CORONARY SINUS CONDUCTION SYSTEM PACING AND DELIVERY

An implantable medical system includes an implantable catheter advanceable into a coronary sinus of a patient's heart. A guide element and an implantable lead receivable in the side lumen is advanceable through an angled opening of the catheter to be deflected laterally away from the catheter at the deflection angle to position the at least one testing electrode or at least one pacing electrode, respectively, in a myocardium of the patient's heart when the distal portion of the catheter is positioned in the coronary sinus.

SUMMARY

The techniques of this disclosure generally relate to cardiac therapy, in particular conduction system pacing, using the coronary sinus as delivery route for a leaded or leadless solution. A lead or other implantable device may be delivered to and positioned in the coronary sinus using a side-access catheter. A distal portion of the lead or device may include an electrode extending from the side of the catheter to “dive” into the myocardium reaching close to the endocardium where conduction system is located. The vicinity of the electrode to conduction system may be assessed by delivery of test pacing pulses as the electrode is advanced while monitoring QRS duration. An abrupt shortening of the QRS duration may signify that the electrode has reached and captured the conduction system. Use of the coronary sinus to access to the conduction system may provide long-term benefits in stability of the implantable medical device.

In one aspect, the present disclosure relates to an implantable medical system. The system includes an implantable catheter advanceable into a coronary sinus of a patient's heart. The catheter includes a sheath body extending between a proximal portion and a distal portion. The catheter includes a side lumen and an angled opening proximal to the distal portion in fluid communication with the side lumen. The side lumen and the angled opening define a deflection angle. The system also includes a guide element receivable in the side lumen. The guide element extending from a proximal portion to a distal portion. The distal portion includes at least one testing electrode. The guide element is advanceable through the angled opening to be deflected laterally away from the catheter at the deflection angle to position the at least one testing electrode in a myocardium of the patient's heart when the distal portion of the catheter is positioned in the coronary sinus. The system also includes an implantable lead receivable in the side lumen. The lead includes a lead body extending from a proximal portion to a distal portion. The implantable lead includes an anchoring element disposed along the lead body and at least one pacing electrode disposed along the distal portion. The lead is advanceable through the angled opening to be deflected laterally away from the catheter at the deflection angle to implant the at least one pacing electrode in the myocardium to pace a conduction system of the patient's heart.

In another aspect, the present disclosure relates to a delivery system for an implantable medical device. The system includes an implantable catheter advanceable into a coronary sinus of a patient's heart. The catheter includes a sheath body extending between a proximal portion and a distal portion. The catheter includes a side lumen and an angled opening proximal to the distal portion in fluid communication with the side lumen. The side lumen and the angled opening define a deflection angle. The system also includes a guide element receivable in the side lumen. The guide element extends from a proximal portion to a distal portion. The distal portion includes at least one testing electrode. The guide element is advanceable through the angled opening to be deflected laterally away from the catheter at the deflection angle to position the at least one testing electrode in a myocardium of the patient's heart when the distal portion of the catheter is positioned in the coronary sinus. The system also includes an implantable lead receivable in the side lumen. The lead including a lead body extending from a proximal portion to a distal portion. The implantable lead includes an anchoring element disposed along the lead body and at least one pacing electrode disposed along the distal portion. The lead is advanceable through the angled opening to be deflected laterally away from the catheter at the deflection angle to implant the at least one pacing electrode in the myocardium to pace a conduction system of the patient's heart. The system also includes an electrical analyzer operably coupled to the at least one testing electrode. The electrical analyzer is configured to provide pacing pulses to a potential implant location when the at least one testing electrode is positioned in the myocardium of the patient's heart and the distal portion of the catheter is positioned in the coronary sinus.

In another aspect, the present disclosure relates to a method including advancing a catheter into a coronary sinus of a patient's heart. The catheter includes a sheath body extending between a proximal portion and a distal portion. The catheter includes a side lumen and an angled opening proximal to the distal portion in fluid communication with the side lumen. The method also includes orienting the angled opening toward a wall of the coronary sinus proximate to a conduction system of the patient's heart. The method also includes advancing a guide element including at least one testing electrode through the side lumen and the angled opening. The guide element extends from a proximal portion to a distal portion. The angled opening is configured to deflect the guide element laterally away from the catheter to position the at least one testing electrode in a myocardium of the patient's heart. The method also includes pacing one or more potential implant locations using the at least one testing electrode positioned in the myocardium. The method also includes monitoring QRS duration corresponding to each potential implant location in response to pacing the one or more potential implant locations. The method also includes implanting at least one pacing electrode of an implantable lead at a selected implant location of the potential implant locations based on a corresponding QRS duration below a duration threshold.

