between a first configuration, in which a portion of the sensor occludes a distal opening of the working channel extending through the body, and a second configuration, in which the sensor is moved away from a central axis of the body so that a tool inserted through the working channel of the body has a clear path for insertion into the vein. 
     In an embodiment, the device may further comprise a cauterizing needle knife slidably housed within the body for creating a hole in a wall of the vein through which the body is insertable to measure the pressure of the vein. 
     The present embodiments are also directed to a method for measuring a pressure in a vein, comprising inserting a needle through a working channel of an endoscope to a target area proximate a vein and piercing a wall of the vein and inserting a distal portion of a pressure sensing device into the vein to measure a pressure thereof, the pressure sensing device including a sensor mounted on the distal portion and connected to a proximal portion of the device via a connection cable. 
    
    
     
       BRIEF DISCLOSURE 
         FIG. 1  shows a schematic view of a system according to an exemplary embodiment of the present disclosure; 
         FIG. 2  shows a longitudinal side view of a distal portion of a pressure sensing device of the system of  FIG. 1 ; 
         FIG. 3  shows a longitudinal side view of a distal portion of a pressure sensing device according to an alternate embodiment; 
         FIG. 4  shows a schematic view of a system according to another exemplary embodiment of the present disclosure; 
         FIG. 5  shows a schematic view of a system according to yet another exemplary embodiment of the present disclosure; 
         FIG. 6  shows a schematic view of a system according to another exemplary embodiment of the present disclosure; 
         FIG. 7  shows a schematic view of the system of  FIG. 6 , including a pressure sensing device according to an alternate embodiment of the present disclosure 
         FIG. 8  shows a schematic view of the system of  FIG. 6 , including a pressure sensing device according to yet another alternate embodiment of the present disclosure; 
         FIG. 9  shows a longitudinal side view of a distal portion of a system according to another exemplary embodiment of the present disclosure, in a first configuration; 
         FIG. 10  shows a longitudinal side view of the distal portion of the system of  FIG. 9 , in a second configuration; 
         FIG. 11  shows a longitudinal side view of the distal portion of the system of  FIG. 9 , in a third configuration; 
         FIG. 12  shows a longitudinal side view of a distal portion a system according to an alternate embodiment of the present disclosure, in a first configuration; 
         FIG. 13  shows a longitudinal side view of the distal portion of the system of  FIG. 12 , in a second configuration; 
         FIG. 14  shows a longitudinal side view of a distal portion of a system according to yet another exemplary embodiment of the present disclosure, in a first configuration; 
         FIG. 15  shows a longitudinal side view of a distal portion of the system of  FIG. 14 , in a second configuration; 
         FIG. 16  shows a schematic view of a system according to another exemplary embodiment of the present disclosure; 
         FIG. 17  shows a longitudinal side view of a pressure sensing device of the present disclosure according to another exemplary embodiment of the present disclosure; 
         FIG. 18  shows a cross-sectional view of the pressure sensing device of  FIG. 17 ; 
         FIG. 19  shows a longitudinal side view a pressure sensing device according to an alternate embodiment; 
         FIG. 20  shows a cross-sectional view of the pressure sensing device of  FIG. 19 ; 
         FIG. 21  shows a schematic view of a system according to yet another exemplary embodiment of the present disclosure; 
         FIG. 22  shows a longitudinal side view of a system according to another exemplary embodiment of the present disclosure, in a first configuration; 
         FIG. 23  shows a longitudinal side view of the system of  FIG. 22 , in a second configuration; 
         FIG. 24  shows an enlarged side view of a sensor of the system of  FIG. 22 ; 
         FIG. 25  shows an enlarged end view of the sensor of  FIG. 24 ; 
         FIG. 26  shows a schematic view of a passive senor according to an exemplary embodiment of the present disclosure; and 
         FIG. 27  shows a schematic view of a passive sensor according to another exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The present disclosure relates to systems and methods for measuring a portal pressure and, in particular, describes insertion of a pressure sensing device into the portal vein via a needle that is guided to the portal vein under endoscopic ultrasound guidance. The pressure sensing device is inserted directly into the portal vein to measure the portal pressure. Thus, the present disclosure provides a non-invasive system and method for providing an accurate measurement of the portal pressure. Although the exemplary embodiments specifically show and describe the pressure sensing device as including a sensor for measuring a pressure within the portal vein, the sensor may also measure additional information, in addition to pressure. Thus, it will be understood by those of skill in the art that the below-described systems and methods may also be utilized for obtaining and measuring information other than portal vein pressure. It should be noted that the terms “proximal” and “distal,” as used herein, are intended to refer to a direction toward (proximal) and away from (distal) a user of the device. 
     As shown in  FIG. 1 , a system  100  for measuring a pressure within a portal vein  10  according to an exemplary embodiment of the present disclosure comprises a needle  102  along with a stylet  104  and a pressure sensing device  106 , each of which are passable through a channel  108  of the needle  102 .  FIG. 1  further shows steps  1 - 4  for gaining access into the portal vein  10  using the system  100 . Initially, the needle  102 , with the stylet  104  received within the channel  108  to prevent tissue from entering the channel  108  during insertion, may be passed through a working channel of a flexible endoscope to be positioned proximate a patient&#39;s portal vein  10 , as shown in step  1 . Once the needle  102  has been placed in a desired position proximate to the vein, the stylet  104  may be removed therefrom, as shown in step  2 , and a sharp distal tip  110  of the needle  102  may be advanced to puncture a wall  12  of the portal vein  10  so that a distal opening of the needle  102  is positioned within the vein  10 , as shown in step  3 . Upon gaining access to the portal vein  10 , the pressure sensing device  106  is inserted through the channel  108  into the portal vein  10 , as shown in step  4 , so that a pressure sensor  112  in a distal portion  114  of the pressure sensing device  106  is exposed to the flow of blood through the portal vein  10  to measure the pressure in the vein  10 . 
