Sutureless retention device

FIELD OF THE INVENTION

0001The invention relates to a device for securing in-dwelling catheters, sheath introducers, or other temporary or implantable medical devices to patients.

0002Such a device is disclosed in the <patcit id="pcit0001" dnum="US5267960A"><text>US 5267960</text></patcit>.

BACKGROUND

0003Medical treatments requiring the delivery or drainage of various solutions such as antibiotics, cancer drug therapy, blood draws, abscessed biliary material or urinary tract fluids, rely upon an indwelling catheter or sheath introducer to be inserted into the patient for an extended period of time such as thirty or even sixty or ninety days at a time. A requirement for maintaining the catheter or sheath within a patient for such a period is that the catheter or sheath be secured so as not to move excessively during the treatment.

0004Typically the physician creates an incision or puncture through the patient's skin with the goal of reaching an artery, vein or other vessel to allow insertion of a catheter to deliver a therapeutic substance to or aspirate body fluids from a specific anatomical site. Currently catheters and sheaths are secured utilizing a tab or eyelet formed in the luer hub or Y-connector through which a suture is taken through the tab and skin. A standard 2-0 suture is most often used for this purpose, which is tied off thus securing the catheter within the patient's body. Suturing a catheter to a patient, however, presents several problems: (1) Suturing a catheter to a patient's body makes it difficult to clean and disinfect the area around the catheter insertion point, resulting in a high rate of infection in the area close to the catheter's insertion; (2) The catheter is subject to being dislodged from the patient following introduction resulting in migration of the catheter during treatment; and (3) A sutured catheter is subject to a disoriented patient ripping the catheter loose and tearing the suture out. This can result in patient injury and often necessitates costly replacement or additional corrective procedures.

0005An additional disadvantage of suturing a catheter to a patient is pain and discomfort to the patient during the period of catheterization, as a result of a long-term suture extending through the patient's skin. Further, different physicians use different suturing and knotting techniques, resulting in a wide variation of pull strengths required to rip out and dislodge the sutured catheter from the patient's body.

0006Another securement method utilizes adhesive tape. In this method a layer of tape is placed over a cleaned external site on the patient's body after catheter or sheath insertion has been accomplished. The catheter or sheath is adhered to the skin by adhesive friction. This method is ineffective at reducing the incidence of infection. Further, it does not prevent the inadvertent and often violent removal of the catheter prior to completion of treatment.

0007What is therefore needed is a retention device for a catheter, sheath introducer, or other medical devices that allows for simple and effective anchoring to the patient's body and also reduces the incidence of infection, migration and dislodgment.

SUMMARY

0008In one embodiment, the invention comprises a device for subcutaneously anchoring a catheter within a patient as further disclosed in claim 1. The device has an anchor sleeve having a chamber defining at least a single port. An anchor mechanism is loaded into the chamber and has a control rod movable within the chamber between a first position and a second position. A tine is fixedly attached to the control rod at a first end, and also has a second free end. The second end of the tine is capable of flexibly and repeatedly moving between a restrained position near the control rod and an unrestrained position away from the control rod. The tine has a trained shape when in the unrestrained position and the length of the tine is such that the tine is restrained within the chamber when the control rod is in the first position. The port is sized and located so the free end of the tine is proximate the port when the tine is in the first position. Moving the control rod from the first position to the second position causes the free second end of the tine to exit the chamber through the port to at least partially assume the trained shape.

0009In another embodiment, the device is attached to an introducer sheath.

0010In yet another embodiment, the device is attached to a catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

