Abstract:
A vascular shunt apparatus ( 10 ) includes a tubular member having first and second end portions ( 16, 20 ) and an aperture extending through the first and second end portions ( 16, 20 ). A transducer ( 64 ) can be associated with the tubular member to provide a signal in response to the flow of fluid through the tubular member. One or both of the end portions ( 16, 20 ) also can be adapted to form respective sealing connections with different parts of a patient&#39;s vascular system.

Description:
TECHNICAL FIELD 
   The present invention relates generally to a vascular shunt for use in surgical procedures. The present invention also relates generally to an apparatus for audibly monitoring fluid flow in a vascular shunt. 
   BACKGROUND OF THE INVENTION 
   Vascular shunts have been utilized in surgical procedures for by-passing a section of a blood vessel. Such vascular shunts channel blood flow from the heart into a tubular passageway past a section of a blood vessel upon which surgery is to be performed. The blood is reintroduced into the same or a different blood vessel at a downstream location, thereby by-passing a portion of the blood vessel to enable that portion to be surgically repaired. 
   Also, in typical blood flow measuring devices, flow data measurements are obtained as operational intelligence tools. Many costly, delicate, and complex methods exist for scientific or medical investigation of steady and unsteady blood flow during a surgical procedure. However many conventional devices are expensive, complex, or otherwise are not wholly satisfactory. 
   SUMMARY OF THE INVENTION 
   The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later. 
   An example embodiment of the vascular shunt of the present invention includes a tubular member having first and second end portions spaced apart by an intermediate portion. The end portions are adapted to provide generally sealing connections with different parts of a patient&#39;s vascular system. A transducer, such as a piezo-electric element, can be operatively associated with the tubular member to provide an electrical signal indicative of blood flowing through the shunt. For example, the transducer is sensitive to pressure variations caused by flow of blood through the shunt. The electrical signal can, in turn, be amplified and supplied to an audio speaker to provide an audible indication of whether blood is flowing normally through the shunt. For example, if the shunt were to clog (in whole or in part) so as to effect a substantial change in the flow of blood through the shunt, the surgeon could discern this from the audible indication. 
   In a particular example of the shunt, one of its end portions (e.g., the second end portion) has an enlarged cross-sectional area or bulge, such as spaced from the opening thereof. The enlarged cross-sectional area helps form a sealing connection with an interior portion of a blood vessel when inserted therein. According to another aspect, the opening at the second end portion can be axially tapered (or chamfered) at an angle to facilitate insertion of the second end portion into the blood vessel. 
   According to another aspect of the present invention, the outlet portion can also have an opening located between the enlarged cross-sectional area and a distal end of the second end portion. The opening mitigates occlusion of the blood vessel relative to the second opening. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features of the present invention will become apparent to one skilled in the art to which the present invention relates upon consideration of the following description of the invention with reference to the accompanying drawings. 
       FIG. 1  is a schematic view of an apparatus in accordance with the present invention. 
       FIG. 2  is a schematic view of the apparatus of  FIG. 1  in position at a surgical site. 
       FIG. 3  is a schematic view of the apparatus of  FIG. 1  in a different position at a surgical site. 
       FIG. 4  is a schematic detail of part of the apparatus of  FIG. 1 . 
   

   DETAILED DESCRIPTION 
   The present invention relates generally to a vascular shunt  10  for diverting blood flow during certain surgical bypass procedures. For example, the shunt  10  can be utilized to divert carotid blood flow during surgery, such as to remove plaque build-up on the internal wall of the carotid artery. A transducer is operatively associated with the shunt  10  to detect the status of blood flow through the shunt. The transducer provides an electrical signal that can be converted into audio to provide a tangible indication of whether or not fluid (e.g., blood) is flowing through the shunt. By using a single transducer to detect flow of blood, the cost of the overall system and associated electronics can be substantially reduced relative to conventional systems. 
   The vascular shunt  10  includes a generally cylindrical, flexible tube. For an example of a carotid shunt, the tube is typically about 12″ in length; although it can be provided in other lengths greater than or less than 12″. The vascular shunt  10  has a first end (or inlet) portion  16  with an inlet opening  18 , a second end (or outlet) portion  20  with an outlet opening  22 , and an intermediate portion  24  fluidly interconnecting the inlet portion and the outlet portion. 
   The diameter of the shunt at the inlet portion  16  can have an outer diameter that is greater than the diameter at the outlet portion  20 , such that the cross-sectional diameter of the shunt tapers from the inlet to the outlet. By way of particular example, the inlet portion  16  can have an inner diameter of about 0.14″ and an outer diameter of about 0.24″, for example. The vascular shunt  10  can taper to an inner diameter of about 0.070″ and an outer diameter of about 0.110″ at the outlet portion  20 . It is to be understood that other relative dimensions of the tubular member between the inlet and outlet portions can be utilized depending, for example, on the size of the patient and where the shunt to utilized in the patient. 
