US20050137672A1 - Myocardial lead - Google Patents

Abstract

The present invention is a lead for use in connection with a myocardial lead attachment system of the type having an anchor for engaging the heart and a tether extending from the anchor. The lead includes a lead body having a proximal end, a distal end and a lumen for accepting the tether. A tapered tip is separate from the lead and positioned adjacent the distal end of the lead. The tip has a longitudinal through-hole for accepting the tether.

Description

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 Attachment System”, 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 anchor 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 the 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.
• Unfortunately, insertion through the myocardium can be somewhat traumatic to the muscle tissue. Accordingly, there is a need for a lead that can be implanted with minimal long-term damage to the physiology of the heart.
SUMMARY OF THE INVENTION
• According to one embodiment, the present invention is a lead for use in connection with a myocardial lead attachment system of the type having an anchor for engaging the heart and a tether extending from the anchor. The lead includes a lead body having a proximal end, a distal end and a lumen for accepting the tether. A tapered tip is separate from the lead body and is positioned adjacent the distal end of the lead body. The tip has a longitudinal through-hole for accepting the tether.
• According to another embodiment, the present invention is a method of implanting a myocardial lead. An anchor mechanism coupled to a distal end of a tether is advanced through the myocardium to an implant site. An appropriate dilating tip having an internal through-hole is selected. The tip and lead are threaded onto the tether such that the tip is distal to the lead. The tip and lead are advanced over the tether to the implant site.
• According to another embodiment, the present invention is a method of implanting a lead into a myocardium of a heart. A proximal end of an anchor mechanism and tether arrangement is attached to a needle. The needle is advanced through the heart at least until the proximal end of thetether45 exits the heart. The needle is detached from the tether and the proximal end of the tether is tensioned to cause the anchor mechanism to engage the heart. A 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 sectional view of a patient's heart showing a portion of the vasculature and a myocardial lead attachment and pacing system according to one embodiment of the present invention.
• FIG. 2 is a side sectional view of a distal portion of the myocardial lead attachment system ofFIG. 1 in accordance with one embodiment of the present invention.
• FIG. 3 is a side sectional view of a distal portion of the myocardial lead attachment system ofFIG. 1 in accordance with another embodiment of the present invention.
• FIG. 4 is a side sectional view of a distal portion of the myocardial lead attachment system ofFIG. 1 in accordance with yet another embodiment of the present invention.
• FIG. 5 is a side sectional view of a distal portion of the myocardial lead attachment system ofFIG. 1 in accordance with still another embodiment of the present invention.
• FIG. 6A is a side sectional view of a distal portion of the myocardial lead attachment system ofFIG. 1 in accordance with another embodiment of the present invention.
• FIG. 6B is a side sectional view of the attachment system ofFIG. 6A following removal of the tip.
• FIG. 7 is a perspective view of a distal portion of the myocardial lead attachment system ofFIG. 1 in accordance with yet 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 andpacing system10 deployed in ahuman heart12 according to one embodiment of the present invention. Theheart12 includes aright atrium14 and aright ventricle16 separated from aleft atrium18 and aleft ventricle20 by aseptum22. During normal operation of theheart12, deoxygenated blood is fed into theright atrium14 through thesuperior vena cava24 and theinferior vena cava26. The deoxygenated blood flows from theright atrium14 into theright ventricle16. The deoxygenated blood is pumped from theright ventricle16 into the lungs, where the blood is re-oxygenated. From the lungs the oxygenated blood flows into theleft atrium18, then into theleft ventricle20. Theleft ventricle20 beats forcefully to pump the oxygenated blood throughout the body.
• The outer walls of theheart12 are lined with a tissue known as theepicardium28. The inner walls of the heart are lined with a tissue known as theendocardium30. The heart muscle, ormyocardium32, is sandwiched between theendocardium30 and theepicardium28. A tough outerpericardial sac33 surrounds theheart12.