0011In the drawings, identical reference numerals indicate identical or equivalent structure where: <ul id="ul0001" list-style="none"><li><figref idref="f0001">FIG. 1</figref> is a side view of a first embodiment of the retention device following insertion through a patient's skin.</li><li><figref idref="f0002">FIG. 2</figref> is a side view of a first embodiment of the invention with an anchor sleeve and anchor mechanism attached to an introducer sheath capable of receiving and securing a catheter, prior to the tine being deployed.</li><li><figref idref="f0002">FIG. 2a</figref> is a cross sectional view taken through the lines 2a-2a of the embodiment of the invention shown in <figref idref="f0002">FIG. 2</figref>, with the anchor mechanism loaded into the anchor sleeve, prior to deployment.</li><li><figref idref="f0002">FIG. 2b</figref> is a cross sectional view taken through the lines 2a-2a of the embodiment of the invention shown in <figref idref="f0002">FIG 2</figref> with the anchor mechanism loaded into and deployed from the anchor sleeve.</li><li><figref idref="f0003">FIG. 3</figref> is a side view of a second embodiment of the invention with the anchor sleeve and anchor mechanism attached to a dual lumen catheter body and hub.</li><li><figref idref="f0003">FIG. 4</figref> is a cross sectional view taken between points 4-4 of the apparatus shown in <figref idref="f0003">FIG. 3</figref>.</li><li><figref idref="f0004">FIG. 5</figref> is a top view of the embodiment of the invention shown in <figref idref="f0003">FIG. 3</figref>.</li><li><figref idref="f0005">FIG. 6a</figref> is a side view of a first embodiment of the anchor mechanism.</li><li><figref idref="f0005">FIG. 6b</figref> is a side view of the first embodiment of the anchor mechanism having tapered tines.</li><li><figref idref="f0005">FIG. 7</figref> is a proximal end view of the first embodiment of the anchor mechanism shown in <figref idref="f0005">FIG. 6a</figref>.</li><li><figref idref="f0006">FIG. 8</figref> is a side view of a second embodiment of the anchor mechanism.</li><li><figref idref="f0006">FIG. 9</figref> is a side view of a third embodiment of the anchor mechanism.</li><li><figref idref="f0007">FIG. 10</figref> is a cut away view of the first embodiment showing the lock mechanism prior to deployment of the tines and showing the key inserted into the recess.</li><li><figref idref="f0008">FIG. 10a</figref> is a cut away view of the first embodiment showing the lock mechanism following deployment of the tines and the key inserted prior to unlocking the lock mechanism.</li><li><figref idref="f0009">FIG. 11</figref> is a cut away view of the first embodiment of the retention device showing the lock mechanism following deployment of the tines with the key removed from the recess.</li><li><figref idref="f0010">FIG. 12</figref> is a partial cut away view of the third embodiment of the anchor mechanism loaded into the first embodiment of the retention device prior to deployment of the tine.</li><li><figref idref="f0010">FIG. 13</figref> is a partial cut away view of the third embodiment of the anchor mechanism loaded into the first embodiment of the retention device following deployment of the tine.</li><li><figref idref="f0011">FIG. 14</figref> is a cut away view of the second embodiment of the retention device showing the lock mechanism prior to deployment of the tines.</li><li><figref idref="f0012">FIG. 15</figref> is a cut away view of the second embodiment of the retention device showing the lock mechanism following deployment of the tines.</li><li><figref idref="f0013">FIG. 16</figref> is a side view of a third embodiment of the retention device showing the anchor mechanism in phantom and the locking mechanism in a cut away view.</li><li><figref idref="f0014">FIG. 17</figref> is a cross sectional view taken through the lines 17-17 of the third embodiment of the retention device.</li></ul>

DETAILED DESCRIPTION

<i>Definitions</i>

0012"Braid" refers to a structure made of interwoven strands.

0013"Catheter" is used in its generic sense and refers to any surgical instrument used to deliver a surgical device or chemical substance to a particular location in to the interior of a patient's body.

0014"Coil" refers to a structure made of a series of rings or spirals.

0015"Distal" refers to the most distant location from the operator.

0016"Longitudinal" refers to a lengthwise dimension.

0017"Port" refers to an opening or a thinning in a wall.

0018"Proximal" refers to the location closest to the operator.

0019"Subcutaneous" refers to the space below the skin/dermis.

0020"Vessel" refers to any anatomical structure that connects organs within a body. Examples include but are not limited to arteries, veins, bile duct, ureter, or other body cavities.

<i>Nomenclature</i>

0021<dl id="dl0001"><dt><b>10</b></dt><dd>Retention Device (First Embodiment)</dd><dt><b>12</b></dt><dd>Catheter</dd><dt><b>14</b></dt><dd>Anchor Sleeve</dd><dt><b>14a</b></dt><dd>Chamber</dd><dt><b>14b</b></dt><dd>Floor of Anchor Sleeve</dd><dt><b>16</b></dt><dd>Introducer Sheath</dd><dt><b>16a</b></dt><dd>Second Lumen</dd><dt><b>18</b></dt><dd>Anchor Mechanism</dd><dt><b>18a</b></dt><dd>Tine</dd><dt><b>18b</b></dt><dd>Control Rod</dd><dt><b>20</b></dt><dd>Port</dd><dt><b>22</b></dt><dd>Membrane</dd><dt><b>24</b></dt><dd>Braid</dd><dt><b>26</b></dt><dd>Hemostasis Valve</dd><dt><b>28</b></dt><dd>Eyelet</dd><dt><b>29</b></dt><dd>Lock Spring</dd><dt><b>32</b></dt><dd>Recess</dd><dt><b>34</b></dt><dd>Key</dd><dt><b>36</b></dt><dd>Liner</dd><dt><b>40</b></dt><dd>Handle</dd><dt><b>100</b></dt><dd>Retention Device (Second Embodiment)</dd><dt><b>112</b></dt><dd>Catheter</dd><dt><b>114</b></dt><dd>Anchor Sleeve</dd><dt><b>114a</b></dt><dd>Chamber</dd><dt><b>118</b></dt><dd>Anchor Mechanism</dd><dt><b>118a</b></dt><dd>Tine</dd><dt><b>118b</b></dt><dd>Control Rod</dd><dt><b>120</b></dt><dd>Port</dd><dt><b>128</b></dt><dd>Eyelet</dd><dt><b>129</b></dt><dd>Lock Spring</dd><dt><b>130</b></dt><dd>Weld</dd><dt><b>218</b></dt><dd>Anchor mechanism</dd><dt><b>218a</b></dt><dd>Tine</dd><dt><b>218b</b></dt><dd>Control Rod</dd><dt><b>228</b></dt><dd>Eyelet</dd><dt><b>229</b></dt><dd>Lock Spring</dd><dt><b>230</b></dt><dd>Weld</dd><dt><b>400</b></dt><dd>Retention Device (Third Embodiment)</dd><dt><b>412</b></dt><dd>Catheter</dd><dt><b>414</b></dt><dd>Anchor Sleeve</dd><dt><b>414a</b></dt><dd>Chamber</dd><dt><b>418</b></dt><dd>Anchor Mechanism</dd><dt><b>418a</b></dt><dd>Tine</dd><dt><b>418b</b></dt><dd>Control Rod</dd><dt><b>420</b></dt><dd>Port</dd><dt><b>428</b></dt><dd>Eyelet</dd><dt><b>429</b></dt><dd>Lock Spring</dd><dt><b>432</b></dt><dd>Recess</dd><dt><b>440</b></dt><dd>Handle</dd><dt><b>S</b></dt><dd>Skin</dd><dt><b>V</b></dt><dd>Vessel</dd></dl>

