an exemplary embodiment of the device of the invention will now be described . fig1 illustrates a schematic representation of the femoral access route and the chambers of the heart , and depicting the implantation accessory according to the present invention bearing an autonomous capsule of the leadless type 10 . such a leadless capsule ( shown in more detail in particular in fig1 ) includes a tubular body 12 provided at one of its ends with a projecting helical anchoring screw 14 axially extending from the tubular body and integral with it in rotation . the anchoring screw 14 includes in its distal portion a length of the order of 1 . 5 to 2 mm of non - contiguous turns , adapted to penetrate the heart tissue so as to secure the capsule there . the screw 14 can be an electrically active screw , comprising the detection / stimulation electrode at least at its distal end , or it can be a passive screw serving only to the anchoring of tubular body 12 in the wall of the heart chamber . in the latter case , the capsule is provided with an axial conductive needle 16 acting as a detection / stimulation electrode in contact with the myocardial tissue . alternatively , it is also possible to provide a surface electrode . the tubular body 12 includes various power supply circuits and methods for signal processing and wireless communication for the exchange of signals with a remote master device , implanted or not . these aspects are in themselves known , and since they are not part of the invention , they will not be described . at its proximal end 18 , the tubular body 12 of the capsule 10 includes an axial lashing rod 20 with a rounded end , the function of which will be described later in the implantation procedure . this lashing rod 20 is smooth on its outer face and has an internal threaded axial hole , a structure which will be explained in more detail with the description of fig4 below . the leadless capsule 10 is intended to be implanted in the right ventricle 22 , especially at the bottom of the ventricle , in the region of the apex 24 . for a conventional stimulation lead ( connected to a remote generator ), the location would typically be performed via the subclavian vein 26 , as illustrated in dashed lines at 28 , so that the end of the lead would be approximately oriented in the δrv axis of the right ventricle and thus could easily pass through the tricuspid valve and reach the apex of the ventricle 24 . however , as mentioned in the introduction , this implantation approach is not feasible for implantation of leadless capsules , the dimensions and , in particular , the external diameter , being far superior to those of the head of a conventional lead . it is therefore necessary to access , via the vena cava 30 , from a femoral puncture 32 . but in this case , the axis of approach , that is to say the δvc axis of the vena cava , has a strong angulation ( angle 34 ) with the axis δrv of the right ventricle . therefore , it is necessary to form a curvature 36 at the right atrium 38 in order to pass the implantation accessory emerging from the sinus 40 of the vena cava to the tricuspid valve 42 to then reach the cavity 22 of the right ventricle . similar difficulties arise for implantation into the left ventricle , the implantation access then involving an arterial femoral puncture and the passage of the aortic arch . such a maneuver can be performed through a “ steerable ” catheter , with a catheter tube 44 handled from the proximal end by an operating handle 46 available to the practitioner . using the handles 48 , 48 ′ the latter can create and adjust a curvature 50 to guide the distal end 52 of catheter 44 accurately , typically with an orientation up to 180 ° in both directions with a variable radius of curvature , of the order of 5 to 60 cm . the handle 46 is also provided with a purge drain lateral track 54 and of a valve 56 , features which are in themselves entirely conventional . with a conventional steerable catheter , if it is possible to precisely adjust the curvature 50 , it is not possible to change the area of the catheter wherein , along its length , the curvature is formed . however , in the particular case illustrated with a femoral approach , with the objective of reaching the bottom of the right ventricle , this limitation can be troublesome with some specific morphologies with very elongated cavity . indeed , the distal portion 52 of the steerable catheter located beyond the curvature of the region 50 may be too short to reach the region of the apex 24 . embodiments of the present invention address this difficulty , as will be explained hereinafter , so that the implementation of the invention is possible using a marketed , pre - existing , steerable conventional catheter to reduce the cost