Patent Description:
Implantable medical devices, for example cardiac pacemakers and defibrillators, often include elongate medical electrical leads having one or more electrodes to sense electrical activity and deliver therapeutic stimulation. With the advent of left ventricular pacing to alleviate heart failure, leads have been advanced into the coronary veins in order to position the electrodes of the leads at left ventricular pacing sites, typically located in proximity to the base of the left ventricle. Although a variety of left ventricular pacing leads, along with methods for implanting such leads, have been developed, there is still a need for a lead including features that facilitate delivery to, and fixation at, sites in the coronary vasculature.

Numerous types of medical electrical leads can be adapted for placement in the coronary vasculature. Exemplary active fixation leads include <CIT>, <CIT>. Shaped leads can also be adapted for placement in the coronary vasculature. Exemplary shaped leads or catheters include <CIT>, <CIT>, <CIT>, issued to Chastain, et al. , <CIT>, <CIT>, <CIT>. The self-anchoring lead disclosed in Pianchi et al. includes radially spaced electrodes that are electrically active around their circumference, which can result in unwanted phrenic nerve stimulation. It is desirable to develop a coronary sinus lead that does not inadvertently cause phrenic nerve stimulation. Document <CIT> discloses an intravenous lead.

The present disclosure may comprise an improvement to the prior art leads as disclosed above. The disclosure is directed to an intravenous medical electrical lead that includes an elongated lead body. The elongated lead body comprises a length between a proximal end and a shaped distal end. The lead body defines a longitudinal axis extending between the proximal end and the shaped distal end. The lead body includes a set of electrodes radially spaced apart. Each electrode includes an electrically active portion and an insulated portion at an outer circumference of the electrode. The lead body is further configured to move through a coronary vein while substantially retaining its shaped or curved distal end. The lead body may freely move longitudinally within a delivery catheter that guides the lead to myocardial tissue. If the lead body rotates within the tubular body of the delivery catheter, the lead body is configured to rotate back into a position such that the electrically active portion of a set of electrodes faces myocardial tissue when exiting the guide catheter while the insulated portion of the lead faces neural tissue such as the phrenic nerve.

In one or more embodiments, the lead disclosed herein includes a set of electrodes in which each electrically active portion is aligned along a first longitudinal plane while a second longitudinal plane diametrically opposed to the first longitudinal plane lacks electrically active electrodes or the electrodes are insulated. The lead disclosed herein operates in a manner similar to an automobile in that the masked or insulated side is like a passenger side while the driver side is the electrically active portion of the electrode which solely directs the electrical current toward the myocardium but not by merely blasting electrical stimuli <NUM> degrees around each electrode. The set of electrodes of the present disclosure is similar to fuel injection vehicles that achieve more miles per gallon by minimizing the amount of current that emanates from each electrode but directing the current towards the viable tissue. Limiting the sweep of the electrical stimuli emanating from each electrode also avoids phrenic nerve stimulation.

Moreover, the medical electrical lead disclosed herein is able to achieve lower pacing thresholds to capture (i.e. evoke a response) cardiac tissue, which means less energy must be expended by the implantable medical device. Additionally, the lead results in higher pacing impedance due to use of electrodes with a decreased surface area. A higher pacing impedance decreases the current drain on the implantable medical device. Decreased current drain and energy consumption may increase the life of the implantable medical device.

The following drawings are illustrative of particular embodiments of the present disclosure and therefore do not limit the scope of the disclosure. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the present disclosure will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements.

The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the following description provides practical illustrations for implementing exemplary embodiments of the present invention. Constructions, materials, dimensions, and manufacturing processes suitable for making embodiments of the present are known to those of skill in the field of the invention.

<FIG> is a plan view of an exemplary intravenous medical electrical lead <NUM> connected through to a guide catheter <NUM> such as the ATTAIN CATHETER® developed and sold by Medtronic, Inc. of Minneapolis, Minnesota. Lead <NUM> is configured to deliver electrical stimulation to tissue (e.g. ventricular cardiac pacing) and/or sense signals from the tissue. Lead <NUM> includes proximal end and a distal end <NUM> with a lead body <NUM> therebetween that generally defines a longitudinal axis. At the proximal end is located an in-line bipolar connector assembly <NUM>. Distal end <NUM>, which includes set of electrodes 104a-d (e.g. ring electrodes, directional electrodes, electrodes shown in <FIG> etc.), can be configured in many different ways to ensure lead <NUM> stays in position to deliver electrical therapy to cardiac tissue. For example, lead <NUM> can be fixed in a location based upon a self-anchoring shape, other passive fixation means (e.g. adhesive etc.) and/or active fixation means (e.g. tines, screw, helix etc.). The self-anchoring shaped lead is configured to wrap or hug the curved-shaped heart.

In the illustrated preferred embodiment, substantially S-shaped (or wave-shaped) distal end <NUM> is configured such that it may freely move longitudinally within the guide catheter but if the distal end <NUM> rotates, the distal end <NUM> will naturally reposition itself such that the electrically active portion of a set of electrodes 104a-d faces myocardial tissue during and/or after exiting the guide catheter while the insulated portion of the lead faces neural tissue (e.g. phrenic nerve). The distal end of lead <NUM>, in its natural state (original shape or expanded configuration), shown in <FIG>, includes three curved areas forming angles Θ<NUM>, Θ<NUM>, and Θ<NUM> (also referred to as first, second, and third angles) at distal end 120A. In one or more embodiments in which lead <NUM> is in its expanded state or unrestrained by the tubular body of the guide catheter, first, second, and third angles comprise <NUM>°, <NUM>° and <NUM>° angles, respectively. Additionally, each radius for each of the first, second and third angles is measured from the center point of each arch. For example, r1, associated with Θ<NUM>, is about <NUM>-<NUM> (<NUM> inches), r2, associated with Θ<NUM>, is about <NUM>-<NUM> (<NUM> inches), and r3, associated with Θ<NUM>, is about <NUM>-<NUM> (<NUM> inches). The length of shaped lead <NUM> that is directly proximal to r1 is about <NUM> (<NUM> inches). The length of the liner that extends over first angle Θ<NUM> is about (I<NUM>) <NUM> (<NUM> inches), second angle Θ<NUM> is about (I<NUM>) <NUM> (<NUM> inches), and third angle Θ<NUM> is about (I<NUM>) <NUM> (<NUM> inches).

