Abstract:
An improved splittable medical device introducer designed to introduce a medical device such as a lead or catheter, into a patient&#39;s vasculature without loss of blood or introduction of air is described. The introducer assembly is designed with a notch provided at the proximal end of the introducer housing. The notch, which may comprise a multitude of cross-sectional geometries, is designed to reduce the force required to separate the housing and the introducer sheath, thereby minimizing the possibility of unintentional dislodgement during separation. The notch also increases the repeatability and consistency of the amount of force required to separate the introducer housing and sheath.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. provisional application Ser. No. 61/510,510, filed on Jul. 22, 2011. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to introducers and introducing assemblies. Specifically, the present invention is directed to a splittable introducer with a notched housing. 
     2. Prior Art 
     Introducer devices provide for access to the venous system and are employed for inserting medical devices such as catheters, guidewires, leads, infusion ports, dialysis ports, dialysis catheters, and others. A typical procedure for gaining access to the central venous system or the arterial system with an introducer is the Seldinger Introduction Method. The Seldinger Method provides for insertion of a needle into the vasculature of a patient. Once the needle is in the vessel, the physician aspirates the needle with a syringe to assure that the needle is in the vessel, and to draw out air present in the bore of the needle. The syringe is removed and discarded. A guide wire is inserted through the needle, and the needle is removed over the guide wire. The introducer, which includes a dilator and a sheath, is placed over the guidewire and inserted into the vessel. With the introducer and wire guide in the vessel, the dilator and wire guide are removed leaving only the sheath in the vessel. The desired medical device is implanted through the passage of the sheath. The sheath is optionally removed from the medical device. 
     The standard method for accomplishing sheath housing separation is by a mechanical breaking or cracking of the sheath housing in two halves. However, there are problems associated with this method. 
     First, the force required to initiate sheath housing separation for prior art introducers is relatively high. The application of such a required force may not be possible due to the varying physical strengths of care providers. Furthermore, exerting such an increased amount of force on the introducer device may result in the unintentional movement or dislodgement of the device within the vasculature. 
     Second, the housing of prior art introducers requires a thin wall thickness. This thin wall thickness is necessitated to promote the initiation and propagation of the crack required to separate the housing. However, the addition of desirable ergonometric and aesthetic features increase the thickness and complexity of the housing, thereby increasing the difficulty and force needed to separate the housing. In addition, such complexities are difficult to manufacture and produce such that the housing consistently splits apart with the application of a repeatable and consistent force. 
     Therefore, what is desired is an introducer device comprising a housing that separates at a reduced force to initiate subsequent splitting or separation of the sheath. In addition, an introducer housing that repeatably and consistently separates upon the application of a consistent separation force is desired. Furthermore, an introducer assembly that is able to be manufactured more easily and consistently is desired. 
     SUMMARY OF THE INVENTION 
     An introducer assembly comprising a notched housing is provided herein. The introducer includes a sheath having a sheath proximal end spaced from a distal end, and a sheath lumen that extends longitudinally therethrough. In addition, the introducer assembly of the present invention comprises a dilator subassembly. The dilator subassembly comprises a dilator sheath having a dilator sheath proximal end spaced from a dilator sheath distal end. The dilator is designed such that the dilator sheath is inserted through the lumen of the introducer sheath. 
     The introducer assembly further comprises a housing subassembly that is positioned over the proximal end of the sheath. The housing subassembly comprises a housing body having a housing body proximal end spaced from a housing body distal end. A housing through-bore extends longitudinally therethrough. A score-line residing within a portion of the thickness of the exterior surface of the housing extends from the housing body proximal end to the housing body distal end. 