DETAILED DESCRIPTION

Reference will now be made to the drawings, which depict one or more aspects described in this disclosure. However, it will be understood that other aspects not depicted in the drawings fall within the scope of this disclosure. Like numbers used in the figures refer to like components, steps, and the like. However, it will be understood that the use of a reference character to refer to an element in a given figure is not intended to limit the element in another figure labeled with the same reference character. In addition, the use of different reference characters to refer to elements in different figures is not intended to indicate that the differently referenced elements cannot be the same or similar.

FIG. 1is a conceptual diagram that illustrates a cutaway view of a patient's heart12. In general, the systems, devices, and methods of the present disclosure may be used with the patient's heart12to deliver an implantable medical device (IMD) to an implant location within the heart12.

Various pacing techniques generally involve pacing one or more of the four chambers of the heart12, including the right atrium (RA), right ventricle (RV), left ventricle (LV), and left atrium (LA). Some therapeutic pacing techniques involve the cardiac conduction system. The cardiac conduction system, like a “superhighway,” may be described as quickly conducting electrical pulses whereas pacing cardiac muscle tissue may slowly conduct electrical pulses, like “traveling on a dirt road.” The cardiac conduction system includes SA node, atrial internodal tracts (i.e., anterior internodal, middle internodal, and posterior internodal), AV node, His bundle (also known as the atrioventricular bundle or bundle of His), and bundle branches including the left bundle branch (LBB) and the right bundle branch (RBB).

The SA node, located at the junction of the superior vena cava (SVC) and RA, is considered to be the natural pacemaker of the heart since it continuously and repeatedly emits electrical impulses. The electrical impulse spreads through the muscles of RA to LA to cause synchronous contraction of the atria. Electrical impulses are also carried through atrial internodal tracts to AV node—the sole connection between the atria and the ventricles.

Conduction through the tissue of the AV node takes longer than through the atrial tissue, resulting in a delay between atrial contraction and the start of ventricular contraction. The AV delay, which is the delay between atrial contraction and ventricular contractor, allows the atria to empty blood into the ventricles. Then, the valves between the atria and ventricles close before causing ventricular contraction via branches of the His bundle.

His bundle is located in the membranous atrioventricular septum near the annulus of the tricuspid valve. The tricuspid valve is between the RA and the RV. His bundle splits into the LBB and RBB and are formed of specialized fibers called “Purkinje fibers.” Purkinje fibers may be described as rapidly conducting an action potential down the ventricular septum, spreading the depolarization wavefront quickly through the remaining ventricular myocardium, and producing a coordinated contraction of the ventricular muscle mass.

As illustrated, a target implantation zone14in the heart12may be positioned adjacent to the triangle of Koch region in the coronary sinus near the coronary sinus ostium. The target implantation zone14is below the mitral valve within the coronary sinus on the LV wall. The angle of implantation into the target implantation zone14may be selected to deliver an LV electrode of the IMD into the upper region of the conduction system, which may include the LBB. The electrode on the device may “dive” into the myocardium reaching close to the endocardium where conduction system is located.

FIGS. 2-4show different views of one example of an implantable medical system100according to the present disclosure.FIG. 2is a conceptual diagram that illustrates a cutaway view of the implantable medical system100. The implantable medical system100may include a delivery system102and an IMD104. The IMD104may be configured to provide coronary sinus conduction system pacing and delivery. The IMD104may be, or include, an implantable lead. The IMD104may be deliverable by the delivery system102to an implant location in the heart of a patient.FIG. 3is a conceptual diagram that illustrates an exploded view of the implantable medical system100.FIG. 4is a conceptual diagram that illustrates a cross-section of the implantable medical system100showing a main lumen122and a side lumen124of the implantable catheter106.

The delivery system102may include an implantable catheter106, a guide element108, an electrical analyzer110, and an external imaging system112. The implantable catheter106may be used to guide the IMD104through the vasculature and heart toward an implant location. The guide element108may cooperatively interact with the IMD104to allow a physician to push, pull, steer, or otherwise guide the IMD104to an implant location particularly when portions of the IMD104extend beyond the implantable catheter106. The electrical analyzer110may be operably coupled to the guide element108to facilitate testing of potential implant sites in the heart. The external imaging system112, which may include an intravenous ultrasound system (IVUS), may be used to provide images that facilitate guidance of the delivery system102. The external imaging system112may be configured to monitor the position of the distal portion of the catheter.