Each curved area is formed and maintained by creating a polymeric liner or jacket that has a durometer of about 30D to about 50D. Exemplary liners that can be used in conjunction with the present disclosure are shown and described with respect to <CIT>, <CIT>, and assigned to the assignee of the present invention. ATTAIN PERFORMA™ Model <NUM> quadripolar lead is another exemplary insulative material that can be used. In one or more embodiments, the curved or shaped polymeric liner exhibits the same or about the same stiffness as the generally linear areas of the remaining portion of the liner for the lead body <NUM>. The curve(s) in the lead can be thermoformed using known techniques. Shaped lead <NUM> can be thermoset in an oven at <NUM>,°C (<NUM>°F) for less than <NUM> minutes.

In an alternate embodiment shown in <FIG>, the curved distal end 120B can include two curves having angles β<NUM> and β<NUM>. β<NUM> can range from about <NUM> to about <NUM> degrees. β<NUM> can range from about <NUM> to about <NUM> degrees.

In yet another embodiment shown in <FIG>, a lead distal end 120C can employ a single sweep curve having an angle Φ of about <NUM> degrees to about <NUM> degrees from the center line (i.e. center of the lead body) or longitudinal axis <NUM> of the lead body <NUM>. In still yet another embodiment shown in <FIG>, the distal end <NUM> is substantially J-shaped. J-shaped lead <NUM> includes an electrically active portion of electrodes on one longitudinal side of the lead <NUM> and an insulated portion (or lacks electrodes) on the other diametrically opposed longitudinal side of the lead <NUM>, which is placed in proximity of neural tissue.

Lead body <NUM> has a proximal portion, to which a connector module <NUM> is coupled thereto as shown in <FIG>. Examples of connector modules may be seen with respect to <CIT>, <CIT>, and assigned to the assignee of the present invention. Connector module <NUM>, as illustrated, takes the form of an IS-<NUM> bipolar connecter, but any appropriate connector mechanism may be substituted. Connector module <NUM> electrically couples a proximal end of a lead <NUM> to various internal electrical components of implantable medical device <NUM>. Lead body <NUM> is formed by an insulative sheath or liner of a biocompatible polymer surrounding internal metallic conductors. Examples of means to insulate conductors and/or lead construction may be seen with respect to <CIT>, <CIT>, and assigned to the assignee of the present invention.

The conductors extend from electrodes 104a-d to connector <NUM>, coupling the electrodes 104a-d to contacts in-line bipolar connector <NUM> in a conventional fashion. Anchoring sleeve <NUM> is used in a conventional fashion to stabilize the lead and seal the venous insertion site.

Electrodes 104a-d can take the form of ring and barrel shaped electrodes, respectively, provided with ring-shaped or other shaped steroid eluting MCRD's as described in <CIT>. Other known electrode designs may of course be substituted. Each electrode is configured to have a smaller electrically active surface area to attain higher impedance compared to conventional electrodes. For example, the electrically active surface area of electrode 104a-d shown in <FIG> is about <NUM> square millimeters (mm<NUM>) out of a total surface area of <NUM><NUM>, which is equal or slightly less than half the surface area of conventional ring electrodes of <NUM><NUM>. In one or more embodiments, the electrodes 104a-d are either machined or made from a mold to form the exemplary shapes shown in <FIG>.

Referring to <FIG>, a non-conductive portion <NUM> is positioned over or coupled to the outer surface of each ring electrode 104a-d in order to prevent electrical stimuli emanating from a portion of each electrode. To limit the range of electrical stimuli from the active portion of the electrode 104a-d, insulated portion <NUM> extends along the outer circumference and the longitudinal length of the electrode <NUM>. For example, insulated portion <NUM> can extend about the length and width of the electrode along one side of the lead. Insulated portion <NUM> partially surrounds electrode 104a-d in the range of about <NUM> degrees to about <NUM> degrees. Exemplary thickness of polymer (e.g. urethane, urethane adhesive etc.) over a portion of the outer circumference of the electrode can range from about <NUM> (<NUM> inches) to about <NUM> ( <NUM> inches). Since the insulated portion <NUM> covers part of electrode 104a-d, the electrical stimuli emanates solely from the electrode's bare or uninsulated portion (also referred to as the active portion) shown in <FIG>. Referring to <FIG>, electrical stimuli can be delivered in the range of up to <NUM> degrees, referred to as γ, and along the length and/or width of the active portion of electrode 104a-d. Electrical stimuli does not conduct through non-conductive portion <NUM> shown in <FIG> which prevents electrical stimuli being delivered of up to <NUM> degrees around the electrode <NUM>. In another embodiment, the electrical stimuli can extend around the active portion (i.e. bare or uninsulated portion) of the electrode in the range of <NUM> degrees up to <NUM> degrees. In this latter example, electrical stimuli does not conduct through non-conductive portion <NUM> (i.e. up to <NUM> degrees). In yet another embodiment, the electrical stimuli can extend around the active portion of the electrode in the range of <NUM> degrees to about <NUM> degrees.

In one or more embodiments, a non-conductive mechanical mechanism, such as a housing, can be used for securing and insulating the electrode 104a-d to the lead body. One exemplary non-conductive electrode housing <NUM> is shown in <FIG> comprising a polymer exhibiting a durometer ranging from about 30D to about 50D or 55D. The electrode housing <NUM> is substantially cylindrical in shape with a first end <NUM> configured to mate with the electrode 104a-d and a second end <NUM> of base portion <NUM> seated longitudinally in the lead body, as shown in <FIG>.

Referring to <FIG>, housing <NUM> extends a total length of L1, which comprises lengths L2, L3, L4 and L5. The base portion <NUM> includes inner and outer diameters D1, D2 respectively and extends a length L2. D1 is about <NUM> (<NUM> inches) and D2 is about <NUM> (<NUM> inches). The length L2 of base <NUM> is about <NUM> (<NUM> inches).