     Positioned at the proximal end of the housing body is a notch that extends at least part way through the thickness of the sidewall and extends from the proximal end of the housing body. This notch, which can comprise a multitude of geometric shapes, is design to concentrate application of the separation force to a specific area or point thus reducing the force required to initiate and propagate the separation crack through the sidewall of the housing body for separating the housing in two. 
     In addition, a retainer ring may be provided. The retainer ring is designed to act as a temporary valve to prevent the flow of fluids, gas and liquid, through the notch of the housing body. The ring is positioned within or adjacent the throughbore at the proximal end of the housing body. A tab extending from the perimeter wall of the ring is positioned within the opening of the notch to thereby prevent potential fluid flow therethrough. 
     Advantageously, the introducer assembly described above provides many benefits. For example, the introducer assembly allows for a removable introducer assembly to seal against instruments such as leads or other instruments and devices. These and other embodiments, aspects, advantages, and features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art by reference to the following description of the invention and referenced drawings. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims and their equivalents. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a perspective view of an embodiment of an introducer assembly device of the present invention. 
         FIG. 1A  shows a perspective view of the components comprising the introducer assembly shown in  FIG. 1 . 
         FIG. 2  illustrates a perspective view of a prior art introducer housing subassembly. 
         FIG. 3  shows a side view of an embodiment of an introducer housing subassembly comprising a notch stress confining feature of the present invention. 
         FIG. 3A  illustrates a magnified view of the embodiment of the notch stress confining feature shown in  FIG. 3 . 
         FIG. 4  shows a side view of an introducer housing subassembly comprising an alternate embodiment of a stress confining feature of the present invention. 
         FIG. 5  shows a side view of an introducer housing subassembly comprising an alternate embodiment of a stress confining feature of the present invention. 
         FIG. 6  illustrates an embodiment of a retainer ring of the present invention. 
         FIG. 7  illustrates the embodiment of the retainer ring of  FIG. 6  being positioned within the introducer assembly of the present invention. 
         FIG. 7A  shows a magnified view of the retainer ring, shown in  FIG. 6 , positioned within the introducer assembly. 
         FIG. 8  illustrates an embodiment of the housing subassembly comprising a break-away flap feature. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Now referring to the figures,  FIGS. 1 and 1A  illustrate an embodiment of an introducer assembly  10  of the present invention. The introducer assembly  10  comprises an elongated introducer sheath  12  connected to an introducer housing subassembly  14 . The sheath  12  is an elongate member having an introducer sheath sidewall  16  extending along a longitudinal axis A-A from a sheath proximal portion  18  to a sheath distal end  20 . The thickness of the sidewall  16  including the proximal section  18  extending to the distal end  20  is from about 0.001 inches to about 0.050 inches. 
     A lumen or passage  22  provides for open communication along the entire length of the sheath  12  and into the introducer housing subassembly  14 . This lumen  22  allows for a medical device, such as a lead or catheter, to be advanced through the assembly  10 . The lumen  22  preferably has a diameter from about 0.05 inches to about 0.50 inches. 
     In addition, as shown in  FIGS. 1 and 1A , the introducer assembly  10  of the present invention comprises a dilator subassembly  24 . As shown, the dilator subassembly  24  comprises an elongated dilator sheath  26  connected to a bulbous dilator head  28 . The dilator head  28  comprises a dilator head through-bore  30  which extends longitudinally through the length of the dilator head  28 . The dilator sheath  26  is an elongate member having a dilator sheath sidewall  32  extending along a longitudinal axis B-B from a dilator sheath proximal portion  34  to a dilator sheath distal end  36 . The thickness of the dilator sheath sidewall  32 , including the proximal section  34  extending to the distal end  36 , is from about 0.001 inches to about 0.050 inches. The diameter of the distal end  36  of the dilator sheath  26  may be narrow than the diameter of the proximal end portion  34  of the dilator sheath  26 . As shown, the distal end  36  of the dilator sheath  26  may comprise a pointed end  38 . 