     The needle  102  extends longitudinally from a proximal end (not shown) to a distal end  116  and includes the channel  108  extending therethrough. The needle  102  is preferably flexible and is sized and shaped to be inserted through a working channel of a flexible endoscope and is particularly configured to be visible under ultrasound guidance so that the needle  102  may be guided to the desired position proximate the portal vein  10 . The distal end  116  of the needle  102 , in this embodiment, includes the sharp distal tip  110  to facilitate puncturing of the portal vein  10 . 
     The stylet  104  extends longitudinally from a proximal end (not shown) to a distal end  118  and is sized and shaped to be slidable within the channel  108  of the needle  102 . The distal end  118  is blunted so that, in an insertion configuration, the stylet  104  is received within the channel of the needle  102  with the blunted distal end  118  aligned with the distal end  116  of the needle  102  or extending slightly distally beyond the distal end  116  of the needle  102  to minimize damage to non-targeted tissue as the tip  110  of the needle  102  is moved to the target site adjacent to the vein  10  (i.e., to prevent the needle  102  from inadvertently piercing or damaging tissue surrounding the path along which the needle is inserted to the target site and to prevent tissue from collecting within the channel  108  during insertion of the needle  102  to the target site. 
     The pressure sensing device  106 , in this embodiment, includes a flexible body  120  and the pressure sensor  112  positioned along a distal portion  114  thereof. Those skilled in the art will understand that the body  120  preferably has a flexibility sufficient to enable the body  120  to be passed through the working channel of a flexible endoscope as the endoscope traverses a tortuous path to the target site adjacent to the vein  10 . The body  120  extends from a proximal end (not shown) to a distal end  122  and is sized and shaped to be slidably inserted into the channel  108  of the needle  102 . The pressure sensor  112  may be connected to a proximal end of the device  106  via, for example, a connection cable  124  or other data transmission medium extending proximally from the pressure sensor  112  through and along a length of the body  120 . The pressure sensor  112  may be an optical sensor or an electrical sensor. As would be understood by those skilled in the art, an optical sensor may require fluid to flow thereacross, which may be analyzed to calculate a corresponding pressure value while an electrical sensor may simply require contact with the blood within the vein to measure a blood pressure thereof. However, those skilled in the art will understand that any sensor capable of measuring the pressure within the vein  10  may be employed and that the sensor may forward data to a data processing arrangement in any known manner including, for example, wireless, optical fiber and wired connections. The pressure sensor  112  may be housed within or mounted along the body  120  in any of a number of configurations as would be understood by those skilled in the art. 
     In one embodiment, as shown in  FIG. 2 , the distal portion  114  of the body  120  includes a recess  126  extending laterally thereinto and in which the sensor  112  is positioned. Where the sensor  112  is, for example, a diaphragm-based optical sensor, the sensor  112  may include an angled diaphragm  113  to allow for adequate flow thereacross. This configuration also permits adequate fluid contact where the sensor  112  is an electrical sensor. In another embodiment, as shown in  FIG. 3 , a distal portion  114 ′ of a body  120 ′ of a pressure sensing device  106 ′ includes a hole  126 ′ extending transversely therethrough so that fluid flows across a distal face  113 ′ of a sensor  112 ′ housed within the distal portion  114 ′ via the hole  126 ′. The sensor  112 ′, in this embodiment, may be, for example, an optical sensor with a distal-facing diaphragm. This embodiment may be particularly suited for reducing/preventing air bubbles from forming around the pressure sensor  112 ′, which could lead to skewed pressure readings. A positioning ring may be housed within the distal portion  114 ′ to secure the pressure sensor  112 ′ therewithin so that the pressure sensor  112 ′ does not come into contact with any portion of the body  120 ′ which might cause damage thereto during insertion of the pressure sensing device  106 ′ through even tortuous paths of the patient body. 
     According to an exemplary technique using the system  100 , the needle  102 , with the stylet  104  received therewithin in the insertion configuration, is inserted through a working channel of an endoscope to a target area proximate a portal vein  10 . As would be understood by those skilled in the art, the needle  102  may be guided to the portal vein  10  under, for example, EUS guidance via, for example, the stomach or duodenum. Once the needle  102  is in a desired position proximate the portal vein  10 , the stylet  104  may be withdrawn from the channel of the needle  102  so that the sharp distal end of the needle  102  is exposed and the needle  102  may be moved distally to penetrate the portal vein  10 . Upon gaining access into the portal vein  10  via the needle  102 , the pressure sensing device may then be inserted through channel  108  of the needle  102  until the pressure sensor  112  extends distally beyond the distal end  116  of the needle  102  within the interior of the portal vein  10 . The pressure sensor  112  within the portal vein  10  then provides a blood pressure measurement thereof. For example, as described above, a flow of blood within the portal vein  10  along diaphragm of the pressure sensor  112  or contact with fluid with the pressure sensor  112  provides a reading for the pressure measurement. Once the pressure measurement of the portal vein  10  has been obtained, the needle  102  and the pressure sensing device  106  may be removed from the patient body. If desired, the pressure sensing device may optionally be removed from the needle  102  and the stylet  104  may be reinserted to the insertion configuration as the needle  102  is withdrawn proximally back into the endoscope for removal from the body. 