Referring to <FIG>, the electrode receptacle portion <NUM> of housing <NUM> has a length comprising lengths L3, L4, and L5, which is about <NUM> (<NUM> inches). The electrode receptacle portion <NUM> includes inner and outer diameters D3, D4, respectively and D5 as shown in <FIG>. D3 is about <NUM> (<NUM> inches) while D4 is about <NUM> (<NUM> inches). Bore <NUM> has a diameter D5, configured to receive the conductor, which is about <NUM> (<NUM> inches) and extends about L7 or about <NUM> (<NUM> inches).

The outer circumference or surface <NUM> of housing <NUM> includes one or more one or more protrusions <NUM>, flange or rails configured to engage with a guide aid <NUM> of a raised electrode <NUM> shown in <FIG>. Housing <NUM> is formed by injection molding or any other suitable thermoforming process. A polymer such as polyurethane can be used in a mold formed to produce housing <NUM> or introduced over the electrode(s).

Guide aid <NUM> can be consecutive L-shapes (or substantially L-shaped) protrusions or a set of steps that extend longitudinally from a first end 113a to a second end 113b. Referring to <FIG>, lip <NUM> (also referred to as a protrusion) engages with corresponding protrusion <NUM> of housing <NUM> such that electrode ends 115a and 115B correspondingly engage with housing ends 170A and 170B. Referring to <FIG>, angle Ω in the range of <NUM> degrees exists between housing ends 170A and 170B thereby assisting in forming a more secure engagement between housing <NUM> and electrode <NUM> since protrusion partially extends over lip end 115a. Simultaneous to electrode lip <NUM> engaging housing protrusion <NUM>, electrode protrusion <NUM> at ends 117C and 117D correspondingly engage with housing protrusion <NUM> at ends 167C and 167D. Referring to <FIG>, the inner surface <NUM> of the electrode <NUM> is configured to mate with an elongated conductor extending from the lead body while electrode inner surface <NUM> mates with the outer surface <NUM> of housing <NUM>.

Raised electrode portion <NUM>, shown in <FIG>, does not have a direct engagement with housing160. Instead, the raised electrode portion <NUM> protrudes away electrode protrusion <NUM> and extends beyond lead body to allow the raised electrode portion <NUM> to more easily contact tissue.

Electrode <NUM> is slid proximally along the inner protrusions or rails <NUM> of housing <NUM> until a distal surface of the electrode <NUM> contacts a distal inner surface <NUM> of housing <NUM>. Electrode <NUM> is optionally retained in this position by means of engaging a short rail (not shown), extending from the inner surface of housing <NUM>, with a groove (not shown) at the distal end of the electrode <NUM>. After the electrode is fully engaged with housing <NUM>, the electrode assembly <NUM> is connected to the conductor. The conductor is placed in groove <NUM> and can be welded or crimped to the electrode using conventional means. The tubing or liner <NUM> can then be introduced over base <NUM> and end <NUM> shown in <FIG>. The tubing or liner <NUM> of the lead body <NUM> surrounds the outer circumference of base <NUM> from second end <NUM> and extends to surface <NUM>. Additionally, the tubing or liner <NUM> surrounds or is introduced over surfaces <NUM> and <NUM> and extends from surface <NUM> to first end <NUM>.

Numerous non-conductive materials can be used to form electrode housing <NUM>. For example, in one or more embodiments, a polymer (e.g. urethane, urethane adhesive etc.) exhibiting a durometer ranging from about 30D to about 35D can be used to form housing <NUM>. In one or more other embodiments, a polymer (e.g. urethane, urethane adhesive etc.) exhibiting a durometer ranging from about 35D to about 40D can be used to form housing <NUM>. In one or more other embodiments, a polymer (e.g. urethane, urethane adhesive etc.) exhibiting a durometer ranging from about 40D to about 45D can be used to form housing <NUM>. In one or more other embodiments, a polymer (e.g. urethane, urethane adhesive etc.) exhibiting a durometer ranging from about 45D to about 50D can be used to form housing <NUM>. In one or more other embodiments, a polymer (e.g. urethane, urethane adhesive etc.) exhibiting a durometer ranging from about 50D to about 55D can be used to form housing <NUM>. Additionally, any combination of polymers as listed above can be used to form housing <NUM>. Numerous methods exist for placing lead <NUM> near and/or into excitable tissue (e.g. cardiac tissue such as myocardial tissue). One such method <NUM>, depicted in <FIG>, describes lead placement corresponding to the positioning of the lead <NUM> as illustrated in <FIG>.

A guide catheter is used to place lead <NUM> in a position such that the active portion of the electrodes face myocardial tissue while the insulated portion of the electrodes face neural tissue (e.g. phrenic nerve). The guide catheter comprises a tubular body with a distal portion and a proximal portion for receiving the lead <NUM>. A lead delivery device (e.g. stylet, guide wire, hybrid guidewire/stylet etc.), such as the ATTAIN HYBRID®, is inserted into an aperture at a proximal end of lead <NUM> that leads directly into a lumen configured to receive the lead delivery device. Lead <NUM> is then inserted directly through an integrated valve of a guide catheter such as Medtronic's ATTAIN CATHETER® and passes through a lumen that is disposed from a proximal to distal end of the tubular body. The guide wire is introduced into a lumen of lead <NUM> by passing the guidewire through a body opening. One embodiment for steering lead <NUM> to the correct position along the coronary sinus involves the guidewire extending through a distal opening of the tubular body of lead <NUM>. Another embodiment for steering lead <NUM> to the correct position involves the stylet extending to a closed distal end of the tubular body of lead <NUM>. In addition to steering the lead, stylets provide increased rigidity to lead <NUM> in order to screw in the lead <NUM> into cardiac tissue.

The curved or shaped lead <NUM> is movable between a compact configuration while within the tubular body of the guide catheter and expands into an expanded configuration after the curved distal portion of the lead <NUM> exits the tubular body of the guide catheter. In one or more embodiments, lead <NUM> can be attached to cardiac tissue using a side helix, as shown and described in <CIT> Alternatively, a helical tip may be used at the distal end of lead <NUM>.