• Thepacing system10 includes apulse generator34 coupled to amyocardial lead36. Thepulse generator34 is typically implanted in a pocket formed underneath the skin of the patient's chest or abdominal region. Thelead36 extends from thepulse generator34 to theheart12 and is implanted in themyocardium32 near an apex38 of theleft ventricle20. Thelead36 delivers electrical signals from thepulse generator34 to at least one electrode located at or near a distal region of thelead36 to accomplish pacing of the heart12 (not visible inFIG. 1). Although shown in implanted near the apex38, thelead36 may be implanted anywhere in theheart12 pacing therapy is needed. Ananchor mechanism44 is coupled to thelead36 via atether45 to secure thelead36 to theheart12 and to facilitate delivery of thelead36 into theheart12.
• Thepacing lead assembly36 andanchor mechanism44 may be implanted in theheart12 with a delivery instrument and according to methods described in the above-identified application “Myocardial Lead Attachment System”. Briefly, the delivery instrument andanchor mechanism44 are advanced through theheart12, forming a tract through the myocardium32 (not visible inFIG. 1). Theanchor mechanism44 is deployed on a surface of theheart12 so that thetether45 extends longitudinally through the tract. Following implantation of theanchor mechanism44, thetether45 is threaded through thelead36 and thelead36 is advanced over thetether45 into themyocardium32. Thetether45 is then tensioned and attached to thelead36 to secure thelead36 in place within themyocardium32. This structure results in a locally-stable myocardial implant.
• Optionally, theanchor mechanism44 may be implanted without the aid of a delivery instrument as is described above, but rather with a curved suture needle. The proximal end of thetether45 is attached to the needle, either directly or to a short length of suture attached to the needle. The needle is used to pierce theepicardium28, is pushed through themyocardium32 and drawn back through theepicardium28, pulling thetether45 through themyocardium32. Thetether45 is cut from the needle and tensioned to bring theanchor mechanism44 in contact with theepicardium28. Thelead36 is threaded onto thetether45 and advanced over thetether45 as previously described.
• FIG. 2 is a sectional view of a distal portion of the myocardiallead attachment system10 according to one embodiment of the present invention. Themyocardial lead36 includes two electrodes, aproximal anode40aand adistal cathode40b.An outer insulatingsheath46 is formed around thelead36 and protects a pair of coiledconductive members48aand48bcoupled to theanode40aandcathode40b,respectively. A second inner insulatingsheath50 forms aninternal lumen43 for receiving thetether45. Amarker band52 is optionally formed on the outer insulatingsheath46.
• Thelead36 includes a taperedtip54 positioned distal to thedistal region42 of thelead36. The taperedtip54 tapers from a first diameter a at aproximal end54ato a second diameter b, smaller than the first diameter a, at adistal end54b.In one embodiment, as shown inFIG. 2, the taperedtip54 is formed in the shape of a cone. In another embodiment, shown inFIG. 3, thetip54 is more rounded and is formed in the shape of a bullet. A bore56 extends through thetip54 in communication with thelumen43 for receiving thetether45.
• As thelead36 is advanced over thetether45 through the during insertion, the taperedtip54 does not cut through themyocardial tissue32, but rather dissects or dilates the tissue. The taperedtip54 provides a streamlined leading edge to thelead36, reducing trauma to themyocardium32. According to one embodiment, the diameter a of theproximal end54ais greater than a diameter of thelead36. Such atip54 gently dilates or expand the tract to facilitate advancement of thelead36. According to other embodiments, thetip54 has any shape having rounded edges and a streamlined shape chosen to reduce trauma to themyocardium32 during insertion.
• Prior to lead implantation, thetip54 may be selected from a plurality of tips having differing shapes based on the physiology of theheart12. Where theepicardium28 and orpericardium33 are generally undisturbed and in relatively healthy condition, the more bullet shaped tip of the embodiment shown inFIG. 3 is sufficient to facilitate advancement of thelead36. However, sometimes the epicardium28 and/orpericardium33 have been damaged, either by disease or previous trauma, resulting in the presence of tough adhesions or scar tissue. The more pointed cone shapedtip54 of the embodiment shown inFIG. 2 may be required to effectively traverse such adhesions or scar tissue. Prior to inserting thelead36, the surgeon may evaluate the implant site and select anappropriate tip54, i.e. pointed or blunt, as deemed necessary to pierce theepicardium28 and orpericardium33 and dilate the tract through theheart12 to facilitate insertion of thelead36.
• According to one embodiment, as shown inFIGS. 2 and 3, the taperedtip54 is configured to securely couple with the bluntdistal tip42 of thelead36. According to one embodiment, the diameter a of theproximal end54aof thetip54 is sized to receive thedistal tip42 of thelead36. According to other embodiments, thetip54 anddistal tip42 of thelead36 are provided with complementary threads for rotational coupling, or are provided with a complementary interlock or other structure for coupling.
