our invention concerns the use of a radially - expandable tubular element in the construction of medical devices containing tubular components and / or channels . in particular , our invention concerns the use of the tubular elements in the construction of device components and channels that function to conduct or convey medical instruments and / or guidewires therethrough . the use of radially expandable tubular elements in the construction of delivery catheters enables their manufacture with lower composite profiles relative to prior art device delivery catheters of comparable delivery capacity . the use of radially expandable guidewire channels in the construction of exchangeable guidewire - directed diagnostic / therapeutic devices enables their manufacture with lower shaft profiles than heretofore possible . although our invention applies to the construction of all devices containing tubular components and / or channels that function to conduct or convey devices and / or guidewires therethrough , we will confine our remarks to the use of radially - expandable tubular elements in the construction of a guiding catheter , percutaneous intravascular sheath and guidewire channel , with the understanding that the scope of our invention is not limited to the focus of this discussion . fig1 a - 1 d are detailed phantom profile views and two cross - sectional views of an ultra - low profile radially - expandable subselective guiding catheter . the device consists of a shaft , stress riser 27 and proximal adapter 20 . the shaft is composed of three sections 5 , 6 , and 7 of progressively increasing rigidity . the luminal profile of shaft section 7 is sufficient to accommodate the profile of the largest device intended for delivery therethrough . the corresponding profiles of shaft sections 5 and 6 are considerably smaller . this circumstance enables the construction of shaft sections 5 and 6 with lower external profiles relative to shaft section 7 . ( see fig1 b and 1d .) the shaft of the device contains at least two layers ; an inner relatively inelastic layer and an outer relatively elastic layer . these are bonded together to provide a delivery channel 15 that is continuous therethrough . the inner layer affords column strength to the shaft . the outer layer functions as a barrier to the flow of fluid and serves to compress the inner layer , thereby reducing the composite profile of the device . because the outer layer is not required to provide column strength , it can be constructed with particularly thin walls . in the preferred embodiment , a lubricous coating is applied to the outer layer to facilitate the introduction and withdrawal of the device within the confines of the body . section 5 is composed of at least two tubular elements ; an outer relatively elastic tubular element 14 and an inner relatively inelastic , yet flexible tubular element 11 . in one embodiment element 14 comprises a low density polyurethane and element 11 comprises a medium density polyurethane . these two layers are joined distally . additionally , these two layers are joined longitudinally by means of an eccentric bond 4 ( see fig1 b ), typically provided by heat or an adhesive . shaft section 6 is similar in configuration to shaft section 5 . the rigidity of the respective inner tubular elements , however , is different . the inner tubular element 10 , contained within shaft section 6 , is more rigid relative to the inner tubular element 11 , contained within shaft section 5 . preferably element 10 comprises a high density polyurethane . this difference affords shaft section 6 enhanced rigidity relative to shaft section 5 . inner tubular elements 10 and 11 are joined together at joint 12 ( see fig1 a ), also by heat or an adhesive . shaft section 7 is composed of three tubular elements ; a low density polyurethane outer tubular element 14 , a high density polyurethane tubular element 10 and a wire braid tubular element 28 sandwiched therebetween . ( see fig1 d .) the wire braid tubular element 28 enhances the rigidity of shaft section 7 compared to shaft section 6 . this design permits the construction of a shaft that is particularly flexible at the distal end and yet relatively rigid at the proximal end . our invention further permits the construction of a similar structure wherein the transition in rigidity occurs gradually . we achieve this variable flexibility by a co - tapered extrusion of the inner and outer tubular elements . variable shaft flexibility affords the device enhanced ‘ pushability ’ and guidewire ‘ trackability ’ relative to conventional devices containing shafts of uniform rigidity throughout . inner tubular elements 10 and 11 contain a slit 13 that extends the length of shaft sections 5 and 6 and terminates distally to shaft section 7 . slit 13 , in conjunction with the elasticity of tubular element 14 enables shaft sections 5 and 6 , and the delivery channel 15 contained within these sections , to expand radially in response to the passage of devices of relatively large profile therethrough . this feature enables the shaft of the delivery catheter described herein to accommodate the passage of devices of larger profile than the