Abstract: A leadless cardiac pacemaker comprises a housing, a plurality of electrodes coupled to an outer surface of the housing, and a pulse delivery system hermetically contained within the housing and electrically coupled to the electrode plurality, the pulse delivery system configured for sourcing energy internal to the housing, generating and delivering electrical pulses to the electrode plurality. The pacemaker further comprises an anti-unscrewing feature disposed on either a fixation device of the pacemaker or on the housing itself. The anti-unscrewing feature can be configured to prevent the fixation device from disengaging the wall of the heart.

Abstract: An implantable medical lead is disclosed herein wherein the lead employs a helical distal tip anchor having improved fixation capabilities. The implantable medical lead may include a body and a helical anchor. The body may include a distal end and a proximal end. The helical anchor may be at least one of extending and extendable from the distal end. The helical anchor may include at least one loop including first and second straight sides that intersect at a first corner.

Abstract: A medical implantable lead has a proximal end and a distal end, a biostable and biocompatible polymeric header, which is arranged at the distal end and has a first tubular portion, a helical fixation element located within the first tubular portion and being extendable from a distal end of the header, and a radiopaque ring. The header further has a second tubular portion, which is arranged coaxially of the first tubular portion and is attached to the first tubular portion at a distal end of the second tubular portion, while having a free proximal end. The tubular portions form a circumferential pocket, wherein the first tubular portion extends from the proximal end of the header at least to said distal end of the second tubular portion. The radiopaque ring is arranged around the first tubular portion and is received in the circumferential pocket.

Abstract: An implant tool for use with an endocardial or other implantable lead having an extendable/retractable active fixation tip includes a housing, a shaft rotatably supported by the housing, and a shaft rotation mechanism for rotating the shaft through a predetermined angular travel. The shaft includes a lead attachment portion for selectively coupling a lead to the shaft such that the lead is rotatable with the shaft. The implant tool may include a control tab slidably supported by the housing, wherein longitudinal movement of the control tab actuates the shaft rotation mechanism. The shaft rotation mechanism may include a gear train, an electric motor, a double acting spring mechanism, or a retractable tape wound around the shaft. The gear train includes an input member coupled to the control tab and an output gear coupled to the shaft. The input member meshes with an input gear supported by the housing.

Abstract: A bipolar electrode (1) that can be implanted is provided with at least two poles at its distal end, namely a cathode (4) and an anode (6) spaced apart therefrom. Further, an anchoring is provided at the distal end of the electrode (1), provided for example as a helical screw (5). The different poles are arranged on different shafts or tubes (3) and (7) displaceable in reference to each other, in which the exterior shaft or tube (7) first can be pushed over the anchor (5) in order to protect it during implantation. In the operational state, the poles are adjusted by a relative motion of the two shafts carrying them with regard to their relative positioning.

Abstract: A medical device that includes a lead having a lead body extending from a proximal end to a distal end, and a housing having a connector block for receiving the proximal end of the lead body. A fixation mechanism is positioned proximal to an electrode coil located at the distal end of the lead body, and a fixation member or a plurality of fixation members extend from the fixation mechanism from a fixation member proximal end to a fixation member distal end. The fixation members are advanceable from a first position corresponding to the fixation member distal end being positioned along the lead during subcutaneous placement of the lead, to a second position corresponding to the fixation member distal end being positioned away from the lead to fixedly engage the lead at a target site.

Abstract: An active fixation cardiac lead is disclosed that includes an elongated lead body having opposed proximal and distal end portions and an interior lumen that extends therethrough. A rotatable fixation element is operatively associated with the distal end portion of the lead body and a tubular torque-transmitting member extends through the interior lumen of the lead body. The tubular torque-transmitting member has a distal end connected to the fixation element and a proximal end connected to a rotatable actuator operatively associated with the proximal end portion of the lead body. Preferably, the rotatable actuator is part of a connector assembly that is operatively associated with the proximal end portion of the lead body.

Abstract: A method for implanting an active fixation medical lead is disclosed herein. The lead may include a lead body distal end, a tissue fixation helical anchor and a structure. The tissue fixation helical anchor may be coupled to the lead body distal end and include a distal tip. The structure may be coupled to the lead body distal end and include a structure distal end including a first radiopaque marker. The structure may be biased to project the structure distal end near the distal tip. When the tissue fixation helical anchor is progressively embedded in the cardiac tissue, the cardiac tissue progressively displaces the structure distal end proximally.