Lead <NUM> is introduced into the vascular system (step <NUM>, <FIG>) by any conventional technique. It is desirable, however, that the physician insert lead <NUM> such that the active portion of electrodes 104a-d face in a downward direction of the guide catheter when looking at the top view of the heart as shown in <FIG>. The lead <NUM> is then moved into the vasculature (e.g. coronary venous system etc.) to a desired location, for example by advancing the lead body <NUM> by means of the guide catheter. The coronary venous system includes the coronary sinus vein, great cardiac vein, middle cardiac vein, left posterior ventricular vein, and/or any other applicable cardiac veins. Lead <NUM> passes through the coronary sinus and into a cardiac vein extending therefrom, while substantially maintaining lead body <NUM> shape.

The lead <NUM> is then advanced further into the coronary venous system (Step <NUM>, <FIG> and <FIG>) around tricuspid valve <NUM>, the mitral valve <NUM>, the aortic valve <NUM> and the pulmonary valve <NUM> and generally travels in a downward path of the coronary vein along the naturally curved shape of the heart. This may be accomplished by passing the lead <NUM> through a guide catheter, or by advancing the lead <NUM> over a guidewire or by means of a stylet inserted into the lead <NUM>. A hybrid guidewire/stylet may also be used to place a lead <NUM> near or adjacent myocardial tissue. Any conventional mechanism for placing the lead <NUM> into and within the coronary venous system may be employed.

While in the coronary venous system, lead <NUM> cannot easily flip or rotate. Even if the lead <NUM> is flipped, twisted or rotated while moving through the guide catheter such that the insulated portion of the electrodes face the myocardium, the mechanical structure (e.g. angle of the curve(s) in distal end <NUM>) and/or the stiffness of curved distal end <NUM> in conjunction with the curved shaped heart causes a rotational force to rotate back to the configuration in which the electrically active portion of lead <NUM> faces and hugs myocardial tissue, as shown in <FIG>.

Lead <NUM> is located at an appropriate location, as determined by the physician (Step <NUM>, <FIG>). Thereafter, the lead body <NUM> may be moved (i.e. advanced and/or retracted) through the guide catheter until the electrodes 104a-d are located in a desirable position (Step <NUM>, <FIG>). Determination of the position for electrode location may be accomplished by any conventional method, such as pacing threshold testing and/or measurement of R-wave amplitudes. The guide catheter analyzer cable interface <NUM> is useful to perform this function. Alternatively or additionally, appropriate electrode locations may also be determined based upon determinations of hemodynamic characteristics of the heart as associated with stimulation of heart tissue at various electrode locations.

The shape of lead <NUM> and/or the weight of the polymer (e.g. housing <NUM> etc.) over the outer circumference of each electrode causes the lead <NUM> to exit the guide catheter such that the electrically active portion of the electrodes, disposed along a same longitudinal plane, are exposed to the intended preferred excitable tissue (e.g. myocardial tissue). In contrast, the insulated outer circumference of the electrodes face neural tissue (e.g. the phrenic nerve) towards pericardial surface.

Once the electrodes <NUM> are placed at the desired location, (Step <NUM>, <FIG>) any equipment not intended for long term implant, e.g. guide catheter, stylet, guidewire, etc. can be removed. Repositioning of the electrodes after implant may also be possible.

By using a lead <NUM> with a set of electrodes 104a-d that are configured to move through the coronary sinus in a manner such that the electrically active portion of the set of electrodes 104a-d finds its way to the myocardial tissue, pacing toward the myocardium becomes more efficient. Increased efficiency of pacing allows each electrode decrease or have a smaller surface area electrode for higher impedance. For example, a large surface area current electrode can be <NUM><NUM> surface electrodes while the present disclosure employs a <NUM><NUM> to <NUM><NUM>, which is slightly less or equal than half the surface area of conventional electrodes. The smaller surface area of the electrode raises the impedance which reduces the amount of current drain. The smaller electrode surface area located on lead <NUM>, directed 104a-d towards the myocardium, is believed to assist in achieving good thresholds (i.e. voltage required to capture the heart) and higher impedance.

<FIG> depict conceptual diagrams illustrating an exemplary therapy system <NUM> that may be used to deliver pacing therapy to a patient <NUM> using S-shaped lead <NUM>. The therapy system <NUM> may include an implantable medical device <NUM> (IMD), which may be coupled to leads <NUM>, <NUM>, <NUM>. The IMD <NUM> may be, e.g., an implantable pacemaker, cardioverter, and/or defibrillator, that provides electrical signals to the heart <NUM> of the patient <NUM> via electrodes coupled to one or more of the leads <NUM>, <NUM>, <NUM>.

The leads <NUM>, <NUM>, <NUM> extend into the heart <NUM> of the patient <NUM> to sense electrical activity of the heart <NUM> and/or to deliver electrical stimulation to the heart <NUM>. In the example shown in <FIG>, the right ventricular (RV) lead <NUM> extends through one or more veins (not shown), the superior vena cava (not shown), and the right atrium <NUM>, and into the right ventricle <NUM>. The left ventricular (LV) coronary sinus lead <NUM> extends through one or more veins, the vena cava, the right atrium <NUM>, and into the coronary sinus to a region adjacent to the free wall of the left ventricle <NUM> of the heart <NUM>. The right atrial (RA) lead <NUM> extends through one or more veins and the vena cava, and into the right atrium of the heart <NUM>.

