Myocardial lead attachment system

Abstract

The present invention is a myocardial lead attachment system for securing a distal end of a lead within a myocardium of a patient's heart. The system includes an anchor, a tether coupled to the anchor, and a delivery instrument for receiving and advancing the anchor through a tract in the heart from a proximal entrance site to a distal exit site in such a manner that the tether extends proximally from the anchor through the tract. The delivery instrument includes a needle having a distal tip and a nest. The nest is positioned proximal to the distal tip and is sized to receive the anchor. The delivery instrument further includes an ejection mechanism for ejecting the anchor from the nest.

Description

CROSS REFERENCES

The present application claims the benefit of the following U.S. Provisional Applications: application Ser. No. 60/514,037 filed Oct. 24, 2003, entitled “Absorbable Myocardial Lead Fixation System”, application Ser. No. 60/514,665 filed Oct. 27, 2003, entitled “Lead Electrode Arrangement for Myocardial Leads”, application Ser. No. 60/514,042 filed Oct. 24, 2003, entitled “Tapered Tip for Myocardial Lead”, application Ser. No. 60/514,714 filed Oct. 27, 2003, entitled “Minimally-Invasive Fixation Systems for Over-the-Tether Myocardial Leads”, application Ser. No. 60/514,039 filed Oct. 24, 2003, entitled “Distal or Proximal Fixation of Over-the-Suture Myocardial Leads”, application Ser. No. 60/514,146 filed Oct. 24, 2003, entitled “Myocardial Lead with Fixation Mechanism”, application Ser. No. 60/514,038 filed Oct. 24, 2003 entitled “Delivery Instrument for Myocardial Lead Placement” and application Ser. No. 60/514,713 filed Oct. 27, 2003, entitled “Drug-Eluting Myocardial Leads”, all of which are incorporated herein by reference.

Reference is hereby made to the following commonly assigned U.S. patent application Ser. No. 10/821,421, filed Apr. 9, 2004, entitled “Cardiac Electrode Anchoring System” and the following commonly assigned U.S. Patent applications filed on an even date herewith, all of which are incorporated herein by reference: application Ser. No. ______, entitled “Myocardial Lead”, application Ser. No. ______ entitled “Distal or Proximal Fixation of Over-the-Tether Myocardial Leads”, application Ser. No. ______, entitled “Myocardial Lead with Fixation Mechanism” and application Ser. No. ______, entitled “Absorbable Myocardial Lead Fixation System.”

FIELD OF THE INVENTION

This invention relates generally to implantable lead assemblies for stimulating and/or sensing electrical signals in muscle tissue. More particularly, it relates to myocardially implanted leads for cardiac stimulation and systems for anchoring the leads.

BACKGROUND OF THE INVENTION

Cardiac rhythm management systems are used to treat heart arrhythmias. Pacemaker systems are commonly implanted in patients to treat bradycardia (i.e., abnormally slow heart rate). A pacemaker system includes an implantable pulse generator and leads, which form the electrical connection between the implantable pulse generator and the heart. An implantable cardioverter defibrillator (“ICD”) is used to treat tachycardia (i.e., abnormally rapid heart rate). An ICD also includes a pulse generator and leads that deliver electrical energy to the heart.

The leads coupling the pulse generator to the cardiac muscle are commonly used for delivering an electrical pulse to the cardiac muscle, for sensing electrical signals produced in the cardiac muscle, or for both delivering and sensing. The leads are susceptible to categorization according to the type of connection they form with the heart. An endocardial lead includes at least one electrode at or near its distal tip adapted to contact the endocardium (i.e., the tissue lining the inside of the heart). An epicardial lead includes at least one electrode at or near its distal tip adapted to contact the epicardium (i.e., the tissue lining the outside of the heart). Finally, a myocardial lead includes at least one electrode at or near its distal tip inserted into the heart muscle or myocardium (i.e., the muscle sandwiched between the endocardium and epicardium). Some leads have multiple spaced apart distal electrodes at differing polarities and are known as bipolar type leads. The spacing between the electrodes can affect lead performance and the quality of the electrical signal transmitted or sensed through the heart tissue.

The lead typically consists of a flexible conductor surrounded by an insulating tube or sheath that extends from the electrode at the distal end to a connector pin at the proximal end. Endocardial leads are typically delivered transvenously to the right atrium or ventricle and commonly employ tines at a distal end for engaging the trabeculae.

The treatment of congestive heart failure (“CHF”), however, often requires left ventricular stimulation either alone or in conjunction with right ventricular stimulation. For example, cardiac resynchronization therapy (“CRT”) (also commonly referred to as biventricular pacing) is an emerging treatment for heart failure, which requires stimulation of both the right and the left ventricle to increase cardiac output. Left ventricular stimulation requires placement of a lead in or on the left ventricle near the apex of the heart. One technique for left ventricular lead placement is to expose the heart by way of a thoracotomy. The lead is then positioned so that one or more electrodes contact the epicardium or are embedded in the myocardium. Another method is to advance an epicardial lead endovenously into the coronary sinus and then advance the lead through a lateral vein of the left ventricle. The electrodes are positioned to contact the epicardial surface of the left ventricle.

The left ventricle beats forcefully as it pumps oxygenated blood throughout the body. Repetitive beating of the heart, in combination with patient movement, can sometimes dislodge the lead from the myocardium. The electrodes may lose contact with the heart muscle, or spacing between electrodes may alter over time.

There is a need for an improved myocardial pacing lead suitable for chronic implantation and a minimally invasive delivery system and method for implanting such a lead.

SUMMARY OF THE INVENTION

The present invention, according to one embodiment, is a myocardial lead attachment system for securing a distal end of a lead within a myocardium of a patient's heart. The system includes an anchor, a tether coupled to the anchor and a delivery instrument for receiving the anchor and advancing the anchor through a tract in the heart from a proximal entrance site to a distal exit site in such a manner that the tether extends proximally from the anchor through the tract. The delivery instrument includes a needle having a distal tip and a nest positioned proximal to the distal tip that is sized to receive the anchor and an ejection mechanism for ejecting the anchor from the nest.