   The opening  22  at the second end portion  20  further can be tapered to facilitate its insertion into a blood vessel. For example, a distal end of the end portion  20  can have an angled end surface angled axially relative to the tubular member. The tapered end can be formed as part of the shunt (e.g., during a dipping process or an injection molding process) or the distal end can be cut at an appropriate angle, such as less that or equal to about 60° (e.g., about 45°), relative to its longitudinal axis to define the tapered opening  22 . The tapered opening  22  thus defines a generally elliptical outlet at the angled end surface of the shunt  10 , which outlet is larger than a cross-section of the tube near the second end portion  20 . The tapered opening  22  facilitates insertion of the end portion  20  into the blood vessel, such as shown in  FIGS. 2 and 3 . 
   The vascular shunt  10  further includes a tubular branch portion  26  extending from the intermediate portion  24  and terminating with a manually operable valve  28 , such as a one-way stopcock. For example, the stopcock can be used to bleed air out of the vascular shunt  10  when positioning the vascular shunt at the surgical site. 
   With reference to  FIGS. 2 and 3 , the inlet portion  18  is adapted for insertion into an incision  30  surgically formed in the wall  32  of a blood vessel  34 , such as at a location upstream relative to a portion  36  of the blood vessel to be operated upon. The incision  30  is one continuous cut exposing the surgical site and the points of insertion of the inlet portion  16  and the outlet portion  20  of the vascular shunt  10 . 
   As viewed in  FIG. 4 , the inlet portion  16  includes an inflatable collar  38 , such as a balloon, disposed about the tubular shunt near the inlet opening  18  of the inlet portion. For example, the collar  38  substantially circumscribes a length of the shunt at a location spaced from the inlet opening  18  and is sealed to an outer wall  40  of the inlet portion by a suitable means, such as an adhesive. 
   The collar  38  defines an annular, inflatable chamber  42  ( FIG. 4 ) that encircles at least a substantial part of the inlet portion  16 . A flexible tube  44  is in fluid communication with the collar  38  and defines a path of flow into and out of the chamber  42 . The flexible tube  44  is used for inflating and deflating the collar  38  connected thereto. As depicted in  FIGS. 1 ,  2  and  3 , a lumen can extend longitudinally through a portion of the shunt  10 , such as between the inner and outer sidewalls thereof. The lumen provides a substantially non-obstructive passage, such as to permit the tube  44  to connect with the inflatable collar  38  located adjacent the inlet portion  16 . Another portion of the tube  44  extends away from the intermediate portion  24  external to the vascular shunt  10 , such as at a location adjacent branch portion  26  for facilitating access to the tube during the surgical procedure. A syringe  46  can be connected to the flexible tube  44  via a stopcock  47 , for example, attached at the end of the tube in order to inflate and deflate the collar  38 . The syringe  46  can be employed to supply a suitable fluid, such as air, a saline solution or other substantially biocompatible gas or liquid material, for inflating the collar  38 . 
   As illustrated in  FIG. 4 , once the inlet portion  16  has been inserted through the incision  30  in the blood vessel  34  and the inlet opening  18  has been properly positioned in the blood vessel, the collar  38  can be inflated by means of the flexible tube  44 . The solution can be introduced into the chamber  42  through the flexible tube  44 , thereby expanding the collar  38  radially outward against the wall  32  of the blood vessel  34  and forming a first sealing connection with the blood vessel at a first location  47 . Blood in the downstream region  48  of the blood vessel  34  is thereby blocked from flowing around an exterior portion of the collar  38  to the upstream region  50  of the blood vessel, and instead is diverted into the inlet opening  18  and through the vascular shunt  10 . 
   For the example of a carotid shunt, the vascular shunt  10  can define a passageway of circular cross-section having an interior diameter of approximately 0.25 inches. Those skilled in the art will understand and appreciate that other diameters can be used to provide vascular shunts according to an aspect of the present invention. 
   The outlet portion  20  is adapted for insertion into the incision  30 , such as upstream of the portion  36  of the blood vessel  34  to be operated upon. Part of the outlet portion  20  has an enlarged cross-sectional area  52  (e.g., a bulge, a generally toroidal protrusion, etc.) for forming a second sealing connection at a second location  54  in the blood vessel  34 . For example, the enlarged area  52  can be a soft flexible material, such as silicone or other polymer, which is fixed to the tube (e.g., by adhesion or friction) at a desired location spaced from the opening  22 . The enlarged cross-sectional area  52  of soft flexible material is more compliant (e.g., it compresses more easily under force) than the tubular structure of the shunt  10 . The enlarged area  52  can be a material that is softer than the body of the shunt, such as to mitigate damage to the vessel as it is urged into the vessel, as shown in  FIGS. 2 and 3 . The enlarged area can be either a solid or hollow member that encircles the outlet portion of the shunt  20 . 