The IMD <NUM> may sense, among other things, electrical signals attendant to the depolarization and repolarization of the heart <NUM> via electrodes coupled to at least one of the leads <NUM>, <NUM>, <NUM>. The IMD <NUM> may be configured to determine or identify effective electrodes located on the leads <NUM>, <NUM>, <NUM> using the exemplary methods and processes described herein. In some examples, the IMD <NUM> provides pacing therapy (e.g., pacing pulses) to the heart <NUM> based on the electrical signals sensed within the heart <NUM>. The IMD <NUM> may be operable to adjust one or more parameters associated with the pacing therapy such as, e.g., AV delay and other various timings, pulse wide, amplitude, voltage, burst length, etc. Further, the IMD <NUM> may be operable to use various electrode configurations to deliver pacing therapy, which may be unipolar, bipolar, quadripoloar, or further multipolar. For example, a multipolar lead may include several electrodes that can be used for delivering pacing therapy. Hence, a multipolar lead system may provide, or offer, multiple electrical vectors to pace from. A pacing vector may include at least one cathode, which may be at least one electrode located on at least one lead, and at least one anode, which may be at least one electrode located on at least one lead (e.g., the same lead, or a different lead) and/or on the casing, or can, of the IMD. While improvement in cardiac function as a result of the pacing therapy may primarily depend on the cathode, the electrical parameters like impedance, pacing threshold voltage, current drain, longevity, etc. may be more dependent on the pacing vector, which includes both the cathode and the anode. The IMD <NUM> may also provide defibrillation therapy and/or cardioversion therapy via electrodes located on at least one of the leads <NUM>, <NUM>, <NUM>. Further, the IMD <NUM> may detect arrhythmia of the heart <NUM>, such as fibrillation of the ventricles <NUM>, <NUM>, and deliver defibrillation therapy to the heart <NUM> in the form of electrical pulses. In some examples, IMD <NUM> may be programmed to deliver a progression of therapies, e.g., pulses with increasing energy levels, until a fibrillation of heart <NUM> is stopped.

<FIG> is a functional block diagram of one exemplary configuration of the IMD <NUM>. As shown, the IMD <NUM> may include a control module <NUM>, a therapy delivery module <NUM> (e.g., which may include a stimulation generator), a sensing module <NUM>, and a power source <NUM>.

The control module <NUM> may include a processor <NUM>, memory <NUM>, and a telemetry module <NUM>. The memory <NUM> may include computer-readable instructions that, when executed, e.g., by the processor <NUM>, cause the IMD <NUM> and/or the control module <NUM> to perform various functions attributed to the IMD <NUM> and/or the control module <NUM> described herein. Further, the memory <NUM> may include any volatile, non-volatile, magnetic, optical, and/or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, and/or any other digital media. An exemplary capture management module may be the left ventricular capture management (LVCM) module described in <CIT>.

The processor <NUM> of the control module <NUM> may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), and/or equivalent discrete or integrated logic circuitry. In some examples, the processor <NUM> may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, and/or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to the processor <NUM> herein may be embodied as software, firmware, hardware, or any combination thereof.

The control module <NUM> may be used to determine the effectiveness of the electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> using the exemplary methods and/or processes described herein according to a selected one or more programs, which may be stored in the memory <NUM>. Further, the control module <NUM> may control the therapy delivery module <NUM> to deliver therapy (e.g., electrical stimulation therapy such as pacing) to the heart <NUM> according to a selected one or more therapy programs, which may be stored in the memory <NUM>. More, specifically, the control module <NUM> (e.g., the processor <NUM>) may control various parameters of the electrical stimulus delivered by the therapy delivery module <NUM> such as, e.g., AV delays, pacing pulses with the amplitudes, pulse widths, frequency, or electrode polarities, etc., which may be specified by one or more selected therapy programs (e.g., AV delay adjustment programs, pacing therapy programs, pacing recovery programs, capture management programs, etc.). As shown, the therapy delivery module <NUM> is electrically coupled to electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, e.g., via conductors of the respective lead <NUM>, <NUM>, <NUM>, or, in the case of housing electrode <NUM>, via an electrical conductor disposed within housing <NUM> of IMD <NUM>. Therapy delivery module <NUM> may be configured to generate and deliver electrical stimulation therapy such as pacing therapy to the heart <NUM> using one or more of the electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

For example, therapy delivery module <NUM> may deliver pacing stimulus (e.g., pacing pulses) via ring electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> coupled to leads <NUM>, <NUM>, and <NUM>, respectively, and/or helical tip electrodes <NUM> and <NUM> of leads <NUM> and <NUM>. Further, for example, therapy delivery module <NUM> may deliver defibrillation shocks to heart <NUM> via at least two of electrodes <NUM>, <NUM>, <NUM>, <NUM>. In some examples, therapy delivery module <NUM> may be configured to deliver pacing, cardioversion, or defibrillation stimulation in the form of electrical pulses. In other examples, therapy delivery module <NUM> may be configured deliver one or more of these types of stimulation in the form of other signals, such as sine waves, square waves, and/or other substantially continuous time signals.

The IMD <NUM> may further include a switch module <NUM> and the control module <NUM> (e.g., the processor <NUM>) may use the switch module <NUM> to select, e.g., via a data/address bus, which of the available electrodes are used to deliver therapy such as pacing pulses for pacing therapy, or which of the available electrodes are used for sensing. The switch module <NUM> may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple the sensing module <NUM> and/or the therapy delivery module <NUM> to one or more selected electrodes. More specifically, the therapy delivery module <NUM> may include a plurality of pacing output circuits. Each pacing output circuit of the plurality of pacing output circuits may be selectively coupled, e.g., using the switch module <NUM>, to one or more of the electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> (e.g., a pair of electrodes for delivery of therapy to a pacing vector). In other words, each electrode can be selectively coupled to one of the pacing output circuits of the therapy delivery module using the switching module <NUM>.

The sensing module <NUM> is coupled (e.g., electrically coupled) to sensing apparatus, which may include, among additional sensing apparatus, the electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> to monitor electrical activity of the heart <NUM>, e.g., electrocardiogram (ECG)/electrogram (EGM) signals, etc. The ECG/EGM signals may be used to measure or monitor activation times (e.g., ventricular activations times, etc.), heart rate (HR), heart rate variability (HRV), heart rate turbulence (HRT), deceleration/acceleration capacity, deceleration sequence incidence, T-wave alternans (TWA), P-wave to P-wave intervals (also referred to as the P-P intervals or A-A intervals), R-wave to R-wave intervals (also referred to as the R-R intervals or V-V intervals), P-wave to QRS complex intervals (also referred to as the P-R intervals, A-V intervals, or P-Q intervals), QRS-complex morphology, ST segment (i.e., the segment that connects the QRS complex and the T-wave), T-wave changes, QT intervals, electrical vectors, etc..

