the following detailed description is exemplary in nature and is not intended to limit the scope , applicability , or configuration of the invention in any way . rather , the following description provides a practical illustration for implementing exemplary embodiments of the invention . fig1 is a plan view with a partial section of a lead 10 including means for retention 15 according to one embodiment of the present invention . fig1 illustrates lead 10 including a lead body 12 , a connector 16 coupled to a proximal end 121 of the lead body 12 and an electrode 14 coupled to a distal end 122 of the lead body 12 ; a conductor 13 , extending within an outer sheath 11 , couples electrode 14 to connector 16 , in order to deliver electrical stimulation , and forms a lumen for slideably engaging a stylet 18 . means and materials for constructing such a lead are well known to those skilled in the art . fig1 further illustrates retention means 15 formed along an outer surface of lead body 12 in proximity to distal end 122 . according to embodiments of the present invention , retention means 15 allows insertion of lead body 12 through a vessel , for example a vessel 607 as illustrated in fig6 , while preventing retraction of lead body 12 within the vessel due to an interference of retention means 15 along a wall of the vessel that contacts lead body 12 . retention means according to some embodiments of the present invention extends along a length greater than or equal to approximately 1 mm and may be implemented along any portion of a lead body alone or in conjunction with other retention means ; further , retention means 15 may be an integral part of outer sheath 11 or may be formed on a separate collar fitted about lead body 12 , either in - line with or about outer sheath 11 . suitable materials for outer sheath 11 and retention means 15 include those that are biocompatible , examples of which include , but are not limited to , silicone and polyurethane . various embodiments of retention means include projections formed along retaining segments as illustrated in fig2 a – d and 4 a – 5 b . it should be noted that alternate embodiments include , but are not limited to , retaining segments extending around an entire circumference of a lead body and segments extending only about a portion of the circumference of the lead body . for example , a plurality of projections may lie in a line , single file , along a length of a retaining segment , as illustrated in fig2 a , or each individual projection may extend circumferentially about all or a portion of a retaining segment , as illustrated in fig2 c , or a plurality of projections may lie approximately side - by - side about all or a portion of a circumference , as illustrated in fig2 d . in some embodiments , retaining segments as a whole or just the projections may be formed of a bioadsorbable material , examples of which include those taught in lines 10 – 24 of u . s . pat . no . 6 , 173 , 206 . according to these embodiments , if a lead body is chronically implanted , the retaining segment or projections would remain intact long enough to hold the body in place for a period of time up to tissue encapsulation of the body ; this may facilitate extraction of a chronically implanted lead . one example of an appropriate bioadsorbable material , polydioxanone is described along with means for molding the material in u . s . pat . no . 4 , 490 , 326 , the teachings of which are incorporated by reference herein . fig2 a is an enlarged plan view of means for retention according to one embodiment of the present invention . fig2 a illustrates a retaining segment 380 including a plurality of barb - like projections 385 positioned in a single - file line along a length of the segment 380 ; each of the plurality of projections 385 include a length l and extend laterally from a lead body 312 toward a proximal end 321 at an angle 33 , which , according to some embodiments , is less than approximately 45 degrees . according to this embodiment of the present invention and various other embodiments illustrated herein length l is greater than approximately 100 microns . fig2 a further illustrates projections 385 as portions of a wall 387 forming retaining segment , having been lifted out of wall 387 according to one embodiment of the present invention . fig2 b illustrates an alternate retaining segment 30 extending along a length of lead body 312 and including tread - like projections 31 extending laterally from lead body 312 to form a textured surface adapted to engage a vessel wall , similar to , for example , a sole of a shoe designed to facilitate traction . according to some embodiments of the present invention , projections , i . e . 385 , 31 , are directly formed in outer surfaces , being integral with a bulk material underlying the surfaces , but , according to alternate embodiments , the projections are formed of separate materials either embedded in or adhered to these surfaces . alternative methods of forming examples of these embodiments will be described herein below . fig2 b further illustrates retaining segment 30 including a coating 36 , which is soluble in body fluids ; according to this embodiment , coating 36 fills in around projections 31 and remains intact temporarily , during positioning of lead body 312 , so that lead body 312 may be moved back and forth through a vessel if repositioning is necessary . suitable materials forming coating 36 are soluble in body fluids ( within a temperature range encompassing normal body temperature ), non - toxic , biocompatible and non - pyrogenic ; examples of such a material include sugar derivatives , such as mannitol and dextrose , salts , such as sodium chloride and potassium chloride , and polyvinylpyrrolidone ( pvp ). portions of u . s . pat . no . 