     Although the system  100  is shown and described as including the pressure sensing device  106  including the pressure sensor  112  along the distal portion  114  of the elongated body  120  thereof so that the pressure sensing device  106  may be immediately removed from the body upon obtaining a pressure measurement, according to another exemplary embodiment, the system  100  may include a pressure sensing device that is deployed within the portal vein  10  to provide periodic monitoring of the portal pressure. In this embodiment, as shown in  FIG. 26 , a pressure sensing device includes a pressure sensor  112 ″, which may be pushed through the needle  102  and into the portal vein  10  via, for example, the stylet  104  or any other delivery device. The pressure sensor  112 ″ may be a wireless passive sensor including a resonant tank circuit of a parallel inductor and capacitor. In one embodiment, as shown in  FIG. 26 , the passive sensor may be formed in a 1 mm by 1 mm form using micro-machined traces for two parallel inductors sandwiching an insulating substrate. The parallel inductive traces can be used to create a parallel plate capacitance for the sensor. The passive sensor may be anchored within the portal vein  10  via, for example, a nitinol anchor wire which may act as an inductor or a part of an inductor of the resonant tank circuit sensor. In another embodiment, as shown in  FIG. 27 , a capacitor may be micromachined on a polymer substrate which is attached to a loop wire. 
     In one embodiment, the inductive wire or coil may be trace engineered to be several 10s of nH&#39;s. In one particular example, the inductance may be 47 nH. The capacitance should be as large as possible to ensure a lower resonant frequency given the physical constraints and, in one example, may have a minimal value of 1 pF. In one embodiment, the polymer substrate, which acts as an insulator, may be formed of a polymer that will give under pressure while maintaining a relative permittivity of greater than 4. According to one example, the polymer substrate may have a thickness of 10 μm. In one embodiment, a high Q (quality factor) is desired and may be achieved by increasing the turns and splitting the coil evenly from the top and bottom layers, keeping the ratio of the L/C high. In one embodiment, a resonant frequency should be low enough to allow coupling from outside of the body (e.g., below 1 GHz) and keeping the form factor small enough so as not to interfere with the blood flow. In one embodiment, the resonant frequency may range from between 800 MHz to 1000 MHz. 
     According to one example, a polymer made of flexible laminate may allow for a dielectric constant (e.g., 9 or 10) which allows for a high Q and smaller dimensions of the passive resonant circuit. A nitinol wire, which may be used to anchor the passive sensor, may allow more flexibility of the anchor. Controlling a length of the anchoring wire would allow for an inductor ranging in value from between 33-47 nH so that a parallel plate capacitor sensor on the end may be valued from between 0.8 pF to 1.2 pF in the space constraints of a disc having a size of 1 mm or smaller to resonate within a range of 800 MHz to 1000 MHz. 
     The passive sensor  112 ″ may be read, for example, by using a near field communication device that can be tuned to the resonant frequency of the passive circuit as it is deployed from the body. The resonant frequency will shift according to the change in pressure so that extrapolating the pressure is achieved from tracking the change in pressure deployed in the system versus its neutral state before being introduced into the system. In one embodiment, a near field communication device may be utilized via a smart phone. A device including a variation of a loop antenna multiplexed from transmit to receive with a voltage controlled oscillator and receiver will be attached to a smart phone and controlled by an application run on the phone. The application will detect peak output from the passive sensor and read the frequency setting while at peak. There will be a linear correlation to frequency and pressure when the passive sensor is fabricated. A calibration of the baseline frequency and sensitivity will be created during initial testing to be used in the application of the smart phone. A reading may be taken off the body by placing the smart phone near the target area until, for example, an optimal signal strength is indicated on the phone. Periodic readings of the frequency may be acquired to monitor changes in pressure. 
     As shown in  FIG. 4 , a system  200  according to another exemplary embodiment of the present disclosure is substantially similar to the system  100  described above, comprising a needle  202  and a pressure sensing device  206 . The system  200 , however, does not require a stylet, as shown in steps  1 - 4  of  FIG. 4 , to gain access to the interior of a portal vein  20 . Rather, the pressure sensing device  206 , which includes a blunt distal end  222 , is received within a channel  208  of the needle  202  during insertion of the needle  202  through a working channel of an endoscope to a target area proximate a portal vein  20 . Similarly to the stylet  104  of the system  100 , the pressure sensing device  206  of this embodiment is positioned within the channel  208  of the needle  202  so that the blunt distal end  222  of the pressure sensing device  206  prevents tissue from entering the channel  208  and/or prevents the sharp tip  210  of the needle  202  from damaging the working channel of the endoscope during insertion of the needle  202  therethrough and also prevents harm to non-targeted tissue as the needle  202  is extended distally from the endoscope. 
