Systems and methods for implanting a medical device using an active guidewire

Systems and methods for implanting a lead. The system includes an active guidewire having proximal and distal ends. The distal end includes a guidewire anchor that is configured to be attached to a target SOI. The active guidewire is configured to be utilized to electrically map the target SOI by at least one of delivering stimulation energy through the active guide wire to the target SOI or sensing an evoked response at the target SOI from the guidewire. The system also includes a lead having a lead body with proximal and distal ends and with a lumen extending between the proximal and distal ends. The distal end of the lead body is configured to receive the proximal end of the active guidewire. The lumen is configured to permit the lead body to be advanced over the active guidewire.

BACKGROUND

Embodiments of the present disclosure relate generally to systems and methods for implanting medical devices within a patient, and more particularly to delivery systems for implanting one or more leads.

Cardiac pacemakers and implantable cardioverter-defibrillators (ICD) use insulated wires (called leads) to monitor the heart and to also deliver electrical signals or shocks. Various techniques exist for implanting cardiac pacemakers, ICDs, and other medical devices, and each technique may use a set of tools designed for that technique. To position a lead, for example, a number of elongated tools (e.g., needles, guidewires, sheaths, and stylets) are inserted into the body. In many cases, the lead is inserted through the lumen of a catheter (or introducer sheath). After the lead is positioned relative to the heart, the catheter is removed.

Removing the catheter without inadvertently displacing the lead can be challenging. The leads are thin and, when finally positioned, may have a number of bends or twists along its path. Furthermore, the proximal end of the lead includes a connector that is larger than the diameter of the sheath's lumen. To address this issue, splittable or peelable sheaths are used. The sheaths are split and separated from each other as the sheaths are withdrawn from the body. As such, the sheaths may be removed while avoiding the connector at the proximal end of the lead.

Although these splittable/peelable sheaths are useful, the withdrawal process can still be challenging, especially for certain procedures. More recently, the His-Purkinje system has been proposed as a physiologic substitute for right-ventricle pacing. Recent clinical trials demonstrated an increased risk of hospitalization for heart failure (HF) in patients having a high burden of right-ventricle (RV) pacing and consequently an increased risk of arrhythmias. His-bundle pacing (HBP) uses native conduction pathways and could prevent the negative effects of RV pacing and promote ventricular synchrony.

It remains challenging, however, to locate the His bundle and achieve true selective capture. During this procedure, a splittable catheter with a dilator is advanced over a guide wire until the dilator end reaches the atrium or right ventricle. With the catheter in place, the implanter removes the guidewire and the dilator and advances a pacing lead through the lumen of the catheter. In some cases, the pacing lead accepts a stylet to provide rigidity and push-ability to the lead. After the pacing lead is positioned, the catheter is slit and removed, leaving the lead in place.

As discussed above, the implanter is careful when withdrawing the catheter so that the catheter does not strike the connector at the proximal end and dislodge the lead from its desired position. If the lead is dislodged, the lead-implantation procedure must begin again. Repeating the process increases the risk of infection in addition to other complications that may arise during such medical procedures.

SUMMARY

In accordance with embodiments herein, a system is provided. The system includes an active guidewire having proximal and distal ends. The distal end is configured to be located proximate to a target site of interest (SOI) within or proximate to a chamber of the heart. The distal end includes a guidewire anchor that is configured to be attached to the target SOI. The active guidewire is configured to be utilized to electrically map the target SOI by at least one of delivering stimulation energy through the active guide wire to the target SOI or sensing an evoked response at the target SOI from the guidewire. The system also includes a lead having a lead body with proximal and distal ends and with a lumen extending along the body between the proximal and distal ends. The distal end of the lead body is configured to receive the proximal end of the active guidewire. The lumen is configured to permit the lead body to be advanced over the active guidewire until the distal end of the lead body is proximate the target SOI.

In some aspects, the system also includes an external programmer device that can configured to be electrically coupled to the proximal end of the active guidewire. The external programmer device may be configured to electrically map the target SOI.

In some aspects, the target SOI may represent a HIS. The guidewire anchor may be configured to attach the distal end of the active guidewire into a wall of the heart proximate the HIS. The external programmer device may be configured to deliver a HIS paced event as the stimulation energy and to sense the evoked response to determine whether HIS capture was achieved based on the His paced event.

In some aspects, the target SOI may represent a left bundle branch. The guidewire anchor can be configured to attach the distal end of the active guidewire a predetermined depth into a septa wall that separates the right and left ventricles. The external programmer device can be configured to deliver the stimulation energy through the distal end of the active guidewire to the left bundle branch.

In some aspects, the target SOI may represent a pacing site. The external programmer device may be configured to deliver a pacing pulse, as the stimulation energy, through the guidewire to the target SOI and sense the evoked response at a sensing site within or proximate the heart separate from the pacing site.

In some aspects, the target SOI may represent a sensing site. The external programmer device may be configured to sense the evoked response at the sensing site following delivery of a pacing pulse at a pacing site within or proximate the heart separate from the sensing site.

In some aspects, the system also includes a catheter configured to be advanced to or proximate the chamber of the heart having the target SOI. The catheter may have a lumen with a size dimensioned to receive the active guidewire. The size of the lumen in the catheter may be smaller than an outer dimension of the lead body, such that the lead does not fit through the lumen of the catheter.

In some aspects, the catheter may include at least one electrode positioned proximate to a distal end of the catheter. The at least one electrode may be configured to at least one of deliver stimulation energy to the target SOI or sense an evoked response at the target SOI.

In some aspects, the lead includes a lead anchor coupled to the distal end of the lead body. The lead anchor defines an anchor passage that is aligned with the lumen of the lead body. The anchor passage is sized to permit the lead anchor to slide over the active guidewire as the lumen is advanced over the active guidewire.

In some aspects, the lead anchor includes a helical screw that wraps about the anchor passage.

In accordance with embodiments herein, a method of implanting a lead is provided. The method includes advancing an active guidewire to a target site of interest (SOI) within or proximate to a chamber of the heart. The method also includes electrically mapping the target SOI utilizing the active guidewire by at least one of delivering stimulation energy through the active guide wire to the target SOI or sensing an evoked response at the target SOI from the guidewire. The method also includes fixating a distal end of the active guidewire at the target SOI. The method also includes advancing a lead over the active guidewire until a distal end of the lead is located proximate the target SOI.

In some aspects, the fixating the distal end of the active guidewire is performed before the electrically mapping the target SOI utilizing the active guidewire.

In some aspects, the target SOI may represent a His bundle region. Fixating the distal end may include attaching the distal end of the active guidewire into a wall of the heart proximate the His bundle region. Electrically mapping may include delivering a His paced event as the stimulation energy. The method may also include assessing whether capture of the His bundle region was achieved based on the His paced event.