baseline dimensions of the distal lumen of the catheter . thus our catheter provides superior device delivery capacity relative to prior art delivery catheters of comparable baseline distal shaft and delivery channel profiles . correspondingly , this feature enables the construction of our catheter with lower baseline distal delivery channel and shaft profiles compared to prior art guiding catheters of comparable delivery capacity and shaft wall thickness . given the recognized relationship between device profile and morbidity , our invention enables the construction of a device delivery catheter that is safer to use than prior art catheters of comparable delivery capacity . in the preferred embodiment , the opposing surfaces of the inner tubular elements , contained within shaft sections 5 and 6 , are superimposed upon one another . ( see fig1 b .) this configuration enables the tubular elements to expand radially within the distal aspect of the catheter and yet remain circumferentially intact , thus precluding the inadvertent escape of a device contained therein through the confines of slit 13 . in the preferred embodiment , the distal shaft expands radially in response to the application of minimal outward directed force . in the preferred embodiment , the tubular elements comprising shaft section 7 are circumferentially bonded together , preferably with heat . the layers comprising shaft sections 5 and 6 are eccentrically bonded together by means of bond 4 that extends longitudinally the length of the shaft sections . the use of an eccentric bond precludes coaxial rotation of the respective tubular elements and yet permits modest inter - component mobility , facilitating radial expansion . the proximal adapter 20 consists of component 23 , side - arm 21 , rotator 24 , and adjustable o - ring valve 25 . ( see fig1 c .) the interface between component 23 and rotator 24 is a right - hand screw . the o - ring valve 25 is disposed within the lumen of the proximal adapter 20 at the interface between component 23 and rotator 24 . this valve allows the distal aspect of the shaft lumen 15 to be sealed and thus preclude the loss of blood therethrough . the function of the o - ring valve 25 can be adjusted by rotation of rotator 24 , relative to component 23 . clockwise rotation of rotator 24 relative to element 23 compresses the o - ring , thus closing the valve , whereas counter - clockwise rotation accomplishes the opposite effect . the use of an adjustable valve enables the operator to control blood loss despite the introduction and withdrawal of devices of variable profile therethrough . side arm 21 provides access to lumen 15 of said device . the infusion of fluid into side arm 21 flushes lumen 15 . side arm 21 is designed to interface with luer - locking components . the proximal adapter is joined to the catheter shaft section 7 by means of a cap 26 and stress riser 27 . the configuration of the catheter tip depends upon the intended use of the device . clearly , the shaft can be shaped to accept a variety of configurations , including tip configurations that are well known to facilitate negotiation of prior art delivery devices within various regions of the body . typically , the device is prepared with a guidewire and advanced within the confines of the body under fluoroscopic control . rotation of the guidewire enables the operator to steer the device within relatively remote regions . the flexibility of the distal shaft facilitates introduction of the device within regions of the vasculature subserved by particularly tortuous vessels . once suitably installed , the guidewire can be removed to enable the subsequent introduction of a diagnostic or therapeutic device therethrough . fig2 a - 2 c illustrate the changes in distal shaft configuration that transpire consequent with the withdrawal therethrough of a guidewire of uniform profile . fig2 d - 2 f illustrate the changes in distal shaft configuration that transpire consequent with the introduction of a relatively large profile diagnostic / interventional device of non - uniform dimensions therethrough . an ultrasonic delivery catheter ball - tipped laser catheter ( u . s . pat . no . 4 , 773 , 413 ) is one example of prior art interventional devices of non - uniform dimensions that require introduction within selected regions of the vasculature via guiding catheters . prior art guiding catheters contain delivery channels that are uniformly larger in profile relative to the maximal profiles of the devices intended for delivery therethrough . hence , the delivery of an interventional / diagnostic device of non - uniform profile via a guiding catheter of the prior art requires the use of a particularly capacious and thus large profile catheter . as evident in fig2 a - 2 f , the use of radially expandable tubular elements enables the construction of lower profile and hence safer delivery devices than prior art devices of comparable delivery capacity . the use of radially expandable guidewire channels in the construction of guidewire - directed diagnostic / interventional devices enables the manufacture of these devices with lower composite profiles than prior art devices . fig3 a - 3 d and 