<i>Construction</i>

0022As shown in <figref idref="f0001">FIG. 1</figref>, in a first embodiment [,] the present invention comprises a retention device <b>10</b> which is useful for securing catheters <b>12</b> and other medical devices beneath the skin <b>S</b> of a patient. In the first embodiment, as shown in <figref idref="f0001">FIGS. 1</figref> and <figref idref="f0002">2</figref>, the invention comprises an anchor sleeve <b>14</b> which is integrally attached to an introducer sheath <b>16</b> by such means as co-injection molding or co-extrusion. Additional methods of attachment between the anchor sleeve <b>14</b> and introducer sheath <b>16,</b> including but not limited to gluing, ultrasonic welding, mechanical fasteners, heat shrinkable tubing or thermal melting are also contemplated by and therefore within the scope of the invention. As shown in <figref idref="f0002">FIGS. 2 and 2a</figref>, the anchor sleeve <b>14</b> defines a chamber <b>14a</b> and the introducer sheath <b>16</b> defines a lumen <b>16a.</b> The chamber <b>14a</b> further defines a floor <b>14b</b> towards the distal end (unnumbered) of the anchoring sleeve <b>14</b> sealably houses the anchor mechanism <b>18, 118, 218.</b> A sealed chamber <b>14a</b> is advantageous as it resists and minimizes the flow of blood and other bodily fluids into and out of the retention device <b>10</b> during the period of anchoring and catheterization, which could cause infection due to the potentially relatively long period of placement of the retention device <b>10</b> within the patient's body. An additional advantage to a sealed chamber <b>14</b> is that tissue in-growth is resisted, which could otherwise potentially interfere with and cause seizure of the anchor mechanism <b>18, 118, 218</b> thereby making normal removal impossible. A hemostasis valve <b>26,</b> which is well known in the art, is attached to the proximal end (unnumbered) and collinear with the introducer sheath <b>16</b> to prevent the leakage of blood and other bodily fluids from the device <b>10</b> during use. The inner diameter of the lumen <b>16a</b> is sized to be able to accommodate the outer diameter of a catheter <b>12.</b> Thus, when the device <b>10</b> is inserted into a patient, a catheter <b>12</b> or other medical device (not shown) will extend first through the hemostasis valve <b>26,</b> then through the lumen <b>16a</b> and finally into the desired vessel <b>V,</b> organ (not shown) or body cavity (not shown).

0023A number of ports <b>20</b> in equal number to the number of tines <b>18a, 118a, 218a</b> are formed through the anchor sleeve <b>14</b> to permit deployment of the tines <b>18a, 118a, 218a</b> during treatment. In a preferred embodiment, a thin membrane 22 <b>[need to bold 22]</b> of a suitable plastic material such as polyurethane, silicone or latex covers the ports 20 <b>[need to bold 20].</b> The membrane <b>22</b> serves to seal the retention device <b>10</b> prior to deployment of the tines <b>18a, 118a, 218a.</b> As explained in greater detail below, during deployment the tines <b>18a, 118a, 218a</b> will puncture the membrane <b>22.</b>

0024As best shown in <figref idref="f0003 f0004">FIGS. 3- 5</figref>, a second embodiment of the retention device <b>100</b> comprises an anchoring sleeve <b>114</b> integrally attached to a catheter <b>112</b> (and associated structures such as a hub/body) by such means as co-injection molding or co-extrusion. The anchoring sleeve <b>114</b> further defines a chamber <b>114a.</b> In additional embodiments the anchoring sleeve <b>114</b> can be attached to the catheter <b>112</b> by any other suitable means, such as by gluing, ultrasonic welding, mechanical fasteners or thermal melting means. The chamber <b>114a</b> further defines a floor <b>114b</b> towards the distal end (unnumbered) of the anchor sleeve <b>114</b> and also sealably accommodates the anchor mechanism <b>18, 118, 218</b> which, as explained in detail below, extends to form lock spring <b>29, 129.</b> This resists and minimizes the inflow of blood and other bodily fluids into the retention device <b>100</b> during the period of anchoring and catheterization, which could cause infection due to the potentially relatively long period of placement of the retention device <b>100</b> within the patient's body. An additional advantage to a sealed chamber is that tissue in-growth is resisted, which could otherwise potentially interfere with and cause seizure of the anchor mechanism <b>18, 118, 218</b> thereby making normal removal impossible. In a manner similar to that shown in <figref idref="f0001">FIG. 1</figref> with regard to the first embodiment of the retention device <b>10,</b> the second embodiment of the retention device <b>100</b> is likewise introduced (not shown) through a patient's skin <b>S</b> and into a vessel <b>V</b> prior to deployment of the tines <b>18a, 118a, 218a</b> to secure the retention device <b>100</b> to the patient's body.