In some aspects, the target SOI represents a left bundle branch. Fixating the distal end may include submerging the distal end of the active guidewire a predetermined depth into a septa wall separating the right and left ventricles. Electrically mapping may include delivering the stimulation energy through the distal end of the active guidewire to the left bundle branch.

In some aspects, the target SOI may represent a pacing site. The electrical mapping may include delivering a pacing pulse, as the stimulation energy, through the guidewire to the target SOI and sensing the evoked response at a sensing site within or proximate the heart separate from the pacing site.

In some aspects, the target SOI may represent a sensing site. Electrical mapping may include sensing the evoked response at the sensing site following delivery of a pacing pulse at a pacing site within or proximate the heart separate from the sensing site.

In some aspects, the method also includes, prior to advancing the active guidewire, advancing a J-tip guidewire, obturator, and catheter to or proximate the chamber of the heart having the target SOI. Prior to advancing the active guidewire, the method may include withdrawing the obturator and J-tip guidewire. The method also includes inserting the active guidewire through the catheter to the target SOI and withdrawing the catheter before advancing the lead over the active guidewire.

In some aspects, advancing the active guidewire may include advancing the active guidewire through the right atrium and through the right ventricle, forcing the distal end of the active guidewire through a septa wall separating the right and left ventricles, advancing the distal end of the active guidewire through the left ventricle and submerging the distal end of the active guidewire into a wall of the left ventricle proximate the Purkinje fiber.

In some aspects, the target SOI may represent at least one of an atrial pacing site, a His bundle pacing site, a left bundle branch pacing site, a right bundle branch pacing site, and LV wall pacing site proximate the LV Purkinje fibers.

In some aspects, the method may also include fixating a distal end of the lead to tissue at the target SOI and removing the guidewire by withdrawing the active guidewire along a lumen within the lead.

DETAILED DESCRIPTION

Embodiments set forth herein include systems for implanting implantable medical devices (IMDs), assemblies or kits of the systems or IMDs, and methods for making and using the same. Particular embodiments use an active guidewire and are implemented in connection with a His-bundle pacing (HBP) strategy or system in which a region of cardiac tissue at or near the His bundle, which is referred to herein as the His bundle region, is stimulated. Although embodiments may be described in relation to HBP, it should be understood that embodiments may be used in connection with a variety of IMDs and medical procedures delivering or using the IMDs. Such procedures may include implanting or extracting leads.

An IMD is a medical device which is intended to be totally or partially introduced into a body (human or animal) and remain in the human body after the procedure. An IMD may include a single component or a system of components that interact to achieve a desired performance. IMDs typically include at least one active component that perform monitoring and/or therapy functions through electrical energy. Non-limiting examples of IMDs include a cardiac monitoring device, a pacemaker, cardioverter, cardiac rhythm management device, defibrillator, neurostimulator, and the like. Many IMDs may provide multiple functions and include implantable cardioverter defibrillators (ICDs) and implantable cardiac resynchronization therapy/defibrillator devices (CRT-Ds).

IMDs often include a control device (e.g., pulse generator) and one or more other components that coordinate with the control device. For example, cardiac IMDs often include a pulse generator and one or more leads. The pulse generator has a power source and electronic circuitry that is configured to monitor the heart. The pulse generator may include one or more processors that implement programmed instructions (e.g., software or firmware) stored in memory of the pulse generator. For example, the pulse generator may be programmed to provide output stimuli (e.g., signals for pacing or a shock) through the lead or leads.

A lead includes one or more insulated electrical conductors that are intended to transfer electrical energy along a length of the lead. For example, the lead may transfer output stimuli from the pulse generator or transmit depolarization potentials from cardiac tissue to a sensing circuit of the pulse generator. A lead typically includes a lead body having an elongated flexible tube or sleeve comprising, for example, a biocompatible material (e.g., polyurethane, silicone, etc.). The lead (or lead body) has a distal end and a proximal end. As used herein, the terms “proximal” and “distal,” when used in reference to a lead (or other elongated instruments, such as an introducer sheath, catheter, guidewire, or stylet) are to be understood in relation to delivering and implanting a medical device. During an implantation procedure, “proximal” is to be understood as relatively close to the implanter and “distal” is to be understood as relatively far away from the implanter. After the implantation, a proximal end of a lead is coupled to a pulse generator, and a distal end of the lead is positioned adjacent to tissue (e.g., cardiac or nerve tissue).

The lead body may include a single lumen (or passage) or multiple lumen (or passages) within the flexible tube. A lead may have multiple electrical conductors (not shown) that electrically couple electrode(s) of the lead to the pulse generator. The electrical conductors may be cabled conductors coated with PTFE (poly-tetrafluoroethylene) and/or ETFE (ethylenetetrafluoroethylene). The electrical conductors are terminated to the respective electrode. The lead body may be configured for receiving a guide wire or stylet that enable positioning of the lead.

The lead may include one or more electrodes or one or more contacts through which electrical energy may leave or enter the conductors of the lead. Electrodes may be positioned adjacent to tissue for monitoring or providing therapy thereto. The lead connector also includes one or more contacts that are communicatively coupled to the one or more electrodes. The lead adaptor and the pulse generator are also described as including contacts. To more readily distinguish electrodes and contacts, the electrodes can be described as being positioned at the distal end and the contacts can be described as being positioned at the proximal end of the lead or as part of a lead adaptor or a pulse generator.

Various types of electrodes and contacts exist, including tip electrodes or contacts, ring electrodes or contacts, contact pads, patch electrodes, spring electrodes, or porous electrodes. Electrodes and contacts may also have a variety of configurations or patterns (e.g., unipolar, bipolar or multi-polar, array, etc.). In particular embodiments, the electrodes/contacts may be arranged according to international standard 1 (IS-1) that are used for low-voltage applications. The configuration may be unipolar or bipolar. A largest dimension of an IS-1 lead connector is 3.2 mm.

The lead adaptor enables an electrical and mechanical connection between the lead connector and the pulse generator. The lead adaptor may be used to upsize or downsize the lead connector in order to mate with the pulse generator. Optionally, the lead adaptor may also function as a lead extender that effectively increases the length of the lead.

Leads also include a lead connector positioned at the proximal end. The lead connector provides an electrical connection between the one or more electrodes of the lead and the one or more contacts of a control device (e.g., pulse generator). As described herein, the lead connector can also mate with a lead adaptor. The lead adaptor may then mate with the pulse generator to electrically connect the electrodes to the pulse generator and mechanically connect the lead to the pulse generator.