     The dilator sheath  26  is designed such that it may be inserted within the introducer sheath lumen  22  and extends longitudinally along axis A-A. As shown, the dilator head  28  mates with the housing subassembly  14 . In a preferred embodiment, a proximal portion  40  of the dilator head  28  comprises a helical ridge or thread  42  positioned along an exterior surface  44  of the dilator head  28 . The helical ridge  42  is designed to threadingly engage within a corresponding groove  46  residing within an interior surface  48  of the housing subassembly  14 . When the dilator  24  is positioned within the lumen  22  of the sheath  12 , the dilator head  28  is rotated to threadingly engage the helical ridge  42  within the groove  46  of the housing subassembly  14  forming a secure fit therebetween. The dilator  24  may be removed from the sheath  12  by reversing the rotation of the dilator head  28  and removing the dilator from the sheath  12  of the introducer  10 . 
     The housing subassembly  14  comprises a housing body  50  having a housing base portion  52  that fluidly extends to an upper housing web portion  54 . As shown, a housing through-bore  56 , defining a housing sidewall  58 , extends longitudinally along axis A-A. A portion of the sheath proximal region  18  is supported within the through-bore  56  of the housing subassembly  14 . More specifically, the portion of the sheath proximal region  18  is designed to be positioned within the through-bore opening  56  of the housing  50 , such that the opening of the lumen  22  and the housing through-bore  56  are aligned. In a preferred embodiment, the base portion  52  of the housing body  50  circumferentially extends around an exterior surface  60  of the introducer sheath  12  forming a tight interference fit therebetween. In a preferred embodiment, the base portion  52  of the housing body  50  may be molded over the proximal end portion  18  of the sheath  12 . 
     Residing within the upper web portion  54  of the housing body  50  is a stress confining feature  62 . More specifically, the stress confining feature comprises a notch  64  that extends from a proximal end  66  of the upper web portion  54  of the housing body  50  to a stress concentration area or point  68  ( FIGS. 3 to 5 ), distal of the proximal end  66 . The notch  64  preferably extends through at least a portion of the thickness of the housing body sidewall  58 . Alternatively, as shown in the embodiment of  FIG. 3 , the notch  64  may extend through the entire thickness of the sidewall  58  of the web portion  54  of the housing  50 . 
     A score-line  70  extends distally from the stress concentration area or point  68  of the stress concentration notch  64 . The score-line  70  preferably resides within a portion of an exterior surface  72  of the housing body  50 . In a preferred embodiment, the score-line  70  extends from the stress concentration point  68  of the notch  64  to a distal end  74  of the base portion  52  of the housing  50 . As will be shown in the following examples and illustrations, the housing subassembly  14  of the introducer assembly  10  of the present invention may comprise a multitude of non-limiting notch geometries. 
     In addition, extending from the housing body  50 , are spaced apart wings  76  and  78 , which give the housing body  50  a butterfly appearance. More specifically, the opposing left and right wings  76 ,  78  fluidly extend from an exterior surface  80  of the upper web portion  54  of the housing body  50 . These wings  76 ,  78  are designed such that when a downward and counter rotated force is applied to them, a separation force is thereby applied to the stress concentration feature  62  or notch  64  of the housing body  50 . The notch  64  then focuses the separation force to the stress concentration point  68  were a housing separation crack is initiated. Upon the application of an additional opposed lateral pulling force, the initiated crack propagates along the score-line  70  thereby separating the housing subassembly  14  and introducer sheath  12 . 