of the implantation accessory of the invention . fig2 to 4 show , in enlarged views , the distal end of the steerable catheter 44 , with the different characteristic elements of the invention . the steerable catheter 44 is provided at its distal end with a tubular protection tip 58 having a central recess 60 ( fig3 ) for housing the capsule 10 in a configuration called “ retracted position ”, corresponding to fig2 - 4 . the main function of the tip 58 is to protect the capsule , including the anchoring screw 14 , during the intravenous passage of curves , angulations , valves , etc . conversely , the cap protects the tissue from the risk of stripping potentially caused by the movement of translation of the screw . the outer diameter of the steerable catheter 44 is typically between 10 and 15 french ( 6 . 6 to 10 mm ), for an inner lumen diameter of between 8 and 12 french ( 2 . 66 mm to 4 mm ). the tubular tip 58 must be able to house the capsule and therefore have an inside diameter of about 21 french ( 7 mm ). furthermore , a catheter of this size must necessarily move into the venous system while being guided by a coiled guidewire previously introduced into the vasculature . as in the illustrated design , the central canal of the catheter 44 is blocked by the capsule . to allow the introduction of a guidewire , the tubular tip is provided with an eccentric lateral lumen 62 extending axially the length of the tip and opening at the distal 64 and proximal 66 sides , preferably extending over the entire length of the tip 58 . the inner diameter of the lateral lumen 62 allows for the introduction of a conventional coiled guidewire of a diameter of 3 french ( 1 mm ), and the sliding of the tip , and therefore of the entire steerable catheter 44 , through the vasculature ( this configuration is notably shown in fig8 , wherein the reference 98 designates the coiled guidewire ). alternatively , the eccentric lateral lumen 62 may be extended along the body of the steerable catheter 44 to facilitate the pushing of the coiled guidewire and prevent any curling phenomenon thereof . note that the eccentricity of the lumen 62 combined to the beveled profile of the tip allows easy progression into the venous system by a “ sidewire ” technique . in addition , the front panel 68 , the most distal area of the tip 58 , is shaped to have a minimum front bearing surface to avoid any risk of perforation in case of accidental operation without the coiled guide . in addition , a radiopaque marker 70 is provided in front of the tubular tip 58 on the most distal surface of this tip , to more efficiently identify the capsule outlet if the tip is made of a radio - transparent material . finally , one or more drain holes 72 are disposed proximal to the tip , to prevent piston effect upon injection of contrast medium , which otherwise would result in pushing the capsule 10 out of the protection tip 58 . the catheter 44 is formed with a reinforced structure , such as a wire mesh or a coil embedded in the thickness of the catheter wall , so as to provide a torque transmission capability exerted on the proximal handle to the distal end ( reinforced structure 74 ). the implantation accessory of the invention further includes , typically , a sub - catheter 76 , introduced into the central lumen of the steerable catheter 44 , and movable in rotation and in translation relative to the latter . the function of this sub - catheter 76 is to ensure the deployment of the capsule out of the protection tip and to advance the capsule to the implant site by a translation movement over a sufficient length , typically from to 2 to 6 cm depending on the anatomy of the patient . in the figure , arrow 78 indicates the translation of the sub - catheter 76 within the steerable catheter 44 , and arrow 80 indicates the translation of the capsule 10 out of the protection tip 58 . the sub - catheter 76 also has the function of ensuring the transmission of torque from the proximal end ( at the operating handle ) to its distal end , and is provided for this purpose of a reinforced structure 82 . it is possible to use as the sub - catheter 76 a conventional guide catheter sized from 4 to 6 french ( 1 . 