     The needle  202  and the pressure sensing device  206  are substantially similar to the needle  102  and pressure sensing device  106  of the system  100 . As described above, the pressure sensing device  206  includes a blunt distal end  222  and prevents the sharp distal tip  210  of the needle  202  from damaging the working channel of the endoscope during insertion. Thus, in an insertion configuration, the pressure sensing device  206  is positioned within the needle  202  such that a position of the bunt distal end  222  is aligned with or protrudes slightly distally beyond the sharp distal tip  210  of the needle  202 . Accordingly, in this embodiment, the pressure sensor  212  must be positioned along a distal portion  214  of a longitudinal body  220  of the pressure sensing device  206  such that, when the pressure sensing device  206  is in the insertion configuration relative to the needle  202 , the pressure sensor  212  is covered by a portion of the needle  202 . In other words, where the sharp distal tip  210  of the needle  202  is formed via a tapering at a distal end  216  of the needle  202 , the pressure sensor  212  should be sufficiently distanced from the distal end  222  of the body  220  such that the pressure sensor  212  is fully covered by a portion of the needle  202  regardless of a rotational orientation of the pressure sensing device  206  within the needle  202 . 
     The system  200  may be used in a manner substantially similar to the system  100 . The needle  202 , however, is inserted to the target area with the pressure sensing device  206  received therewithin in the insertion configuration, as shown in step  1 . Once the needle  202  has reached the target area, the pressure sensing device  206  may be drawn proximally with respect to the needle  202  so that the sharp distal tip  210  of the needle  202  is exposed, as shown in step  2 . The needle  202  is then advanced distally so that a wall  22  of the portal vein  20  is punctured via the sharp distal tip  210  and the needle  202  extends into an interior thereof, as shown in step  3 . Upon gaining access to the interior of the portal vein  20 , the pressure sensing device  206  is moved distally with respect to the needle  202  until the pressure sensor  212  is extends distally past the distal end  216  of the needle  202  to measure pressure within the portal vein  20 , as shown in step  4 . 
     As shown in  FIG. 5 , a system  300  according to another exemplary embodiment may be substantially similar to the system  100  described above, comprising a needle  302 , a stylet  304  and a pressure sensing device  306 .  FIG. 5  shows steps  1 - 5  for gaining access into a portal vein  30  using the system  100 . Similarly to the system  100 , the needle  302  may be inserted through a working channel of an endoscope to a target area proximate a portal vein  30 , with the stylet  304  received therein, in an insertion configuration. In this embodiment, however, the portal vein  30  is pierced via a sharp distal tip  318  of the stylet  304  rather than via the needle  302 . 
     The needle  302  may be substantially similar to the needle  102  described above. A distal end  316  of the needle  302 , however, does not need to include a sharp tip. The distal end  316  may, for example, include a distal face that extends substantially transverse to a longitudinal axis of the needle  302 , as the needle  302  is not required for puncture the portal vein  30 . 
     In this embodiment, the stylet  304  may be substantially similar to the stylet  104  described above with regard to the system  100 . The stylet  304 , however, includes a sharp distal tip  318 . The sharp distal tip  318  may be formed in any of a number of configurations. In one example, the sharp distal tip  318  may be formed via a tapered distal-facing surface extending at a non-perpendicular angle with respect to a longitudinal axis of the stylet  304 . 
     In the insertion configuration, the stylet  304  is received within a channel  308  of the needle  302  so that the distal tip  318  is aligned with the distal end  316  of the needle  302  or slightly proximal thereto, as shown in step  1 . This prevents the sharp distal tip  318  of the stylet  304  from damaging the working channel of the endoscope while also preventing any inadvertent collection of tissue therewithin. Once the needle  302  and stylet  304  have reached the target are proximate the portal vein  30 , however, the needle  302  is drawn proximally relative to the stylet  304  so that the sharp distal tip  318  of the stylet  304  is exposed in a piercing configuration, as shown in step  2 . The needle  302  and stylet  304 , in the piercing configuration, are moved distally until the sharp distal tip  318  of the stylet  302  penetrates the portal vein  30 , as shown in step  3 . After the stylet  304  has pierced the portal vein  30 , the needle  302  is advanced distally over the stylet  304  to enter the portal vein  30 . After the distal end  316  of the needle  302  has been positioned as desired within the portal vein  30 , the stylet  304  may be removed, as shown in step  4  and, as shown in step  5 , the pressure sensing device  306  may then be inserted through the needle  302  until a pressure sensor  312  mounted and/or positioned along a body  320  of the pressure sensing device  306  is exposed to the fluid flowing through the portal vein  30  to generate a portal pressure measurement. 
     As shown in  FIG. 6 , a system  400  may be substantially similar to the systems  200 ,  300  described above. Similarly to the system  200 , the system  400  comprises a needle  402  and pressure sensing device  406 , which may be used to access the portal vein  40 , as shown in steps  1  and  2  of  FIG. 6 . Similarly to the system  200 , the system  400  does not require a separate stylet as the needle  402  is inserted through a working channel of an endoscope to a target area proximate the portal vein  40  with the pressure sensing device  406  received therewithin in an insertion configuration. In this embodiment, however, the portal vein  40  is pierced via a sharp distal tip  422  of a pressure sensing device  406 , rather than via a distal end  416  of the needle  402 . Thus, the needle  402  is substantially similar to the needle  302 , as described above with respect to the system  300 , which does not include a sharp distal tip. 