     In contrast, an embodiment of a housing subassembly  82  of the prior art, as shown in  FIG. 2 , does not comprise such a stress confining feature or notch. As shown, the prior art housing  82  comprises only the score-line  70  that extends longitudinally from its proximal portion to the distal portion of the housing  82 . The lack of such a stress confining feature  62  such as the present notch  64  means that a relatively greater force is required to separate the prior art housing  82  to initiate subsequent splitting separation of the sheath  12 . 
       FIGS. 3 ,  3 A,  4  and  5  illustrate preferred embodiments of introducer housing subassemblies. Specifically,  FIGS. 3 ,  3 A,  4  and  5  show preferred embodiments of various stress confining features  62  of the present invention. In particular,  FIGS. 3 and 3A  illustrate an embodiment of an introducer housing subassembly  84  comprising a notch  86  having a rectangular cross-section. As shown, the notch  86  is formed by removing a portion of the thickness of the sidewall  58  of the upper web portion  54  of the housing  84 . More specifically, as shown in  FIG. 3A , the notch  86  comprises a notch width  87 , a notch length  89 , and a notch depth. In a preferred embodiment, the notch width  87  may range from about 0.01 inches to about 0.25 inches, the notch length  89  may range from about 0.01 inches to about 0.25 inches, and the notch depth may also range from about 0.01 inches to about 0.25 inches. In a preferred embodiment, the width of the notch  86  may be greater than the width of the prior art score-line  70  ( FIG. 2 ). The length of the notch  86  may also range from about 5% to about 50% of the length of the upper web portion  54  of the hosing body  50 . Furthermore, the depth of the notch  86  may be about equal to the thickness of the sidewall  58  of the housing  50 , particularly the sidewall thickness of the upper web portion  54  of the housing  50 . 
       FIG. 4  illustrates an alternate embodiment of an introducer housing subassembly  88  comprising a notch  90  having a “V” or wedge-like cross-section. As shown this notch  90  comprises a first notch sidewall  92  and a second notch sidewall  94  that converge at the stress concentration point  68 . In a preferred embodiment, each of the first and second sidewalls  92 ,  94  has a notch angle  96  that ranges from about 5° to about 90°. The notch angle  96  is defined as the angle between longitudinal axis A-A and a surface  98  of the notch sidewall  92 ,  94 . The first or second notch sidewalls  92 ,  94  may have a similar or different notch angle  96 . The notch also comprises a notch depth that approximates the thickness of the sidewall  58  of the web portion  54  of the housing body  50 . 
       FIG. 5  illustrates yet another alternate embodiment of an introducer housing subassembly  100  comprising a notch  102  having a curved cross-section. As shown, the notch  102  comprises a curved surface  104  that resides within a portion of the thickness of the sidewall  58  of the housing body  50 . In a preferred embodiment, the curved surface of the notch has a notch radius of curvature that ranges from about 0.1 inches to about 0.25 inches. 
     The notch  102  comprises a notch depth  106  that penetrates through a portion of the length of the web portion  54  of the housing  50 . As shown, the notch depth extends from the proximal housing end  66  of the upper web portion  54  to a point distal of the proximal end  66 . In a preferred embodiment, the notch depth  106  may range from about 0.01 inches to about 0.25 inches. Alternatively, the notch depth  106  may range from about 5 percent to about 25 percent of the length of the web portion  54 . The notch also comprises a notch width that may span about the thickness of the sidewall of the upper web portion  54 . 
     TEST DATA 
     A series of mechanical tests were performed comparing the measured separation force of the introducer assembly  10  of the present invention to that of the force required to separate the housing  82  of the prior art ( FIG. 2 ). Specifically, introducer assemblies  10  comprising the curved notch housing subassembly embodiment  100  ( FIG. 5 ) were tested against the housing  82  of the prior art introducer assembly illustrated in  FIG. 2 . 
     Table I, shown below, summarizes the mechanical test data of the introducer assembly of the prior art. As shown, the average measured forces required to separate the housing  82 , of various introducer diameters, i.e., French sizes, of the prior art design are detailed below in Table I. During the test, separation forces were measured and averaged for a total of 10 introducer samples per French size, sizes 7 French to 17 French in total. The French size scale is commonly used in the medical device arts to denote the diameter of a lead or a catheter. A French size of 1 equates to a diameter of about 0.33 mm. 
     