The present invention, according to another embodiment, is a myocardial lead attachment system for securing a distal end of a lead within a myocardium of a patient's heart. The system includes an anchor having a longitudinal bore extending therethrough, a tether coupled to the anchor and a delivery instrument for receiving the anchor and advancing the anchor through a tract in the heart from a proximal entrance site to a distal exit site in such a manner that the tether extends proximally from the anchor through the tract. The delivery instrument includes a needle having a proximal end, a distal end formed with a nest for receiving the anchor and a central lumen extending therethrough. The delivery instrument further includes a stylet slidably received in the needle lumen and the anchor bore and an ejector plug formed on the stylet for engaging the anchor.

The present invention, according to another embodiment, is a method for using a delivery instrument to implant a myocardial lead having at least a first electrode with a delivery instrument into a heart. A myocardial anchor coupled to a tether. is mated to a distal end of the delivery instrument. The distal end of the delivery instrument is advanced through a tract in the heart. The anchor is deployed into the heart. The delivery instrument is withdrawn through the tract in such a manner that the tether extends through the tract. A myocardial lead is threaded onto the tether. The lead is advanced over the tether into the heart.

This summary is not intended to describe each embodiment or every implementation of the present invention. Advantages and a more complete understanding of the invention will become apparent upon review of the detailed description and claims in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a portion of the vasculature and a myocardial lead attachment system according to one embodiment of the present invention.

FIG. 2 is a side view of a delivery instrument for use in conjunction with the myocardial lead attachment system of FIG. 1 according to one embodiment of the present invention.

FIG. 3A is a side view of a distal portion of the delivery instrument of FIG. 2 according to one embodiment of the present invention.

FIG. 3B is a side view of the distal portion of the delivery instrument of FIG. 2 according to another embodiment of the present invention.

FIG. 3C shows a side sectional view of the distal portion of the delivery instrument shown in FIG. 3A.

FIG. 3D is a perspective view of the distal portion of the delivery instrument shown in FIG. 3A.

FIG. 4A is a sectional view of a proximal portion of the delivery instrument of FIG. 2 according to one embodiment of the present invention.

FIG. 4B is a perspective view of a distal portion of the delivery instrument of FIG. 2 according to one embodiment of the present invention.

FIG. 4C is a partial sectional view of a distal portion of the delivery instrument of FIG. 2 according to another embodiment of the present invention.

FIG. 5A is a side view of an adjustable length delivery instrument in an extended position according to one embodiment of the present invention.

FIG. 5B is a side view of the delivery instrument of FIG. 5A in a retracted position.

FIG. 6 is a sectional side view of a portion of an adjustable length delivery instrument according to another embodiment of the present invention.

FIG. 7 is a sectional view of a distal portion of a delivery instrument for use in conjunction with the myocardial lead attachment system of FIG. 1 according to one embodiment of the present invention.

FIG. 8 is a sectional view of a distal portion of a delivery instrument for use in conjunction with the myocardial lead attachment system of FIG. 1 according to another embodiment of the present invention.

FIG. 9 is a sectional view of a distal portion of a delivery instrument for use in conjunction with the myocardial lead attachment system of FIG. 1 according to still another embodiment of the present invention.

FIG. 10 is a sectional side view of a distal portion of a delivery instrument for use in conjunction with the myocardial lead attachment system of FIG. 1 according to yet another embodiment of the present invention.

FIG. 11 is a sectional side view of a distal portion of a delivery instrument for use in conjunction with the myocardial lead attachment system of FIG. 1 according to another embodiment of the present invention.

FIG. 12 is a side view of a distal portion of a delivery instrument for use in conjunction with the myocardial lead attachment system of FIG. 1 according to still another embodiment of the present invention.

FIG. 13 is a side view of a delivery instrument for use in conjunction with the myocardial lead attachment system of FIG. 1 according to another embodiment of the present invention.

FIG. 14 is a side view of a delivery instrument for use in conjunction with the myocardial lead attachment system of FIG. 1 according to another embodiment of the present invention.

FIG. 15A is a sectional view of the heart schematically illustrating the use of a delivery instrument in conjunction with a myocardial lead attachment system in an epicardial-epicardial procedure according to one embodiment of the present invention.

FIG. 15B is a sectional view of the heart schematically illustrating the use of a delivery instrument in conjunction with a myocardial lead attachment system in an epicardial-endocardial configuration according to one embodiment of the present invention.

FIG. 15C is a sectional view of a portion of the heart schematically illustrating the use of a delivery instrument in conjunction with a myocardial lead attachment system in an intra-myocardial procedure according to another embodiment of the present invention.

FIG. 15D is a sectional view of a portion of the heart schematically illustrating the use of a delivery instrument in conjunction with a myocardial lead attachment system in a pericardial-pericardial procedure according to yet another embodiment of the present invention.

FIG. 16A is a sectional view of a portion of the heart and a schematically illustrated distal portion of a myocardial lead attachment system having a unipolar electrode arrangement according to one embodiment of the present invention.

FIG. 16B is a sectional view of a portion of the heart and a schematically illustrated distal portion of a myocardial lead attachment system having a pseudo-unipolar electrode arrangement according to one embodiment of the present invention.

FIG. 16C is a sectional view of a portion of the heart and a schematically illustrated distal portion of a myocardial lead attachment system having a pseudo-unipolar electrode arrangement according to yet another embodiment of the present invention.

FIG. 16D is a sectional view of a portion of the heart and a schematically illustrated distal portion of a myocardial lead attachment system having a pseudo-unipolar electrode arrangement according to still another embodiment of the present invention.

FIG. 16E is a sectional view of a portion of the heart and a schematically illustrated distal portion of a myocardial lead attachment system having a bipolar electrode arrangement according to another embodiment of the present invention.

While the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1 shows a myocardial lead attachment system 10 deployed in a human heart 12 according to one embodiment of the present invention. The heart 12 includes a right atrium 14 and a right ventricle 16 separated from a left atrium 18 and a left ventricle 20 by a septum 22. During normal operation of the heart 12, deoxygenated blood is fed into the right atrium 14 through the superior vena cava 24 and the inferior vena cava 26. The deoxygenated blood flows from the right atrium 14 into the right ventricle 16. The deoxygenated blood is pumped from the right ventricle 16 into the lungs, where the blood is re-oxygenated. From the lungs the oxygenated blood flows into the left atrium 18, then into the left ventricle 20. The left ventricle 20 beats forcefully to pump the oxygenated blood throughout the body.