0025A number of ports <b>120</b> in equal numbers to the numbers of tines <b>18a, 118a, 218a</b> are formed through a side wall (unnumbered) of the anchor <b>sleeve 114</b> to permit deployment of the tines <b>18a, 118a, 218a</b> during treatment. In a preferred embodiment, a thin membrane <b>22</b> of a suitable low durometer plastic material such as polyurethane, silicone and latex covers the ports <b>120.</b> The membrane <b>22</b> serves to seal the retention device <b>10</b> prior to deployment of the tines <b>18a, 118a, 218a.</b> As explained in greater detail below, during deployment, the tines <b>18a, 118a, 218a</b> will puncture the membrane <b>22.</b>

0026Suitable materials for the anchor sleeve <b>14, 114</b> and introducer sheath <b>16</b> include various plastic materials including polyurethane, polyamide, pvax, polyethylene or PTFE reinforced by stainless steel, titanium or nitinol braid <b>24</b> or coil (not shown). Carbon fiber materials comprise an alternative braiding material. The reinforcing braid <b>24</b> is necessary to add additional strength to constrain the tines <b>18a, 118a, 218a</b> from premature deployment through the anchor sleeve. In an alternative embodiment, as shown in <figref idref="f0002">FIGS. 2a and 2b</figref>, the anchor sleeve <b>14, 114</b> is reinforced by a liner 36 made of a stronger material such as ultra high density polyethylene, high density polyethylene or nylon and derivatives or combinations of the above. The liner <b>36</b> can be a separately molded inserted piece or be incorporated into the anchor sleeve <b>14, 114</b> during the molding process. It is also contemplated to insert a liner <b>36</b> impregnated (not shown) with a braid <b>24</b> or coil (not shown).

0027The outer surfaces (unnumbered) of the retention device <b>10, 100</b> can be coated (not shown) with a variety of commercially available compounds. These include but are not limited to antithrombogenic, antibacterial, or anti-inflammatory compounds to reduce tissue ingrowth, or prevent infection due to the presence of the retention device <b>10, 100</b> in the patient for extended periods. These compounds are also useful in improving the biocompatibility of the retention device <b>10, 100</b> and include but are not limited to heparin complex solutions, benzalkonium heparinate, triodoecylmethylammonium heparinate, chlorhexidine-silver sulfadiazine, myococycline and rifampin.

0028Upon introducing a catheter, sheath introducer, or other medical device incorporating the retention device <b>10</b> through a patient's skin <b>S</b> and into a vessel <b>V</b> such as an artery (not specifically shown), vein (not specifically shown) or other duct (not specifically shown), vessel or organ (not specifically shown), the tines <b>18a, 118a, 218a</b> of the anchor mechanism <b>18, 118, 218</b> are deployed through the ports <b>20, 120</b> thereby securing the catheter <b>12,112,</b> introducer sheath <b>16</b> or other device (not shown) to the patient's body subcutaneously. The mechanism facilitating tine <b>18a, 118a, 218a</b> deployment is more fully explained below.

0029A preferred embodiment of an anchor mechanism <b>18</b> is best shown in <figref idref="f0005">FIGS. <b>6a, 6b</b> and 7</figref>. This embodiment of the anchor mechanism <b>18</b> comprises at least a single tine <b>18a</b> and in a preferred embodiment has two tines <b>18a</b> but may also have additional numbers of tines <b>18a</b> such as three (not shown), four (not shown), five (not shown), six (not shown) or even greater numbers of tines <b>18a</b> (not shown). The tips (unnumbered) of the tines <b>18a</b> may be sharp (not shown), dull as shown in <figref idref="f0002">FIG. 2b</figref> or rounded as shown in <figref idref="f0005">FIGS. 6a</figref> and <figref idref="f0006">8-9</figref>. A control rod <b>18b</b> is integrally attached to the tines <b>18a.</b> At the proximal end (unnumbered) of the control rod <b>18b</b> is an eyelet <b>28</b> formed integrally with the control rod <b>18b,</b> which serves either as a convenient grip or as the connector for an attached handle <b>40.</b> The control rod <b>18b</b> extends proximally and is trained to bend over to form an eyelet <b>28.</b> The control rod <b>18b</b> and eyelet <b>28</b> then reverse direction to a distal direction to form the lock spring <b>29</b> which is raised above the length of the control rod <b>18.</b> Together the tines <b>18a</b> and control rod <b>18b</b> comprise the anchor mechanism <b>18.</b> As will be explained in greater detail below, deployment of the tines <b>18a</b> through the ports <b>20, 120</b> in the anchor sleeve <b>14, 114</b> secures the retention device <b>10, 100</b> within the body of the patient for a period sufficient to complete the desired treatment. Moving the control rod <b>18b</b> in a proximal direction thus simultaneously moves the fixedly attached tines <b>18a</b> in a proximal direction, eventually causing the tines <b>18a</b> to extend through the ports <b>20,120</b> following introduction of the retention device <b>10, 100</b> within a patient. As shown in <figref idref="f0005">FIG. 6a</figref> the tines <b>18a</b> may have a consistent width or, in an alternative embodiment, as shown in <figref idref="f0005">FIG. 6b</figref>, the tines <b>18a</b> may be tapered.