A lead may be delivered and positioned relative to tissue using a catheter (or introducer sheath). A catheter is a tube or cannula that is introduced into the body (e.g., through the vascular system, for example), typically over another elongated instrument, such as a needle, dilator, or guidewire. The catheter includes a lumen that permits passage of other elongated instruments, such as the lead. The catheter may form part of a delivery system (or kit) that includes one or more other elongated instruments, such as a needle, a guidewire, a syringe, a dilator, and one or more other sheaths.

In particular embodiments, the catheter is non-splittable or non-peelable. In such embodiments, the catheter may be removed while the active guidewire is secured to a target SOI. With the catheter removed, an implantable lead may be guided to the target SOI using the active guidewire. In addition to using non-splittable or non-peelable catheters, particular embodiments may enable catheters having a smaller-sized lumen as it is not necessary for the lumen to accommodate the implantable lead.

FIG.1illustrates a schematic cutaway view of a heart10relative to an IMD50. The heart10includes a right atrium RA, a right ventricle RV, a left atrium LA, and a left ventricle LV. During normal operation of the heart10, deoxygenated blood from the body is returned to the right atrium RA from the superior vena cava12and inferior vena cava14. The right atrium RA pumps the blood through the atrioventricular or tricuspid valve16to the right ventricle RV, which then pumps the blood through the pulmonary valve18and the pulmonary artery20to the lungs for reoxygenation and removal of carbon dioxide. The newly oxygenated blood from the lungs is transported to the left atrium LA, which pumps the blood through the mitral valve22to the left ventricle LV. The left ventricle LV pumps the blood through the aortic valve24and the aorta26throughout the body.

FIG.2is another schematic cutaway view of the heart10showing a location of the bundle of His30in the heart. The bundle30consists of fast-conducting muscle fibers that begin at the atrioventricular node in the right atrium and pass to the interventricular septum. The bundle30divides in the septum into a right branch that travels along the right side of the septum and supplies excitation to the right ventricle, and a pair of left branches that travel along the left side of the septum and supply excitation to the left ventricle. The fibers in the branches terminate in an extensive network of Purkinje fibers which distribute excitation pulses to the layer of cells beneath the endocardium.

Returning toFIG.1, the IMD50includes a pulse generator52that is operably coupled to an implantable lead54through a lead adaptor56. The lead adaptor56is configured to receive a lead connector (not shown) of the lead54. Although the IMD50includes only one lead inFIG.1, a number of other leads (e.g., two, three, four, etc.) may be used. The lead54is designed to penetrate the endocardium in contact with His bundle30. The lead54may enter the vascular system through one of several possible vascular access sites and extends through the superior vena cava12to the right atrium RA.

InFIG.1, the IMD50is a cardiac pacemaker. In other embodiments, however, the IMD50may include an ICD, a CRT-D, an ICD coupled with a pacemaker, and the like. The IMD50may be a dual-chamber stimulation device capable of treating both fast and slow arrhythmias with stimulation therapy, including cardioversion, defibrillation, and pacing stimulation, as well as capable of detecting heart failure, evaluating its severity, tracking the progression thereof, and controlling the delivery of therapy and warnings in response thereto. The IMD50may be controlled to sense atrial and ventricular waveforms of interest, discriminate between two or more ventricular waveforms of interest, deliver stimulus pulses or shocks, and inhibit application of a stimulation pulse to a heart based on the discrimination between the waveforms of interest and the like.

Although not shown, the IMD50may wirelessly communicate with an external device. For example, the external device may initiate the pulse generator52. The external device and the pulse generator may communicate identification data (e.g., obtain model and serial number) between one another. The external device may generate a chart that correlates to the patient having the pulse generator52. The external device may instruct the pulse generator52to perform an electrode integrity check and measure parameters of the electrodes (e.g., impedance of shock electrode(s)). The external device and/or the pulse generator may determine a sensing configuration for the pulse generator based on cardiac activity. During initiation of the pulse generator52, therapy parameters may be selected by the user of the external device.

FIG.3is a schematic diagram of a system100, which is hereinafter referred to as an implantable medical device (IMD)100. The IMD100is not assembled inFIG.3. In some embodiments, the IMD100may be grouped or packaged as a set or kit. The IMD100includes an implantable pulse generator102and a lead assembly104. The pulse generator102has a connector cavity103that is configured to mate with the lead assembly104. The lead assembly104includes an implantable lead106and a lead adaptor108. The lead106includes a lead body107that extends lengthwise along a longitudinal axis111between a distal end110and a proximal end112. The term longitudinal axis encompasses both linear and non-linear axes. For example, the longitudinal axis111may extend along a curved path that changes as the lead body107is flexed, bent, twisted, or otherwise manipulated.

The lead body107includes a lumen115extending along the lead body107between the proximal and distal ends112,110. The longitudinal axis111may extend through a geometric center of the lead body107. The distal end110of the lead body107is configured to receive a proximal end (not shown) of an active guidewire, such as the active guidewire150(shown inFIG.5). The lumen115is configured to permit the lead body107to be advanced over the active guidewire until the distal end110of the lead body107is proximate a target SOI.

The lead106may include a plurality of electrodes120,122positioned at the distal end110. The electrodes120,122are arranged in a bipolar configuration but other configurations may be used. The lead106also has a lead connector124positioned at the proximal end112. The lead connector124includes a portion of the lead body107and lead contacts126,128that are communicatively coupled to the electrodes120,122through a plurality of conductors (not shown) that are contained within the lead body107. In the illustrated embodiment, the lead body107is iso-diametric such that a diameter of the lead106is essentially uniform throughout. The iso-diametric body107may permit a catheter (not shown) to slide over the lead connector124when the catheter is removed.

Various combinations of the electrodes and contacts may be used in connection with sensing cardiac signals and/or delivering stimulation therapies. For example, the electrodes120,122include a tip electrode120and a ring electrode122, and the lead contacts126,128include a tip contact126and a ring contact128. In other embodiments, however, the electrodes and contacts may include any number of electrodes/contacts and have a variety of types or shapes.

As described herein, the lead body107may have a body outer envelope that is configured to fit within a lumen of a catheter and the lead connector124has a connector outer envelope configured to fit within the lumen of the catheter. The lead body107includes an insulating sheath or housing of a suitable insulative, biocompatible, biostable material such as, for example, silicone rubber or polyurethane, extending substantially the entire length of the lead body and surrounding the conductors.

The lead adaptor108is configured to interconnect the implantable lead106and the pulse generator102. As shown, the lead adaptor108has an insertable connector132that includes mating contacts134,136. The lead adaptor108also includes and an adaptor cavity138that includes cavity contacts. The cavity contacts are positioned to engage the lead contacts126,128of the lead connector124when the lead connector124is inserted into the adaptor cavity138of the lead adaptor108. The insertable connector132is configured to be inserted into the connector cavity103of the pulse generator102.