The outer walls of the heart 12 are lined with a tissue known as the epicardium 28. The inner walls of the heart are lined with a tissue known as the endocardium 30. The heart muscle, or myocardium 32, is sandwiched between the endocardium 30 and the epicardium 28. A tough outer pericardial sac 33 surrounds the heart 12.

The myocardial lead attachment system 10 includes a pulse generator 34 coupled to a myocardial lead 36. The pulse generator 34 is typically implanted in a pocket formed, underneath the skin of the patient's chest or abdominal region. The lead 36 extends from the pulse generator 34 to the heart 12 and is implanted in the myocardium 32 near an apex 38 of the heart 12. The lead 36 delivers electrical signals from the pulse generator 34 to an electrode located at or near a distal tip to accomplish pacing of the heart 12 (not shown in FIG. 1). An anchor mechanism 44 is coupled to the lead 36 via a tether 45 to secure the lead 36 to the heart 12 and to retain the electrode in a chosen location.

According to one embodiment, and generally shown in the following figures, the anchor mechanism 44 is an elongated T-bar, in which the tether 45 is coupled to the anchor mechanism 44 between its opposite ends and preferably at a mid-point to form the “T”. According to other embodiments, the anchor mechanism 44 has any other shape suitable for forming an anchor against the heart 12 to retain the lead 36 in the desired location. An important feature of the anchor mechanism 44 is that its shape is configured to engage the heart tissue following implantation through a tract (not visible in FIG. 1) in the heart 12 to reduce the likelihood of re-entry of the anchor mechanism 44 into the tract. According to one embodiment, the length of the anchor mechanism 44 is greater than the diameter of the tract. The “T” configuration is such that tension exerted on the mid-point of the anchor mechanism 44 via the tether 45 tends to position the anchor mechanism 44 cross-wise over the tract, preventing the anchor mechanism from siding proximally through the tract. The lead 36 is then advanced over the tether 45 into the myocardium 32. The anchor mechanism 44 resists the tensioning force exerted on the tether 45 such that the lead 36 may be easily advanced through the tract.

Placement of the lead 36 and anchor mechanism 44 of FIG. 1 may be accomplished by exposing a portion of the heart 12, for example by way of a sternotomy, thoracotomy or mini-thoracotomy. According to other embodiments, the heart 12 may be accessed via an endoscopic procedure according to known methods. Although shown implanted near the apex 38, the lead 36 may be implanted in the heart 12 anywhere pacing therapy is needed. The anchor mechanism 44 is delivered to the heart 12 with a delivery instrument according to any of the following embodiments.

FIG. 2 shows a delivery instrument 50 according to one embodiment of the present invention. The delivery instrument 50 includes a needle portion 58 having a distal tip 60 and a nest 62. The nest 62 is sized to receive at least a portion of the anchor mechanism 44 (not visible in FIG. 2). The delivery instrument 50 further includes an ejection mechanism 66 coupled to an actuator (not visible in FIG. 2) for ejecting the anchor mechanism 44 from the nest 62.

The delivery instrument 50 includes a handle 52 having a proximal end 54 and a distal end 56. The needle portion 58 is coupled to the handle 52 and extends from the distal end 56. The needle portion 58 is of a hypotube construction with an internal lumen 59. The handle 52 has an internal lumen 64 continuous with the needle lumen 59. The ejection mechanism 66 is located on the handle 52 and is operable within the internal lumen 64. According to other embodiments, the ejection mechanism 66 is located elsewhere on the handle 52.

The handle 52 is sized with a length a and diameter b for easy grasping and manipulation. According to one embodiment of the present invention, a diameter b of about 5 mm provides a mechanical advantage allowing stable control over the direction of the distal needle tip 60. Further, a diameter b of about 5 mm can be used within a standard 7 mm or larger thoracic port, which is commonly used in minimally-invasive thoracoscopic procedures to access the heart 12.

An outer surface 70 of the handle 52 includes a surface feature 68. Surface feature 68 may include bumps, ribs, or bulging features on the outer surface 70 chosen to enhance the friction between the handle 58 and the surgeon's hand. Surface feature 68 advantageously reduces slippage between the surgeon's hand and the handle 52 while in wet, slippery environments. The handle 52 can be made of any sterilizable metal or polymeric material, including stainless steel, polypropylene, and polyurethane.

The shape of the distal needle portion 58 is configured to facilitate access to the heart 12 via thoracotomy or other procedures, such as those mentioned above. According to one embodiment of the present invention, the needle portion 58 is shaped with a curved portion 72. The shape of the curved portion 72 will be dictated in part by patient anatomy (e.g., overall heart size, peculiarities in geometry due to dilation, epicardial fat, infarct, and vessels), location of the thoracotomy (posterior or anterior to an imaginary mid-axillary line bisecting the heart 12), and size of the incision into the heart tissue. According to one embodiment, the curved portion 72 has a radius of curvature R₇₂ of about 22 mm, a shape intended to be approximately what the physician would need for implanting the lead 36 via a thoracotomy. According to other embodiments, the radius of curvature R₇₂ of curved portion 72 is from about 10 to about 35 mm (not shown). According to other embodiments, the curved portion 72 is constructed of multiple curved segments, or is straight (not shown).

According to one embodiment, the needle portion 58 is constructed of stainless steel. The curved portion 72 may be formed according to a variety of methods. The curved portion 72 may be formed by mechanically bending the needle portion 58. Alternately, the needle portion 58 is heat-set so that the needle portion 58, or a smaller portion thereof, is malleable. A chosen curvature can be imparted to the needle portion 58 contemporaneous with the implantation procedure according to the surgeon's needs.

FIG. 3A shows a portion of the needle portion 58 according to one embodiment of the present invention. The tip 60 and nest 62 are shown as previously described. A distal end 60b of the tip 60 is configured to minimize trauma to the myocardium 32 during insertion. This is accomplished by dissecting the myocardium 32 as opposed to cutting the myocardium 32. According to one embodiment, the tip 60 is generally conical in shape, terminating at a slightly rounded point.