       
         
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE I 
               
             
             
               
                   
                   
               
               
                   
                 Dia. 
               
             
          
           
               
                   
                 7 
                 8 
                 9 
                 10 
                 11 
                 12 
                 13 
                 14 
                 15 
                 16 
                 17 
               
               
                   
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
               
               
                   
                   
               
             
          
           
               
                 Avg. 
                 14.8 
                 18.0 
                 17.2 
                 17.5 
                 15.1 
                 14.2 
                 16.2 
                 17.6 
                 17.8 
                 19.0 
                 16.6 
               
               
                 Force 
               
               
                 (lbs-f) 
               
               
                 Std. 
                 0.5 
                 0.2 
                 0.3 
                 0.4 
                 0.4 
                 0.3 
                 1.5 
                 0.9 
                 0.4 
                 0.9 
                 0.5 
               
               
                 Dev. 
               
               
                 Cpk 
                 3.6 
                 4.6 
                 2.8 
                 1.9 
                 4.7 
                 5.9 
                 0.8 
                 0.9 
                 1.7 
                 0.4 
                 2.5 
               
               
                   
               
             
          
         
       
     
     Table II, shown below, summarizes the mechanical test data of the force required to separate the housing subassembly  100  of the present invention among various French sizes. More specially, separation forces were measured and averaged on a total of 10 introducer samples per French size, sizes 7 French to 17 French in total. The test samples comprised the curved notch feature embodied in  FIG. 5 . 
     
       
         
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE II 
               
             
             
               
                   
                   
               
               
                   
                 Dia. 
               
             
          
           
               
                   
                 7 
                 8 
                 9 
                 10 
                 11 
                 12 
                 13 
                 14 
                 15 
                 16 
                 17 
               
               
                   
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
               
               
                   
                   
               
             
          
           
               
                 Avg. 
                 11.4 
                 13.6 
                 13.6 
                 13.2 
                 10.6 
                 9.8 
                 11.4 
                 13.2 
                 14.0 
                 14.9 
                 12.7 
               
               
                 Force 
               
               
                 (lbs-f) 
               
               
                 Std. 
                 0.4 
                 0.4 
                 0.3 
                 0.3 
                 0.4 
                 0.2 
                 0.4 
                 0.6 
                 0.8 
                 0.6 
                 0.6 
               
               
                 Dev. 
               
               
                 Cpk 
                 6.6 
                 5.0 
                 6.2 
                 9.0 
                 7.2 
                 16.4 
                 7.5 
                 4.0 
                 2.4 
                 2.9 
                 4.3 
               
               
                   
               
             
          
         
       
     
     As can be seen from the test data, the overall average force required to separate the notched housing  100  of the introducer assembly  10  of the present invention was less than the average force required to separate the housing  82  of introducer assembly of the prior art. The test data therefore, illustrates a direct reduction in the separation force of the introducer assembly  10  of the present invention comprising the notched housing  100 . 
     In addition, the increased process capability index values (Cpk) resulting from the testing of the introducer design of the present invention, as shown in Table II, illustrate the increased repeatability of the force required to separate the test samples. Process capability index is herein defined as a statistical measure of process control. The greater the Cpk value, the greater the repeatability and control the process, or in this case, the measured separation force values. 
     
       
         
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE III 
               
             
             
               
                   
                   
               
               
                   
                 Dia. 
               
             
          
           
               
                   
                 7 
                 8 
                 9 
                 10 
                 11 
                 12 
                 13 
                 14 
                 15 
                 16 
                 17 
               
               
                   
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
                 Fr 
               
               
                   
                   
               
             
          
           
               
                 Percent 
                 22.5 
                 24.2 
                 20.6 
                 24.4 
                 29.9 
                 30.8 
                 29.7 
                 25.1 
                 21.1 
                 21.5 
                 23.3 
               
               
                 Diff. 
               
               
                   
               
             
          
         
       
     