     The pressure sensing device  406  may be substantially similar to the pressure sensing devices  206  described above, comprising a longitudinally extending body  420  and a pressure sensor  412  positioned along a distal portion  414  thereof. Rather than a blunted distal end, however, a distal end  422  of the body  420  includes a sharp tip  428 , which may be formed via a tapering of the distal end  422 . The sharp tip  428  may have any of a number of configurations. In one example, the sharp tip  428  may be formed via a tapered distal-facing surface which extends at a non-perpendicular angle relative to a longitudinal axis of the body  420 . In another example, as shown in  FIG. 7 , a distal end  422 ′ of a body  420 ′ of a pressure sensing device  406 ′ may be substantially conically tapered to form a sharp tip  428 ′. In yet another example, as shown in  FIG. 8 , a distal end  422 ″ of a body  420 ″ may include blunted edges  430 ″ with the sharp tip  428 ″ extending distally therefrom. The sharp tip  428 ″ may be substantially conically shaped. In both of the examples shown in  FIGS. 7 and 8 , the sharp tips  428 ′,  428 ″ are substantially centered relative to a longitudinal axis of the body  420 ′,  420 ″, respectively. Since the sharp tips  428 ′,  428 ″ are centered, a likelihood of the sharp tips  428 ′,  428 ″ damaging the working channel of the endoscope is reduced so that, if so desired, the pressure sensing devices including the sharp tips  428 ′,  428 ″ may be inserted directly through the working channel of an endoscope, without the use of the needle  402 , to gain access to the portal vein. 
     As shown in  FIGS. 9-11 , a system  500  according to yet another exemplary embodiment of the present disclosure may be substantially similar to the systems  200 ,  400  described above, comprising a needle  502  and a pressure sensing device  506 . The needle  502  and the pressure sensing device  506 , however, include additional features which allow the needle  502  and the pressure sensing device  506  to interface with one another so that, when moved from an insertion configuration to a pressure sensing configuration, a distal end  522  of the pressure sensing device  506  moves distally beyond a distal end  516  of the needle  502  by a predetermined distance. It will be understood by those of skill in the art that this feature may be useful for measuring the pressure within a portal vein since the portal vein is quite small in comparison to other veins. Thus, the predetermined distance between the distal end  522  of the pressure sensing device  506  and the distal end  516  of the needle  502  in the pressure sensing configuration may be set so that, when the system is in the pressure sensing configuration in an operative position (i.e., in the portal vein), the distal end  522  of the pressure sensing device  506  does not contact and/or pierce a far wall of the portal vein into which it has been inserted preventing damage to the portal vein. 
     The needle  502  may be substantially similar to either of the needles  202  or  402 , including a channel  508  through which the pressure sensing device  506  may be inserted. The pressure sensing device  506  may be substantially similar to either of the pressure sensing devices  206  or  406 , including a body  520  with a pressure sensor (not shown) positioned along a distal portion thereof. A distal end of either the needle  502  or the body  520  may include a sharp tip for piercing the portal vein and gaining access thereto. To prevent the pressure sensing device  506  from moving beyond the predetermined distance relative to the needle  502 , the body  520  includes fins  532  movable between a constrained configuration, in which the fins  532  are moved toward an exterior surface  534  of a body  520  of the pressure sensing device  506 , and a outwardly biased configuration, in which the fins  532  are moved radially outward, away from the exterior surface  534  of the body  520 . When the fins  532  are in the constrained configuration, the pressure sensing device  506  may be received within the channel  508  of the needle  502  so that the system  500  is in the insertion configuration. As the pressure sensing device  506  is moved distally relative to the needle  502  toward the pressure sensing configuration, the fins  532  revert to their outwardly biased configuration to engage a portion of the needle  502 , thereby preventing further distal movement of the pressure sensing device  506  with respect to the needle  502 . 
     The fins  532  may be constrained via an interior surface of the channel  508  of the needle  502 , when in the insertion configuration. Upon moving the pressure sensing device  506  distally with respect to the needle  502 , the fins  532  are freed to revert to their outwardly biased configuration to engage a distal portion of the needle  502  (e.g., a recess or groove along a distal portion of the interior surface of the channel  508 ), when in the pressure sensing configuration. In this embodiment, movement of the fins  532  may be controlled via one or more pull wires  536  so that, if it is desired to draw the pressure sensing device  506  back into the needle  502  toward the insertion configuration, the pull wire  536  may be drawn proximally relative to the pressure sensing device  506  so that the fins  532  are moved toward the constrained configuration, and the pressure sensing device  506  may be drawn back into the channel  508 . 
     According to another example, as shown in  FIGS. 12-13 , a system  500 ′ may be substantially similar to the system  500 , comprising a needle  502 ′ and a pressure sensing device  506 ′ including features which interface so that a distal end  522 ′ of the pressure sensing device  506 ′ is moved distally beyond a distal end  516 ′ of a needle  502 ′ via a predetermined distance, when in a pressure sensing configuration. Similarly to the pressure sensing device  506 , a body  520 ′ of the pressure sensing device  506 ′ includes fins  532 ′ movable between a constrained configuration and an outwardly biased configuration, in which the fins  532 ′ engage a corresponding portion of the needle  502 ′ when in the pressure sensing configuration. The fins  532 ′ in the embodiment, however, are not controllable via pull wires. Rather, the fins  532 ′ are connected to the body  520 ′ and configured so that, when it is desired to move the system  500 ′ from the pressure sensing configuration to the insertion configuration, moving the pressure sensing device  506 ′ proximally relative to the needle  502 ′ causes the fins  532 ′ to be constrained toward the constrained configuration so that the pressure sensing device  506 ′ may be drawn into a channel  508 ′ of the needle  502 ′. 