FIG. 3B shows another embodiment in which the distal end 60b of the tip 60 is more rounded or blunt than the embodiment shown in FIG. 3A. A rounded or blunted tip 60 is understood to be less traumatic and less likely to damage coronary vessels when passing through the myocardium 32. According to one embodiment, the tip 60 is generally isodiametric. An isodiametric configuration generally exerts force equally on the myocardial tissue 32 about the tip 60 when passing through tissue. A uniform force distribution reduces excessive force on the myocardial tissue 32 in directions other than along the axis of dissection. According to other embodiments, the tip 60 is provided with a sharp cutting edge.

The nest 62 is sized with a length d and a width e chosen such that the nest 62 retains the anchor mechanism 44 when the needle portion 58 is advanced through the myocardium 32 (anchor mechanism 44 not visible in FIGS. 3A and 3B—see FIG. 3D). According to one embodiment, the nest 62 is an elongated slot in the needle portion 58 opening to the needle lumen 59. The nest 62 further includes a tether slot 78 located near its proximal end. The tether slot 78 is adapted to accept the tether 45 when the needle portion 58 is advanced through the myocardium 32 (See FIG. 3D).

FIG. 3C shows the needle portion 58 of FIG. 3A. A proximal end 60a of the tip 60 is sized with a diameter c chosen to mate with the needle lumen 59. The nest 62 includes a distal angled face or ramp 76 facing the interior of the nest 62. The. ramp 76 is disposed at an angle θ relative to a longitudinal axis 77 of the needle 58.

FIG. 3D shows the anchor mechanism 44 received in the nest 62. The anchor mechanism 44 is placed in the slot 62 and slid proximally into the needle lumen 59. The tether 45 is received in the tether slot 78, permitting the anchor mechanism 44 to be slid further into the lumen 59. The ramp 76 is inclined away from the anchor mechanism 44 at the angle θ at distal sliding of the anchor mechanism 44 along the axis 77 causes the anchor mechanism 44 to ride up the ramp 76 and out of the nest 62.

FIG. 4A shows a proximal portion of the handle 52 and FIG. 4B shows a distal portion of the needle portion 58, both detailing the ejection mechanism 66. The ejection mechanism 66 includes an elongated member 80 extending from the proximal end 54 of the handle 52, through the handle lumen 64 and needle lumen 59, and terminating proximal to the nest 62. A proximal end 82 of the elongated member 80 is operationally coupled to an actuator 84. According to one embodiment, the actuator 84 is a depressible button operable to slide the elongated member 80 distally from a neutral or retracted position to an advanced position. FIG. 4B shows the elongated member 80 in an advanced position such that a distal end 86 of the elongated member 80 has engaged the anchor mechanism 44 and is pushing the anchor mechanism 44 distally within the nest 62. Doing so forces the anchor mechanism 44 to slide distally along the ramp 76 and out of the nest 62.

According to one embodiment, shown in FIGS. 4A and 4B, the elongated member 80 is a solid tubular member sufficiently flexible to navigate the curved portion 72 (see FIG. 2) of the needle portion 58. According to another embodiment, as shown in FIG. 4C, the elongated member 80 is constructed of a combination of a solid member 88 and a helically-wound member 89. The solid member 88 extends through the needle lumen 59 to the curved portion 72 and transfers axial force to the distally positioned helical member 89, which extends through the needle lumen 59 at the curved portion 72. The helical member 89 is sufficiently flexible to navigate the curved portion 72, while the solid member 88 may be rigid. According to other embodiments, the elongated member 80 is a rigid member. Elongated member 80 may be constructed of a polymer or metal.

Returning to FIG. 4A, the handle lumen 64 is formed with a ledge 90 forming a mechanical stop. The ledge 90 blocks actuation of the actuator 84 (i.e. further depression of the button), and prevents over-advancement of the elongated member 80. A biasing mechanism 92, including a resilient member 93, such as a spring, is interposed between the actuator 84 and the handle 52. The biasing mechanism 92 biases the actuator 84 to a neutral position in which the elongated member 80 is retracted.

According to one embodiment, the ejection mechanism 66 and actuator 84 are operable to advance the elongated member 80 to one of a plurality of pre-set positions. According to another embodiment, the present invention is an automatic or semi-automatic delivery instrument. In this embodiment a lever mechanism, or trigger and spring mechanism, drives the needle portion 58 from a retracted position into the myocardium 32 in a prescribed path, ejects the anchor mechanism 44 and retracts the needle portion 58 to its original position.

FIGS. 5A and 5B show a delivery instrument 50′ which is generally similar to the delivery instrument 50 shown FIG. 2. The length of the needle portion 58′ of the instrument 50′ extending from the handle 52′ is adjustable by sliding portions of the needle portion 58′ into the handle lumen 64′. In one embodiment, needle portion 58′ is retained in a chosen position within the handle lumen 64′ via a keeper mechanism, such as a set screw 94′, extending through the handle 52′. If the physician desires more needle length, N, as shown in FIG. 5A, either for patients with thick thoracic walls requiring a deeper reach to the epicardium 28 or for thoracoscopic procedures, he may adjust accordingly. If he requires less length N′, as shown in FIG. 5B, the needle portion 58′ may be retracted into the lumen 64′.

FIG. 6 shows another embodiment of the adjustable length delivery instrument 50′ in which the needle portion 58′ is adjustably coupled to the handle 52′ via a collet mechanism 95′. According to one embodiment, the needle portion 58′ is provided with a sleeve 96′ having an open end 96a′ facing proximally and a distal end 96b′ coupled to the needle portion 58′ via guide member 98′. The sleeve 96′ is sized to receive the distal end 56′ of the handle 52′. The sleeve 96′ and the distal end 56′ of the needle 52′ are provided with complementary threads 97′. Rotation of the sleeve 96′ about the handle threads 98′ advances the sleeve 96′ onto the handle 52′, shortening the effective length of the needle portion 58′. Reverse rotation advances the needle portion 58′ distally from the handle 52′, increasing the effective length of the needle 58′. According to other embodiments, the needle 58′ and handle 52′ may be provided with complementary teeth or other means for providing an adjustable length coupling.