33 to 2 mm ), which is an existing , simple and cost - saving device meeting the current constraints torque transmission , low coefficient of friction inside and outside , flexibility , etc . sub - catheter 76 may have a proximal “ luer - lok ” connection for the rapid mounting of a multifunction adapter such as a rotational hemostasis valve or other adapter compatible with this sealed connection standard . alternatively , the sub - catheter 76 can be used to inject a contrast to the back of the capsule 10 so as to accurately monitor the operation under fluoroscopy . a fastening mechanism according to the present invention is directed to the coupling of an implantation device including a hollow or not elongated tubular member ( such as a catheter ) with an autonomous ( such as a leadless capsule ) or not ( such a probe head of a pacing lead ) medical device , said device being provided at its distal end with an anchoring mechanism adapted to penetrate a cardiac or else body tissue . the fastening mechanism according to the invention employs an elastic deformable component , such as helical spring 84 , which is not used for its properties of elasticity in axial traction / compression ( effect resulting from the elongation or the reconciliation of the coils of the spring ), but for its radial compression properties , that is to say for the pinch or throttle effect can such a spring can exert around a rigid component , such as a core inserted into the helical form . in other embodiments , the elastic deformable component may be a lamella that provides radial compression about the core . the geometry of the elastic deformable component , such as a spring , and the elasticity of the material which constitutes it are chosen so as to produce between the elastic component and the core , in the absence of external stress , an interference fit ( caused by the radial compression resulting from the pinch effect ). in the illustrated example of fig4 of the leadless capsule 10 , the core is constituted by the lashing rod 20 with rounded end , located axially on the proximal portion 18 of the capsule 10 and outwardly oriented . this lashing rod 20 may be shaped to optimize the disengagement function . the spring 84 is shown in detail and in isolation in fig5 and 6 . the spring 84 is secured to the distal end of the sub - catheter 76 by turns 86 . this securing in translation and in rotation , for example by welding or gluing , must be kept regardless of the degree of stress normally applied to the sub - catheter 76 and to the spring 84 . the turns 88 located distally of the spring 84 are free turns , which are surrounding the lashing rod 20 but which are not mechanically fastened to the latter by connection mechanisms other than interference fit with tightening obtained in the static configuration of these two elements . in addition , the distal end of the spring 84 is preferably a rounded end to prevent tissue injury and hang at various manipulations . the inactive turns 86 and / or the active turns 88 may be either touching or not contiguous . once the capsule 10 is fixed to the implant after complete penetration of the anchoring screw 14 to the front face of the capsule , the practitioner continues to make the sub - catheter 76 turn , thereby generating an excess torque . the excess torque has the effect of reducing the force exerted by the free turns 88 on the lashing rod 20 , to cause rotational sliding of these turns on this same rod . by combining this rotational movement to a slight tensile load , the compression spring 84 is released from the lashing rod 20 , by longitudinal sliding of the turns on the rod , thus releasing the capsule 10 from the spring 84 , and thus from the sub - catheter 76 . in an alternative embodiment of the first fastening mechanism , shown in fig7 a - 7d , the deformable plastic member is a lamella 184 that is positioned in a socket created by a hollow cylinder 186 . the lamella 184 is radially deformable relative to the cylinder axis . the rigid component is provided in the form of a non - deformable plug element 188 configured to be introduced into the socket of the hollow cylinder 186 . the introduction causes deformation of the lamella 184 , thereby producing a radial force between the plug element 188 and the lamella 184 , as shown in 7 d . relative rotational movement between the hollow cylinder 186 and the plug element 188 generates a tangential calibrated friction and therefore creates a limitation in the torque applied to the components of the system . the radial compression spring 84 or lamella 184 thus act as torque limiter . indeed , with the anchoring screw of a standard leadless capsule , if the practitioner continued rotation of the sub - catheter 76 and therefore of the capsule 10 , the torque would increase and exceed a limit c coring . this increases the risk of the anchoring screw locally tearing the tissues under the effect of the rotation of the screw advance thereof , causing a tearing of the tissues and , in the extreme , a perforation of the wall , with the risk of tamponade . this is not the case with the device and methods provided by the invention . the practitioner may indeed safely continue rotating the sub - catheter 76 , always in the same direction ( usually clockwise ), because the extra torque due to the reaction of the anchoring