• FIG. 4 shows another embodiment, in which the taperedtip54 is positioned adjacent to thedistal tip42 of thepacing lead36 without securely coupling to thelead36. The taperedtip54 rides along thetether45 in front of thelead36 to facilitate thelead36 in passing through themyocardium32. Atip54 according to the present embodiment may be used in conjunction with any such commercially available myocardial lead. According to another embodiment, the taperedtip54 is integrally formed at thedistal end42 of thelead36.
• FIG. 5 shows another embodiment in which the system is further provided with alock60 and lockhousing61 as is described in the above-identified application “Distal or Proximal Fixation of Over-the-Tether Myocardial Leads”. The tip bore56 has a diameter c greater than the diameter of thetether45 such that thetip54 easily passes over thetether45, but smaller than a diameter of thelock60 formed on thetether45. Thetip54 and lead36 are easily threaded over thetether45 and advanced along thetether45. When thetip54 contacts thelock60, thetip54 and lead36 are prevented from advancing further along thetether45. The taperedtip54 is used to prevent the lead36 from advancing over thelock60, and to provide spacing between the lead36 and theanchor mechanism44.
• According to another embodiment, thetip54 is made from a water-soluble material, such that thetip54 will dissolve upon placement within themyocardium32. Thetip54 may be made from any biocompatible, water-soluble material known in the art, such as a sugar. In one embodiment, thetip54 is made from mannitol. In another embodiment, thetip54 is made from polyethylene glycol (“PEG”). The molecular weight of the PEG can be selected to achieve a desired dissolution time of the taperedtip54. In yet another embodiment, additives known in the art are used to further control the dissolution time. According to another embodiment, thetip54 is made of an ablatable material.
• Adissolvable tip54 reduces the amount of foreign matter located in theheart12 following dissolution. This may reduce irritation in theheart12, as well as the formation of scar tissue. Addition of thetip54 does not increase the overall size of thelead36 chronically implanted in theheart12. Following dissolution of thetip54, thelead36 may be advanced over thelock60 to mate thelock60 with thelock housing61. In addition, the dissolved portion of the dissolvingtip54 provides a lubricating coating or film within the tract to further facilitate passage of thelead36.
• FIGS. 6A and 6B show another embodiment of thelead36, in which afixation mechanism62 is provided at thedistal tip42 of thelead36. Such afixation mechanism62 facilitates fixation of thelead36 tomyocardial tissue32. The above-identified application “Myocardial Lead with Fixation Mechanism” describes various fixation mechanisms suitable for use with a lead36 according to the present embodiment. The taperedtip54 is dissolvable as previously described and is configured to mate with thefixation mechanism62. According to one embodiment, thefixation mechanism62 is received in the tip bore56.
• Throughout insertion of thelead36 into theheart12, the taperedtip54 facilitates passage of thelead36 through the tract and masks thefixation mechanism62, which may include sharp edges or points. Upon dissolution of thetip54, thefixation mechanism62 is revealed and operable to retain thelead36 in a stable position. According to one embodiment, thefixation mechanism62 is retained in the tip bore56 in a first collapsed or retracted configuration, as is shown inFIG. 6A. Following dissolution of thetip54, thefixation mechanism62 deploys to a second expanded configuration, as is shown inFIG. 6B.
• According to another embodiment, thetip54 contains a pharmaceutical additive to treat implant trauma. Such an additive may be provided to reduce myocardial irritation or inflammation. This pharmaceutical additive may administer a “bolus” therapeutic agent to treat the implant trauma. In one embodiment, thetip54 is made of a dissolvable material as described above but which also includes a steroid (or other therapeutic drug) released as thetip54 dissolves. According to another embodiment, thetip54 is formed of a material provided with a coating that is drug eluting. Thetip54 may be chosen to have an appropriate amount of steroid (or other therapeutic drug) for a particular situation.
• In one embodiment, pharmaceutical additives as previously described are provided on other portions of thelead36 in addition to or instead of thetip54. In one embodiment, the drug eluting feature is provided as one or more discrete steroid/polymeric rings orcollars64 positioned on thelead36 to contact themyocardium32 upon implantation and anchoring (SeeFIG. 2). In another embodiment, the implanted portion of thelead20 is coated with a drug (e.g., steroid) eluting coating, such as a paint stripe (not shown). In another embodiment, shown inFIG. 7, a polymericlead body tubing66 may be fashioned from a steroid-loaded polymer composite. In each of these embodiments, a therapeutic amount of steroid is included on the implanted portion of thelead36.
• Various controlled-release techniques known in the art may be incorporated into these embodiments to deliver the therapeutic drug in the right amount and with the right time distribution.
• 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 (26)