     Table III details the percent difference in the average measured forces required to separate the respective housing subassemblies. As shown, the average force required to separate the housing assembly  82  of the prior art design was greater for every diameter size. For example, the force required to separate a 10 French diameter prior art introducer assembly measured, on average, about 17.5 lb-force. In comparison, the average force required to separate the housing  100  of the introducer assembly  10  of the present invention comprising the curved notch  102  measured about 13.2 lb-force. This, as shown in Table III, corresponds to a reduction in separation force of about 24.4 percent. Therefore, as can be seen from the test data above, the force required to separate the notched introducer assembly of the present invention is not only less than the force required to separate the introducer assembly of the prior art but also exhibits greater consistency and repeatability. 
       FIGS. 6 ,  7  and  7 A, illustrate an embodiment of a retainer ring  108 . The retainer ring  108  may be used with the introducer assembly  10  of the present invention as a means to prevent the possible flow of fluids such as a gas or liquid through the opening of the notch  64 . The ring  108  is designed to be either placed adjacent to or inserted within the proximal end  66  of the housing subassembly  14 . As shown, the retainer ring  108  comprises an annular retainer body  110  in which a retainer through-bore  112  extends. Extending from a perimeter sidewall  114  of the ring  108  is a tab  116  that is designed to be inserted within the notch  64  of the housing body  50 . In a preferred embodiment, at least two opposing tabs  116  project from the perimeter sidewall  114  of the retainer ring  108 . The tab or tabs  116  are dimensioned to fit within the opening of the notch  64 . In a preferred embodiment, the tab  116  is of a rectangular cross-section however, the tab  116  may comprise a cross-sectional dimension such that the tab  116  fits within the various embodiments of the notches. 
     As shown in  FIG. 7 , the retainer ring  108  maybe positioned over or within the through-bore opening of the proximal end  66  of the housing subassembly  14 . A clip  118  portion of the housing body  50 , as shown in  FIG. 7A , may be used to hold the retainer ring  108  in place within or over the through-bore  56  of the proximal end  66  of the housing subassembly  14 . The clip  118  is positioned within a recess  119  of the perimeter sidewall  114  of the retainer ring  108  ( FIG. 6 ). The clips  118  are diametrically opposite to each other and preferably offset 45° from the tabs  116 . 
       FIG. 8  illustrates yet another alternate embodiment of a housing subassembly  120  of the present invention. Similar to the previous embodiments of the housing subassemblies, this embodiment comprises a housing body  122  having opposing left and right wings  76 ,  78  that extend from the exterior surface  72  of the body  122 . Similar to the previous housing subassemblies of the present invention, the score-line  70  resides within a portion of the thickness of the exterior surface  72  extending from the upper web portion  54  to the distal base portion  52  of the housing  120 . The central throughbore  56  extends therethrough. 
     However, unlike the previous embodiments of the housing subassemblies, this embodiment  120  comprises a flap  124  that is designed to break away when a force is applied to the left and right wings  76 ,  78 . Furthermore, the housing subassembly  120  comprises a series of raised ridges  126  residing within the left and right wings  76 ,  78 . These ridges  126  are designed to add strength and rigidity to the wings  76 ,  78 . 
     In an embodiment, the flap  124  is connected between the opposing left and right wings  76 ,  78  of the housing subassembly  120 , such as by molding. More specifically, as shown in  FIG. 8 , the flap  124  is positioned and connected between respective left and right sides  122 A,  122 B of the upper housing portion  54 . Each flap  124  resides within a corresponding notch  128  within the sidewall  58  of the housing upper portion  54  of the housing subassembly  120 . In an embodiment, each flap  124  may be composed of a rigid polymeric material that easily breaks under a mechanical stress. In addition, the flap  124  may be composed of santoprene, silicone, polyether block amides and the like. 
     When a force is applied to the opposing left and right wings  76 ,  78  the flap  124  breaks off, of the left and right side  122 A,  122 B of the upper housing portion  54 , thereby exposing the notch  64  positioned within the sidewall  58  of the housing body  122 . Thus, when the flap  124  breaks off, the notch  128  concentrates application of the separation force to the score-line  70 , thereby initiating a separation crack therebetween. 