     For example, a proximal end  538 ′ of the fins  532 ′ may be connected to the body  520 ′ so that a distal end  540 ′ of the fins  532 ′ are movable toward and away from an interior surface  534 ′ of the body  520 ′ in the insertion and pressure sensing configurations, respectively. The fins  532 ′ may be configured to engage a correspondingly sized and shaped groove  542 ′ along a distal portion of the channel  508 ′ in the pressure sensing configuration. The groove  542 ′ may include, for example, an angled surface  544 ′ extending proximally therefrom so that, when the fins  532 ′ are slid proximally against the angled surface  544 ′, the fins  532 ′ are moved toward the constrained configuration so that the pressure sensing device  506 ′ may be drawn proximally into the channel  508 ′ of the needle  502 ′. 
     As shown in  FIGS. 14-15 , a system  500 ″ may be substantially similar to the systems  500 ,  500 ′ described above, comprising a needle  502 ″ and a pressure sensing device  506 ″ including a body  520 ″ with fins  532 ″ for allowing a distal end  522 ″ of the pressure sensing device  506 ″ to move distally beyond a distal end  516 ″ of the needle  502 ″ via a predetermined distance. The fins  532 ″ in this embodiment, however, are not movable. Rather, the system  500 ″ is configured so that a distal end  540 ″ of the fins  532 ″ abuts against a radially inwardly extending protrusion  542 ″ of a channel  508 ″ of the needle” preventing any further distal motion of the pressure sensing device  506 ″ relative to the needle  502 ″. Thus, the radially inwardly extending protrusion  542 ″ of the needle  502 ″ acts as a stop preventing movement of the fins  532 ″ of the pressure sensing device  506 ″ distally therebeyond. 
     Although the systems  500  (along with systems  500 ′ and  500 ″) specifically show and describe fins  532  for controlling a distance via which the distal end  522  of the body  520  of the pressure sensing device  506  extends distally from the distal end  516  of the needle  502 , it will be understood by those of skill in the art that the above-described systems may include in any of a variety of other features for controlling the distance via which the distal end  522  of the pressure sensor  506  extends beyond the distal end  516  of the needle. For example, a handle member of the system  500  may include features (e.g., a spring loaded slider, a slider with twisting lock, button) which causes the distal end  522  of the pressure sensing device  506  to protrude from the needle  502  via a predetermined distance. 
     As shown in  FIG. 16 , a system  600  according to another exemplary embodiment comprises a pressure sensing device  606  which, similarly to the pressure sensing devices described above, includes a longitudinally extending body  620  with a pressure sensor  612  positioned along a distal portion  614  thereof. The pressure sensing device  606 , however, further includes a retractable needle knife  646  longitudinally movably housed within the body  620  for cutting a small hole through a wall  62  of the portal vein  60  to gain access thereinto. Since the pressure sensing device  606  in this embodiment includes the needle knife  646  for gaining access to the portal vein  60 , a separate needle and/or stylet is not required. 
     The pressure sensing device  606  may include a lumen  650  extending longitudinally though the body  620 , within which the needle knife  646  is slidably received. The needle knife  646  may be movable between an insertion configuration, in which a distal end  648  of the needle knife  646  does not extend distally beyond a distal end  622  of the body  620  of the pressure sensing device  606 , to a cutting configuration, in which the needle knife  646  is moved distally with respect to the body  620  so that the distal end  648  of the needle knife  646  extends distally beyond the distal end  622  of the body  620  to cut a small hole though the wall  62  of the portal vein  60 . In one embodiment, the distal end  648  of the needle knife  646  may be sharp enough to create a small hole through the vein, through which the body  620  of the pressure sensing device  606  may be inserted. In another embodiment, the needle knife  646  may utilize hot cautery to create a small hole through the wall  62  of the portal vein  60 . The needle knife  646  may be able to create a smaller hole in the wall  62  of the portal vein than one formed via a conventional needle, which may be advantageous depending on the level of disease the patient is experiencing. 
       FIG. 16  shows steps  1 - 4  for gaining access to a portal vein  60  using the pressure sensing device  606 . The pressure sensing device  606  may be inserted directly through a working channel of an endoscope to a target area within a patient body, with the needle knife  646  housed within the body  620 , in the insertion configuration. As shown in step  1 , a distal end  622  of a body  620  of the pressure sensing device is positioned proximate a wall  62  of a portal vein  60  in a target position. Once the pressure sensing device  506  is in the target position, the needle knife  646  is moved from the insertion configuration to the cutting configuration, as shown in step  2 . The distal end  648  of the needle knife  646  may then be used to a form a small hole in the wall  62  of the portal vein  60 , through which the distal end  622  of the body  620  may follow through, as shown in step  3 . As shown in step  4 , the body  620  is inserted through the small hole until the pressure sensor  612  is exposed to a flow of blood through the portal vein  60 . Once the portal vein  60  has been accessed by the body  620 , the needle knife  646  is retracted into the body toward the insertion configuration to prevent damage to the portal vein  60  as the pressure reading is being taken. 