4 b - 4 d illustrate this principle . these figures depict an angioscopy catheter containing a guidewire channel using an embodiment of our invention . fig3 a - 3 d contain a phantom profile view and two shaft cross - sectional views of the device . the shaft contains a relatively low profile , relatively flexible section 30 and a relatively larger profile , relative inflexible section 31 . the shaft is composed of at least two tubular elements , an outer relatively elastic element 36 and an inner relatively inelastic tubular element 38 . two fiber - optic bundles 40 and 41 , are imbedded within tubular element 38 . ( see fig3 b .) these bundles function respectively to conduct light in an antegrade direction and return an image in the retrograde direction . these fiber - optic bundles exit the confines of the device via side arm 46 . the guidewire channel 34 , contained within shaft section 30 is radially expandable by virtue of slit 44 and the elasticity of tubular element 36 . slit 44 extends longitudinally the length of shaft section 30 and terminates distal to shaft section 31 . the guidewire channel 34 contained within shaft section 31 is sufficiently large in profile to accommodate the largest profile segment of the guidewire intended for introduction or withdrawal therethrough and it does not permit radial expansion . [ 0054 ] fig3 e is a cross section of the section 30 illustrating an alternative embodiment of the invention . for the embodiment depicted in fig3 b , a slit was employed to allow radial expansion . for the embodiment depicted in fig3 e , the inner tubular element 38 includes a section 45 which is contiguous , but which has been folded in the overlapped configuration shown . in this manner , as channel 34 is expanded , that portion 45 of the inner element will unfold as necessary . because the guidewire lumen within the distal aspect of this device is radially expandable , the device can be constructed to conform to the surface of a guidewire of non - uniform profile and yet accommodate the introduction and withdrawal of said guidewire therethrough . hence , the use of this device , in conjunction with a guidewire component containing a low profile segment that extends through the distal confines of the catheter component , provides a lower composite profile than functionally comparable guidewire - directed systems of the prior art that are designed to accommodate guidewires of uniform profile throughout . reducing the profile of the guidewire channel of a prior art device , with the intent to reduce the composite profile of the device , is constrained by the need to maintain the dimensions of the guidewire channel sufficiently large to accommodate the largest profile segment of the guidewire disposed proximal to this region . stated differently , reducing the profile of the distal guidewire channel obligates reducing the profile of the proximal aspect of the guidewire mandrel . any departure from this basic principle precludes the ability to separate the guidewire component from the catheter component of the device intraoperatively . reducing the profile of the mandrel invariably compromises the directional control of the composite device . hence , further progress in reducing the profile of guidewire - directed diagnostic / therapeutic devices of the prior art , that afford independent catheter - guidewire coaxial mobility , is constrained by the need to : ( 1 ) maintain the proximal profile of the guidewire mandrel within a range that confers satisfactory directional control to the system and ( 2 ) maintain the corresponding profile of the distal guidewire channel sufficiently large to accommodate the proximal profile of said guidewire mandrel , thus enabling withdrawal of the catheter component from the guidewire component of the system . a guidewire of non - uniform profile , containing a low profile region , can be constructed that is functionally comparable to prior art stand alone guidewires of uniform profile throughout . this circumstance obtains because : ( 1 ) the mandrel components are largely responsible for the function of prior art guidewires and ( 2 ) prior art guidewires of uniform profile contain progressively tapered mandrels with low profile distal segments . the wire coil components of stand alone guidewires of the prior art : ( 1 ) afford flexibility to the distal aspect of the guidewire that extends beyond the region of the mandrel and ( 2 ) render the device uniform in profile . in effect , the coil disposed proximal to the end of the mandrel , in the case of prior art stand alone guidewires , functions largely to enhance the profile of the tapered segment of the mandrel and affords no significant advantage to the wire in terms of directional control ( i . e ., rotational torque delivery potential ). hence , this coil can be removed , exposing the tapered mandrel contained therein , enabling the construction of a guidewire of non - uniform profile , that contains a low profile distal segment and yet provides comparable directional control relative to prior art guidewires of uniform profile . [ 0058 ] fig4 a is an enlarged profile view of such a guidewire of our design . the guidewire contains