FIG. 7 shows a delivery instrument 100 for use in conjunction with the myocardial lead attachment system 10 of FIG. 1 according to another embodiment of the present invention. The instrument 100 includes a tube or needle 102 having a nest 106 for receiving an anchor mechanism 108, and an ejection mechanism 109 for ejecting the anchor mechanism 108 from the nest 106. A proximal portion of the needle 102 may be attached to a handle to facilitate manipulation (not shown).

According to the present embodiment, the nest 106 is an open sleeve at a distal end of the needle 102. The anchor mechanism 108 is received in the nest 106 and protrudes outwardly from the nest 106. The needle 102 includes a crimp or detent 110 near to and proximal to the nest 106 for contacting a proximal or trailing edge 112 of the anchor mechanism 108. An inside diameter f of the nest 106 is slightly greater than an outside diameter g of the anchor mechanism 108, such that the anchor mechanism 108 can readily release from the nest 106 upon application of a relatively small force on the anchor mechanism 108 directed distally from the needle 102. The anchor mechanism 108 is coupled to a tether 113 as previously described. The needle 102 is further provided with a central lumen 114 extending therethrough.

The ejection mechanism 109 is a stylet 115 coupled to an ejection plug 116. The stylet 115 has a sharpened distal tip 117 shaped to effectively dissect the tissue of the myocardium 32. According to other embodiments, the tip 117 is blunt or rounded to reduce trauma to the myocardium 32. The stylet 115 extends through the needle lumen 114 and through a bore 118 extending longitudinally through the anchor mechanism 108. The ejector plug 116 is spherical and is sized and shaped smaller than an inside diameter h of the needle 102 at the crimp 110 so as to pass through the crimp 110 but larger than an inside diameter I of the bore 118 in the anchor mechanism 108 so as to contact the trailing edge 112 of the anchor mechanism 108. According to other embodiments, the ejector plug 116 has a cylindrical or other shape. According to still other embodiments, the ejector plug 116 is not formed integrally with the stylet 115 but rather is a separate member such as a clip that is affixed to the stylet 115.

During implantation, the anchor mechanism 108 is received in the nest 106. The tip 117 of the stylet 115 extends through the bore 118 in the anchor mechanism 108 and protrudes from the bore 118. The tube 102 and the stylet 115 are used to guide the anchor mechanism 108 through the myocardium 32. The crimp 110 contacts the trailing edge 112 of the anchor mechanism 108 to force the anchor mechanism 108 through the myocardium 32. Once the anchor mechanism 108 emerges from the myocardium 32, the ejection mechanism 109 is actuated by advancing the stylet 115 distally with respect to the tube 102, such that the ejection plug 116 contacts the trailing end 112 of the anchor mechanism 108 and ejects the anchor mechanism 108 from the nest 106. This deploys the anchor mechanism 108 on the surface of the heart 12. The needle 102 and stylet 115 are then withdrawn.

According to one embodiment, the ejection mechanism 109 is coupled to an actuator as described with respect to the embodiment shown generally in FIGS. 2-6 to distally advance the stylet 106 (not shown). According to other embodiments, the ejection mechanism 109 is actuated by manually advancing the stylet 115 with respect to the needle 102.

FIG. 8 shows a distal portion of delivery instrument 120 according to another embodiment of the present invention. As shown in FIG. 8, the instrument 120 includes many of the same components as the delivery instrument 100 of FIG. 7. The instrument 120 includes a tube or needle 122 having a nest 123, an ejection mechanism 124 including a stylet or guide wire 126 and an anchor mechanism 128 coupled to a tether 130. The instrument 120 does not include a crimp or detent 110 as described with respect to instrument 100 of FIG. 7, but instead includes a ledge 132 forming an internal stop in the needle 122 proximal to the nest 123. The ledge 132 contacts a trailing edge 134 of the anchor mechanism 128 to drive the anchor 128 forward during implantation. The outer profile of the needle 102 is smooth and continuous.

The stylet 126 is provided with an ejector plug 136 as described previously. According to the present embodiment, however, the ejector plug 136 is cylindrical in shape. According to the embodiment shown, the anchor mechanism 128 includes an angled or tapered leading edge 138. Tapered edge 138 facilitates dissection of the myocardium 32 during implantation. The leading edge 138 of the anchor mechanism 128 may have a blunt or rounded profile similar to the profile of the needle tip 60 described with reference to the embodiment shown in FIGS. 3A and 3B. The instrument 120 is used in a similar manner as described above with reference to the embodiment shown in FIG. 7.

FIG. 9 shows a sectional view of a distal portion of a stylet delivery instrument 140 according to another embodiment of the present invention. The instrument 140 includes many of the same components as the delivery instruments 100 and 120 of FIGS. 7 and 8. The instrument 140 includes a tube or needle 142 having a nest 143 and an ejection mechanism 144. The ejection mechanism 144 is a stylet or guide wire 146 having an ejector plug 145 as described previously. An anchor mechanism 148 having a stepped outside diameter is received in the nest 143. A distal portion 150 of the anchor mechanism 148 has a diameter j that is roughly equal to an outside diameter k of the needle 142. A proximal portion 152 of the anchor mechanism 148 has a diameter l slightly smaller than an inside diameter m of the needle 142, such that the anchor mechanism 148 can be inserted into the nest 143. In this embodiment, a leading edge 154 of the tube 142 serves to contact the anchor mechanism 148 and transmit axial force during implantation. In this embodiment, the anchor 148 may include either a blunt or a tapered leading edge 156 as described previously. The instrument 140 is used in the manner described above with reference to FIG. 7.

FIG. 10 shows a sectional view of a distal portion of a delivery instrument 160 according to another embodiment of the present invention. The instrument 160 includes a stylet 162 and an anchor mechanism 164. The stylet 162 includes a distal tip 166, which is shaped for efficient dissection of the myocardium 32. A distal end 168 of the stylet 162 is provided with a raised region 170 forming a mechanical stop. According to one embodiment, a tubular sleeve 172 is positioned about the stylet 162 to form the raised region 170. According to other embodiments the raised region 170 is integrally formed with the stylet 162. The anchor mechanism 164, which is coupled to a tether 174, has an inner bore 176 extending therethrough. An inner surface of the bore 176 includes a ledge 178. A distal end 168 of the stylet 162 is received in the bore 176, such that the tip 166 protrudes from the bore 176. The ledge 178 is adapted to mate with and contact the raised region 170 of the stylet 162 such that upon application of an axial force on the stylet 162, the raised region 170 contacts the ledge 178 and forces the anchor mechanism 164 to advance distally.