The implantable catheter106may be a sheath advanceable into a coronary sinus of a patient's heart. The implantable catheter106may include a main lumen122and a side lumen124. A catheter guide element123is receivable in the main lumen122to allow a physician to push, pull, steer, or otherwise guide the implantable catheter106through the vasculature and heart toward an implant location. The IMD104and the guide element108are receivable in the side lumen124of the implantable catheter106. The main lumen122and the side lumen124may be open or closed.

The implantable catheter106may include a tapered tip portion118and a visible tip portion120. The visible tip portion120may extend, or protrude, distal to the tapered tip portion118. The visible tip portion120may be at least partially formed of an ultrasound visible material. The visible tip portion120may be detectable during the implantation process using the external imaging system112.

The catheter guide element123(FIG. 4) may be a stylet or guide wire. The catheter guide element123may be advanced through a main lumen122of the implantable catheter106. In some embodiments, a distal portion of the main lumen122is closed. The catheter guide element123may be used to push, pull, steer, or otherwise guide the implantable catheter106. In some embodiments, a distal portion of the main lumen122is closed. In some embodiments, the distal portion of the main lumen122may terminate at the tapered tip portion118.

The implantable catheter106may also include an angled opening126in fluid communication with the side lumen124. The side lumen124may be described as being open on the distal end. The side lumen124and the angled opening126define a deflection angle116. In some cases, the deflection angle116may be defined from the orientation of the angled opening126relative to the orientation of the side lumen124. For example, deflection angle116may be defined as an angle between a first longitudinal axis along the side lumen124and a second longitudinal axis along the angled opening126. Additionally, or alternatively, the deflection angle116may be measured by the orientation of a distal portion of the IMD104as it exits the angled opening126compared to the implantable catheter106. In particular, the deflection angle116may be defined as an angle between a first longitudinal axis aligned along the implantable catheter106and a second longitudinal axis aligned along the distal portion of the IMD104as it exits the angled opening126of the catheter.

In general, the deflection angle116is selected to deflect at least a distal portion of the guide element108or at least a distal portion of the IMD104laterally away from the implantable catheter106at the deflection angle to implant at least one testing electrode130of the guide element108or at least one pacing electrode132of the IMD104in the myocardium of the heart when the distal portion of the implantable catheter106is positioned in the coronary sinus. In general, each of the electrodes130,132may each be operably coupled via an electrical conductor to corresponding circuitry, such as the electrical analyzer110or the controller114.

The guide element108may be a stylet or guide wire. The guide element108may be receivable in the side lumen124of the implantable catheter106. In some embodiments, a distal portion of the guide element108includes at least one testing electrode130. Testing electrodes130may be used to electrically test one or more potential implant locations when the guide element108extends past the IMD104and implantable catheter106.

The IMD104may include an implantable controller114. The controller114may be operably coupled to one or more pacing electrodes132. The implantable controller114may be operably coupled to the IMD104to provide pacing pulses to a selected implant location for pacing therapy.

Any suitable IMD104may be used. In some embodiments, the IMD104is, or includes, a bipolar lead having two or more pacing electrodes132. A bipolar pacing lead may allow for pacing at more than one implant location in the myocardium. [←Is this correct?] One example of a suitable IMD104includes an ATTAIN ABILITY™ AND ATTAIN™ PERFORMA™ Attain left-heart leads available from Medtronic plc of Dublin, Ireland, which may not use the anchoring element134as a pacing electrode132.

Non-limiting examples of IMDs include a leaded or leadless pacemaker, an implantable cardioverter defibrillator (ICD), a cardiac resynchronization device with or without defibrillation capability (CRT or CRT-D), a leaded or leaded monitoring device, or an extravascular implantable cardioverter defibrillator (EVICD). One of the leads or leadlets of such devices may be configured to enter into the coronary sinus as described herein.

As used herein, “leadless” refers to a device being free of a lead extending out of the heart. In other words, a leadless device may have a lead that does not extend from outside of the patient's heart to inside of the patient's heart. Some leadless devices may be introduced through a vein, but once implanted, the device is free of, or may not include, any transvenous lead and may be configured to provide cardiac therapy without using any transvenous lead. A leadless device, in particular, does not use a lead to operably connect to an electrode in the ventricle when a housing of the device is positioned in the atrium. A leadless electrode may be coupled to the housing of the medical device without using a lead between the electrode and the housing. As used herein, “intracardiac” refers to a device configured to be implanted entirely within a patient's heart, for example, to provide cardiac therapy.