Abstract: An implantable medical electrical lead for electrical stimulation of body tissue that includes at least one shape memory polymer portion that has a first configuration and a second configuration, wherein the second configuration is obtained upon exposure of the shape memory polymer portion to a transition stimulus, and wherein the second configuration of the modifiable portion exhibits a greater resistance to movement of the lead within the body tissue than does the first configuration; and at least one electrode configured to provide electrical stimulation of body tissue, wherein the lead has a proximal end and a distal end. Systems and kits as well as methods of utilizing the leads of the invention are also included.

Abstract: A cardiac rhythm management device that includes a lead and a pulse generator. The lead can comprise a lead body, a helical composite electrode, a composite conductor and a proximal connector. The helical composite electrode can have first and second electrodes in a co-axial configuration. The composite connector can electrically connect the first and second electrodes to the proximal connector. The proximal connector can be configured to couple to the pulse generator.

Abstract: An implantable medical lead for active fixation to cardiac tissue is disclosed herein. The lead may include a lead body distal end, a tissue fixation helical anchor and a structure. The tissue fixation helical anchor may be coupled to the lead body distal end and include a distal tip. The structure may be coupled to the lead body distal end and include a structure distal end including a first radiopaque marker. The structure may be biased to project the structure distal end near the distal tip. When the tissue fixation helical anchor is progressively embedded in the cardiac tissue, the cardiac tissue progressively displaces the structure distal end proximally.

Abstract: A transvenously implantable medical device (TIMD) includes an electrical lead and a control module. The electrical lead includes one or more electrodes and is adapted for transvenous implantation. The electrical lead is also pre-biased to expand from a collapsed state to an expanded state to mechanically engage an internal wall of a blood vessel. The control module is secured to and in electrical communication with the electrical lead. The control module includes a signal management component and a power component disposed in a housing adapted for implantation into the blood vessel. The control module is adapted for at least one of stimulating and sensing a physiologic response using the one or more electrodes of the electrical lead.

Abstract: A medically implantable lead configured for insertion into a human or animal body to be attached in the body with its distal end to tissue inside the body, as a rotatable helix at a distal end thereof that can be screwed into the tissue. The helix serves as an attachment of the lead to the tissue as well as a conductor for conducting electrical signals to the tissue through electrically conducting surfaces on the helix. The surfaces of the helix are partly insulated so as to restrict the conducting of signals between the helix and the tissue to desirable regions. The surfaces of the helix facing inwardly, toward an inner bore of the helix, are electrically insulated. In a method for manufacturing such a lead, the wire forming the helix has protrusions in desired areas and the wire including the protrusions is coated with an electrically insulating layer. The protrusions are uncovered from the insulating layer in desired regions.

Abstract: A system of an autonomous intracardiac capsule and its implantation accessory. The autonomous capsule (10) includes a tubular body (12) with an anchoring screw (14) for penetrating the wall of a cavity of the heart, and at least one coupling finger (20, 22) radially projecting outwards. The implantation accessory (26) includes a lead body (28) with a sheath (30, 32) of deformable material supporting on the distal side a helical guide (36, 52), for guiding and driving by rotation the capsule. This helical guide is integral with the lead body, and its inner diameter is homologous to the outer diameter of the cylindrical body of the capsule so the latter can be housed it in, the coupling fingers protruding between the coils of the guide. The helix direction of the helical guide (36) is opposite to that of the anchoring screw (14). The helical guide is resiliently compressible in axial direction, and its helix pitch (38) is increased in the free distal end portion (40).

Abstract: A cardiac rhythm management system includes a lead assembly for intracardiac mapping, pacing, and drug delivery. The lead assembly includes an implantable endocardial lead having a proximal end for connection to an implantable cardiac rhythm management device and a distal end for disposal in an intracardiac region. The lead includes a pacing-sensing electrode and a drug delivery device, both located at or near the distal end. A lumen is within and extends throughout the lead, with an opening at or near the proximal end and another opening at or near the distal end. The lumen provides for access to the intracardiac region by a steerable stylet and a hollow needle, one at a time. The steerable stylet allows for electrophysiological mapping of the intracardiac region. The hollow needle allows for delivery of chemical, biochemical, and/or biological substance to the intracardiac region.