FIG.4is a schematic side view of an active guidewire150formed in accordance with an embodiment. The active guidewire150includes a proximal end152and a distal end154and a wire body (or core)156that extends between the proximal and distal ends152,154. The wire body156may comprise, for example, stainless steel, nickel-titanium alloy (Nitinol), or the like.

The active guidewire150is configured to be communicatively coupled to an external programmer device170. The external programmer device is configured to electrically map the target SOI. To this end, the external programmer device170includes one or more processors and memory that stores program instructions directing the processors to perform electrical mapping operations. For example, one or more processors of the device may control the external programmer device170to deliver stimulation energy through the active guide wire to the target SOI. One or more processors of the device may control the external programmer device170to sense an evoked response at the target SOI from the active guidewire.

The external programmer device170is configured to locate a target site of interest (SOI) of tissue, such as a target SOI within or proximate to a chamber of the heart. The target SOI may be a pacing site or a sensing site. The target SOI may represent at least one of an atrial pacing site, a HIS pacing site, a left bundle branch pacing site, a right bundle branch pacing site, and LV wall pacing site proximate the LV Purkinje fibers.

The proximal end152of the active guidewire150may be directly or indirectly coupled to the external programmer device170as shown inFIG.4. In some embodiments, the proximal end152may be directly coupled to a terminal of the external programmer device170. Alternatively, the proximal end152may be directly coupled to a transmitter that communicates with the external programmer device170. The external programmer device170may receive mapping data in the form of electrical signals that are transmitted through the active guidewire150.

The active guidewire150may include a coil158that is wrapped about the wire body156. As shown inFIG.5, the coil158is wrapped about a distal segment160of the active guidewire150that includes the distal end154. In particular embodiments, the distal segment160of the active guidewire150has a designated shape.

The active guidewire150also includes a fixation anchor162. In the illustrated embodiment, the fixation anchor162is shaped such that, when directed toward the target SOI and rotated about a central axis, the fixation anchor162is driven into the tissue, thereby affixing the distal end154to the tissue. The designated shape of the distal segment160may decrease the likelihood that the fixation anchor162inadvertently engages or snags other tissue while the active guidewire150is advanced through the body. For example, the distal segment160may yield a J-shaped tip when the distal segment160is in an unbiased state.

In some embodiments, the active guidewire150has an average operating diameter164that is between 0.040″ and 0.025″. The average working diameter is a diameter of the active guidewire that is inserted into the body or, more particularly, inserted into the heart. In certain embodiments, the active guidewire150has an average operating diameter164that is between 0.036″ and 0.028″ or, more particularly, between 0.034″ and 0.030″.

The coil158and/or the fixation anchor162may have a cross-sectional shape that is circular, oval-like, or ribbon-like. The coil158and/or the fixation anchor162may comprise discrete elements or may be shaped from the same piece of material. For example, a wire that defines the coil158and/or the fixation anchor162may comprise a stiff metal having a high shear modulus. For example, the wire may include platinum, platinum iridium alloy, 304 stainless steel, 316 stainless steel, 316L stainless steel, or the like. The wire may have an outer diameter that is between 0.003″ and less than 0.011″ or, more specifically, between 0.004″ and less than 0.010″. In particular embodiments, the wire has an outer diameter that is between 0.005″ and less than 0.009″.

Optionally, the active guidewire150may include one or more coatings165. For example, the one or more coatings165may include an electrically-insulative coating, such as parylene, PTFE, ethylene tetrafluoroethylene (ETFE), or the like. Optionally, the one or more coatings165may include a hydrophobic or hydrophilic coating along a portion or an entirety of the wire to reduce the friction between the guidewire150and the lead. A lumen of the lead may include an inner surface comprising polytetrafluoroethylene, ETFE, or the like. For example, the lumen may be defined by a cylindrical core comprising polytetrafluoroethylene, ETFE, or the like. In some embodiments, the lead is similar or identical to one or more embodiments described in U.S. Pat. No. 9,623,235, which is hereby incorporated by reference in its entirety.

The fixation anchor162is electrically active such that fixation anchor may function as an electrode. For example, the fixation anchor162may form part of a conductive pathway that is configured for at least one of pacing or sensing electrical activity of the tissue. The fixation anchor162may also be used for mapping. By way of example, a length of the fixation anchor162may be at least 1.0 mm. In some embodiments, the fixation anchor162has a length that enables a deeper penetration into tissue. In particular embodiments, the fixation anchor162has a length between 2.0 mm and 5.0 mm that is configured to reach into septal tissue to achieve left or right bundle branch block correction. Optionally, when the fixation anchor162is greater than 2.00 mm a portion of the fixation anchor may be coated with parylene so that the proximity of the target tissue may be more precisely identified.

The fixation anchor162may be configured to sense electrical activity to identify the target SOI. Sensing with the fixation anchor162may be achieved in a unipolar mode while sensing between fixation anchor162and a remote electrode (not shown). The remote electrode may be, for example, a surgical clamp positioned at the pocket or incision.

Alternatively, a local electrogram may be obtained by using one or more electrodes positioned at a distal end of a catheter. For example, the distal end may include a pair of electrodes. If the electrode pair detects the designated site of tissue, it may not be necessary to use both the electrode pair and the fixation anchor162for mapping. Under some circumstances, it may be uncertain whether the His potential is from the electrode pair104or the guidewire fixation screw112.

For some implementations, the target SOI may represent a left bundle branch (LBB). The fixation anchor162may be configured (e.g., sized, shaped, and oriented) to attach the distal end154of the active guidewire150to the target SOI. The fixation anchor162may enable achieving a predetermined depth into a septa wall that separates the right and left ventricles. In such embodiments, the external programmer device170may deliver stimulation energy through the distal end154of the active guidewire150to the LBB.

For other implementations, the target SOI represents a pacing site and the external programmer device170is configured to deliver a pacing pulse, as the stimulation energy, through the guidewire150to the target SOI. The external programmer device170may sense the evoked response at a sensing site within or proximate the heart in which the sensing site is separate from the pacing site.

Yet in other implementations, the target SOI represents a sensing site and the external programmer device is configured to sense the evoked response at the sensing site following delivery of a pacing pulse at a pacing site within or proximate the heart that is separate from the sensing site.