The instrument 160 is advanced through the heart 12, and the stylet 162 is manipulated into the heart 12 and position the anchor mechanism 164. When the anchor mechanism 164 has been properly positioned, the stylet 162 is withdrawn.

FIG. 11 shows a sectional view of a distal portion of a stylet delivery instrument 180 according to another embodiment of the present invention. The instrument 180 includes a stylet 182 and an anchor mechanism 184. The anchor mechanism 184 includes a blind bore 186 extending from a proximal end 188 of the anchor mechanism 184 but not all the way through to a distal end 190. The inner surface of the blind bore 186 has a diameter sized to receive a distal end 192 of the stylet 182. As shown, the anchor 184 has a tapered leading edge 194 to facilitate dissection of the myocardium 32. A tether 196 is attached to the anchor 184. The stylet 182 is used to advance the anchor mechanism 184 through the myocardium 32. When the anchor mechanism 184 is located in a chosen position, for example, on the endocardial surface 30, the stylet 182 is withdrawn.

FIG. 12 shows a side view of a stylet delivery instrument 200 according to another embodiment of the present invention. The instrument 200 includes a guide wire or stylet 202 and an anchor mechanism 204 coupled to a tether 206. The stylet 202 includes a tapered tip 208 shaped for efficient dissection of the myocardium 32. The anchor mechanism 204 is coupled to a catch mechanism 210 for receiving the stylet 202. The catch mechanism 210 is a ring-shaped member and may be formed from a looped region of the tether 206 or formed separately and attached to the anchor mechanism 204. According to one embodiment, the catch mechanism 210 is generally flexible. According to another embodiment, the catch mechanism 210 is rigid.

The catch mechanism 210 has an inner diameter smaller than an outside diameter n of the stylet 202, such that the stylet tip 208 can be inserted partially into the catch mechanism 210, but the stylet 202 cannot fully pass through the catch mechanism 210. The stylet tip 202 is inserted into the catch mechanism .210 so that the anchor 204 lies adjacent the length of the stylet 202. According to other embodiments, the stylet 202 is provided with a circumferential groove for receiving the catch mechanism 210 (not shown). The stylet 202 is inserted into the myocardium 32, drawing the anchor mechanism 204 along via the catch mechanism 210. Once the stylet tip 208 and the anchor mechanism 204 emerge from the myocardium 32, the stylet 202 is withdrawn, disengaging from the catch mechanism 210. Following implantation, the catch mechanism 210 may be removed or may be left in place.

FIG. 13 shows a delivery instrument 300 in accordance with another embodiment of the present invention. The delivery instrument 300 includes many of the features of the delivery instrument 50 shown in FIGS. 2-6. In addition, the delivery instrument 300 may be used for identifying an appropriate or desired implant site. The delivery instrument 300 includes a handle 302, a needle 304, an anchor mechanism 306 and an ejection mechanism 308 as previously described. According to the present embodiment, the needle 304 is electrically conductive and extends nearly to a proximal end 310 of the handle 302. The needle 304 is electrically isolated or masked via a non-conductive insulating or dielectric material polymer sleeve 311 extending the length of the needle 304. According to one embodiment, the sleeve 311 is formed of a heat shrinkable polyimide. According to other embodiments, the sleeve 311 is formed of a conformal polymer such as parylene or ethylene-tetrafluoro ethylene. According to another embodiment, the needle 304 is coated with a layer of non-conductive polymer material.

The needle 304 is electrically exposed at a distal tip 312 and at a proximal region 314. The proximal exposed region 314 is accessible via a cut-out or window 316 formed in the handle 302. The needle 304 acts as an electrical conductor between the exposed proximal region 314 and the exposed distal tip 312. Alligator clips or other electrical connectors may be coupled to the needle 304 through the window 316 to electrically couple the exposed distal tip 312 to a pacing and sensing analyzer for performing sensing and pacing functions (not shown).

The exposed area at tip 312 is brought into contact with the epicardium 28 or myocardium 32 to perform sensing and pacing functions prior to ejection of the myocardial anchor 306. Additionally, acute therapeutic benefit at a particular site may be assessed using said embodiment. If acute benefit is unacceptable, the implant site may be changed prior to implanting the lead 36.

FIG. 14 shows a delivery instrument 400 according to another embodiment of the present invention. The delivery instrument 400 includes a handle 402 coupled to a needle 404, an anchor mechanism 406 and an ejection mechanism 408 as previously described with respect to various embodiments. In addition, the delivery instrument 400 may be used for identifying an appropriate or desired implant site. According to one embodiment, this is accomplished by electrically isolating the needle region 404 except for a small exposed or electrically active area 410 on the conical tip 412. The needle region 404 may be electrically isolated according to the techniques described with respect to the previously described embodiment shown in FIG. 13. A conductive wire 414 with a terminal end 416 in electrical communication with the electrically active area 410 is located in the handle 402. The wire 414 is connected to a pacing and sensing analyzer 418. The electrically active area 410 is brought into contact with the epicardium 28 or myocardium 32 to perform sensing and pacing as previously described.

The systems shown in FIGS. 2-14 are amenable to minimally-invasive introduction into the heart 12, such as by known thoracoscopic, mini-thoracoscopic or endoscopic techniques. In one embodiment employing an endoscopic technique, a small subxiphoid incision is made to gain visualization of the apex 38 of the heart 12. The pericardium 33 is perforated to gain access to the epicardial surface 28. An endoscopic probe having an open working channel is then introduced into the chest. The endoscopic probe includes common features such as a light tube, fiber optic visualization, and means to accomplish distal deflections of the tube or needle when formed of a malleable material as described above.