     In operation, the dilator  24  is received inside the lumen  22  of the introducer sheath  12 . This allows for the introducer assembly to be introduced into the vasculature of a patient, for instance, over a guide wire (not shown). This positions the distal end  20  of the sheath  12  inside the vasculature while the proximal section  18  and the housing subassembly  14  remain outside the patient. After the introducer assembly  10  is inserted into a patient and the dilator has been removed from the sheath  12 , other medical instruments can be easily inserted into and through the sheath  12  and introduced into the patient. The retainer ring  108  may be positioned within the through-bore  56  of the housing subassembly  14  at its proximal end  66  to prevent blood and other body fluids from leaking out of the vasculature and outside air from getting in. 
     Then, once the lead or catheter is properly positioned in the vasculature, the introducer assembly  10  of the present invention is split apart for removal from the vasculature. This is done by holding the wings  76 ,  78  between the thumb and fore finger and counter rotating them with respect to each other while slowly moving the wings further apart. The housing body  50  is readily separated. This occurs at the score-line  70  that runs along the base portion  52  of the housing body  50 . 
     As the wings  76 ,  78  of the housing  50  are moved apart, the resulting halves of the housing begin to exert a force on the proximal end  18  of the sheath  12 . These forces are concentrated at the notch  64 , particularly at the stress concentration point  68  to initiate a tear at the proximal end of the score-line  70 . The force generated by further manipulation of the wings  76 ,  78  is concentrated at the lower extent or distal stress point/area  68  of each notch feature  64 . This concentrated force is sufficient to cause the material of the housing subassembly  14  to sever or tear apart from the sheath  12 . 
     The housing subassembly  14  of the present invention is preferably composed of an acrylic based polymeratial, such as polymethyl methacrylate. In addition, the housing subassembly  14  may also be composed of ethyl acrylate, 2-chloroethyl vinyl ether, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, butyl acrylate, butyl methacrylate and the like. 
     The sheath  12  of the present invention preferably comprises polytetrafluoroethylene (PTFE). While PTFE is the most preferred material for the housing  14 , other fluoropolymeric materials may also be used. These include polyhexafluoropropylene, tetrafluoroethylene-hexafluoropropylene copolymers, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, polytrifluoroethylene, ethylene-tetrafluoroethylene copolymers, fluoroethylene-hydrocarbon vinyl ether copolymers, polychlorotrifluoroethylene, ethylene-chlorotrifluoroethylene copolymers, polyvinyl fluoride, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymers, fluorinated (meth)acrylate resins, 2-fluoroacrylate resins, fluorinated epoxy resins, fluorinated epoxy (meth)acrylate resins, fluorinated polyether resins, fluorinated polyimide resins, fluorinated polyester resins, fluorinated polyamide resins, fluorinated polycarbonate resins, fluorinated polyformal resins, fluorinated polyketone resins, fluorinated polyazomethine resins, fluorinated polyazole resins, and fluorinated polyallyloxysilane resins, vinylidene fluoride-hexafluoropropylene fluoroelastomer, vinylidene fluoride-tetrafluoroethylene fluoroelastomer, tetrafluoroethylene-perfluoroalkyl vinyl ether fluoroelastomer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene fluoroelastomer, vinylidene fluoride-tetrafluoroethylene-perfluoroalkyl vinyl ether fluoroelastomer, tetrafluoroethylene-perfluoroalkyl vinyl ether fluoroelastomer, propylene-tetrafluoroethylene fluoroelastomer, fluorosilicone rubber, fluorinated phosphazene rubber, fluorinated thermoplastic rubbers, and flexible fluorocarbon resins. 
     The present invention thus provides the upper web portion  54  of the introducer  10  with structures that concentrate the tearing forces created by moving the wings  76 ,  78  apart to stress confining features  62  located diametrically opposite each other in the housing sidewall  58 . However, the present invention is not meant to be limited to the notch embodiments discussed and illustrated. Any structure located at the upper web portion  54  of the housing body  50  that serves to concentrate the tearing forces to a confined area is contemplated by the scope of the present invention. 
     Thus, the present invention has described several structures suitable as stress confining structures for concentrating the separating forces exerted at the upper web portion  54  of the housing body  50  by a pulling manipulation of the wings  76 ,  78 . In each structure, the total forces imparted to the wings  76 ,  78  are concentrated at either diametrically opposed surfaces along the proximal end  66  of the upper web portion  54 . Together with the unique molecular properties afforded by PTFE as the preferred material for the sheath  12 , once a tear begins it propagates the entire length of the sheath, no matter how long, in an extremely smooth manner that provides the physician with a very desirable tactile feel. 
     It is, therefore, apparent that there has been provided, in accordance with the present invention, an introducer assembly comprising a housing supported on the proximal end of a sheath having a novel structure for removal from the venous system of a patient. While this invention has been described in conjunction with preferred embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the broad scope of the appended claims.