FIG.5Ais a side view of a delivery system200formed in accordance with an embodiment. The delivery system200includes a catheter (or introducer sheath)202, a handle204, a connector assembly206, and a fluid flushing assembly208. Each of these components may be similar or identical to components described in greater detail in U.S. application Ser. No. 16/452,223, filed on Jun. 25, 2019, and U.S. application Ser. No. 16/907,515, filed on Jun. 22, 2020, each of which is incorporated herein by reference in its entirety.

The connector assembly206includes an electrical connector210coupled to a trailing end of handle204. The electrical connector210is electrically coupled to one or more electrodes along the catheter202. For example,FIG.5Bis an enlarged cross-sectional view of a distal segment224of the catheter202as identified by the dashed circle inFIG.5A. In the illustrated embodiment, the electrical connector210(FIG.5A) is communicatively coupled to electrodes270,272(FIG.5B) and optionally an electrode274(FIG.5B) through conductors280that are embedded within the catheter202. The electrodes270,274are proximate to a distal tip (or end)227of the catheter202. In particular embodiments, the electrodes270,272are split-ring electrodes. The connector assembly206is configured to communicatively couple to an electrogram mapping system (not shown).

As shown inFIG.5A, the handle204may include a hemostasis hub212for accepting and coupling to (e.g., tethering to) a proximal end of the catheter202. The catheter202has a catheter lumen282(FIG.5B) that is sized to receive a guidewire, such as the guidewires305(FIG.9A),307(FIG.7). The hemostasis hub212includes an entrance that permits access to the catheter lumen282. The fluid flushing assembly208is also configured to mechanically couple to the hemostasis hub212and fluidly couple to the catheter lumen280through the hemostasis hub212.

The catheter202is configured to introduce a guidewire and/or lead into a designated anatomical region (e.g., a patient's heart). Optionally, the catheter202may be steerable so that an end of the distal end segment224may be located proximate to and face the target SOI. To this end, the catheter202may include a plurality of sheath segments or portions. For example, the catheter202may include a proximal segment221, a body segment222, a deflectable segment223, and the distal end segment224. Based on its intended use, the catheter202may be configured to exhibit various properties. For example, the catheter may be maneuverable and have a sufficient columnar strength for being inserted through a tortuous vascular system. The catheter may also have sufficient kink-resistance so as to bend smoothly. Multiple layers of the catheter may be configured to have these and other properties.

The delivery system200may also include an obturator/dilator220. InFIG.5A, a proximal end292of the obturator/dilator220is shown and a distal end225of the obturator/dilator220is also shown. The distal end225may be wedge-shaped or cone-shaped (e.g., conical). As discussed below, the obturator/dilator220is configured to enlarge an opening for access to the vascular system and/or to provide support for the catheter202as the catheter202is being maneuvered.

FIG.5Cis an enlarged cross-sectional view of the distal end110of the implantable lead106. The lumen115of the implantable lead106may have a diameter119that is sized to allow the active guidewire150to pass therethrough. For example, the lumen115of the implantable lead106may have a proximal opening (not shown) and a distal opening121that are sized relative to the active guidewire150so that the active guidewire150may move through each of the openings. For example, the distal opening121may be sized to allow the fixation anchor162and at least a portion of the coil158to pass therethrough.

The tip electrode120may constitute a fixation anchor that is configured to fixate with tissue at the target SOI. The tip electrode120may also be sized relative to the active guidewire150. For example, the tip electrode120may define an anchor passage123that is aligned with the lumen115of the lead body107. The anchor passage123may have a diameter DP that is sized to permit the tip electrode120to slide over the active guidewire150(or vice versa) as the active guidewire150slides through the lumen115. More specifically, the anchor passage123and the wire body156are configured so that the implantable lead106may be inserted over the proximal end (not shown) of the active guidewire150and advanced along the active guidewire150toward the target SOI. Likewise, the fixation anchor162of the active guidewire150and the anchor passage123of the tip electrode120are configured so that the fixation anchor162may pass through the anchor passage123as the active guidewire150is withdrawn from the target SOI. For example, the diameter DP may be between 0.025″ and 0.045″ or, more particularly, between 0.030″ and 0.040″.

Also shown inFIG.5C, the tip electrode120has a length LA. The length LA may be increased or decreased based on the target SOI. For example, the length LA may be increased to reach His bundles or bundle branches that are greater than 2.0 millimeters below the endocardial surface. In such embodiments, a proximal end of the tip electrode120(e.g., end that is closer to the lead body) may be coated with an insulating material, such as parylene, to maintain the impedance of the tip electrode within a desired range for pacing electrodes. Likewise, the tip electrode120may be configured based upon the tissue near the target SOI to ensure that the tip electrode120may reach a desired region within the target SOI. For example, the diameter of the wire that defines the tip electrode120may be increased or may have a material selected for its particular application.

FIG.6is a flowchart illustrating a method450of positioning an implantable lead with respect to cardiac tissue. The method450is described with reference toFIGS.7-14. The method450is illustrated in the context of HBP but may be suitable for other procedures. Particular embodiments utilize an electrically-active mapping guidewire with active fixation for use with a HIS-bundle implantation catheter. The systems and methods may promote normal conduction through the HIS-Purkinje system. Pacing at the bundle of His may prevent the negative effects of RV pacing and promote ventricular synchrony.

With reference toFIG.7, a guidewire307is inserted through an access point of the vascular system. In some embodiments, the guidewire307is a catheter-positioning guidewire that is intended to be removed after a catheter is positioned within a designated space of the vascular system but prior to the lead being affixed to tissue. As such, the guidewire307may not be an active guidewire. In other embodiments, however, the guidewire307may be an active guidewire that may be used to position the catheter within the designated space and also to identify a location of a target SOI303.

The guidewire307has a distal segment310. Optionally, the distal segment310may have a predetermined shape to aid positioning of the guidewire307. For example, the distal segment310may provide a J-shaped distal end or tip of the guidewire307. As the guidewire307is navigated through the vascular system, the curved distal segment310may reduce the likelihood of the guidewire307inadvertently snagging or engaging other tissue.

The access point may be created by a needle (not shown) that is inserted through an incision of the body and into the vascular system. This process may be similar to the Seldinger technique. For example, a venous needle stick may be inserted through the subclavian vein or another vein, thereby creating an access point. After identifying the vein, the guidewire307may be inserted, at425(FIG.6), through the access point and into the vascular system. The guidewire307is directed into a predetermined region of the vascular system having a target SOI303.

The guidewire307and the distal segment310in particular may be guided and positioned within the chamber using medical imaging. For example, the guidewire307may be tracked using fluoroscopy. As shown inFIG.7, the distal segment310may be directed into a chamber of the heart having the target SOI303. InFIG.7, the chamber is the right atrium312. In other embodiments, however, the chamber may be the right ventricle314.