The switch module <NUM> may be also be used with the sensing module <NUM> to select which of the available electrodes are used, or enabled, to, e.g., sense electrical activity of the patient's heart (e.g., one or more electrical vectors of the patient's heart using any combination of the electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>). Likewise, the switch module <NUM> may be also be used with the sensing module <NUM> to select which of the available electrodes are not to be used (e.g., disabled) to, e.g., sense electrical activity of the patient's heart (e.g., one or more electrical vectors of the patient's heart using any combination of the electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), etc. In some examples, the control module <NUM> may select the electrodes that function as sensing electrodes via the switch module within the sensing module <NUM>, e.g., by providing signals via a data/address bus.

In some examples, sensing module <NUM> includes a channel that includes an amplifier with a relatively wider pass band than the R-wave or P-wave amplifiers. Signals from the selected sensing electrodes may be provided to a multiplexer, and thereafter converted to multi-bit digital signals by an analog-to-digital converter for storage in memory <NUM>, e.g., as an electrogram (EGM). In some examples, the storage of such EGMs in memory <NUM> may be under the control of a direct memory access circuit.

In some examples, the control module <NUM> may operate as an interrupt driven device, and may be responsive to interrupts from pacer timing and control module, where the interrupts may correspond to the occurrences of sensed P-waves and R-waves and the generation of cardiac pacing pulses. Any necessary mathematical calculations may be performed by the processor <NUM> and any updating of the values or intervals controlled by the pacer timing and control module may take place following such interrupts. A portion of memory <NUM> may be configured as a plurality of recirculating buffers, capable of holding one or more series of measured intervals, which may be analyzed by, e.g., the processor <NUM> in response to the occurrence of a pace or sense interrupt to determine whether the patient's heart <NUM> is presently exhibiting atrial or ventricular tachyarrhythmia.

The telemetry module <NUM> of the control module <NUM> may include any suitable hardware, firmware, software, or any combination thereof for communicating with another device, such as a programmer. For example, under the control of the processor <NUM>, the telemetry module <NUM> may receive downlink telemetry from and send uplink telemetry to a programmer with the aid of an antenna, which may be internal and/or external. The processor <NUM> may provide the data to be uplinked to a programmer and the control signals for the telemetry circuit within the telemetry module <NUM>, e.g., via an address/data bus. In some examples, the telemetry module <NUM> may provide received data to the processor <NUM> via a multiplexer.

The various components of the IMD <NUM> are further coupled to a power source <NUM>, which may include a rechargeable or non-rechargeable battery. A non-rechargeable battery may be selected to last for several years, while a rechargeable battery may be inductively charged from an external device, e.g., on a daily or weekly basis.

<FIG> is another embodiment of a functional block diagram for IMD <NUM>. <FIG> depicts bipolar RA lead <NUM>, bipolar RV lead <NUM>, and bipolar LV CS lead <NUM> without the LA CS pace/sense electrodes and coupled with an implantable pulse generator (IPG) circuit <NUM> having programmable modes and parameters of a bi-ventricular DDD/R type known in the pacing art. In turn, the sensor signal processing circuit <NUM> indirectly couples to the timing circuit <NUM> and via data and control bus to microcomputer circuitry <NUM>. The IPG circuit <NUM> is illustrated in a functional block diagram divided generally into a microcomputer circuit <NUM> and a pacing circuit <NUM>. The pacing circuit <NUM> includes the digital controller/timer circuit <NUM>, the output amplifiers circuit <NUM>, the sense amplifiers circuit <NUM>, the RF telemetry transceiver <NUM>, the activity sensor circuit <NUM> as well as a number of other circuits and components described below.

Crystal oscillator circuit <NUM> provides the basic timing clock for the pacing circuit <NUM>, while battery <NUM> provides power. Power-on-reset circuit <NUM> responds to initial connection of the circuit to the battery for defining an initial operating condition and similarly, resets the operative state of the device in response to detection of a low battery condition. Reference mode circuit <NUM> generates stable voltage reference and currents for the analog circuits within the pacing circuit <NUM>, while analog to digital converter ADC and multiplexer circuit <NUM> digitizes analog signals and voltage to provide real time telemetry if a cardiac signals from sense amplifiers <NUM>, for uplink transmission via RF transmitter and receiver circuit <NUM>. Voltage reference and bias circuit <NUM>, ADC and multiplexer <NUM>, power-on-reset circuit <NUM> and crystal oscillator circuit <NUM> may correspond to any of those presently used in current marketed implantable cardiac pacemakers.

If the IPG is programmed to a rate responsive mode, the signals output by one or more physiologic sensor are employed as a rate control parameter (RCP) to derive a physiologic escape interval. For example, the escape interval is adjusted proportionally to the patient's activity level developed in the patient activity sensor (PAS) circuit <NUM> in the depicted, exemplary IPG circuit <NUM>. The patient activity sensor <NUM> is coupled to the IPG housing and may take the form of a piezoelectric crystal transducer as is well known in the art and its output signal is processed and used as the RCP. Sensor <NUM> generates electrical signals in response to sensed physical activity that are processed by activity circuit <NUM> and provided to digital controller/timer circuit <NUM>. Activity circuit <NUM> and associated sensor <NUM> may correspond to the circuitry disclosed in <CIT> and <CIT>. Similarly, the exemplary systems, apparatus, and methods described herein may be practiced in conjunction with alternate types of sensors such as oxygenation sensors, pressure sensors, pH sensors and respiration sensors, all well known for use in providing rate responsive pacing capabilities. Alternately, QT time may be used as the rate indicating parameter, in which case no extra sensor is required. Similarly, the exemplary embodiments described herein may also be practiced in non-rate responsive pacemakers.

Data transmission to and from the external programmer is accomplished by way of the telemetry antenna <NUM> and an associated RF transceiver <NUM>, which serves both to demodulate received downlink telemetry and to transmit uplink telemetry. Uplink telemetry capabilities will typically include the ability to transmit stored digital information, e.g. operating modes and parameters, EGM histograms, and other events, as well as real time EGMs of atrial and/or ventricular electrical activity and marker channel pulses indicating the occurrence of sensed and paced depolarizations in the atrium and ventricle, as are well known in the pacing art.

