High impedance electrode assembly

A lead having an electrode assembly has a high impedance electrode. The high impedance electrode includes a partially insulated sleeve electrode or a wire filament. The high impedance electrode includes an exposed surface of less than 1.2 mm2. One or more eluting drugs are disposed adjacent to the high impedance electrode.

FIELD OF THE INVENTION

The present invention relates generally to leads for conducting electrical signals to and from the heart. More particularly, it pertains to a high impedance electrode assembly for delivering electrical charges to and from the heart.

BACKGROUND OF THE INVENTION

Leads implanted in or about the heart have been used to reverse certain life threatening arrhythmias, or to stimulate contraction of the heart. Electrical energy is applied to the heart via the leads to return the heart to normal rhythm. Leads have also been used to sense in the atrium or ventricle of the heart and to deliver pacing pulses to the atrium or ventricle.

Cardiac pacing may be performed by the transvenous method or by leads implanted directly onto the epicardium. Permanent transvenous pacing is performed using a lead positioned within one or more chambers of the heart. A lead may be positioned in the ventricle or in the atrium through a subclavian vein, and the lead terminal pins are attached to a pacemaker which is implanted subcutaneously. The lead provides the electrical connection between the pulse generator and the heart tissue which is to be excited.

The pacemaker includes a power source for the electrical energy which is applied to the heart from the pacemaker. Since pulse generators are implanted subcutaneously within the patient, it is undesirable when excessive current drain is placed on the power source for the pacemaker. High stimulation thresholds can in result in excessive current drain from the power source. In addition, larger surface areas of electrodes require larger amounts of energy to deliver pacing pulses. A shorter battery life for a pacemaker also results increased number of medical procedures for the patient. The increased number of medical procedures result in increased risk and cost to the patient.

Accordingly, there is a need for a high impedance electrode for pacing and/or sensing the atrium and/or the ventricle. In addition, there is a need for an electrode which does not excessively drain the power source of a pacemaker.

SUMMARY OF THE INVENTION

A lead assembly includes a lead body which extends from a proximal end to a distal end. The lead body has at least one conductor and the body is defined in part by a circumference. At least one electrode is electrically coupled with the conductor, where the electrode comprises a wire filament disposed about the circumference of the lead body. The wire filament is bonded with the lead body. In one embodiment, a conductor coil is disposed within the lead body, where a portion of the conductor coil extends through the lead body and around the circumference of the lead body to form the wire filament disposed about the lead body.

In another embodiment, a lead assembly has a lead body which extends from a proximal end to a distal end and defined in part by a circumference. The lead body has a conductor coil, and an electrode assembly including at least one electrode electrically coupled with the conductor coil. The electrode comprises a conductive sleeve which is partially masked by the lead body.

The lead assembly further includes, in another embodiment, at least one drug elution collar adjacent to the electrode. In yet another embodiment, the lead assembly further includes a first drug elution collar and a second drug elution collar. The first drug elution collar and the second drug elution collar straddle the exposed electrode surface. In one embodiment, the first drug elution collar has a first drug therein, the second drug elution collar has a second drug therein, and the first drug is different than the second drug. The lead further comprises a porous member disposed on the lead body proximate to the electrode.

In yet another embodiment, the lead assembly includes an electrode having an exposed electrode surface, where the exposed electrode surface is offset from a surface of the lead body. Alternatively, the exposed electrode surface is flush with a surface of the lead body. The exposed electrode surface, in another embodiment, extends about the circumference of the lead body.

In another embodiment, a lead assembly includes a lead body which extends from a proximal end to a distal end. The lead body has a conductor coil and an electrode is electrically coupled with the conductor. The electrode has a high pacing impedance, where the electrode has a surface area less than about 1.2 mm2. In one embodiment, the electrode comprises a conductive sleeve partially masked by the lead body. Optionally, at least one drug elution collar is disposed adjacent to the electrode. The drug elution collar includes a first drug elution collar and a second drug elution collar, where each collar is disposed on opposite sides of the sleeve. In one embodiment, the first drug elution collar has a first drug which is different than a second drug of the second drug elution collar. The lead assembly, in another embodiment, further includes a porous member on the lead body proximate to the electrode.

In yet another embodiment, the lead assembly includes an electrode having an exposed electrode surface, where the exposed electrode surface is offset from a surface of the lead body. Alternatively, the exposed electrode surface is flush with a surface of the lead body. The exposed electrode surface, in another embodiment, extends about the circumference of the lead body. In another embodiment, a conductor coil is disposed within the lead body, where a portion of the conductor coil extends through the lead body and around the circumference of the lead body to form the wire filament disposed about the lead body. Optionally, the wire filament is bonded with the lead body.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1Aillustrates a single-pass lead100for delivering electrical pulses to stimulate a heart101and/or for receiving electrical pulses to monitor the heart101. The lead100extends from a distal end102to a proximal end104, and has an intermediate portion105therebetween. The distal end102is adapted for connection within a patient, the proximal end104has a terminal connector which electrically connects the various electrodes and conductors within the lead body to a pulse generator and signal sensor109. The pulse generator and signal sensor109contains electronics to sense various electrical signals of the heart and also produce current pulses for delivery to the heart101.