Turning toFIGS.8A and8B, with the distal segment310positioned within the designated chamber, a catheter301can be inserted through the access point. The catheter301is advanced, at454(FIG.6), along the guidewire307. The catheter301may include features that are similar or identical to the catheter202(FIG.5A) and may be controlled by a delivery system, such as the delivery system200(FIG.5A).

Optionally, the catheter301may include an obturator/dilator220within a lumen322of the catheter301. The obturator/dilator220may also include a passage (not shown) through which the guidewire307may extend. The obturator/dilator220can have a wedge-shaped or cone-shaped distal end225that aids in enlarging the access point. When initially inserted through the access point, the catheter301may have a substantially straight configuration and may include the obturator/dilator220positioned at or near the distal end of the catheter301to enlarge the access point and to provide support for the catheter301as it is being maneuvered. The straight configuration of the catheter301may aid its passage through the superior vena cava and into the right atrium. Upon entry into the vein, the implanter may remove the obturator/dilator220and advance the catheter301over the guidewire307to the right atrium312. Alternatively, the guidewire307may be removed before or after the obturator/dilator220is removed or along with removing the obturator/dilator220.

Once a distal end324(FIG.8B) of the catheter301has entered the right atrium312, the catheter301may be further advanced toward the target SOI303. For embodiments in which the guidewire307remains, the catheter301slides over the distal segment310and the distal segment310may be partially deflected. For example, the J-shaped distal segment310may partially straighten while also causing the catheter301to curve toward the target SOI303. Alternatively, the distal end324of the catheter301may be steered within the right atrium312by the implanter without assistance from the guidewire307.

For embodiments in which the catheter-positioning guidewire307is used, the method450(FIG.6) may also include replacing the catheter-positioning guidewire307with an active guidewire305(shown inFIG.9B). After removing the catheter-positioning guidewire307, an active guidewire305may then be inserted, at455, through the lumen322and advanced toward the target SOI303as guided by the catheter301. At456(FIG.6), the distal end324of the catheter301may be positioned adjacent to tissue having the target SOI303. AlthoughFIG.6indicates that the catheter301is positioned adjacent to the tissue after inserting the active guidewire305, it should be understood that the catheter301may be positioned prior to the active guidewire305being inserted or as the active guidewire305is inserted.

FIG.9Ashows a distal end320of the active guidewire305disposed within the lumen322of the catheter301. The distal end320includes a fixation anchor330. InFIG.9A, the active guidewire305is in a retracted position such that a tip of the fixation anchor330is located within the lumen322and the catheter301surrounds the entirety of the fixation anchor330. In the retracted position, the fixation anchor330may not be aligned with or not co-located with electrodes332,334of the catheter301. For example, the fixation anchor330may be positioned at a depth336that is measured between a tip of the fixation anchor330and a tip of the distal end324of the catheter301(or an end of the lumen322). The depth336may be configured such that electrodes332,334of the catheter301are positioned closer to the target Sal303and such that the conductive material of the fixation anchor330does not interfere with the electrodes332,334ability to detect electrical signals and/or supply electrical current.

FIG.9Bshows the distal end320of the active guidewire305in a projected (or protracted) position. In the projected position, the fixation anchor330may be pressed against a surface of the target SOI303. InFIG.9B, the surface is the endocardial surface of the right atrium. The fixation anchor330may be positioned at a clearance (or a separation distance)338that is measured between the fixation anchor330and the tip of the distal end324of the catheter301. The clearance338may be configured such that the fixation anchor330is positioned in front of the electrodes332,334and closer to the target SOI303. The clearance338may be configured to improve detection of electrical signals from the target SOI during a mapping operation. For example, the clearance338may be configured to improve sensing between the active guidewire fixation anchor electrode330and332and/or334electrodes.

FIG.9Cshows the distal end320of the active guidewire305fixated to tissue of the target SOI303. To secure the fixation anchor330, the implanter may rotate the active guidewire305while pressing the fixation anchor330into the surface. The fixation anchor330may pierce the tissue and forces provided by rotating the fixation anchor330and pressing the fixation anchor330forward may drive the fixation anchor330into the tissue.

At any of the configurations and spatial relationships shown inFIGS.9A,9B, and9C, the target SOI303may be electrically mapped to identify a more precise location for implanting a lead. In particular embodiments, the target SOI303includes the His bundle. For most individuals, the His bundle is located within a membranous portion of the interventricular septum. A portion of the proximal bundle may exist within a right atrial portion of the septum superior to the tricuspid valve annulus. At this location, the His bundle may be surrounded by fibrous connective tissue. Within the right ventricular portion of the septum, the His bundle divides to form the right and left bundles.

The target SOI may be electrically mapped, at258, by (a) the catheter301alone, (b) a combination of the catheter301and the active guidewire305, or (c) the active guidewire305only. Optionally, the mapping process may include detecting signals from only two of (a), (b), or (c) or include detecting signals from each of (a), (b), or (c). In some embodiments, the mapping process may only include detecting signals from either (b) or (c) or from each of (b) and (c). For example, under control of one or more processors configured with specific executable instructions, an external programmer device may deliver stimulation energy through at least one of the catheter or the active guide wire to the target SOI. Alternatively or in addition to delivering stimulation energy, the external programmer device may sense an evoked response at the target SOI from at least one of the catheter or the active guidewire.

Returning toFIG.9A, the distal end324of the catheter301may be steered toward the target SOI. In some embodiments, the target SOI303may be initially mapped (or approximately located) using the electrodes332,334of the catheter301. Sensing between332and334provides a small dipole that allows for precisely targeting a site proximate the His or bundle branch, the SOI330. The implanter may operate a delivery system, such as the delivery system200(FIG.5A), to position the distal end324of the catheter301. Deflecting the catheter301may be accomplished by an actuator (e.g., actuator235shown inFIG.5A) that is operably coupled to segments (e.g., segments221-223shown inFIG.5A). With a proximal segment of the catheter301positioned in the superior vena cava, the actuator may move a deflectable segment of the catheter301such that a distal end324of the catheter301will point generally toward a wall surface335. The wall surface335may be, for example, the surface of an atrial wall proximate to where the target SOI is believed to be located. The distal end324may be in close proximity to the septum, such as within 15 millimeters or less.

An external programmer device may be configured to be electrically coupled to a proximal end of the catheter301. The catheter301may communicate electrical signals between the external programmer device and the electrodes332,334for electrically mapping the target SOI303. For example, the electrodes332,334may sense electrical signals and communicate these electrical signals to the external programmer device for electrically mapping the target SOI303. In such instances, it may be desirable to position the fixation anchor330at least the depth336within the lumen322. If electrical signals are received from the electrodes332and334, the implanter may know that the distal end324of the catheter301is at least approximately aligned with the target SOI303.