Abstract: A pacing lead for implantation in the pericardial space includes an elongated lead body, a compression fixation element, and at least one electrode on either the lead body or the fixation element. The fixation element defines a resilient structure, and is positioned and dimensioned so that when the lead is disposed in the pericardial space, the resilient fixation element is compressed between the parietal and visceral pericardium, thereby biasing the electrode against the myocardium and providing positional stabilization to the lead. Further positional stability may be provided mechanically with structures enabling the application of adhesive or with fixation screw or tine elements.

Abstract: A medical electrical lead includes a glue segment to adhere the lead to a treatment site. The glue segment, which may be disposed within a tip electrode of the lead, includes tissue adhesive which may encapsulated within a capsule.

Abstract: Methods and systems for transvenously accessing the pericardial space via the vascular system and atrial wall, particularly through the superior vena cava and right atrial wall, to deliver treatment in the pericardial space are disclosed. A steerable instrument is advanced transvenously into the right atrium of the heart, and a distal segment is deflected into the right atrial appendage. A fixation catheter is advanced employing the steerable instrument to affix a distal fixation mechanism to the atrial wall. A distal segment of an elongated medical device, e.g., a therapeutic catheter or an electrical medical lead, is advanced through the fixation catheter lumen, through the atrial wall, and into the pericardial space. The steerable guide catheter is removed, and the elongated medical device is coupled to an implantable medical device subcutaneously implanted in the thoracic region. The fixation catheter may be left in place.

Abstract: An implantable medical lead of the invention comprises an electrically active helix electrode extendable and retractable relative to a distal tip of the lead, an electrically conductive mapping collar disposed at the lead's distal tip and a proximal end carrying an electrical connector assembly. The electrical connector assembly comprises a first terminal connected to the helix electrode and a second terminal separately connected to the mapping collar. An advantage of the independent helix electrode and mapping collar circuits is that the implanting physician can confirm from separate electrode impedance readings that the helix is in fact extended and fully embedded within the myocardium. Further, the independent mapping collar and helix electrode circuits may be used, in conjunction with a configurable or programmable switch network, to provide the implanting physician with a choice of electrode impedances.

Abstract: A system and method for assessing coupling of a lead to tissue are provided. The inventive system includes a lead body with an electrode and a fixation element disposed near a distal end of the lead body. The fixation element is configured to anchor the distal end of the lead body in the tissue. The system further includes a meter configured to generate a signal indicative of an amount of energy between the electrode and the fixation element. The amount of energy may comprise capacitance or inductance between the electrode and the fixation element. The system further includes an electronic control unit configured to determine a degree of coupling between the lead and the tissue responsive to the signal.

Abstract: An implantable medical lead is disclosed herein. The lead includes a first electrode and a first electrical circuit. The first electrode is near a distal portion of the lead. The first electrical circuit extends through the lead to the first electrode and includes at least one conductor and a first band stop filter coupled between the distal end of the conductor and the electrode. The first band stop filter includes a first group of inductors in parallel and a second group of inductors in parallel. The first group is in series with the second group. The first group of inductors may include a self resonant L. The first group of inductors may include a self resonant tank LC. The first group of inductors may include a miniature self resonant L or miniature self resonant tank LC. The first group of inductors may include an integrated circuit of L and C components.

Abstract: A medical electrical lead for transvascularly stimulating a nerve, muscle or other tissue from an adjacent vessel is described. The lead includes a bifurcated distal portion including a first elongate member forming a first spiral and a second elongate member forming a second spiral. The spirals can be in parallel or serial alignment with one another.

Abstract: An insulative housing formed about a distal end of a medical electrical lead body includes a cavity and a port; an ionically conductive medium fills the cavity and is in intimate contact with an electrode surface contained within the cavity. When a current is delivered to the electrode surface contained within the cavity, a first current density generated at the electrode surface is smaller than a second current density generated out from the port of the insulative housing; thus, the port forms a high impedance and low polarization tissue-stimulating electrode.

Abstract: An implantable lead may have a distal assembly including a coupler and a fixation helix secured to the coupler. The fixation helix may be formed of a filar having a non-circular cross-sectional profile having a major dimension and a minor dimension. The major dimension may be disposed transversely to a longitudinal axis of the helical electrode.