Microcomputer <NUM> contains a microprocessor <NUM> and associated system clock and on-processor RAM and ROM chips 82A and 82B, respectively. In addition, microcomputer circuit <NUM> includes a separate RAM/ROM chip 82C to provide additional memory capacity. Microprocessor <NUM> normally operates in a reduced power consumption mode and is interrupt driven. Microprocessor <NUM> is awakened in response to defined interrupt events, which may include A-TRIG, RV-TRIG, LV-TRIG signals generated by timers in digital timer/controller circuit <NUM> and A-EVENT, RV-EVENT, and LV-EVENT signals generated by sense amplifiers circuit <NUM>, among others. The specific values of the intervals and delays timed out by digital controller/timer circuit <NUM> are controlled by the microcomputer circuit <NUM> by way of data and control bus from programmed-in parameter values and operating modes. In addition, if programmed to operate as a rate responsive pacemaker, a timed interrupt, e.g., every cycle or every two seconds, may be provided in order to allow the microprocessor to analyze the activity sensor data and update the basic A-A, V-A, or V-V escape interval, as applicable. In addition, the microprocessor <NUM> may also serve to define variable, operative AV delay intervals and the energy delivered to each ventricle.

In one embodiment, microprocessor <NUM> is a custom microprocessor adapted to fetch and execute instructions stored in RAM/ROM unit <NUM> in a conventional manner. It is contemplated, however, that other implementations may be suitable to practice the present invention. For example, an off-the-shelf, commercially available microprocessor or microcontroller, or custom application-specific, hardwired logic, or state-machine type circuit may perform the functions of microprocessor <NUM>.

Digital controller/timer circuit <NUM> operates under the general control of the microcomputer <NUM> to control timing and other functions within the pacing circuit <NUM> and includes a set of timing and associated logic circuits of which certain ones pertinent to the present invention are depicted. The depicted timing circuits include URI/LRI timers 83A, V-V delay timer 83B, intrinsic interval timers 83C for timing elapsed V-EVENT to V-EVENT intervals or V-EVENT to A-EVENT intervals or the V-V conduction interval, escape interval timers 83D for timing A-A, V-A, and/or V-V pacing escape intervals, an AV delay interval timer 83E for timing the A-LVp delay (or A-RVp delay) from a preceding A-EVENT or A-TRIG, a post-ventricular timer 83F for timing post-ventricular time periods, and a date/time clock <NUM>.

The AV delay interval timer 83E is loaded with an appropriate delay interval for one ventricular chamber (e.g., either an A-RVp delay or an A-LVp delay as determined using known methods) to time-out starting from a preceding A-PACE or A-EVENT. The interval timer 83E triggers pacing stimulus delivery, and can be based on one or more prior cardiac cycles (or from a data set empirically derived for a given patient).

The post-event timer 83F time out the post-ventricular time period following an RV-EVENT or LV-EVENT or a RV-TRIG or LV-TRIG and post-atrial time periods following an A-EVENT or A-TRIG. The durations of the post-event time periods may also be selected as programmable parameters stored in the microcomputer <NUM>. The post-ventricular time periods include the PVARP, a post-atrial ventricular blanking period (PAVBP), a ventricular blanking period (VBP), a post-ventricular atrial blanking period (PVARP) and a ventricular refractory period (VRP) although other periods can be suitably defined depending, at least in part, on the operative circuitry employed in the pacing engine. The post-atrial time periods include an atrial refractory period (ARP) during which an A-EVENT is ignored for the purpose of resetting any AV delay, and an atrial blanking period (ABP) during which atrial sensing is disabled. It should be noted that the starting of the post-atrial time periods and the AV delays can be commenced substantially simultaneously with the start or end of each A-EVENT or A-TRIG or, in the latter case, upon the end of the A-PACE which may follow the A-TRIG. Similarly, the starting of the post-ventricular time periods and the V-A escape interval can be commenced substantially simultaneously with the start or end of the V-EVENT or V-TRIG or, in the latter case, upon the end of the V-PACE which may follow the V-TRIG. The microprocessor <NUM> also optionally calculates AV delays, post-ventricular time periods, and post-atrial time periods that vary with the sensor based escape interval established in response to the RCP(s) and/or with the intrinsic atrial rate.

The output amplifiers circuit <NUM> contains a RA pace pulse generator (and a LA pace pulse generator if LA pacing is provided), a RV pace pulse generator, and a LV pace pulse generator or corresponding to any of those presently employed in commercially marketed cardiac pacemakers providing atrial and ventricular pacing. In order to trigger generation of an RV-PACE or LV-PACE pulse, digital controller/timer circuit <NUM> generates the RV-TRIG signal at the time-out of the A-RVp delay (in the case of RV pre-excitation) or the LV-TRIG at the time-out of the A-LVp delay (in the case of LV pre-excitation) provided by AV delay interval timer 83E (or the V-V delay timer 83B). Similarly, digital controller/timer circuit <NUM> generates an RA-TRIG signal that triggers output of an RA-PACE pulse (or an LA-TRIG signal that triggers output of an LA-PACE pulse, if provided) at the end of the V-A escape interval timed by escape interval timers 83D.

The output amplifiers circuit <NUM> includes switching circuits for coupling selected pace electrode pairs from among the lead conductors and the IND_CAN electrode <NUM> to the RA pace pulse generator (and LA pace pulse generator if provided), RV pace pulse generator and LV pace pulse generator. Pace/sense electrode pair selection and control circuit <NUM> selects lead conductors and associated pace electrode pairs to be coupled with the atrial and ventricular output amplifiers within output amplifiers circuit <NUM> for accomplishing RA, LA, RV and LV pacing.

The sense amplifiers circuit <NUM> contains sense amplifiers corresponding to any of those presently employed in contemporary cardiac pacemakers for atrial and ventricular pacing and sensing. High impedance P-wave and R-wave sense amplifiers may be used to amplify a voltage difference signal that is generated across the sense electrode pairs by the passage of cardiac depolarization wavefronts. The high impedance sense amplifiers use high gain to amplify the low amplitude signals and rely on pass band filters, time domain filtering and amplitude threshold comparison to discriminate a P-wave or R-wave from background electrical noise. Digital controller/timer circuit <NUM> controls sensitivity settings of the atrial and ventricular sense amplifiers <NUM>.