1. A lead for use in connection with a myocardial lead attachment system of the type having an anchor for engaging the heart and a tether extending from the anchor, the lead including:

a lead body having a proximal end, a distal end and a lumen for accepting the tether; and

a tapered tip separate from the lead and positioned adjacent the distal end of the lead body, wherein the tip has a longitudinal through-hole for accepting the tether.

2. The lead ofclaim 1 wherein the tip is coupled to the distal end of the lead body.

3. The lead ofclaim 1 wherein the tip is free from fixed connection to the lead.

4. The lead ofclaim 1 wherein the tip has a reduced diameter in a direction from a proximal end to a distal end to reduce trauma to the heart as the lead is advanced through the myocardium.

5. The lead ofclaim 4 wherein the tip is cone shaped.

6. The lead ofclaim 4 wherein the tip is bullet shaped.

7. The lead ofclaim 1 wherein the tip is made from a dissolvable material.

8. The lead ofclaim 7 wherein the tip is formed from a water-soluble material.

9. The lead ofclaim 7 wherein the tip is formed from one of sugar, mannitol or polyethylene glycol.

10. The lead ofclaim 7 wherein a period of time necessary to dissolve the tip is less than a period of time in which scar tissue forms about the tip.

11. The lead ofclaim 7 further comprising a fixation mechanism coupled to the distal end of the lead, wherein the tip has an opening to receive the fixation mechanism and retain the fixation mechanism in a retracted configuration and upon dissolution of the tip the fixation mechanism deploys to an expanded configuration.

12. The lead ofclaim 7 wherein the tip includes a therapeutic drug for release as the tip dissolves.

13. The lead ofclaim 12 wherein the therapeutic drug is a steroid.

14. The lead ofclaim 1 wherein the tip is formed from a therapeutic drug-eluting material.

15. The lead ofclaim 14 wherein the drug is a steroid.

16. The lead ofclaim 1, further comprising a therapeutic drug attached to an outer surface of a portion of the lead body.

17. The lead ofclaim 16 wherein the therapeutic drug is a steroid.

18. The lead ofclaim 16 wherein the drug is attached onto an implanted portion of the lead.

19. The lead ofclaim 1 wherein the tip is formed from an ablatable material.

20. The lead ofclaim 1 further comprising:

a lock housing on the lead; and

a lock formed on a distal end of the tether and lock having a first diameter, wherein the tip through-hole has an internal diameter smaller than the lock first diameter.

21. A method of implanting a myocardial lead, the method comprising:

advancing an anchor mechanism coupled to a distal end of a tether through the myocardium to an implant site;

selecting an appropriate dilating tip having an internal through-hole;

threading the tip and lead onto the tether such that the tip is distal to the lead; and

advancing the tip and lead over the tether to the implant site.

22. The method ofclaim 21 further comprising coupling the tip to a distal end of the lead.

23. The method ofclaim 21 further comprising allowing the tip to dissolve.

24. The method ofclaim 23 wherein threading the tip and lead onto the tether further comprises inserting a fixation mechanism coupled to a distal end of the lead into an opening in the tip in a retracted configuration and dissolving the tip further includes allowing the fixation mechanism to deploy to an expanded configuration.

25. The method ofclaim 23 further comprising releasing a therapeutic drug from the tip as the tip dissolves.

26. A method of implanting a lead into a myocardium of a heart, the method comprising:

attaching a proximal end of an anchor mechanism and tether arrangement to a needle;

advancing the needle through the heart at least until the proximal end of the tether45 exits the heart;

detaching the needle from the tether;

tensioning the proximal end of the tether to cause the anchor mechanism to engage the heart; and

advancing a lead over the tether into the heart.

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