If the electrodes332,334are not receiving electrical signals, or if the signals are very faint, the implanter may maneuver the distal end324of the catheter301by small movements of the actuator (e.g., in either a forward or reverse direction) to scan the atrial wall as indicated by the dashed arrows inFIG.9A. The small movements of the actuator will deflect the deflectable section of the catheter301by small amounts. A surface point340(shown inFIG.9B) may be identified when the signals received by the electrodes332,334are strongest.

Alternatively or in addition to using the catheter301, the surface point340may be identified using the fixation anchor330of the active guidewire305. More specifically, the fixation anchor330may be pressed against a series of points along the wall surface335. When against the wall surface335, the active guidewire307may at least one of deliver stimulation energy or detect an evoked response.

The point having the strongest signal may be designated as the surface point340through which the fixation anchor330will be submerged. Optionally, the electrical mapping may occur in unipolar mode by sensing between the fixation anchor330and a remote electrode (not shown), such as a surgical clamp at the pocket. In other embodiments, the electrical mapping may occur by sensing between the fixation anchor330and at least one of the electrodes332,334. The external programmer device may be communicatively coupled to the active guidewire305so that the electrical programmer device may receive signals sensed by the active guidewire305.

Accordingly, the surface point340may be generally located by mapping with the catheter301to identify a local region along the wall surface335and then more precisely located by measuring a series of points within this local region to identify the surface point340. Alternatively, the surface point340may be identified by mapping only with the catheter301. In such instances, the surface point340may be any point within the local region identified by the catheter301. As yet another alternative embodiment, the surface point340is identified, without initially mapping, by measuring a series of points along the wall surface335.

FIG.9Cshows the fixation anchor330after piercing through the surface point340and submerging within the tissue of the target SOI303. With the surface point340identified, the method includes fixating, at460(FIG.6), the distal end324of the active guidewire305to the target SOI303. More specifically, the fixation anchor330may be pressed against the wall surface335as the active guidewire305is rotated. In addition to urging the fixation anchor330into the tissue, the rotational force provided to the fixation anchor330by the implanter further drives the active guidewire305into the tissue. At462(FIG.6), additional measurements may be acquired to assess whether capture of the target SOI303has been achieved. These measurements may be acquired at different depths within the tissue.

At464(FIG.6), the catheter301may be withdrawn. As shown inFIG.9D, the active guidewire305may remain embedded within the tissue of the target SOI303. At466(FIG.6), an implantable lead456(FIG.9E) may be advanced over the active guidewire305. More specifically, a proximal end of the active guidewire305may inserted into a lumen365(FIG.9E) of the implantable lead356. The implantable lead356may be inserted through the access point and urged toward the target SOI while tracking along the active guidewire305.

FIG.9Eshows a lead anchor370of the implantable lead356fixated to the tissue of the target SOI. With the fixation anchor330of the active guidewire305remaining secured to the target SOI, a lead anchor370of the implantable lead356is guided to the surface point340. At468(FIG.6), the lead anchor370may be fixated to the tissue that is proximate the target SOI303. Similar to the fixation anchor330, the lead anchor370may be pressed against the wall surface335as the implantable lead305is rotated. In addition to urging the lead anchor370into the tissue, the rotational force provided to the lead anchor370by the implanter drives the lead anchor370into the tissue.

FIG.9Fshows the implantable lead356in an operating position with the lead anchor370functioning as a tip electrode of the implantable lead356. At470, the lead anchor370may sense electrical activity from the target SOI303to verify capture of the target SOI303. The fixation anchor330may also be used at this time to verify capture. InFIG.9F, the target SOI is the His bundle.

At472, the active guidewire305may be withdrawn. For example, the implanter may gently pull the active guidewire305while also rotating the active guidewire305in an opposition direction. As described with respect toFIG.5C, the active guidewire305may be removed through an anchor passage (not shown) of the lead anchor370.

FIGS.10A and10Billustrate another embodiment of the method450(FIG.6) in which a target SOI403is one of the bundle branches located in the septum wall between the right and left ventricles. As shown inFIG.10A, a fixation anchor430of an active guidewire405is capable of driving greater depths into the septum wall. In such instances, a catheter401may provide additional support to the active guidewire405. For example, the active guidewire405at the surface point440may be held straight by the catheter401so that the force applied by the implanter does not cause the active guidewire405to bend or kink. For embodiments in which the target SOI403has greater depths, such as the depths where bundle branches may be located, the implantable lead456may be driven to greater depths using lead anchors470have greater lengths. As described herein, such lead anchors may be coated with an insulating material to control impedance.

FIGS.11A and11Billustrate another embodiment of the method450(FIG.6) in which a target SOI503is located on an opposite side of a septum wall507. In such instances, the target SOI503is proximate the Purkinje fiber through the opposite left ventricle wall. In alternative embodiments, the target SOI is identified as513and is located on an opposite side of a septum wall517proximate to the Bachmann's bundle. The following is with reference to the septum wall507and the Purkinje fiber but may be similarly applied to the septum wall517and the Bachmann's bundle.

As shown inFIG.11A, the active guidewire505may be driven through the septum wall507, through the left ventricle, and into the septum wall that includes the Purkinje fiber. The active guidewire505may identify the target SOI503and whether it has been located as described above with respect to the target SOI303. Accordingly, in some embodiments, the active guidewire505may be advanced through the right atrium and through the right ventricle. The distal end of the active guidewire505may be forced through the septa wall507separating the right and left ventricles, advanced through the left ventricle, and submerged into a wall of the left ventricle proximate the Purkinje fiber.

As shown inFIG.11B, an implantable lead556may be advanced along the active guidewire505, through the septum wall507, and into the left ventricle. After the lead anchor570is submerged within the wall, the active guidewire505may be removed. In other embodiments, however, the catheter501may be removed and the active guidewire505may remain and function as a pacing lead. In such embodiments, the implantable lead556is not used.

FIG.12illustrates a block diagram of an exemplary IMD that is configured to be implanted into the patient in accordance with embodiments herein. The IMD600may treat both fast and slow arrhythmias with stimulation therapy, including cardioversion, pacing stimulation, an implantable cardioverter defibrillator, suspend tachycardia detection, tachyarrhythmia therapy, and/or the like.

The IMD600has a housing661to hold the electronic/computing components. The housing661(which is often referred to as the “can,” “case,” “encasing,” or “case electrode”) may be programmably selected to act as the return electrode for certain stimulus modes. The housing661further includes a connector (not shown) with a plurality of terminals601,602,604,606,608, and610. The terminals may be connected to one or more leads that are located in various locations within and about the heart. Each lead may have one or more electrodes. The type and location of each electrode may vary. For example, the electrodes may include various combinations of ring, tip, coil, shocking electrodes, and the like.