screw anchored in the tissue is absorbed by the connection between , for example , the spring 84 and the lashing rod 20 ( phenomenon of sudden increase of the torque when the front face of the capsule contacts the cardiac tissue ). more specifically , the geometry and elasticity of the spring 84 are chosen so as to define a predefined torque c release lower to the coring limit , c coring , corresponding to a limit holding torque of the anchoring screw in this tissue , without coring of the tissue , while providing a full screw ( tissue contacting the front face of the capsule ). thus , when the c release torque is reached , the further rotation of the sub - catheter 76 in the clockwise direction causes , in combination with a slight traction force , the gradual release of the spring 84 with the lashing rod 20 by longitudinal sliding of the turns of the radial spring along the rod . in case of any excess torque , the turns of the radial spring slide in rotation on the securement ring therefore no longer transmit torque elevation . the clutch release torque c release is adjusted to a typical value of about 0 . 01 to 0 . 05 n · cm . furthermore , in a static configuration , the pinch force of the free portion 88 of the spring 84 on the lashing rod 20 is selected so as to prevent accidental disassembly by a traction force ( axially directed force ) lower to a sufficient threshold , typically a threshold which provides holding even for a traction exerted on the sub - catheter 76 under a force of up to 20 n . note also that if it is desirable to unscrew the capsule , for example because after a first implantation it is found that the electrical performance of the site are not satisfactory , the coupling system by the spring 84 will have no release effect during unscrewing . since the spring will then be driven in reverse rotation ( usually counterclockwise ), this will further increase the effect of the tightening of the turns 88 of the lashing rod 20 . another advantage of the spring 84 is after the release of the capsule , the implantation device is present with a screw at its end in the form illustrated in fig5 and 6 . in particular , the free turns 88 of the spring 84 form a screw . in case of reoperation intraoperative , that is to say , if it is desirable to secure the new sub - catheter 76 to the capsule , the screw formed by the spring 84 will have the advantage of requiring no angular adjustment to secure the lashing rod 20 of the capsule to be retrieved ( unlike the systems using a male / female connector which require positioning to allow the interlocking of the two elements ). finally , note that the torque limiter comprising spring 84 is conveniently located in the chain of transmission of forces . specifically , any loss of fidelity in the transmission of torque between the proximal end of the sub - catheter 76 ( that is to say from the handle manipulated by the practitioner ) and its distal end ( the location of the coupling spring 84 ) has no effect on the maximum or minimum torque at the interface between the anchoring screw and the tissue , which is a guarantee of complete fixation . this is not the case for a detachable system that would be located further upstream , typically in the operating handle 46 . note also that all of these features are obtained via a very economical component of very simple and compact design . the release of the capsule may thus be effected by a combined screwing and traction movement in two steps . first , screwing of the capsule in the heart wall , by clockwise rotation of the sub - catheter 76 ( e . g . 10 rpm ) under a slight push . second , release of the capsule by a further clockwise rotation of the sub - catheter 76 ( e . g . 5 turns ) under slight tension to allow removal of the sub - catheter after release of the spring 84 . to obtain this result , the direction of the turns of the spring is of course selected in the same direction as that of the anchoring screw , preferably with a right - engaging thread , so that the screwing of the capsule and then its release correspond to a rotation of the sub - catheter 76 in the clockwise direction , the most conventional one . advantageously , the implantation kit also includes a security thread or retainer 90 of “ breadcrumb ” wire - type connected to the capsule 10 on the distal side , extending over the entire length of the sub - catheter 76 and exceeding it proximally , that is to say on the side of the operating handle 46 . as shown in fig1 and 12 , once the capsule 10 is implanted and dropped , its operation is tested , including the establishment of good wireless communication between the capsule and the remote master device as well as the stimulation electrical performance . once the steerable catheter 44 and the sub - catheter 76 are completely removed , the retaining wire allows for intraoperatively retrieving the capsule , with reintroduction of the implantation accessory by making it slide along the retaining wire until the protection tip 58 caps the capsule . the latter can then be re - coupled to the sub - catheter by a clockwise rotation ( the clutch - limiter functionality being always effective ). the capsule can then be unscrewed from the wall 100 by a counterclockwise rotation and repositioned at another site by the same principle as what has been described above , by a clockwise rotation of the sub - catheter . the retaining wire is for example a wire of 1 french diameter ( 0 . 