     Although the pressure sensing device  600  is shown and described as being inserted directing through the working channel of the endoscope to gain access to the portal vein  60 , it will be understood by those of skill in the art that the pressure sensing device  606  may also be utilized with a needle, substantially as described above with respect to the systems  200 ,  400 . Inserting the pressure sensing device  606  with a needle may be particularly useful where there is concern regarding accessing the portal vein through the stomach or duodenum. The needle knife  646  may be used to access the vein once the needle is in the liver, reducing potential bleeding. 
     As shown in  FIGS. 17-18 , a pressure sensing device  706  according to another exemplary embodiment may be utilized in any of the systems  100 - 500 , as described above. The pressure sensing device  706  may be substantially similar to the pressure sensing devices  106 - 506  including a longitudinally extending body  720  including a pressure sensor  712  positioned along a distal portion  714  of the body  720  and connected to a proximal portion of the pressure sensing device  706  via a connection cable  724  (e.g., electrical, optical fiber) extending proximally from the pressure sensor  712  along a length of the body  720 . The pressure sensing device  706 , however, further includes a working channel  752  extending through the body  720  so that other diagnostic and/or therapeutic tools may be inserted through the working channel  752  into the portal vein. The working channel  752  may extend along an axis substantially parallel to a central longitudinal axis of the body  720 . 
     The pressure sensor  712  may also be offset from the central longitudinal axis of the body  720  so that the connection cable  724  extends substantially parallel to the central longitudinal axis of the body  720 . In one embodiment, the pressure sensor  712  may have a distal-facing diaphragm  713  and/or reading surface such that the pressure sensor is mounted within a distal end  722  of the body  720  so that the distal-facing diaphragm is substantially flush with the distal end  722 . The pressure sensing device  706  may be used in substantially the same manner as described above with respect to the systems  100 - 500  (e.g., inserted through a channel of a needle) to gain access to portal vein and take a pressure measurement thereof. 
     According to an alternate embodiment, as shown in  FIGS. 19-20 , a pressure sensing device  706 ′ may be substantially similar to the pressure sensing device  706 , comprising a longitudinal body  720 ′ including a pressure sensor  712 ′ connected to a proximal end of the device  706 ′ via a connection cable  724 ′ along with a working channel  752 ′ extending longitudinally through the body  720 ′. The pressure sensor  712 ′, however, may be mounted within a recess  726 ′ extending laterally through a distal portion  714 ′ of the body  720 ′, similarly to the pressure sensor  112  shown and described with respect to  FIG. 2 . Since the pressure sensor  712 ′, in this embodiment, is distanced from a distal end  722 ′ of the body  720 ′, the distal end  722 ′ may be blunt (as shown) or, alternatively, may include a sharp tip for piercing the portal vein. Similarly to the pressure sensing device  706 , the pressure sensing device  706 ′ may be used in a manner substantially similar to the portal veins  106 - 506 , as described above with respect to the systems  100 - 500 . 
     As shown in  FIG. 21 , a system  800  may be substantially similar to the systems (e.g., systems  200 ,  400 ) described above, comprising a needle  802  and a pressure sensing device  806 , which may be substantially similar to the pressure sensing device  706 .  FIG. 21  shows steps  1  and  2  for measuring a pressure within and/or providing treatment to a portal vein in which the pressure sensing device  806  is inserted. The needle  802  may be substantially similar to the needles  202 ,  402 , including a longitudinal channel  808  through which the pressure sensing device  806  may be slidably received. The pressure sensing device  806  may be substantially similar to the pressure sensing device  706  including a working channel  852  extending through a longitudinally extending body  820  of the pressure sensing device  806  for the passage of another tool  860  such as, for example, a diagnostic and/or therapeutic tool. A pressure sensor  812 , however, is not fixed within or along the body  820 . Rather, the pressure sensor  812  is movably housed within the body  820  between a first configuration (step  1 ), in which the pressure sensor  812  is received within a distal end  822  of the body  820 , and a second configuration (step  2 ), in which the pressure sensor  812  is moved distally out of the distal end  822  so that the pressure sensor  812 , which is connected to a proximal end of the pressure sensor device via a connection cable  824 , is moved laterally away from the distal end  822  as it extends distally thereoutof. Although the distal end  822  of the body  820  is shown as including a sharp tip while a distal end  816  of the needle  802  is shown as being blunted, it will be understood by those of skill in the art that, as described earlier with respect to systems  200  and  400 , either the needle  802  or the pressure sensing device  806  may include the sharp tip for piercing the wall of the portal vein to gain access thereinto. 