0030Making the anchor mechanism <b>18</b> involves acquiring nitinol tubing having a length sufficient to allow a control rod <b>18b</b> long enough to extend through the proximal end of the anchor sleeve <b>14, 114</b> so as to be able to connect control rod <b>18b</b> to the handle <b>40.</b> The tubing preferably has a wall thickness between .005 to .030 inches, however, lesser and greater wall thicknesses are also contemplated by and therefore within the scope of the invention. Portions of the length of tubing are then cut away by means of well known techniques such as EDM (electron discharge machining), laser cutting, traditional machining or water jet. The remaining portions of the tubing comprise the anchor mechanism <b>18,</b> and its integrally attached tines <b>18a,</b> control rod <b>18b.</b> As explained in detail above, eyelet <b>28</b> and lock spring <b>29</b> are formed following cutting of the nitinol tubing. Using this manufacturing technique, anchor mechanisms <b>18</b> having wide variations are possible. It is also contemplated by the invention to make an integral anchor mechanism <b>18</b> from a flat sheet of nitinol. In this embodiment, at least the tines <b>18a</b> and lock spring <b>29</b> are processed so as to have a trained shape when in an unrestrained state somewhere below human body temperature of 37 degrees C. The trained shape of the tines <b>18a</b> can be a partial arc as shown in <figref idref="f0002">FIGS. 2b</figref>, <figref idref="f0005">6a, 6b 7</figref>, <figref idref="f0006">8, 9</figref>, <figref idref="f0009">11</figref>, <figref idref="f0010">13</figref> and <figref idref="f0012">15</figref>, a semi circular arc (not shown) or even a complete arc (not shown). It should be mentioned that the anchor mechanism could also be made from stainless steel or other alloys such as elgiloy, MP35N, incoloy or other superalloys.

0031Two alternative embodiments of the anchor mechanism <b>118, 218</b> are shown in <figref idref="f0006">FIGS. 8 and 9</figref>. These anchor mechanisms <b>118, 218</b> differ from the anchor mechanism <b>18</b> shown in <figref idref="f0005">FIGS. 6a, 6b and 7</figref> in that they are constructed from pieces of nitinol ribbon wire comprising tines <b>118a, 218a</b> and control rod <b>118b, 218b</b> having welds <b>130, 230</b> at a distal end (unnumbered) of the anchor mechanism <b>118, 218.</b> In a preferred embodiment the welds <b>130, 230</b> are accomplished by a laser, however, other welding technologies such as resistance welding and friction welding could also be used. Additionally, hypotubing could used to attach the tines <b>118a, 218a</b> to the control rod <b>118b, 218b.</b> The anchor mechanism <b>118</b> shown in <figref idref="f0006">FIG. 8</figref> has two tines <b>118a</b> welded to the control rod <b>118b;</b> the anchor mechanism <b>218</b> shown in <figref idref="f0006">FIG. 9</figref> has only a single tine <b>218a</b> welded to the control rod <b>218b.</b> Control rod <b>118b, 218b</b> extends proximally and is trained to bend over to form an eyelet <b>128, 228.</b> The wire forming the control rod <b>118b, 218b</b> and eyelet <b>128, 228</b> then reverse direction to a distal direction to form the lock spring <b>129, 229</b> which is raised above the length of the control rod <b>118b, 218b.</b> Anchor mechanisms <b>118, 218</b> function in a similar manner as the anchor mechanism <b>18</b> described above. <figref idref="f0010">FIG. 12</figref> shows the third embodiment of the anchor mechanism <b>218</b> loaded into the first embodiment of the retention device <b>10</b> prior to deployment of the tine <b>218a.</b><figref idref="f0010">FIG. 13</figref> shows the third embodiment of the anchor mechanism <b>218</b> loaded into the first embodiment of the retention device <b>10</b> following deployment of the tine <b>218a.</b>

0032Making the alternative embodiments of the anchor mechanism <b>118, 218</b> involves acquiring lengths of nitinol ribbon wire. Separate pieces eventually becoming control rod <b>118b</b> and tines <b>118a</b> are then cut to appropriate lengths and attached at a distal end <b>130, 230</b> by means of laser welding. In an alternative embodiment, the tines <b>118a, 218a</b> could also be attached to the control rod <b>118b, 218b</b> by soldering, gluing or mechanical bonding. It should also be mentioned that anchoring mechanisms <b>118, 218</b> could also be similarly made from round wire (not shown) and square wire (not shown). Further, alternative materials such as stainless steel or elgiloy could also be used.

0033As shown in <figref idref="f0005">FIG. 6b</figref>, the tines <b>18a, 118a, 218a, 418a</b> can be tapered toward the free end (unnumbered). The advantage to this configuration is that tapered tines <b>18a, 118a, 218a, 418a</b> would have increased buckling at the attached end (unnumbered) as well as improved trauma characteristics at the free end (unnumbered).