4 , 827 , 940 teaching methods for forming and applying a mannitol solution are incorporated by reference herein . according to an alternate embodiment , a covering in the form of a thin wall tube may be deployed over retaining segment 30 in place of coating 36 . it should be noted that any of the embodiments described herein may include such a coating or a covering facilitating positioning of lead bodies . fig2 c is an enlarged plan view of means for retention according to another embodiment . fig2 c illustrates a retaining segment 300 coupled to a portion of lead body 312 and including a proximal end 3210 and a plurality of projections 310 , each of which extend around all or a portion of a circumference of lead body 312 and extend laterally from lead body 312 at angle 33 with terminal ends 311 of projections 310 directed toward proximal end 3210 . fig2 d is an enlarged partial section view of means for retention according to yet another embodiment of the present invention . fig2 d illustrates a retaining segment 350 including a plurality of fish scale - like projections 355 positioned side - by - side about a circumference of lead body 312 and along a length of segment 350 and including terminal ends 351 directed toward a proximal end 3215 . fig2 d further illustrates projections 355 as discrete elements embedded in an underlying surface 375 of segment 350 according to one embodiment of the present invention . fig2 d also illustrates , by way of a dashed line connecting projections 355 around a circumference , another embodiment in which embedded elements forming projections may be rings or portions of a coil circling a portion of or the entire circumference of segment 350 creating projections similar to projections 310 illustrated in fig2 c . according to further alternate embodiments , some or all projections of a retaining segment , for example projections 385 , 31 , 310 and 355 ( fig2 a – d ), each include micro - features further enhancing engagement of the projections with the vessel wall . in fig2 a such a feature is illustrated on one of projections 385 as a hole or indentation 25 ; in fig2 b such a feature is illustrated as a modified surface 26 on one of projections 31 wherein surface 26 includes texture , adhesive spots , or some material promoting thrombotic adhesion to vessel wall . methods for forming various embodiments of retaining segments , for example those depicted in fig2 a – d , include , but are not limited to , molding , extrusion , cutting , laser ablation , and coating . these methods may form projections directly in outer surfaces , such that they are integral with a bulk material underlying the surfaces , or may integrate the projections with the surface by embedding or adhering . according to some embodiments of the present invention , transfer or injection molding , using methods known to those skilled in the art , are used to form a retaining segment including projections , examples of which include those depicted in fig2 b – c . according to other embodiments , a cutting process may be used to create projections on a retaining segment , for example segment 380 illustrated in fig2 a ; a blade may be used to nick the surface or to cut all the way through a wall of the retaining segment . alternatively , laser ablation may be used to create projections from a bulk material of a retaining segment , i . e . fig2 b – c , or by exposing , at a surface of the segment , portions of materials which have been embedded within the bulk material underlying the surface during , for example , a molding or extrusion process , i . e . fig2 d . u . s . pat . no . 5 , 580 , 699 describes a suitable laser ablation process , which may be used to form retaining segments and the pertinent teachings of the &# 39 ; 699 patent are incorporated by reference herein . u . s . pat . no . 4 , 272 , 577 describes an extrusion process for forming ski bases having direction - dependent friction coefficients wherein harder particles , within a plastic matrix flowing through a slit nozzle , become obliquely oriented relative to the surface of the base ; in one case , by means of a temperature gradient across the nozzle . we contemplate that similar methods may be developed by those skilled in the art , according to the teachings of the &# 39 ; 577 patent , in order to extrude retaining segments according to the present invention , and incorporate by reference the pertinent teachings of the &# 39 ; 577 patent herein . some composite materials suitable for embodiments of the present invention include but are not limited to polyamide and polyimide particles , polyester fibers , carbon fibers or particles and any combination thereof blended with silicone . according to further alternate embodiments a coating applied to a surface of a retaining segment may form projections and or micro - features on projections , for example similar to those illustrated in fig2 b – c . stewart et al . describe an example of a suitable coating process via plasma deposition in commonly assigned u . s . pat . no . 6 , 549 , 811 , which is incorporated by reference in its entirety herein . furthermore coatings including particles blended within , for example a silicone medical adhesive including biocompatible metal particles or hard plastic particles may form an embodiment of the present invention for example similar to those illustrated in fig2 b and 2d . fig3 is a plan view of a lead 40 , which may incorporate retention means according to embodiments of the present invention . fig3 illustrates lead 40 including a proximal portion 43 , a first preformed bend 41 extending from proximal portion 43 to an intermediate segment 45 and a second preformed bend 42 extending from intermediate segment 45 to distal segment 46 , which is terminated by a tip 44 . such a lead is fully described in commonly assigned u . s . pat . no . 