A target region of the heart 12 is approached and advanced sensing probes may be used to assess the suitability of the location. This assessment may include typical measurements such as pacing thresholds, sensing amplitudes, and tissue impedance. These functions may be accomplished with a delivery instrument in accordance with the embodiments shown in FIGS. 13 and 14. The working channel may also be used to assess the physiological suitability of the heart tissue. Temporary pacing of the heart 12 may also be performed at the location through the working channel.

After a determination that the location is suitable for lead implantation, an anchor mechanism 44 as is shown in FIG. 1 is advanced through the working channel with a delivery instrument 50 as is shown in FIGS. 2-6 in accordance with one embodiment of the present invention. A separate channel for fiber optic visualization may be used to assist the operator in guiding the delivery instrument 50 through the myocardial tissue 32. In one embodiment, the visualization channel is further used to avoid tissue structures, such as vessels, fat pads, nervous system tissue, and infarcts.

FIGS. 15A -15D illustrate the use of the delivery instrument 50. The needle portion 58 of the delivery instrument 50 is used to create a channel or tract 37 through the tissue of a patient's heart 12. FIG. 15A shows an epicardial-epicardial procedure, in which the needle portion 58 is inserted in the direction shown by the arrow 99′, such that it both enters and exits the myocardium 32 through the epicardium 28. According to one embodiment, the needle tip 60 is rounded or blunt, as previously described to reduce trauma to the myocardial tissue 32 during advancement. During insertion through the myocardium 32, the anchor mechanism 44 is located within the nest 62. A tether 45 is attached to the anchor 44 and extends along the outside of the needle portion 58 and the handle 52.

FIG. 15B shows an epicardial-endocardial procedure, in which the needle portion 58 travels in the path indicated by the arrow 99′, such that it enters the myocardium 32 through the epicardium 28 and exits through the endocardium 30. Again, the anchor mechanism 44 is located within the nest 62 and a tether 45 travels along the outside of the needle portion 58 and handle 52.

FIG. 15C shows an intra-myocardial procedure, in which the needle portion 58 travels in the path indicated by arrow 99′, such that it enters the myocardium 32 through the epicardium 28. The anchor mechanism 44 is ejected into the myocardium 32 and the delivery instrument 50 is withdrawn. The anchor mechanism 44 remains positioned within the myocardium 32.

FIG. 15D shows a pericardial-pericardial procedure, in which the needle portion 58 travels in the path indicated by arrow 99′ such that it enters and exits through the pericardium 33 without traversing the myocardium 32.

Once the delivery instrument 50 emerges through the epicardium 28 (or the endocardium 30, pericardium 33, or myocardium 32), the ejection mechanism 66 is activated to dislodge the anchor mechanism 44 from the nest 62. The delivery instrument 50 is then withdrawn back through the tract 37 and removed. The tether 45 is then tensioned to cause the anchor 44 to engage against the epicardium 28 (or endocardium 30, pericardium 33 or myocardium 32).

According to other embodiments (see FIGS. 7-10C, but referring generally to FIG. 7), a stylet or guide wire 106 in combination with a needle 102 and an anchor mechanism 108 is used to create the tract 37 through the myocardium 32 for delivery of the anchor mechanism 108. Once the distal end of the needle 104 and anchor mechanism 108 have emerged through the epicardium 28 (or endocardium 30, the myocardium 32 or pericardium 33), the stylet 106 is advanced. The ejector plug 116 engages the trailing edge 112 of the anchor mechanism 108 to eject the anchor mechanism 108 from the needle lumen 104. The needle 102 and stylet 106 are then withdrawn through the tract 37.

According to still other embodiments (see FIGS. 11 and 12, but referring generally to FIG. 11), a stylet or guide wire 182 in combination with an anchor mechanism 184 is used to create the tract 37 through the myocardium 32 for delivery of the anchor mechanism 184. Once the distal end 192 of the stylet or guide wire 182 and anchor mechanism 184 have emerged through the epicardium 28 (or endocardium 30, myocardium 32 or pericardium 33) the stylet 182 is withdrawn. The anchor mechanism 184 remains in place. The tether 196 is tensioned and the lead 36 advanced as described above. According to other embodiments, the stylet 182 and anchor mechanism 184 are advanced through the working channel rather than creating a separate tract 37.

Following delivery of the anchor mechanism 44 to the epicardial surface 28 (or the myocardium 32, the endocardial surface 30 or the pericardial surface 33) according to any of the aforementioned embodiments, the tether 45 is tensioned and the lead 36 advanced as described above. Following implantation of the myocardial lead 36, the tether 45 is tensioned and secured to the myocardial lead 36 to secure the myocardial lead 36 within the myocardium 32. According to other embodiments, the myocardial lead 36 is provided with additional means to secure the myocardial lead 36 within the myocardium 32 following delivery.

The lead 36 is positioned in the heart 12 and anchored, as described above, to position the lead electrode 40 in chosen locations in the heart 12. Although generally shown in implanted near the apex 38, the lead 36 may be implanted anywhere in the heart pacing therapy is needed. For example, the lead 36 may be implanted in the free wall of the left ventricle 20. According to one embodiment, shown in FIG. 16A, the lead 36 is configured as a unipolar lead. The electrode 40 is inserted into the heart tissue and is an active “can.” The electrode 40 may be positioned in the myocardium 32, as shown, or may contact the epicardium 30 or the pericardium 33.

FIG. 16B shows another embodiment in which the lead 36 has two electrodes, a proximal anode 40a and a distal cathode 40b. According to one embodiment, the lead 36 is implanted in a pseudo-unipolar arrangement, such that the cathode 40b is positioned within the myocardial tissue 32 and the anode 40a is positioned on the lead body 36, but not in contact with the heart tissue.

FIG. 16C shows another embodiment, in which the lead electrode arrangement is pseudo-unipolar, such that the cathode 40b is positioned in the heart and the anode 40a partially contacts the exterior epicardial tissue 28 of the heart 12.

FIG. 16D shows yet another pseudo-unipolar embodiment in which the cathode 40b is positioned in the myocardium 32 and the anode 40a is positioned in alignment with the outer layers of the epicardial tissue 28 of the heart 12. The anode 40a may, for example, straddle the epicardium 28 such that a portion anode 40a is within the heart tissue and another portion is exposed to a space outside of the heart 12.

FIG. 16E shows another embodiment in which the lead 36 has a bipolar arrangement wherein the cathode 40b and anode 40a are completely within the myocardial tissue 32.