0034Following formation of the various embodiments of the anchor mechanism <b>18, 118, 218, 418</b> as described above, it is necessary to process at least the tines <b>18a, 118a, 218a, 418a</b> to have the proper shape upon deployment to anchor the anchoring device within the patient. It is similarly necessary to process the shape of the lock spring <b>29,129, 229</b> to have a shape extending away from the length of the control rod <b>18b, 118b, 218b,</b> the function of which is explained in detail below. The shape training process also imparts superelasticity, as explained in detail below, to at least the tines <b>18a, 118a</b>, and <b>218a, 418a</b> assuming they are made out of nitinol. When the integral anchor mechanism <b>18, 418</b> is cut from its source material and when the welded anchor mechanisms <b>118, 218</b> are assembled, the tines <b>18a, 118a, 218a, 418a</b> and lock spring <b>29, 129, 229</b> are placed in a forming jig (not shown) which acts as a restraint holding the tines <b>18a, 118a, 218a, 418a</b> and lock spring <b>29, 129, 229</b> in the position they will eventually be trained into. In a preferred embodiment, the tines <b>18a, 118a, 218a, 418a</b> and lock spring <b>29,129, 229</b> are subjected to a temperature of 500 degrees C plus or minus 100 degrees C for less than thirty minutes, depending on the alloy chemistry, dimensions, fixturing and heat source. Different heat sources include salt bath, hot air torch and oven. A heavier and larger fixture will take a longer length of heat treatment time. Following heat treatment, the heated anchor mechanism <b>18,118, 218, 418</b> should be quickly cooled as by an air fan. Making the anchor mechanism <b>18, 118, 218, 418</b> from non-superelastic materials such as stainless steel, spring steel or carbon fiber is also contemplated by and therefore within the scope of the invention.

0035In a preferred embodiment, the anchor mechanism <b>18, 118, 218, 418</b> is formed from nitinol wire, sheet or tubing that has been processed to exhibit superelasticity at human body temperature (around 37 degrees C). The invention also contemplates forming the anchor mechanism <b>18, 118, 218, 418</b> from nitinol processed to exhibit thermal shape memory characteristics at human body temperature. Nitinol is an approximate stoichiometric alloy of nickel and titanium; however, other elements such as vanadium are sometimes added in small amounts to alter the mechanical characteristics of the alloy. Chemical composition and processing history primarily determine the particular mechanical properties of a shape memory/superelastic metallic alloy. In general, such an alloy will exist in either one or the other, or combinations of two crystallographic phases. Austenite is the parent crystallographic phase and exists at higher temperatures. Martensite is the other phase and is formed by either subjecting the alloy to lower temperatures or by placing mechanical or physical stress on the alloy while it is in the austenitic phase. Transition temperatures between these two phases can be experimentally determined for a particular alloy. Processing history includes high temperature annealing as well as low temperature forming and deformation. Following standard material and processing specifications, the transitional temperatures that define the alloy's mechanical characteristics are predictable and controllable. Standard transitional temperature designations are given as: M_s for the start of the transition to the martensitic phase, M_f for completion of the transition to martensite, A_s for the start of the transition to the austenitic phase, and A_f for the completed transition to austenite.

0036Superelasticity is based on phase transition from austenite to martensite. Mechanically induced phase transition from austenite to martensite occurs when the alloy temperature is above A_f and a physical restraint is applied to the alloy. As long as the restraint is in place, the portion of the alloy receiving the stress reverts to the martensitic phase, which remains as long as the stress is maintained. Unless the shape recovery limits are exceeded, when the restraint is removed and the stress is released the alloy returns to its original austenitic phase and shape as long as the temperature is maintained above A_f. Thus, when the austenitic, trained shape of the alloy is deformed and held by stress in a new shape, a certain amount of force is exerted by the alloy against the restraint as it resists the new, untrained shape.

0037The thermal shape memory effect of these alloys has been known much longer than superelasticity. Thermal shape memory occurs as the result of a piece of shape memory alloy metal being deformed while in the lower temperature martensitic phase and then being reheated to a temperature somewhere above A_s which causes the alloy to reform in the austenitic phase. When the crystallographic nature of the alloy is completely austenitic, the alloy's shape returns to the previously trained shape. Shape memory training occurs when a thermal shape memory/superelastic metallic alloy is annealed (heat treated) while restrained in a certain shape. The trained shape will then be maintained unless it is deformed while in the low temperature martensitic phase. Upon reheating the alloy to the austenitic phase, the original shape, which was "learned" in the annealing process, will be "remembered" and returned to. Thus, temperature change is one way of controlling the crystallographic phase of a shape memory/superelastic metallic alloy.

0038One practical advantage of a shape memory/superelastic alloy over non-superelastic materials is that it can be deformed to a far greater degree without taking a permanent set or kink. In the case of superelastic alloys (i.e., alloys processed to exhibit superelasticity at body temperature), assuming the alloy is above the A_f temperature, removal of the restraint alone is sufficient to resume the original, trained shape. When the alloy is processed to have shape memory characteristics, the martensitic phase alloy need only be subjected to temperatures somewhere above A_f and the alloy will eventually return to its original, trained shape. It is also possible to use a restraint in conjunction with alloys trained to exhibit thermal shape memory characteristics.

