there is shown in fig1 a delivery device 12 constructed in accordance with teachings of the invention for use in delivering a therapeutic solution to the tissue of a heart , especially a beating heart . the device 12 includes a needle assembly 14 adapted to be coupled to a syringe or other solution supply device 15 . the distal end of the needle assembly 14 is designated generally as 16 and the proximal end is designated as 18 . the needle assembly 14 includes an elongated body or cannula 20 with a sharpened needle tip 22 at its distal end . in the embodiment illustrated , the needle tip 22 is of a smaller diameter than the needle body 20 . a bore 24 extends through the needle assembly 14 and is in communication with the solution supply device 15 . during use , the device 12 may , for example , be inserted through a thoracoscopic port ( not shown ), giving thoracoscopic access to the patient &# 39 ; s heart . the therapeutic solution may then be injected from the solution supply device 12 through the bore 24 of the needle assembly 14 directly into the cardiac tissue in a predetermined quantity . in the currently preferred embodiment of the invention , the solution supply device is a conventional syringe 15 . the syringe 15 includes a hollow cylindrical body 30 having a distal necked - in end 32 . a plunger shaft 34 with a plunger 36 mounted on the distal end thereof and a thumb button 38 mounted to the proximal end thereof is slidably disposed within the cylindrical body , the plunger extending outward from the body . during use , the operator may actuate the plunger 36 by depressing the plunger thumb button 38 to deliver the therapeutic solution . the needle assembly 14 may be coupled to the syringe 15 by any appropriate coupling 39 . in the currently preferred design , a metal hub 39 is utilized which has a large bore for receiving the distal necked - in end 32 of the syringe 15 . the hub 39 further includes a smaller bore which communicates with the large bore and the bore 24 of the needle assembly 14 to establish fluid communication between the syringe 15 and the needle tip 22 for delivery of therapeutic fluid . while the solution supply device has been explained with regard to a syringe 15 , it will be appreciated by those of skill in the art that the supply device can be of any appropriate design . additionally , the supply device may include any appropriate metering device to control the amount of therapeutic substance injected at the injection site . for example , and as explained in international patent application wo 99 / 44656 , the syringe 15 may include a shaft having screw threads or include a ratchet mechanism which permits the plunger button to advance within the cylindrical body only a predetermined distance to permit only a predetermined amount of therapeutic solution to be administered at a given injection site . alternately , the administration of a controlled amount of the therapeutic solution may be facilitated by a computer controlled device . in accordance with the invention , the movement of the distal end 16 of the needle assembly 14 may be controlled by a steering mechanism ( designated generally as 40 ). the needle assembly 14 and steering mechanism 40 are enlarged and schematically illustrated in fig2 - 4 . the steering mechanism includes a steering cable 42 which is coupled to the needle body 20 at a distal attachment 44 toward the distal end 16 of the needle body 20 . the steering cable 42 extends toward the proximal end 18 of the needle assembly 14 and substantially the length of the needle assembly 14 . it will be appreciated by those of skill in the art that the assertion of a tensioning force on the proximal end 46 of the steering cable 42 flexes or arches the distal end 16 of the needle assembly 14 back towards the proximal end 18 of the needle assembly 14 along a dynamic radius of flexure as shown in fig3 . it will be appreciated by those of skill in the art that the needle assembly 14 increasingly arches , that is , the radius of flexure will decrease , as the level of tensioning force on the steering cable 42 is increased . to further control this radius of flexure and the location of the bend , a moveable steering sleeve 50 is provided . the steering sleeve 50 is essentially a hollow tube having an internal bore 52 , which is disposed about the needle body 20 such that the sleeve 50 may slide axially along the needle assembly 14 , the steering cable 42 extending through the bore 52 . as may be seen in fig3 and 4 , during operation , the length of the needle body 20 which remains straight and the length of the needle assembly 14 which arches is determined by the position of the steering sleeve 50 relative to the distal attachment 44 of the steering cable 42 . in this way , the radius of flexure is determined , at least in part , by the position of the steering sleeve 50 as the steering cable 42 is tensioned by the user . in order to move the steering sleeve 50 in the distal and proximal directions along the needle assembly 14 , a steering sleeve adjustment cable 54 is provided . the steering sleeve adjustment cable 54 may be of any appropriate material , so long as it is sufficiently rigid to push the sleeve 50 along needle assembly 14 . the currently preferred embodiment comprises a stainless steel cable on the order of 1 - 3 mm in diameter . those of skill in the art will appreciate that the needle body 20 must be sufficiently rigid