Abstract: Some embodiments of an electrode delivery system may be used to deliver a plurality of wired electrodes into one or more chambers of the heart. In particular embodiments, the plurality of wired electrodes may be delivered into a heart chamber through a single guide sheath device. Such a system may be used to deliver one or more wired electrodes to inner wall of the left atrium, the left ventricle, or both.

Abstract: A medical electrical lead includes an inductance augmenter assembly. The assembly includes an inductor coil formed of an insulated wire, which is wound about a non-conductive core and is electrically coupled in series between a conductor coil of the lead and an electrode of the lead.

Abstract: A medical electrical lead and methods of implanting medical electrical leads in lumens. Leads in accordance with the invention employ preformed biases to stabilize the lead within a lumen and to orient electrodes in a preferred orientation.

Abstract: An implantable lead may have a distal assembly including a coupler, a terminal pin and a conductive member rotatably secured to both the coupler and the terminal pin. The conductive member may be a fine-wire, multiple-filar coil. The conductive member may be welded to the coupler and/or the terminal pin by welding through banded portions formed within the distal and proximal ends, respectively, of the conductive member.

Abstract: A lead body includes an electrode coupled to an intermediate portion of the lead body. A distal end of the lead includes a pre-formed, biased shape adapted to passively fixate the distal end of the lead within a pulmonary artery with the electrode positioned in the right ventricle or ventricular outflow tract. The lead body can include a preformed J-shape, with the electrode coupled to the intermediate portion of the lead body and located distally from a bottom of the pre-formed J-shape. The lead body can include a section of the intermediate portion of the lead body being less stiff than adjacent sections of the lead body with the electrode coupled to the intermediate portion of the lead body and located distally from the less stiff section.

Abstract: An implantable active fixation lead includes an outer sheath, a protector member having a peripheral surface extending between its distal and proximal end surfaces with a helical groove formed in the peripheral surface, and a fixation helix integral with the outer sheath. The fixation helix includes a tip end engageable with body tissue and slidably engaged with the helical groove for relative translation and rotation. A longitudinal force on the lead firmly engages the protector member's distal end surface with the body tissue. With the fixation helix initially retracted proximally of the protector member's distal end surface and disengaged from the body tissue, upon application of torque to the outer sheath, the distal end surface of the protector member is moved proximally with respect to the fixation helix which, simultaneously, is extended distally beyond the distal end surface of the protector member to an extended position into engagement with the body tissue.

Abstract: A medical implantable lead to be inserted into a human or animal body and attached to an organ inside the body for monitoring and/or controlling the function of the organ has a header in a distal end, a fixation arrangement and an electrode arranged in the header. The fixation arrangement attaches the distal end of the lead to the organ and the electrode is arranged to transmit or receive electrical signals to or from the organ. The lead also has a connector in a proximal end that includes a connector pin and is adapted to be connected to a monitoring and/or controlling device, and an inner coil, which extends inside an outer casing of the lead and is adapted to transmit electrical signals between the monitoring and/or controlling device and the electrode. The inner coil is attached to the connector pin. The inner coil extends through a bore inside the connector pin and is attached to the connector pin in its proximal end. A method for manufacturing of such a lead is also provided.

Abstract: A system implantable in the coronary venous system, including a pacing lead with an anchoring screw is disclosed. The system includes a stimulation lead (10) for stimulating a left heart cavity of a patient, and a removable catheter (26) for implanting the lead. The lead (10) has at least one stimulation electrode having an anchoring screw (14) that penetrates into the epicardial tissue of the patient. The catheter tube (26) is a pre-shaped tube with two curvatures in the absence of stress. The two curvatures are inscribed in two separate surfaces (38, 40) for self-orientating the distal end of the catheter tube into the target vein and maintaining the axis of the anchoring screw towards the epicardial wall during the screwing of the lead head.

Abstract: An implantable lead may include a housing and a laminate distal seal disposed across a distal end of the housing. A coupler and a fixation helix secured to the coupler may be disposed within the housing. The fixation helix may have a retracted position in which the fixation helix does not penetrate the laminate distal seal and an extended position in which the fixation helix has pierced the laminate distal seal and extends therethrough.

Abstract: An implantable lead may have a distal assembly including a coupler, a fixation helix secured to the coupler and a housing in which the fixation helix and the coupler are disposed. The distal assembly may include an annular seal that is disposed between the coupler and the housing and that provides an at least substantially fluid-tight seal between the coupler and the housing.