0039Thus, when an anchor mechanism <b>18, 118, 218, 418</b> made of nitinol is processed to exhibit superelastic characteristics at human body temperature, it uses superelasticity in two different ways. First, superelasticity (stress-induced martensite) allows the anchor mechanism <b>18,118, 218, 418</b> to be deformed to a degree sufficient to enable it to be loaded into the chamber <b>14a, 114a, 414a</b> of the anchor sleeve <b>14, 114, 414</b> without taking a permanent set or kink. While the anchor mechanism <b>18,118, 218, 418</b> is restrained within the chamber <b>14a, 114a, 414a</b> assuming the anchor mechanism <b>18, 118, 218, 418</b> is maintained at a temperature above A_f, the tines <b>18a, 118a, 218a, 418a</b> contacting the inner walls (unnumbered) of the chamber <b>14a, 114a, 414a</b> are exerting an amount of force against the chamber <b>14a, 114a, 414a</b> due to the formation of stress-induced martensite. The force exerted by the tines <b>18a, 118a, 218a, 418a</b> against the chamber <b>14a, 114a 414a</b> cause the anchor mechanism <b>18, 118, 218, 418</b> to remain in place until the physician determines the retention device <b>10, 100, 400</b> is properly introduced into the patient. Following proper introduction, the tines <b>18a, 118a, 218a, 418a</b> are then deployed through the ports <b>20, 120, 420</b> to secure the catheter <b>12,112, 412</b> or sheath introducer (not shown) in place below the skin for the duration of the treatment period. The second way the retention device <b>10, 100, 400</b> uses superelasticity is that the processing of nitinol can be varied to program a desired amount of force into the tines <b>18a, 118a, 218a, 418a.</b> This is advantageous because certain uses of the retention device <b>10, 100</b> may require a stronger pull strength than other uses. By programming the superelastic nitinol to a greater or lesser amount of strength, tines <b>18a, 118a, 218a, 418a</b> can be created that will release at a particular pull strength, rather than be painfully ripped out of the patient.

0040When the anchor mechanism <b>18, 118, 218, 418</b> is formed to exhibit thermal shape memory characteristics at body temperature, the A_f is programmed into the alloy to be somewhere below human body temperature. The A_s of the anchor mechanism <b>18, 118, 218, 418</b> is somewhere below room temperature prior to introduction into the patient's body. Alternatively, the anchor mechanism <b>18, 118, 218, 418</b> (and consequently the whole retention device <b>10, 100, 400</b> into which the anchor mechanism <b>18, 118, 218, 418</b> is permanently loaded) can be cooled to a temperature below M_f to place the anchor mechanism <b>18, 118, 218, 418</b> in the martensitic phase prior to introduction into the patient's body. When the retention device <b>10, 100, 400</b> is being introduced into the body (not shown), means must be used to maintain the temperature of the retention device <b>10, 100, 400</b> below A_s. Typically, a cold saline drip (not shown) is maintained through the chamber <b>14a, 114a, 414a</b> during the introduction procedure. Following arrival of the retention device <b>10, 100, 400</b> at the treatment site within the patient's body, the tines <b>18a, 118a, 218a, 418a</b> are advanced from the ports <b>20, 120, 420</b> of the anchor sleeve <b>14, 114, 414,</b> whereupon it is exposed to body temperature, which is above the A_f of the alloy. Exposure to body temperature raises the temperature of the alloy to a point where the tines <b>18a, 118a, 218a, 418a</b> are in the austenitic phase, returning the tines <b>18a, 118a, 218a, 418a</b> toward their original, trained shape. Because the tines <b>18a, 118a, 218a, 418a</b> are deployed beneath the patient's skin S, they may be somewhat restrained by anatomical space limitations and therefore may not fully assume the trained shape.

0041As shown in <figref idref="f0007 f0008 f0009">FIGS. 10-11</figref> and <figref idref="f0011 f0012">14-15</figref>, the retention device <b>10,100</b> is provided with a lock mechanism (unnumbered) comprising a lock spring <b>29</b> and a recess <b>32.</b> In the predeployment position, the lock spring <b>29</b> is compressed against the inner dimension (unnumbered) of the chamber <b>14a, 114a.</b> This is due to the normal, trained shape of the lock spring <b>29</b> being greater than the inner dimension (unnumbered) of the chamber <b>14a, 114a.</b> When the control rod <b>18b, 118b</b> is distally moved by the physician, as discussed above, the tines <b>18a, 118a, 218a</b> will deploy through the ports <b>20, 120.</b> Upon reaching a predetermined proximal distance, when the tines <b>18a, 118a, 218a</b> are fully deployed, the lock spring <b>29</b> will reach the internal recess <b>32</b> of the chamber <b>29</b> and move outward, to fit into the recess <b>32,</b> thus locking the retention device <b>10, 100</b> in the deployed position and securing it in place in the patient. To remove the retention device <b>10, 100</b> a key <b>34</b> is provided which permits the physician to externally depress the lock spring <b>29,</b> thus making distal movement of the control rod <b>18b, 118b</b> possible, allowing eventual removal of the retention device <b>10, 100</b> from the patient. It is also contemplated and therefore within the scope of the invention to have a series of recesses (not shown) along the length of the inner dimension of the chamber <b>14a, 114a</b> allowing the physician a degree of control over the amount of tine <b>18a, 118a, 218a</b> that is deployed.