5 , 999 , 858 , which is herein incorporated by reference in its entirety . according to embodiments of the present invention , first and second bends 41 and 42 acting as means for retention of lead body in a coronary vessel , for example a coronary sinus 605 or a branch vessel 607 thereof illustrated in fig6 , are supplemented by any of the retaining segments described herein , which may be formed along the lead body surface at first bend 41 , intermediate segment 45 , second bend 42 , distal segment 46 , or any combination thereof . any other combination of bends within a lead body is within the scope of the present invention . fig4 a – b are partial plan views of one embodiment of lead 40 showing only a portion at first bend 41 , which includes a retaining segment formed by projections 51 . according to some embodiments of the present invention a retaining segment may be activated by a bending of a lead body as illustrated in fig4 a – b . if a stylet , for example stylet 18 shown in fig1 , is inserted into lead 40 to straighten preformed bend 41 , projections 51 become approximately parallel with an outer surface of lead 40 , as illustrated in fig4 a . once the stylet is removed preformed bend 41 reforms such that projections 51 protrude laterally and are thus activated to prevent rearward motion of lead 40 within a vessel . if it becomes necessary to reposition lead 40 , the stylet may be reinserted to straighten bend 41 thus bringing projections into approximate alignment with the surface of lead 40 . it should be noted that the embodiment illustrated in fig2 d may be of the type illustrated in fig4 a – b . fig3 further illustrates lead 40 including an anchoring sleeve 48 positioned about proximal portion 43 thereof . according to an additional embodiment of the present invention , means for retention as illustrated herein , may be formed along an outer surface of proximal portion to provide frictional forces complementing anchoring sleeve 48 at a venous entry point . the means for retention may either engage an inner surface of anchoring sleeve 48 or engage a vein wall in proximity to the entry point . fig5 a – b schematic views of a portion of a lead body including retention means according to yet another embodiment . fig5 a – b illustrate a lead body 20 including a plurality of hair - like projections or fibers 205 each attached at one end to lead body 20 and directed by their attachment points 23 to extend out from and along a length of body 20 toward a proximal end 221 of body 20 . according to the illustrated embodiment , as lead body 20 is advanced distally in a vessel 207 per arrow a , as in fig5 a , projections 205 are suspended proximally ; when lead body 20 is retracted proximally per arrow b , as in fig5 b , projections 205 are forced toward a distal end 222 of body 20 to become bunched up and wedged between body 20 and a wall of vessel 207 , thereby providing retention means for lead body 20 . projections may be formed from a bioadsorbable polymer , for example polyglyocolic acid or polylactic acid . alternately projections 205 may be formed from polyester fibers or some other material promoting thrombotic adhesion with the vessel wall to enhance retention within vessel 207 ; such thrombotic projections may include a non - thrombogenic coating adapted to dissolve after the lead is positioned per fig5 b , examples of which include a benzalkonium chloride - heparin solution and polyvinylpyrrolidone . projections 205 may be attached at attachment points 23 by embedment within lead body 20 or by adhesive attachment , for example by means of silicone medical adhesive . fig6 is a schematic view of an exemplary medical device , which may incorporate retention means according to embodiments of the present invention . fig6 illustrates the medical device including a therapy generator 600 coupled to a lead 60 implanted within branch vessel 607 emanating from coronary sinus 605 . lead 60 including a connector terminating a proximal portion 62 , an electrode in proximity to a distal end 66 and a conductor extending through an outer insulative sheath ( similar to lead 10 illustrated in fig1 ) may deliver electrical therapy , or may deliver infusions of therapeutic fluids from generator 600 through a central lumen . fig6 further illustrates potential retention segment sites 65 , 61 , and 63 along lead 60 where projections of retention segments according to embodiments of the present invention would engage a wall of vessels 605 and 607 to prevent rearward dislodgment of lead 60 from vessel 607 . although embodiments of the present invention are described in the context of therapy delivery , diagnostic devices adapted for insertion within a blood vessel may also incorporate retention means described herein and thus fall within the scope of the present invention . in the foregoing detailed description , the invention has been described with reference to specific embodiments . however , it may be appreciated that various modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims .
a medical device having retention means extending along a length of an elongate body of the medical device including a plurality of projections adapted to interfere with a wall of a generally tubular vessel to retain the body within the vessel .