43 mm ) having at its distal end 92 a thread 94 able to cooperate with a mating internal thread 96 formed in a threaded axial bore of the stowage axis 20 ( fig4 ). this retaining wire is preferably sufficiently flexible in its distal part ( 6 to 8 cm ), while being able to transmit to the distal end 92 an unscrewing torque resulting from a rotation exerted from the proximal end , at the operating handle . note that , because of the very small diameter of the screwing system 94 , 96 , the torque to be exerted to produce the unscrewing is very small ( of the order of 0 . 02 n · cm ), and may not in any way exert trigger a rotation movement of the capsule 10 which is firmly secured to the heart wall by the anchoring screw . the retention wire may be colored in different colors for each of the implanted capsules , so as to more easily identify the appropriate capsule in the event of reoperation . the technique of the invention therefore provides triple security through the release system which allows at the release of the capsule : to ensure complete screwing of the capsule in the tissue ; to prevent coring of the heart wall ; and to ensure the practitioner to recover the capsule after dropping in case of difficulty , through the retaining wire . the procedure for setting up the leadless capsule through the implantation accessory as described above comprises the following steps , each of which is relatively conventional and can be easily performed by a practitioner without requiring special skills or additional maneuvers : right or left femoral puncture , in order to access the inferior vena cava 30 ; optional percutaneous introduction of a 23 french haemostatic introducer ( 7 . 66 mm ); insertion of the steerable catheter 44 on a spiral guidewire ( illustrated at 98 in fig8 ), typically a 3 french ( 1 mm ) guidewire on which the tubular tip 58 , and thus the steerable catheter 44 will slide and move to the right atrium 38 ; turning maneuver of the tip of the steerable catheter 44 ( as shown at 36 in fig1 ) and introduction of the tip 58 in the right ventricle ; release of the capsule 10 to the apex of the ventricle by translation of the sub - catheter 76 in the steerable catheter 44 ( configuration shown in fig1 ); visualization of the cardiac walls by injection of contrast medium through the sub - catheter ; fine positioning of the capsule to the selected target site , with the possibility of translation once in the cardiac cavity by a more or less important deployment of the sub - catheter 76 from the steerable catheter 44 , allowing fine adjustment to suit a wide variety of anatomies ; screwing of the capsule in the heart wall to the release of the radial compression spring 84 ; separation of the sub - catheter 76 with the capsule 10 , and removing of the sub - catheter 76 out of the steerable catheter 44 ( configuration shown in fig1 ); electrical test of the capsule ; complete removal of steerable catheter 44 and of the sub - catheter 76 ; final release of the capsule , with withdrawal of the retaining wire 90 by low torque unscrewing ; and closure of the puncture site .
an assembly includes a medical device provided with an anchoring member adapted to penetrate tissue of a cavity of the heart . the assembly further includes an implantation accessory including an elongated tubular element provided with a fastening mechanism for handling and guiding the medical device to an implantation site . the fastening mechanism includes an elastic deformable component cooperating with a rigid component , that is able to disconnect the medical device from the tubular element under the effect of a rotation exerted to the tubular element . the elastic deformable component cooperates with the rigid component such that the elastic deformable component exerts on the latter a radial constriction effect , and the elastic component and the rigid component being disconnected under the combined effect of a torsion torque and a traction exerted to the elastic deformable component , to thereby reduce the radial constriction until release of the rigid component .