0042<figref idref="f0013">FIG. 16</figref> shows an additional embodiment of the retention device <b>400</b> where the anchor mechanism <b>418</b> surrounds the lumen <b>412</b> of the catheter <b>412</b> to which an anchor sleeve <b>414</b> is attached. The anchor sleeve <b>414</b> defines a chamber <b>414a</b> into which the anchor mechanism <b>418</b> is loaded prior to deployment. A control rod 418b is distally attached to a plurality of tines <b>418a.</b> When the control rod <b>418b</b> is moved proximally the tines <b>418a</b> will extend through ports <b>420</b> that correspond to the individual tines <b>418a</b> as more fully discussed above. The retention device <b>400</b> is fitted with a lock spring <b>429</b> which fits into a recess <b>432</b> following deployment of the tines <b>418a.</b> An eyelet <b>428</b> is formed at the proximal end (unnumbered) of the control rod <b>418b.</b> A handle <b>440</b> is preferably attached around the eyelet <b>428</b> to facilitate deployment of the tines <b>418a</b> following insertion into the patient. <figref idref="f0014">FIG. 17</figref> shows a cross sectional view of the embodiment of the retention device <b>400</b> following deployment of the tines <b>418a.</b>

<i>Use</i>

0043Using the retention device <b>10, 100, 400</b> involves the physician creating an external incision or skin puncture proximate the internal area to be accessed. In most cases it will also be necessary to create an incision by a scalpel or needle in an underlying vessel <b>V</b> to facilitate placement of an indwelling catheter <b>12, 112, 412.</b> The embodiments of the retention device <b>10, 400</b> shown in <figref idref="f0002 f0003 f0004">FIGS. 2-5</figref> and <figref idref="f0011 f0012 f0013 f0014">14-17</figref> have the anchor sleeve <b>114, 414</b> directly attached to a catheter <b>12, 412.</b> The embodiment of the retention device <b>10</b> shown in <figref idref="f0001">FIGS. 1</figref> and <figref idref="f0007 f0008 f0009 f0010">10-13</figref> show the anchor sleeve <b>14</b> attached to an introducer sheath <b>16.</b> In this embodiment of the retention device <b>10,</b> following introduction into a patient, a separate catheter <b>12</b> is navigated through the lumen <b>16a</b> of the introducer sheath <b>16.</b> The catheter <b>12, 112, 412</b> when inserted serves as a direct conduit for infusing therapeutic solutions, draining body fluids or delivering mechanical devices to an anatomical site. A needle (not shown) or guidewire (not shown) or dilator/sheath/guiding catheter system (not shown) is used to access the underlying vessel V the interior of which is then entered. The retention device <b>10, 100, 400</b> is then adjusted (not shown) to the desired depth but not into the vessel V. Following this, the physician moves the control rod <b>18b, 118b, 218b, 418b</b> in a proximal direction by grasping and sliding the handle 40 which simultaneously moves tines <b>18a, 118a 218a, 418a</b> in a proximal direction. The control rod <b>18b, 118b, 218b, 418b</b> is prevented from excess proximal movement by the length of the tines <b>18a, 118a, 218a, 418a</b> and locked into the desired position by the lock spring <b>29</b> rising into the internal recess <b>32</b> in the chamber <b>14a, 114a, 414a.</b> Moving the control rod <b>18b, 118b, 218b, 418b</b> proximally thus results in the tines <b>18a, 118a 218a, 418a</b> puncturing the membranes <b>22</b> and thus exiting the anchor sleeve <b>14, 114, 414</b> through ports <b>20, 120, 420.</b> By means of various lock positions available to the physician as a result of the lock system, the tines <b>18a, 118a 218a, 418a</b> can be extended to the degree desired by the physician. Thus, the tines <b>18a, 118a 218a, 418a</b> can be extended so as to define a partial arc as shown in <figref idref="f0001">FIGS. 1</figref>, <figref idref="f0002">2b</figref>, <figref idref="f0005 f0006 f0009 f0010 f0012">6-9, 11, 13 and 15</figref>. Alternatively, if the tines <b>18a, 118a 218a, 418a</b> have been trained to assume a longer circumference, they can be more fully extended to assume a semi-circular (not shown) or even fully circular (not shown), shape.

0044Removing the retention device <b>10, 100, 400</b> from the patient involves unlocking the lock system by depressing the lock spring <b>29</b> from the recess <b>32</b> with the key <b>34</b> and moving the control rod <b>18b, 118b, 218b, 418b</b> via the handle <b>40</b> in a distal direction. This results in the tines <b>18a, 118a 218a, 418a</b> simultaneously moving in a distal direction whereby the tines <b>18a, 118a 218a, 418a</b> reenter the anchor sleeve <b>14, 114, 414</b> through the ports <b>20, 120, 420</b> whereby the retention device <b>10, 100, 400</b> is removed from the patient following completion of the course of treatment.