   In the example shown in  FIGS. 1–3 , the enlarged area  52  encircles at least a substantial part of the circumference of the outlet portion  20  near, but at a location spaced apart from the opening  22 . The enlarged cross-sectional area  52  has a generally fixed cross-sectional dimension, which can be formed as part of the tube or be another structure attached about the second end portion near the opening  22 . In the illustrated example, the enlarged cross-sectional area  52  has its largest cross-section near its middle and tapers curves from the middle to the ends of the area to a cross-section that generally approximates the cross-section of the tube at such ends. 
   By way of example, subsequent to the inlet portion  16  being positioned at the first location  47 , the balloon being inflated to form the first sealing connection, and air being bled out of the vascular shunt  10 , the outlet portion  20  is inserted into the blood vessel  34  at the second location  54 . An outer surface  56  of the enlarged area  52  engages the wall  32  of the blood vessel  34  and creates the second sealing connection. 
   The outlet portion  20  can further have a plurality of visual indicators (or indicia)  57  for displaying to the surgeon the depth of insertion of the outlet portion (See  FIG. 2 ). The indicators  57  are, for example, spaced at one centimeter increments upstream of the enlarged area  52 , as measured from the distal end of the enlarged area. 
   In accordance with another aspect of the present invention, the outlet portion  20  can further include an opening  58  extending between an inner surface  60  of the outlet portion  20  and an outer surface  62  of the outlet portion. For example, the opening  58  can be a circumferentially extending, generally circular opening formed through the sidewall  40  located adjacent a distal end of the opening  58 . When the outlet portion  20  is positioned at the second location  54  of a blood vessel  34  (e.g., the carotid artery), blood can flow downstream through the opening  58  and along the outer surface  62  of the outlet portion  20 . This other stream of blood flow helps mitigate occlusion of the blood vessel  34  near the end portion  20  of the shunt  10 . 
   The vascular shunt  10  is flexible and thus can easily be bent while positioning it at the surgical site. As viewed in  FIGS. 2 and 3 , the vascular shunt  10  can be completely inserted in the area of the blood vessel  34  to be operated upon ( FIG. 2 ), or it may be looped in order to pickup any extra length of the vascular shunt ( FIG. 3 ). For example, the vascular shunt  10  is formed of flexible plastic material, such a polyvinyl chloride or plastisol. However, alternative nontoxic flexible, fluid-tight materials can also be employed in accordance with an aspect of the present invention. 
   Blood flowing through the vascular shunt  10  is pulsatile, such as caused by pressure velocity variations resulting from blood flow due to the pumping of the heart. The pressure velocity variations due to the flow of blood, when amplified to an audible level, provides a distinct sound well known to surgeons and other medical professionals. This sound thus can provide an indication as to whether blood is flowing through the shunt adequately. 
   In accordance with another aspect of the present invention, a transducer  64  can be operatively associated with vascular shunt  10 . For example, the transducer  64  can be attached to the exterior wall  66  adjacent to the branch portion  26  by suitable means, such as adhesive. The transducer  64  should be attached by means which will not only securely fasten the transducer to the vascular shunt  10 , but also facilitate transmission of ultrasonic waves from within the shunt to the transducer (e.g., introduce minimum sound attenuation). Alternatively, the transducer  64  can be formed integrally within at least a portion of the sidewall of the shunt  10 . The transducer  64  can be located adjacent the intersection of the branch portion  26  and the intermediate portion  24  fixed to the intermediate portion of the tube. 
   By way of example, the transducer  64  is a piezo-electric crystal pick-up sensitive to pressure velocity variations caused by the flow of blood through the shunt  10  in response to the beating heart of the patient. The electric signals produced by the transducer  64  can be transmitted to an associated electronic circuit  67  ( FIG. 2 ) remote from the transducer by a direct wire connection. The wire  68  extends away from the transducer  64  along the branch portion  26  and can terminate with a plug-type connector  70  (e.g., a male or female connector part). The connector  70  allows easy electrical hook-up once the vascular shunt  10  is positioned at the surgical site. 
   By way of further example, the transducer  64  generates electrical signals corresponding to pressure variations within the shunt that operate on the transducer. The wire  68  and connector  70  can communicate the electrical signals to a conventional amplifier  72 , which is operative to amplify the signals to a desired level to facilitate their conversion into audible sound. For example, the amplified electric signals are then communicated to an audio device  74 , such as a speaker, for audibly informing the surgeon of the status of the blood flow in the shunt. 
   It is to be understood and appreciated that because the transducer  64  of the shunt provides simple electrical signals that can be directly converted to audio-only status information, no other electronic equipment is necessary to obtain such information and convert it to audio. As a result, the cost of the shunt and associated monitoring equipment can be significantly less than traditional complicated monitoring equipment, which employs multiple transducers to obtain information and processors to compute the flow rate. The audible indication of flow status through a shunt according to an aspect of the present invention further means that the surgeon need not look away from the surgical site to receive any data in this manner. It is to be further appreciated that the combination of piezo-electric crystal with vascular catheters for monitoring should have a widespread application in cardiovascular medicine. 
   What has been described above are examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.