The sense amplifiers are typically uncoupled from the sense electrodes during the blanking periods before, during, and after delivery of a pace pulse to any of the pace electrodes of the pacing system to avoid saturation of the sense amplifiers. The sense amplifiers circuit <NUM> includes blanking circuits for uncoupling the selected pairs of the lead conductors and the IND-CAN electrode <NUM> from the inputs of the RA sense amplifier (and LA sense amplifier if provided), RV sense amplifier and LV sense amplifier during the ABP, PVABP and VBP. The sense amplifiers circuit <NUM> also includes switching circuits for coupling selected sense electrode lead conductors and the IND-CAN electrode <NUM> to the RA sense amplifier (and LA sense amplifier if provided), RV sense amplifier and LV sense amplifier. Again, sense electrode selection and control circuit <NUM> selects conductors and associated sense electrode pairs to be coupled with the atrial and ventricular sense amplifiers within the output amplifiers circuit <NUM> and sense amplifiers circuit <NUM> for accomplishing RA, LA, RV and LV sensing along desired unipolar and bipolar sensing vectors.

Right atrial depolarizations or P-waves in the RA-SENSE signal that are sensed by the RA sense amplifier result in a RA-EVENT signal that is communicated to the digital controller/timer circuit <NUM>. Similarly, left atrial depolarizations or P-waves in the LA-SENSE signal that are sensed by the LA sense amplifier, if provided, result in a LA-EVENT signal that is communicated to the digital controller/timer circuit <NUM>. Ventricular depolarizations or R-waves in the RV-SENSE signal are sensed by a ventricular sense amplifier result in an RV-EVENT signal that is communicated to the digital controller/timer circuit <NUM>. Similarly, ventricular depolarizations or R-waves in the LV-SENSE signal are sensed by a ventricular sense amplifier result in an LV-EVENT signal that is communicated to the digital controller/timer circuit <NUM>. The RV-EVENT, LV-EVENT, and RA-EVENT, LA-SENSE signals may be refractory or non-refractory, and can inadvertently be triggered by electrical noise signals or aberrantly conducted depolarization waves rather than true R-waves or P-waves.

The techniques described in this disclosure, including those attributed to the IMD <NUM>, the computing apparatus <NUM>, and/or various constituent components, may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, various aspects of the techniques may be implemented within one or more processors, including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components, embodied in programmers, such as physician or patient programmers, stimulators, image processing devices, or other devices. The term "module," "processor," or "processing circuitry" may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry.

Many alternatives leads can employ the teaching disclosed herein. For example, alternative medical electrical leads can include active or passive fixation mechanisms (e.g. helix, tines, adhesive etc.). For example, <FIG> depicts a substantially J-shaped lead <NUM>. J-shaped lead <NUM> can include a set of electrodes 104a-d that are masked along a first longitudinal plane and the electrically active portion of electrodes along a second longitudinal plane that is diametrically opposed to the first longitudinal plane.

Additionally, while <FIG> illustrate the electrodes 104a-d as advancing through the coronary sinus, it should be understood that other locations in the heart's venous system may also be accessed using this lead. Electrode placement may alternatively be optimized for atrial stimulation and/or sensing. Alternatively, the lead may be useful in other vascular or non-vascular location within the body wherein the distance between a suitable fixation location and a desired electrode location may be variable.

Numerous alternatives exist to the embodiments disclosed herein. While non-conductive portion <NUM> can be a mechanical structure engaged with the electrode, non-conductive portion <NUM> can also be a polymer placed over the electrode. For example, one or more different embodiments can be directed to masking a ring electrode. Each ring electrode 104a-d can also be configured to be longitudinally aligned along an outer circumference of each electrode 104a-d.

Any technique can be used to apply the polymer to the outer circumference of the electrode 104a-d. For example, after lead <NUM> is manufactured, the polymer can be directly applied to the set of electrodes 104a-d along the same longitudinal plane while the remaining portion of the electrodes 104a-d are not covered with polymer and can conduct current to tissue. Alternatively, each electrode 104a-d can be individually masked and then assembled in a fashion such that each electrically active portion of each electrode 104a-d is aligned along a same longitudinal plane as another electrically active portion of an electrode while the masked portions of the electrodes 104a-d align along a different longitudinal plane. Application of the polymer can be performed automatically by a machine operation or manually by an operator using any available technique such as brushing polymer onto the surface of the electrode.

One or more embodiments relate to dimension D3 which is about <NUM> (<NUM> inches). With respect to <FIG>, dimension L7 can be about <NUM> (<NUM> inches). In one or more embodiments, L7 can be <NUM> (<NUM> inches). With respect to <FIG>, dimension <NUM> was stated as a summation of L3+L4+L5 which equaled <NUM> (<NUM> inches) but can also be <NUM> (<NUM> inches).

In another alternate embodiment, the one or more grooves are formed on the outer surface of electrode through use of placing molten metal into a mold that is either substantially ring-shaped mold (not shown) or a mold formed to produce the electrode disclosed herein.

Claim 1:
An intravenous lead comprising:
a lumen extending from a proximal end to a distal end, wherein a lead delivery device can be disposed into the lumen; and
an elongated lead body (<NUM>) comprising a length between a proximal end and a shaped distal end (<NUM>), the lead body defining a longitudinal axis extending between the proximal end and the shaped distal end, the lead body having an outer circumference and provided with a set of electrodes (104a-d) circumferentially spaced apart, each electrode having an electrically active portion and an insulated portion at an outer circumference, the lead body (<NUM>) further configured to move through a tubular body of a guide catheter while having a first shape that substantially retains its shaped non-linear distal end while the lead is disposed within the tubular body, and the shaped distal end expanding to a second shape or original shape upon exiting the tubular body of the guide catheter such that the electrically active portion of each electrode faces myocardial tissue while the insulated portion of each electrode faces a phrenic nerve of a patient, characterized in that, if the lead (<NUM>) is rotated such that the insulated portions face myocardial tissue, the mechanical structure and the stiffness of the shaped distal end (<NUM>) of the lead in conjunction with the curved shaped heart are configured to cause a rotational force to rotate back to the configuration in which the electrically active portions of the lead (<NUM>) face myocardial tissue .