The lead100includes a lead body115, an elongate conductor116contained within the lead body115, and at least one electrode130coupled with the lead100. The at least one electrode130is electrically coupled with the elongate conductor116. The lead body115is covered with a biocompatible insulating material122, for instance silicone rubber. The elongate conductor116defines a lumen therein and thereby is adapted to receive a stiffening stylet that extends through the length of the lead100. The stylet is used to stiffen the lead100, and is manipulated to facilitate the insertion of the lead100into and through a vein and through an intracardiac valve to advance the distal end102of the lead100into, for example, the ventricle of the heart101. A stylet knob is coupled with the stylet for rotating the stylet, advancing the conductor into tissue of the heart, and for manipulating the lead100.

In one embodiment, as shown inFIG. 1B, the at least one electrode130is disposed proximate to the distal end102of the lead100. The distal end102of the lead100, in one embodiment, is disposed within a ventricle of a heart, and the at least one electrode130delivers ventricular therapy. The at least one electrode130comprises, in one embodiment, a pacing and/or sensing electrode. In yet another embodiment, the at least one electrode130is disposed at the intermediate portion105between the distal end102and the proximal end104of the lead100.

In another embodiment, a plurality of electrodes132are disposed on the lead100. The plurality of electrodes132comprise a first electrode160disposed at the distal end102of the lead, where the first electrode160provides ventricular therapy. The plurality of electrodes132further comprises a second electrode162and/or a third electrode164. The second and third electrodes162,164are positioned on the intermediate portion105of the lead100to provide atrial therapy, for example, when disposed within a heart. In yet another embodiment, a fourth electrode166is provided on the lead immediately proximal to the first electrode to provide additional ventricular therapy.

FIG. 2illustrates one embodiment of a lead200, which includes a lead body215, at least one electrode230, and an elongate conductor280electrically coupled with the at least one electrode230. The at least one electrode230is used for any or all of the electrodes discussed above. In one embodiment, the at least one electrode230comprises a sleeve electrode210positioned between insulated lead body sections216and218. The lead body sections216,218partially mask the sleeve electrode210, leaving an exposed electrode surface212which is lesser in surface area than the unmasked sleeve electrode210. In another embodiment, resistive material other than the lead body215is used to partially mask the sleeve electrode210. The exposed electrode surface212, in one embodiment, is flush with an outer surface of the lead body215.

The exposed electrode surface212has a significantly smaller surface area than the unmasked sleeve electrode210. The exposed electrode surface212, in yet another embodiment, extends about a circumference of the lead body. The impedance of the electrode230is controlled by the amount of lead body215which masks the electrode230. To achieve high impedance, the surface area of the exposed electrode surface212is reduced by the lead body215. In one embodiment, the surface area of exposed electrode surface212is less than about 1.2 mm2. In another embodiment, the surface area of exposed electrode surface212is 0.8 mm2-1.2 mm2. In yet another embodiment, the surface area of exposed electrode surface212is about 1 mm2.

In another embodiment, as shown inFIG. 3, the exposed electrode surface212is offset from the lead body215. The exposed electrode surface212, in yet another embodiment, extends about a circumference of the lead body. The impedance of the electrode230is controlled, in one embodiment, by the amount of lead body215which masks the electrode230. In one embodiment, the surface area of exposed electrode surface212is less than about 1.2 mm2. In another embodiment, the surface area of exposed electrode surface212is 0.8 mm2-1.2 mm2. In yet another embodiment, the surface area of exposed electrode surface212is about 1 mm2.

FIG. 4illustrates another embodiment of a lead400, which includes a lead body415, at least one electrode430, and an elongate conductor480electrically coupled with the at least one electrode430. The at least one electrode430is used for any or all of the electrodes discussed above. In one embodiment, the at least one electrode430comprises a wire filament432is disposed about the circumference of the lead body415. In one embodiment, the wire filament432is partially disposed about the circumference of the lead body415. The wire filament432is electrically coupled with the conductor480. In one embodiment, the wire filament432is formed by extending the conductor480through the lead415, and exposing a portion of the conductor480exterior to the lead body415. In another embodiment, the wire filament432is formed of a wire electrically coupled with the conductor480. The wire filament is coupled with the lead body415, in one embodiment, using fillets450.