a progressively tapered mandrel 50 , a flat wire ribbon ( not shown ) and a radiopaque tip coil 52 . the radiopaque tip coil 52 extends over the distal aspect of mandrel 50 . the wire ribbon ( not shown ) extends throughout the length of the interior of the tip coil 52 . the tip coil 52 is joined proximally to mandrel 50 and to the flat wire ribbon . distally , the tip coil is joined to the flat wire ribbon . the use of a guidewire of this configuration , in conjunction with a diagnostic / therapeutic catheter containing a radially expandable guidewire channel that is designed to conform to the surface configuration of said guidewire , enables the construction of a guidewire - directed assembly with comparable steerability and coaxial guidewire mobility relative to the prior art . it further enables the assembly to have a lower composite profile than functionally comparable devices of the prior art . fig4 b - 4 d are a series of profile views of the angioscopy catheter illustrated in fig3 a - 3 d . these figures illustrate the changes in shaft and guidewire channel configuration that transpire consequent with the withdrawal of the angioscopy catheter over the guidewire illustrated in fig4 a . given the recognized relationship between device profile and safety , the use of a radially expandable guidewire channel in conjunction with a guidewire of non - uniform profile , containing at least one low profile distal segment , enables the construction of a highly steerably system that is lower in distal profile and thereby safer to use than functionally comparable devices of the prior art . although we describe the use of our guidewire / guidewire channel system in conjunction with an angioscopy catheter , it should be understood that our system has application to all guidewire - directed exchangeable interventional / diagnostic systems and that the use of our system in their construction enables their manufacture with lower composite profiles than heretofore possible . in addition to the aforementioned applications , the use of radially expandable tubular elements can be applied to the construction of intravascular sheaths . fig5 a is a profile view of a side - arm guidewire - directed intravascular sheath and dilator assembly that contains a radially expandable shaft of our design . fig5 b contains an enlarged mid - shaft cross - sectional view of same . fig6 a is a longitudinal cross - sectional view of the side arm sheath 90 . fig6 b and 6c are corresponding views of two guidewire - directed dilators 150 , 160 intended for use with the sheath . the sheath assembly consists of a side arm sheath 90 and one or more dilators 150 , 160 . the sheath consists of a shaft and a proximal hub . the shaft is composed of an inner tubular element 100 and an outer tubular element 101 . a relatively rigid material , for example polypropylene , is preferable for the construction of inner tubular element 100 . conversely , a thermoplastic elastomer is preferable for the construction of outer tubular element 101 . the inner tubular element 100 is designed to accommodate positive radial expansion over a specific range of radial dimensions . this is accomplished by constructing the element with overlapping surfaces and disposing at their interface a ratcheting mechanism consisting of a series of longitudinally disposed teeth 103 and a latch 102 . the passage of a device therethrough of larger profile than the baseline luminal profile of the shaft engages latch 102 with successive teeth 103 and thereby radially expands the shaft of the sheath and maintains the shaft in its expanded configuration . the outer tubular element 101 is bonded eccentrically to the inner tubular element 100 forming an interior lumen 104 . this outer tubular element : ( 1 ) prevents the passage of fluid through the walls of the shaft and ( 2 ) compresses the inner tubular element 100 and thereby maintain the desired degree of expansion of said element . because the outer tubular element 101 is not required to provide column strength to the shaft , it can be constructed with particularly thin walls . the external surface of outer component 101 is preferably coated with a lubricous substance to facilitate the introduction of the device within the confines of the body . the proximal hub contains a side - arm 107 and hemostatic valve 106 . the side arm terminates with a stopcock 108 designed to interface with luer - locking components . the lumen of said side - arm is continuous with the lumen of the sheath . the infusion of fluid into the side - arm functions to flush the contents of the sheath . the hub consists of a body 105 which contains a one - way multi - leaved valve 106 . valve 106 functions to accommodate the passage of devices introduced therethrough and yet prevent the exit of blood and / or bodily fluids therefrom . the port 110 at the proximal end of the proximal hub is coaxial to the center of valve 106 and channel 104 and functions to expedite the introduction of devices therethrough . a strain relief 109 extends across the interface between the hub and shaft . the leading edge of said strain relief is tapered . typically , the sheath is prepared with the dilator 150 