The IMD600includes a programmable microcontroller620that controls various operations of the IMD600, including cardiac monitoring and stimulation therapy. The microcontroller620includes a microprocessor (or equivalent control circuitry), one or more processors, RAM and/or ROM memory, logic and timing circuitry, state machine circuitry, and I/O circuitry. The IMD600further includes a pulse generator622that generates stimulation pulses for connecting the desired electrodes to the appropriate I/O circuits, thereby facilitating electrode programmability. The switch626is controlled by a control signal628from the microcontroller620.

Optionally, the IMD600may include multiple pulse generators, similar to the pulse generator622, where each pulse generator is coupled to one or more leads/electrodes and controlled by the microcontroller620to deliver select stimulus pulse(s) to the corresponding one or more electrodes. The IMD600includes sensing circuit644selectively coupled to one or more electrodes that perform sensing operations, through the switch626to detect the presence of cardiac activity in the chamber of the heart. The output of the sensing circuit644is connected to the microcontroller620which, in turn, triggers, or inhibits the pulse generator622in response to the absence or presence of cardiac activity. The sensing circuit644receives a control signal646from the microcontroller620for purposes of controlling the gain, threshold, polarization charge removal circuitry (not shown), and the timing of any blocking circuitry (not shown) coupled to the inputs of the sensing circuit624.

In the example ofFIG.12, the sensing circuit644is illustrated. Optionally, the IMD600may include multiple sensing circuits644, where each sensing circuit is coupled to one or more leads/electrodes and controlled by the microcontroller620to sense electrical activity detected at the corresponding one or more electrodes. The sensing circuit624may operate in, for example, a unipolar sensing configuration or a bipolar sensing configuration.

The IMD600further includes an analog-to-digital (A/D) data acquisition system (DAS)650coupled to one or more electrodes via the switch626to sample cardiac signals across any pair of desired electrodes. The A/D converter650is configured to acquire intracardiac electrogram signals, convert the raw analog data into digital data and store the digital data for later processing and/or telemetric transmission to an external device690(e.g., a programmer, local transceiver, or a diagnostic system analyzer). The A/D converter650is controlled by a control signal656from the microcontroller620.

The microcontroller620is operably coupled to a memory660by a suitable data/address bus662. The programmable operating parameters used by the microcontroller620are stored in the memory660and used to customize the operation of the IMD600to suit the needs of a particular patient. The operating parameters of the IMD600may be non-invasively programmed into the memory660through a telemetry circuit664in telemetric communication via communication link667(e.g., MICS, Bluetooth low energy, and/or the like) with the external device690.

The IMD600can further include one or more physiological sensors670. Such sensors are commonly referred to as “rate-responsive” sensors because they are typically used to adjust pacing stimulation rates according to the exercise state of the patient. However, the physiological sensor670may further be used to detect changes in cardiac output, changes in the physiological condition of the heart, or diurnal changes in activity (e.g., detecting sleep and wake states). Signals generated by the physiological sensors670are passed to the microcontroller620for analysis. While shown as being included within the IMD600, the physiological sensor(s)670may be external to the IMD600, yet still, be implanted within or carried by the patient. Examples of physiological sensors might include sensors that, for example, sense respiration rate, pH of blood, ventricular gradient, activity, position/posture, minute ventilation, and/or the like.

A battery672provides operating power to all of the components in the IMD600. The battery672is capable of operating at low current drains for long periods of time, and is capable of providing a high-current pulses (for capacitor charging) when the patient requires a shock pulse (e.g., in excess of 2 A, at voltages above 2 V, for periods of 10 seconds or more). The battery672also desirably has a predictable discharge characteristic so that elective replacement time can be detected. As one example, the IMD600employs lithium/silver vanadium oxide batteries.

The IMD600further includes an impedance measuring circuit674, which can be used for many things, including sensing respiration phase. The impedance measuring circuit674is coupled to the switch626so that any desired electrode and/or terminal may be used to measure impedance in connection with monitoring respiration phase. The IMD600is further equipped with a communication modem (modulator/demodulator)640to enable wireless communication with other devices, implanted devices and/or external devices. In one implementation, the communication modem640may use high frequency modulation of a signal transmitted between a pair of electrodes. As one example, the signals may be transmitted in a high frequency range of approximately 10-80 kHz, as such signals travel through the body tissue and fluids without stimulating the heart or being felt by the patient.

Optionally, the microcontroller620may control a shocking circuit680by way of a timing control632. The shocking circuit680generates shocking pulses as controlled by the microcontroller620. The shocking circuit680may be controlled by the microcontroller620by a control signal682.

Although not shown, the microcontroller620may further include other dedicated circuitry and/or firmware/software components that assist in monitoring various conditions of the patient's heart and managing pacing therapies. The microcontroller620further includes a timing control632, an arrhythmia detector634, a morphology detector636and multi-phase therapy controller633. The timing control632is used to control various timing parameters, such as stimulation pulses (e.g., pacing rate, atria-ventricular (AV) delay, atrial interconduction (A-A) delay, ventricular interconduction (V-V) delay, etc.) as well as to keep track of the timing of RR-intervals, refractory periods, blanking intervals, noise detection windows, evoked response windows, alert intervals, marker channel timing, and the like.

The morphology detector636is configured to review and analyze one or more features of the morphology of cardiac activity signals. For example, in accordance with embodiments herein, the morphology detector636may analyze the morphology of detected R waves, where such morphology is then utilized to determine whether to include or exclude one or more beats from further analysis. For example, the morphology detector636may be utilized to identify non-conducted ventricular events, such as ventricular fibrillation and the like.

The arrhythmia detector634may be configured to apply one or more arrhythmia detection algorithms for detecting arrhythmia conditions. By way of example, the arrhythmia detector634may apply various detection algorithms. The arrhythmia detector634may be configured to declare a ventricular fibrillation episode based on the cardiac events.

The therapy controller633is configured to perform the operations described herein. The therapy controller633is configured to identify a multi-phase therapy based on the ventricular fibrillation episode, the multi-phase therapy including a pacing therapy. The therapy controller633is configured to manage delivery of the burst pacing therapy at a pacing site in a coordinated manner after the one or more shocks. The pacing site may be located at a target SOI, such as a His Bundle. Optionally, other pacing sites may be located at one of a left ventricular (LV) site or a right ventricular (RV) site. The therapy controller633may configured to manage delivery of the shock along a shocking vector between shocking electrodes.