to support the steering mechanism 40 , while being sufficiently flexible to permit the needle body 20 to arch or flex as a tensioning force is applied to the steering cable 42 . further , the needle body 40 must be sufficiently resilient such that it remains biased in a substantially straight position to permit its manipulation and use in successive injections if so desired . the needle assembly 14 portion of the device 12 will typically be approximately 300 - 400 mm long . a needle body 20 on the order of 20 - 25 ga . has been found to be adequately flexible , yet sufficiently rigid to permit proper functioning of the steering mechanism 40 and placement of the needle tip 22 . inasmuch as the steering mechanism 40 does not act directly upon the needle tip 22 , it is not necessary for the needle tip 22 to be as rigid as the needle body 20 . moreover , it is preferable that the needle tip 22 be of a smaller gauge in order to facilitate penetration of the needle tip 22 into body tissue and to minimize extravasation of injectate . it has been determined that a 25 - 30 ga . ( e . g ., 28 ga .) cannula is particularly appropriate . while the illustrated needle tip 40 includes a bevel sharp tip 56 , it will be appreciated that an alternate tip geometry or structure may be provided . it will be appreciated that the device 12 can be readily constructed from “ off - the - shelf ” type components so that it may be economically manufactured . thus , the manufacture is not cost prohibitive , and the device may be utilized as a single use , disposable device . during use , the elongated needle body 20 is inserted into the patient &# 39 ; s body cavity through an opening . the opening in a true percutaneous technique is the opening formed by the needle assembly 14 itself as it is inserted into the chest wall and through the ribs to the heart . under these circumstances , the opening is substantially equivalent to the diameter of the device 12 . alternately , the needle may be inserted through a small trocar . if , for example , the device 12 has a diameter of 3 mm , the trocar might have a diameter of 5 mm . the opening might also be in the form of an airtight port 56 in the chest wall as illustrated in fig5 and disclosed , for example in international patent application wo 99 / 44656 . once inserted , the needle assembly 14 is steered into the desired position using the steering mechanism 40 . that is , the physician exerts a tensile force on the proximal end 46 of the steering cable 42 , the distal end 44 of the steering cable 42 being coupled to the needle body 20 toward the body distal end 16 to steer the body distal end 16 along a flexion radius . the physician may adjust the flexion radius by locating the steering sleeve 50 at a desired position along the needle body 20 using the steering sleeve adjustment cable 52 . once appropriately positioned , the physician can pass the sharpened needle tip 22 into the heart tissue 62 , and depressing the syringe 15 thumb button 38 to advance the plunger 36 and deliver the therapeutic substance to the patient &# 39 ; s heart . according to another important aspect of the invention , the delivery device 12 is particularly useful when access to heart tissue is obscured by other tissue and cannot be readily separated . for example , in the procedure set forth in international patent application wo 99 / 44656 , the patient &# 39 ; s lung is collapsed or partially collapsed in order to provide working space in the thoracic cavity . in reoperative patients , however , the lung tissue 60 frequently adheres to the target heart tissue 62 , as illustrated in fig6 . in accordance with the invention , the needle assembly 14 may be advanced directly through the lung tissue 60 and into the heart tissue 62 . in order to facilitate this passage , the smaller diameter needle tip 22 is sufficiently elongated to allow the needle tip 22 to penetrate and advance through the lung tissue 60 and into the cardiac tissue 62 . in this regard , the needle tip 22 is preferably on the order of 1½ to 2 inches ( approximately 35 - 50 mm ) long . it will be appreciated by those of ordinary skill in the art , however , that the needle tip 22 may be shorter or longer , as conditions warrant . in order to determine when the needle tip 22 touches or penetrates the cardiac tissue 62 , an electrode 64 similar to that disclosed in international patent application wo 99 / 44656 , may be provided at the needle tip 22 , the remainder of the needle assembly 14 being insulated therefrom . alternately , the needle tip 22 itself may serve as an electrode if the needle tip 22 is made from a conductive material . electrical connection of this electrode 64 to an electrocardiograph (“ ecg ”) ( schematically illustrated as 66 ) may be made by running an electrical conductor 68 along the needle assembly 14 to the ecg 66 located outside the patient &# 39 ; s body . standard surface ecg leads 70 are likewise applied to the patient . when the electrode 64 enters the patient &# 39 ; s myocardium 62 ( see fig6 ), the event shows as a current injury . in this way , the cardiologist may ensure that the desired positioning and contact is made with the myocardium 62 prior to actuation of the solution supply device 12 . it will be appreciated that the inclusion of the electrode 64 additionally permits the cardiologist to track or electronically mark the injection sites . accordingly , the cardiologist may follow the marking to ensure that adequate therapeutic solution is applied to the target cardiac tissue to provide optimum conditions for a desired effect . additionally , such marking facilitates use of the needle assembly 14 in positions that are typically beyond the line of sight provided by way of a surface incision . it will be further appreciated that alternate marking means and methods may be utilized . for example , markers that may be detected ultrasonographically , radiographically , as , for example , by x - ray or catscan , or electrocardially are appropriate . virtual marking or mapping may likewise be utilized . such methods are disclosed , for example , in u . s . application ser . no . 