     In the first configuration, a portion of the pressure sensor  812  partially occludes a distal opening  854  of the working channel  852 . In one embodiment, when it is desired to insert the additional tool  860  through the working channel  852 , a physician or other user may control the movement of the pressure sensor  812  from the first configuration to the second configuration via a mechanism coupled to a handle portion of the pressure sensing device  806  such as, for example, a pull wire or spring loaded mechanism connected to the connecting cable  824 . Alternatively, the pressure sensor  812  may automatically move from the first configuration toward the second configuration (and vice versa) via a mechanical switch or sensor which extends along the working channel  852  so that, when the additional tool  860  is moved distally through the working channel  852 , the mechanical switch or sensor is triggered to move the pressure sensor  812 , via a distal movement of the connection cable  824  relative to the body  820 , distally beyond the distal end  822 , toward the second configuration. In the second configuration, the pressure sensor  812  is moved distally past the distal end  822  of the body  820  to extend laterally relative to a longitudinal axis of the pressure sensing device  806 . In other words, as the pressure sensor  812  is moved distally past the distal end  822 , the connection cable  824  bends so that the pressure sensor  812  falls away from the longitudinal axis of the pressure sensing device  806  to provide a clear path for the additional tool  860  to enter the portal vein. In one embodiment, the connection cable  824  may include shape memory characteristics so that, the connection cable  824  bends toward a predetermined configuration, when the pressure sensor  812  is pushed out of the body  820 . 
     Upon removal of the additional tool  860  from the working channel  852 , the pressure sensor  812  may be manually drawn back into the body  820  toward the first configuration or, alternatively, may be drawn back into the body  820  automatically via a mechanical switch or sensor that is triggered as the additional tool  860  is moved proximally through the working channel  852 . 
     As shown in  FIGS. 22-25 , a system  900  according to another exemplary embodiment of the present disclosure may be substantially similar to the system  800 , comprising a needle  902  and a pressure sensing device  906 . As described above, a portal vein may be pierced via one of the needle  902  and the pressure sensing device  906  so that a pressure of the portal vein may be measured via a sensor  912  of the pressure sensing device  906 , which is inserted into the portal vein. The pressure sensing device  906  may be substantially similar to the pressure sensing device  806 , including a body  920  having a working channel  952  extending longitudinally therethrough to allow an additional tool  960  to be inserted therethrough to access the portal vein. Similarly to the pressure sensing device  806 , in a first configuration, the pressure sensor  912  occludes a portion of a distal opening  954  of the working channel  952  so that, the pressure sensor  912  must be moved toward a second configuration to permits passage of the additional tool  960  through the working channel  952  and into the portal vein. Rather than being moved distally past a distal end  922  of the body  920 , however, in the second configuration, the pressure sensor  912  is moved into correspondingly sized, shaped and positioned cavity  956  formed along an interior surface of the body  920 . 
     In particular, as shown in  FIGS. 22-23 , the pressure sensing device  906  is comprised of the longitudinally extending body  920  through which the working channel  952  extends, substantially parallel to a central longitudinal axis of the body  920 . The pressure sensor  912  is positioned at the distal end  922  of the body  920  and is connected to a proximal portion of the pressure sensing device  906  via a connection cable  924  extending longitudinally through the body  920 . The connection cable  924  may also extend substantially parallel to the central longitudinal axis of the body  920 . The connection cable  924  and the pressure sensor  912  are in a longitudinally fixed position with respect to the body  920 . However, the pressure sensor  912  is laterally movable with respect to the central longitudinal axis of the body  920 . Specifically, the body  920  includes a cavity  956  that is sized and shaped to correspond with the pressure sensor  912 . The cavity  956  is axially aligned with the pressure sensor  912  so that, when the pressure sensor  912  is moved toward the second configuration, the pressure sensor  912  drops into and/or is pushed into the cavity  956  to provide a clear path via which the additional tool  960  may be inserted into the portal vein via the working channel  952 . 
     In one embodiment, the pressure sensor  912  may include a housing or casing  958  that is movably connected to the connection cable  924 . The housing  958  may be slid laterally relative to the connection cable  924  between the first configuration and the second configuration. In particular, the housing  958  may include a slot or track  959 , as shown in  FIG. 25 , within which a distal end  925  of the connection cable  924  may slid to permit movement of the pressure sensor  912  between the first and second configuration, as shown in  FIG. 24 . The distal end  925  may include an enlarged end received within the track  959  to prevent the connection cable  924  from being inadvertently disconnected from housing  958 . 
     In an embodiment, the pressure sensor  912  may be biased toward the first configuration. When the additional tool  960  is inserted distally through the working channel  952  of the body  920 , a distal end  962  of the additional tool  960  may be pushed against a rounded edge of the housing  958 , which pushes the pressure sensor  912  into the cavity  956  toward the second configuration so that the additional tool  960  may be moved distally therepast into the portal vein. Upon removal of the additional tool  960 , the pressure sensor  912  may revert to its biased first configuration. 
     As discussed above with respect to the systems  100 - 900 , pressure sensing devices may be guided to the portal vein under EUS guidance. In some cases, the portal sensing devices described above may also include an additional sensor for enabling magnetically driven tracking and/or mapping. This feature may be particularly useful where the pressure measuring device  606  is used without ultrasound, or for training purposes to spatially verify the location of the wire in the anatomy during an EUS procedure. Alternatively or in addition, a magnetically driven or fiber optic 3D shaping sensor could be added as an additional control to track the sharp tip of the pressure sensing device, needle, or stylet used to gain access to the portal vein during the procedure. Information provided to the user (e.g., physician) may be used as safety feedback to ensure that an opposite side of the vein (i.e., a far wall of the vein) is not inadvertently punctured. 
     It will be apparent to those skilled in the art that various modifications may be made in the present disclosure, without departing from the scope of the disclosure.