Abstract: An implantable medical lead is disclosed herein. The implantable medical lead may include a body including an electrical insulation tube, a distal portion with an electrode, and a proximal portion with a lead connector end. The electrical insulation tube may be coaxial with a longitudinally extending center axis of the body. The lead may also include an electrical pathway extending between the electrode and lead connector end, the electrical pathway including an inductor comprising an electrical conductor helically wound directly on an outer circumferential surface of the insulation tube.

Abstract: An electrode arrangement has a stimulation electrode (7) that can be implanted transvenously for the Tawara node (5) allocated to the left ventricle (3) of a human heart (1). In order to not have to feed the stimulation electrode (7) via coronary veins, an element that can be inserted into the right ventricle (2) and that is used for piercing or forming a channel in the tissue of the heart (1) toward the Tawara node (5) of the left ventricle (3) is part of the electrode arrangement, so that the stimulation electrode (7) can be implanted in the region of the Tawara node (5) of the left ventricle (3). The feeding element can be a hollow needle (8) or a first stimulation electrode (6) for the right ventricle (2). The channel can be formed by a stiletto blade (9) or guide wire (10) or the helical coil of the second stimulation electrode (7) itself.

Abstract: An implantable lead for delivering electrical stimuli to a human heart has a stimulating electrode for transmitting electrical stimuli to the myocardium after implantation, and a mapping electrode for use during implantation. The mapping electrode is configured to deliver electrical stimuli to the heart and to sense intrinsic cardiac activity, for the purpose of finding a suitable fixation position in the myocardium. During the implantation procedure, the mapping electrode is electrically connected to the conductor. The lead is configured to electrically disconnect the mapping electrode from the conductor after a suitable fixation position has been determined.

Abstract: A medical electrical lead includes a proximal insulation segment, a distal insulation segment, a conductor extending within the proximal and distal segments, and an electrode coupled to the conductor and disposed in proximity to a distal end of the distal insulation segment. A fixation element of the lead is coupled to a distal end of the proximal insulation segment and includes a wire wound in a helix, which extends distally from the proximal segment, over the distal insulation segment.

Abstract: An implantable medical system for delivering pacing pulses to HIS bundle of a heart of a patient when implanted in said patient includes a medical lead, which is adapted to be attached with a distal end to tissue of said heart, including a at least two electrodes arranged being electrically separated from each other. The implantable medical device connectable to the medical lead includes a pacing circuit adapted to deliver the pacing pulses to said heart via the medical lead, a selection device connected between the pacing circuit and the electrodes adapted to selectively activate at least one of said electrodes, and a processing device adapted to control the selection device to selectively activate at least one of the electrodes to direct the pacing pulses to the HIS bundle.

Abstract: Devices and methods for placing medical leads using minimally invasive techniques. One lead includes a lead body connected to a lead head having an aperture for providing fiber optic access to the interior of a helical electrode. The fiber optic shaft may be disposed within or along-side a drive shaft releasably coupled to the head to rotate the head. The drive shaft and lead body may be delivered using a delivery catheter. The delivery catheter can be advanced though a small incision to the target tissue site, and the site remotely visualized through the fiber optic scope extending through the lead head aperture. Some catheters include a distal mapping electrode readable from the catheter proximal portion or handle. The lead head can be rotated, rotating the helical electrode into the tissue, and the catheter, drive shaft, and fiber optic probe removed.

Abstract: An implantable active fixation lead includes an outer sheath, a protector member having a peripheral surface extending between its distal and proximal end surfaces with a helical groove formed in the peripheral surface, and a fixation helix integral with the outer sheath. The fixation helix includes a tip end engageable with body tissue and slidably engaged with the helical groove for relative translation and rotation. A longitudinal force on the lead firmly engages the protector member's distal end surface with the body tissue. With the fixation helix initially retracted proximally of the protector member's distal end surface and disengaged from the body tissue, upon application of torque to the outer sheath, the distal end surface of the protector member is moved proximally with respect to the fixation helix which, simultaneously, is extended distally beyond the distal end surface of the protector member to an extended position into engagement with the body tissue.