09 / 393 , 873 . according to another important feature of the invention , in order to stabilize the needle assembly 14 during injection , a platform 74 is provided which contacts the surface of the lung tissue 60 or the pericardium 72 . to ensure contact of the platform 74 with the tissue and the desired stabilization , the platform 74 is moveable relative to the needle tip 22 . in the embodiment illustrated in fig5 - 8 , the movable platform 74 is in the form of a collapsible structure . the platform 74 is preferably in the form of an inflatable and deflatable , or collapsible donut - shaped balloon coupled to the periphery of the needle tip 22 . a platform 74 on the order of 4 - 6 mm in diameter when fully inflated is currently considered adequate to provide desired stabilization against tissue . during insertion into the lung or other tissue 60 obstructing access to the heart 62 , the platform is fully collapsed against the needle tip 22 . in this way , the platform 74 does not interfere with the penetration of the needle tip 22 into and through the lung 60 or other tissue . rather , the platform 74 passes through the lung 60 or other tissue . the collapsible platform 74 is particularly appropriate when the device 12 is utilized in a true percutaneous technique wherein no incision is made in the chest wall . air or other inflating gas is supplied to the platform 74 via an air line 76 . the air line 76 extends from a source of gas at its proximal end 78 , such as from a compressed gas source or a simple syringe ( not shown ), along the needle body 20 and needle tip 22 , to the platform disposed generally toward the distal end 16 of the needle assembly 14 . the deflated , or collapsed , platform 74 is shown in fig7 while the inflated platform is shown in fig8 . the platform 74 is spaced from the distal end 16 of the needle tip 22 to limit the penetration of the needle tip 22 into the cardiac tissue . during use , the collapsed platform 74 is passed through the lung or other obstructing tissue . when the needle tip 22 has penetrated the heart tissue a desired depth , the platform 74 may be inflated to stabilize the needle along the tissue . the platform 74 is preferably inflated , as shown in fig6 and 8 , at a position between the heart tissue 72 or myocardium 62 , and the lung tissue 60 . in this way , the platform 74 limits the depth to which the needle tip 22 penetrates the cardiac tissue 62 . in other words , the platform 74 is preferably spaced from the distal tip 16 of the needle tip 22 a distance equal to the desired needle penetration . it is presently anticipated that the distal surface of the platform 74 will be disposed on the order of 5 - 10 mm from the distal tip 45 , although alternate spacing may be dictated by factors such as the particular therapeutic solution utilized , or the physical characteristics of the tissue upon which the procedure is to be performed . in an alternate embodiment of the invention , the movable platform 80 is in the form of a disk which is axially slidable relative to the needle tip 22 , as shown in fig9 - 11 . in this way , the platform 80 may be moved into position against the penetrated tissue at substantially any location along the needle tip 22 in order to stabilize the needle assembly 14 relative to the tissue . in contrast to the movable platform 74 of fig5 - 8 , which moves by collapsing yet remains stationary relative to the axis of the needle tip 22 , the platform 80 of fig9 - 11 is movable relative to the axis of the needle tip 22 . further , while the collapsible platform 74 is preferably disposed directly against the heart , the platform 80 steadies the needle tip 22 by placement against the first entered tissue , e . g ., the lung tissue . the platform 80 may be of any appropriate shape or size and formed of any appropriate material . it has been determined that a platform 80 formed of stainless steel and on the order of 4 - 6 mm in diameter is particularly suitable . the platform 80 includes a central opening 82 which closely receives the needle tip 22 . in order to prevent the platform 80 from separating from the needle tip 22 , the needle tip 22 preferably includes an enlarged portion 84 . it will be appreciated that the enlarged portion 84 is slightly larger than or presents an interference with the central opening 82 of the platform 80 to prevent the platform 80 from slipping from the end of the needle tip 22 . it will further be appreciated that it is not necessary for the enlarged portion 84 to extend about the circumference of the needle tip 22 , as is shown . rather , the enlarged portion 84 need only present sufficient interference to prevent passage of the platform central opening over the enlarged portion 84 . to