FIG. 5illustrates one embodiment of a lead500, which includes a lead body515, at least one electrode530, and an elongate conductor580electrically coupled with the at least one electrode530. The at least one electrode530is used for any or all of the electrodes discussed above. In one embodiment, the at least one electrode530comprises a sleeve electrode510positioned between insulated lead body sections516and518. In addition, the at least one electrode530includes drug releasing sleeves540and542which partially mask the sleeve electrode510, leaving an exposed electrode surface512. It should be noted that one drug releasing sleeve would also be appropriate to use to partially mask the sleeve electrode510. The drug releasing sleeves540,542, in one embodiment, have an identical composition. One example of the composition of at least one drug sleeve is dexamethasone acetate in a simple silicone medical adhesive rubber binder. Alternatively, the drug releasing sleeves540,542contain different compositions.

The exposed electrode surface512, in one embodiment, has a significantly smaller surface area than the unmasked sleeve electrode510. The exposed electrode surface512, in yet another embodiment, extends about a circumference of the lead body. The impedance of the electrode530is controlled, in one embodiment, by the amount of lead body515which masks the electrode530and/or by the drug releasing sleeves540,542. In one embodiment, the surface area of exposed electrode surface512is less than about 1.2 mm2. In another embodiment, the surface area of exposed electrode surface512is 0.8 mm2-1.2 mm2. In yet another embodiment, the surface area of exposed electrode surface512is about 1 mm2. The at least one electrode530, in one embodiment, is disposed within an atrium of a heart to deliver atrial therapy.

FIG. 6illustrates yet another embodiment of a lead600, which includes a lead body615, at least one electrode630, and an elongate conductor680electrically coupled with the at least one electrode630. The at least one electrode630is used for any or all of the electrodes discussed above. In one embodiment, the at least one electrode630comprises a sleeve electrode610positioned between insulated lead body sections616and618. In addition, the at least one electrode630includes at least one drug releasing sleeve640which partially masks the sleeve electrode610, and leaves an exposed electrode surface612. One example of the composition of at least on drug sleeve is dexamethasone acetate in a simple silicone medical adhesive rubber binder. Disposed at a position opposite the exposed surface612is a porous lead body section642. The porous lead body section642allows for tissue ingrowth. The porous lead body section642is provided, in one embodiment, as a porous collar643coupled with the lead body615. In another embodiment, the porous collar643includes a drug eluting collar initially containing a water soluble medication, where the medication is released from a collar formed of inert porous binder material. Examples of medication to be used include, although are not limited to: steroid, dexamethasone sodium phosphate, dexamethasone acetate, dexamethasone, antibiotics, or anticoagulation active agents.

The exposed electrode surface612, in one embodiment, has a significantly smaller surface area than the unmasked sleeve electrode610. The exposed electrode surface612, in yet another embodiment, extends about a circumference of the lead body615. The impedance of the electrode630is controlled, in one embodiment, by the amount of lead body615and/or drug collar640which masks the electrode630. In one embodiment, the surface area of exposed electrode surface612is less than about 1.2 mm2. In another embodiment, the surface area of exposed electrode surface612is 0.8 mm2-1.2 mm2. In yet another embodiment, the surface area of exposed electrode surface612is about 1 mm2. The at least one electrode630, in one embodiment, is disposed within an atrium of a heart to deliver atrial therapy.

During use of the lead assembly shown inFIG. 1B, the first electrode160disposed at the distal end102of the lead provides ventricular pacing and/or sensing, and the second electrode162is disposed in the atrium. In one embodiment, the first electrode160is cathodic in polarity, and the second electrode162is anodic in polarity. In another embodiment, the second electrode162comprises a floating electrode. In yet another embodiment, the first electrode160is anodic in polarity and the second electrode is cathodic in polarity. The choice of polarity as described alters the effectiveness of the therapy delivered. For example, in a study using a wire filament for an atrial electrode, the bipolar pacing impedance of the lead was at least 708 Ω, and may be as high as 1000-1200 Ω. The higher pacing impedance provided by the lead described and shown in the figures is advantageous in the interest of increasing pulse generator longevity.

Advantageously, the above described lead provides dual chamber pacing therapy delivered by a single lead of simple design which is capable of the high impedance pacing and low threshold. The lead also allows for steroid elution. The high impedance features and the steroid elution increase the longevity of the pacing device since the current drain from the power source is reduced and stimulation thresholds are lowered. The lead uses smaller electrodes which stimulate smaller areas of tissue with high current density, resulting in less energy consumption.

It is to be understood that the above description is intended to be illustrative, and not restrictive. Although the use of the lead has been described for use in a cardiac pacing system, the lead could as well be applied to other types of body stimulating systems. It should be noted that features of the various above-described embodiments may be interchanged to form additional combinations. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.