illustrated in fig6 b and this assembly is introduced over a guidewire within the confines of the vasculature . the dilator 150 contains a guidewire channel 122 and provides : ( 1 ) increased column strength to the sheath during introduction within the body , ( 2 ) a wedge shaped leading edge to the assembly and ( 3 ) a means of dilating the sheath to a suitable channel profile following introduction of the sheath within the confines of the vasculature . the dilator 150 is formed of a rigid material . proximally , it contains a groove 128 that is designed to interface with taper 111 contained in port 110 of the sheath . this tongue and groove configuration functions to couple the two assembly components together during the process of introducing the sheath within the confines of the vasculature and yet permit separation of said components following introduction of said sheath therein . distally , the dilator 150 contains a bulbous region 127 . this bulbous region is defined by a leading taper 123 and expansion taper 124 . the sheath and dilator are designed such that the distal end of the sheath is proximal to the bulbous region 127 of said dilator . this sheath / dilator assembly configuration affords numerous advantages over prior art assemblies containing radially non - expandable shafts . this configuration enables the introduction of the assembly through a lower profile arteriotomy or venotomy than the prior art because our device is designed to be introduced in a radially contracted state and to expand radially subsequent to insertion . the maximal profile of the bulbous region 127 of dilator 150 corresponds to the intended channel profile of the device . introduction of the sheath assembly is accomplished in the conventional manner . withdrawal of the dilator , however , through the confines of the sheath , increases the profile of the delivery channel to the desired profile as bulbous region 127 is withdrawn through the shaft . as with the above - described devices , this feature enables the insertion of our assembly with decreased morbidity relative to prior art devices of similar device delivery capacity . our device further can be reconfigured to accept progressively larger profile devices simply by installing dilators of progressively larger cross - sectional profiles therethrough . fig6 c is a profile view of such a dilator . this feature enables the insertion of an intra - aortic counter - pulsation balloon catheter or angioplasty guiding catheter through the confines of a baseline low profile sheath that otherwise could not be used to convey these devices . this feature circumvents the need to exchange sheaths to enable the introduction of such devices , among others , following the performance of an angiography . angiography is commonly performed , prior to the performance of an angioplasty or the insertion of an intra - aortic balloon pump . angiography can be accomplished with the use of a 6 french sheath whereas the performance of an angioplasty and intra - aortic counter - pulsation requires the use of substantially larger sheaths . this circumstance currently mandates exchanging sheaths , a process that invariably provokes local trauma to the vasculature and blood loss . our sheath permits the performance of both procedures without the need to exchange the sheath in the interim and circumvents the need to install a large bore sheath at the outset to accomplish this end . in summary , our invention concerns the use of radially - expandable tubular elements in the manufacture of medical devices and components of medical devices that conduct or convey devices and / or guidewires therethrough . the use of our invention enables the construction of guiding catheters on lower profile and superior delivery capacity than prior art devices . the use of our tubular elements enables the construction of percutaneous sheaths with lower profiles and superior functional versatility than prior art devices . the use of our tubular elements in the construction of guidewire channels for guidewire - directed diagnostic / therapeutic systems enables the construction of assemblies with lower composite profiles and comparable directional control and inter - component coaxial mobility than functionally comparable systems of the prior art . given the relationship between device profile and morbidity , the use of radially - expandable tubular elements enables the construction of medical devices containing tubes and / or channels that are safer to use than prior art devices .
a radially expandable intravascular medical device is disclosed . the device typically includes two members . the first member is an outer tube - shaped sheath which is radially expandable by being formed from elastic material or other means and having relatively low column strength . the second member is an inner portion extending throughout the outer tube . this inner portion includes a slit to allow it to expand radially as well . using the structure diagnostic , therapeutic , or other desired objects may be conveyed through the device yet still enable the device to have a smaller cross - sectional area throughout most of its length than the object conveyed therethrough .