facilitate proper placement of the platform 80 against the penetrated tissue , a platform adjustment mechanism 86 is provided . in the illustrated embodiment , platform adjustment mechanism is in the form of an adjustment sleeve 86 , although an alternate arrangement may be provided . the sleeve 86 is slightly larger than and axially slidably disposed about the needle body 20 . in this way , the adjustment sleeve 86 may be manually advanced toward the distal end 16 of the device 12 to contact and move the platform 80 distally and into contact with the tissue . it will be appreciated that the sleeve 86 may likewise be used to position the platform 80 toward the distal end 16 of the needle tip 22 prior to penetration into the tissue . in this way , sleeve 86 moves in the proximal direction as the needle tip 22 penetrates the tissue and the platform 80 contacts the tissue and slides proximally along the needle tip 22 . alternately , the platform 80 may remain in a more proximal location along the needle tip 22 until the needle tip 22 has penetrated the tissue . the sleeve 86 may then be used to advance the platform 80 into contact with the tissue to steady the needle in the tissue . in order to permit the surgeon to utilize the steering mechanism 40 , the steering sleeve 50 preferably is disposed about the platform adjustment sleeve 86 , as may best be seen in fig9 and 10 . in this way , the steering sleeve 50 may be advanced along the body 20 to provide the desired bending of the body 20 in conjunction with a tensioning force exerted on the steering cable 42 . additionally , the adjustment sleeve 86 includes a slot 88 for receiving the steering cable 42 . thus , as the platform adjustment sleeve 86 moves axially along the needle body 20 , the slot 88 moves along the steering cable 42 such that the sleeve 86 does not interfere with the use of the steering cable 42 . it will be appreciated that the platform adjustment sleeve 86 should be fabricated from a material which is sufficiently rigid that it can be pushed axially along the needle body 20 and engage and move the platform 80 , yet sufficiently flexible that it can be readily flexed as the device 12 is steered into a desired position for injection . it has been determined that a semi - rigid elastomer or rubber is particularly suitable for this application , although it is envisioned that other materials may be utilized . in summary , the invention provides a delivery device 12 that may be easily steered into a desired position and utilized for successive injections . the flexibility of the elongated needle body and the versatility of the control mechanism permit the needle to contour the path of delivery to the cardiac and thoracic geometry , providing the cardiologist great latitude in placement of the needle , and precise delivery of the injectant from a remote distance through a relatively small incision . during use , the needle is advanced into position , and the needle tip penetrates the heart tissue , either directly or through adhering lung tissue or other obscuring tissue . an electrode on the needle indicates when the cardiac tissue has been penetrated , and injection site may be marked to ensure injections occurred to desired relative locations . the platform limits the depth of penetration and allows stabilization of the needle against the epicardial surface of the heart or the surface of the lung or other tissue . the solution then can be injected into the cardiac tissue by actuating the syringe . the device is formed of readily available materials and , accordingly , may be economically constructed . all of the references cited herein , including patents , patent applications , and publications , are hereby incorporated in their entireties by reference . while this invention has been described with an emphasis upon preferred embodiments , it will be obvious to those of ordinary skill in the art that variations of the preferred embodiments may be used and that it is intended that the invention may be practiced otherwise than as specifically described herein . accordingly , this invention includes all modifications encompassed within the spirit and scope of the invention as defined by the following claims .
the invention provides a steerable device for the delivery of a therapeutic solution , in particular , an angiogenesis - promoting substance into a heart , and a method of delivering such a substance into the heart . the device includes an elongated needle which the physician may steer by asserting a tensioning force on a steering cable coupled to the needle toward its distal end . a axially - slidable steering sleeve is disposed about the needle and the steering cable , and the position of the steering sleeve may be adjusted to control the radius of flexure of the needle . the needle body is flexible enough to maneuver around thoracic and cardiac geometry , yet sufficiently rigid to facilitate such maneuvering . the needle may also have a stop , or platform , spaced from the distal needle tip to stabilize the needle in the cardiac tissue . according to a method of the invention , the needle may be inserted into the heart tissue through lung tissue adhering to the heart , as is common in re - operative patients . the platform may either transit the needle as the platform contacts the lung or heart tissue , or the platform may move forward to contact tissue as needle contact with heart tissue is confirmed .