Abstract: A retractable screw-type stimulation or defibrillation intracardiac lead is disclosed. According to one embodiment, the lead comprises a flexible hollow sheath (12) having at its distal end a lead head (10) and a connector (66) at its proximal end. The connector comprises a pin (62) connected to a lead head electrode (18). The lead head comprises a tubular body (28), at least one electrode (18, 20) for stimulation or defibrillation, a moving element translationally and rotationally moving within the tubular body in a helical motion, and an anchoring screw (24) axially moving with respect to the tubular body, and a deployment mechanism (22) to deploy the anchoring screw out of the tubular body (28).

Abstract: An implantable lead includes a lead body, having a distal end and a proximal end, configured to be implanted in a patient. An electrode assembly is provided at the distal end of the lead body, wherein the electrode assembly includes an electrode that is configured to deliver stimulating pulses. The electrode extends between a base and a tip at a distal end of the electrode. A shielding member is provided on the electrode assembly and is positioned to cover at least a portion of the electrode to electrically shield the electrode from RF fields. Optionally, the shielding member may include a shielding conductor that wraps about and extends longitudinally along a length of the electrode from the base to the tip. The shielding conductor may extend from the proximal end of the lead body at least to the distal end of the lead body.

Abstract: An implantable lead includes a lead body, a header body, a fixation mechanism, a rotatable shaft and a rotation limit element. The fixation mechanism is disposed in the header body and is extendable out of the header body for securing the header body to cardiac tissue of the patient. The shaft is provided in the header body and is coupled to the fixation mechanism for translating rotational movement of the shaft into linear displacement of the fixation mechanism. The rotation limit element is disposed in the header body. The rotation limit element engages the header body once the shaft is linearly displaced by a predetermined distance with respect to the header body to prevent further rotation of the shaft and limit additional displacement of the fixation mechanism with respect to the header body.

Abstract: An implantable medical lead is disclosed herein wherein the lead employs a helical distal tip anchor having improved fixation capabilities. The implantable medical lead may include a body and a helical anchor. The body may include a distal end and a proximal end. The helical anchor may be at least one of extending and extendable from the distal end. The helical anchor may include at least one loop including first and second straight sides that intersect at a first corner.

Abstract: An implantable medical lead for active fixation to cardiac tissue is disclosed herein. The lead may include a lead body distal end, a tissue fixation helical anchor and a structure. The tissue fixation helical anchor may be coupled to the lead body distal end and include a distal tip. The structure may be coupled to the lead body distal end and include a structure distal end including a first radiopaque marker. The structure may be biased to project the structure distal end near the distal tip. When the tissue fixation helical anchor is progressively embedded in the cardiac tissue, the cardiac tissue progressively displaces the structure distal end proximally.

Abstract: An implantable lead for a medical device includes a lead body having a proximal end and a distal end, an electrical connector coupled to the proximal end of the lead body, an electrode coupled to the distal end of the lead body, and electrically conductive conductor coil extending between the proximal and the distal end of the lead body, the conductor coil wound in a first winding direction under tension. The lead body also includes a plastic ribbon wound around the conductor coil in a second winding direction opposite to the first winding direction without releasing the tension of the conductor coil.

Abstract: An active fixation cardiac electrode lead having a fixation helix movably placed in a housing at the electrode lead's distal end so as to be extended out of the housing's distal end and retraced into an inner space enclosed by the housing. The housing has a wall and a protrusion formed in the wall that protrudes into the inner space into interspaces between windings of the fixation helix. The protrusion causes an axial movement of the helix when the helix is rotated around its longitudinal axis. The protrusion is an integral part of the housing's wall which is bent or embossed to form the protrusion.

Abstract: The present invention provides compositions and methods related to epicardial pacing systems. In particular, the present invention provides a novel delivery sheath and cardiac pacing lead to be deployed in the pericardial space via a percutaneous approach.

Abstract: Electrical medical leads having active fixation electrodes, particularly helix electrodes intended to be screwed into body tissue, e.g., the heart, are disclosed having selectively applied insulation to optimize exposed electrode surface area and dispose the exposed electrode surface area toward tissue that is less traumatized by injury caused by screwing in the fixation helix. In a preferred fabrication method, an outer helical surface is masked by contact with a masking tube while a dielectric coating is applied to the inner helical surface of the coil turns of the helix, and the masking tube is removed when the dielectric coating has set. In one variation, at least one aperture is formed through the masking tube sidewall exposing an area of the outer helical surface thereby interrupting the uninsulated outer helical electrode.