In one embodiment, the cathode 40b has an active electrode surface area of about 1 square mm. The cathode 40b is located near the distal tip 35 of the lead body 36. An electrode spacing between the cathode 40b and anode 40a of more than about 2 cm would generate a unipolar lead, as defined above. An electrode spacing of between about 1 and about 2 cm would generate a pseudo-unipolar lead, as defined above. An electrode spacing of less than about 1 cm would generate a bipolar lead, as defined above.

In the epicardium to epicardium configuration, the epicardium to endocardium configuration and the intramyocardial configuration, once implanted, the lead body 36 will serve to block the tract in the myocardium 32 created by the delivery instrument 50 and prevent further loss of blood from the heart 12. If it becomes necessary to reposition the lead 36 and create a second tract, a porous, clot-promoting “plug” material can be fed over the tether 45 into the tract 37 to serve as a seal. Following implantation of the myocardial lead 36, the tether 45 is tensioned and secured to the myocardial lead 36 to secure the myocardial lead 36 within the myocardium 32.

Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. Accordingly, the scope of the present invention is intended to embrace all such alternative, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof.

Claims

1. A myocardial lead attachment system for securing a distal end of a lead within a myocardium of a patient's heart, the system comprising:

an anchor;

a tether coupled to the anchor; and

a delivery instrument for receiving and advancing the anchor through a tract in the heart from a proximal entrance site to a distal exit site in such a manner that the tether extends proximally from the anchor through the tract, said delivery instrument comprising: a needle having a distal tip and a nest positioned proximal to the distal tip and sized to receive the anchor, and an ejection mechanism for ejecting the anchor from the nest.

2. The lead attachment system of claim 1 wherein the ejection mechanism further comprises an actuator for ejecting the anchor from the nest.

3. The lead attachment system of claim 1 wherein a distal portion of the needle is formed with a radial curvature.

4. The lead attachment system of claim 2 wherein the ejection mechanism further comprises an elongated member slidable from a retracted position to an extended position in response to actuation of the actuator to engage the anchor mechanism.

5. The lead attachment system of claim 4 further comprising:

a mechanical stop for limiting extension of the elongated member; and

a resilient member biasing the actuator to retract the elongated member.

6. The lead attachment system of claim 1 wherein the delivery instrument further comprises:

a distal electrically active area on the needle; and

a conductive member for connecting the electrically active area to an external electrical device.

7. The lead attachment system of claim 1 wherein the nest further includes a slot for receiving the tether.

8. The lead attachment system of claim 1 wherein the nest includes a ramp adapted to assist in ejection of the anchor.

9. The lead attachment system of claim 1 further comprising a lead body having a proximal end, a distal end, and at least a first electrode near the distal end, said lead body adapted to advance over the tether through the tract.

10. The lead attachment system of claim 9 wherein the lead body is a unipolar lead.

11. The lead attachment system of claim 10 wherein the lead body includes a second electrode spaced apart the first electrode apart by about at least 2 cm.

12. The lead attachment system of claim 9 wherein the lead body is a pseudo-unipolar lead.

13. The lead attachment system of claim 9 wherein the lead body is a bipolar lead.

14. A myocardial lead attachment system for securing a distal end of a lead within a myocardium of a patient's heart, the system comprising:

an anchor having a longitudinal bore extending therethrough;

a tether coupled to the anchor; and

a delivery instrument for receiving and advancing the anchor through a tract in the heart from a proximal entrance site to a distal exit site in such a manner that the tether extends proximally from the anchor through the tract, said delivery instrument comprising: a needle having a proximal end, a distal end formed with a nest for receiving the anchor and a central lumen extending therethrough; a stylet slidably received in the needle lumen and the anchor bore, and an ejector plug formed on the stylet for engaging the anchor.

15. The lead attachment system of claim 14 wherein the nest is an open sleeve at the distal end of the needle.

16. The lead attachment system of claim 15 wherein the nest has an internal stop for transmitting an axial force to the anchor.

17. The lead attachment system of claim 15 wherein the anchor has a proximal region sized to be received in the nest and a distal region sized to be retained outside of the nest.

18. The lead attachment system of claim 15 wherein the anchor has a tapered distal face shaped to dissect the tissue of the myocardium.

19. The lead attachment system of claim 14 wherein the stylet has a pointed distal end shaped to dissect the tissue of the myocardium.

20. A method for using a delivery instrument to implant a myocardial lead into the heart, said lead having at least a first electrode, the method comprising:

mating a myocardial anchor coupled to a tether to a distal end of the delivery instrument;

advancing the distal end of the delivery instrument through a tract in the heart;

deploying the anchor into the heart;

withdrawing the delivery instrument through the tract in such a manner that the tether extends through the tract;

threading a myocardial lead onto the tether; and

advancing the lead over the tether into the heart.

21. The method of claim 20 further comprising:

advancing the anchor through the epicardium, into the myocardium, and back through the epicardium; and

deploying the anchor mechanism on the epicardial surface.

22. The method of claim 20 further comprising:

advancing the anchor through the epicardium, into the myocardium and through the endocardium; and

deploying the anchor on the endocardial surface.

23. The method of claim 20 further comprising:

advancing the anchor through the epicardium and into the myocardium; and

deploying the anchor into the myocardium.

24. The method of claim 20 further comprising:

advancing the anchor into the pericardium and out of the pericardium without traversing the epicardium; and

deploying the anchor on the pericardial surface.

25. The method of claim 20 further comprising advancing the lead body until the first electrode is in contact with the heart.

26. The method of claim 20 further comprising advancing the lead body until the first electrode is in contact with the myocardium.

27. The method of claim 26 wherein the lead body includes a second electrode proximal to the first electrode and further comprising advancing the lead body until the second electrode is at least partially in contact with the heart.

28. The method of claim 27 further comprising advancing the lead body until the second electrode straddles the epicardium.

29. The method of claim 27 further comprising advancing the lead body until the second electrode is in contact with the myocardium.

30. The method of claim 20 further comprising:

forming a working channel and a visual channel to the heart with an endoscopic probe; and

advancing the anchor and delivery instrument to the heart through the working channel.