The IMD104may also include an anchoring element134(FIG. 3) to facilitate secure attachment of the IMD104to the vasculature or the heart. In some embodiments, the anchoring element134may be a spiral helix or helical structure configured to engage the vessel wall of the coronary sinus. In other embodiments, the anchoring element134may be a dart or other linear structure. The IMD104may be receivable in the side lumen124of the implantable catheter106. The IMD104and the guide element108may be advanceable through the implantable catheter106. The IMD104and the guide element108may separately be advanceable or retractable relative to one another. In some embodiments, the guide element108is advanceable through a lead lumen147(FIG. 4) of the IMD104to a potential implant location.

In some embodiments, the anchoring element134may be at least partially, or entirely, formed of an electrically conductive material, which m ay be used as one of the pacing electrodes132of the IMD104. In one example, the anchoring element134may be used as a pacing backup in response to problems with one of the pacing electrodes132. Allowing the anchoring element134to function as a pacing electrode132may be used when the patient's conduction system has an exit block leading to loss of pacing capture.

During implantation, the IMD104and the guide element108may be advanced through an angled opening126of the implantable catheter106to be deflected laterally away from the catheter at the deflection angle116. When the distal portion of the implantable catheter106is positioned in the coronary sinus, the guide element108may be advanced to protrude out from the angled opening126to test a potential implant location in the myocardium using one or more testing electrodes130. The guide element108may be retracted and removed after testing is completed and an implant location is identified. The IMD104may be advanced to protrude out from the angled opening126to implant one or more pacing electrodes132in the myocardium to pace a conduction system of the patient's heart. The implantable catheter106may be retracted and removed after the IMD104is implanted.

An implant location may be selected from the one or more potential implant locations tested using the one or more testing electrodes130. The electrical analyzer110may be operably coupled to one or more testing electrodes130of the guide element108to generate electrical pulses for testing implant locations.

As can be seen with respect toFIG. 3, the implantable catheter106may include a sheath body141extending between a distal portion140and a proximal portion142. The tapered tip portion118and the visible tip portion120may be positioned on the distal portion140. The visible tip portion120may be positioned distal to the tapered tip portion118. The tapered tip portion118may be positioned distal to the angled opening126. The angled opening126may be positioned on the distal portion140or along the sheath body141between the distal portion and the proximal portion142such that the angled opening is positioned proximal to the distal portion140.

The IMD104may include a lead body145extending between a distal portion144and a proximal portion146. The distal portion144may include at least one pacing electrode132. In some embodiments, the IMD104includes two or more pacing electrodes132. In the illustrated embodiment, the pacing electrodes132include two electrodes with one electrode distal to the other electrode. The anchoring element134may be positioned on the distal portion140. As illustrated, the anchoring element134is integrally formed with the distal pacing electrode132.

The guide element108may extend from a distal portion148to a proximal portion150. At least one testing electrode130may be positioned on the distal portion148. In some embodiments, the guide element108includes two or more testing electrodes130. In the illustrated embodiment, the testing electrodes130include two electrodes with one electrode distal to the other electrode.

FIG. 5is a conceptual diagram that illustrates another example of an IMD204that may be used in the implantable medical system100according to the present disclosure. Many of the parts and components of the IMD204are the same or similar to those depicted in, and described with regard to, the IMD104ofFIGS. 2-3. The IMD204differs from the IMD104in that the anchoring element234is positioned proximal to the at least one, two, or more pacing electrodes232. The anchoring element234may be disposed distal to the distal portion along the lead body. For example, the anchoring element234may be disposed along the lead body and the pacing electrodes232may be disposed on the distal portion. The anchoring element234may or may not be used as a pacing electrode232for backup pacing. The anchoring element234may have a spiral helix or helical structure. The anchoring element234may be configured to engage the coronary sinus vessel wall of the patient to provide structural stability for the IMD204and to optionally provide backup pacing.

FIG. 6is a flow diagram that illustrates one example of a method300of using the implantable medical system100according to the present disclosure. The method300may include advancing the catheter into the coronary sinus of the heart in block302.

The catheter may be oriented such that the angled opening is directed toward a wall of the coronary sinus proximate to the conduction system of the heart in block302. The advancement of the catheter may be monitored using an intraventricular ultrasound (IVUS) system.

The guide element may be advanced through the side lumen and the angled opening of the catheter in block306. The angled opening may be configured to deflect the guide element laterally away from the catheter to position the at least one testing electrode of the guide element in the myocardium of the patient's heart.

The one or more testing electrodes of the guide element may be used to pace a potential implant location when positioned in the myocardium in block308. The implant location may be selected based on the QRS duration and/or pacing threshold corresponding to the potential implant location in response to pacing in block310. In one example, the QRS duration may be compared to a QRS duration threshold. The method300may continue to block312in response to the QRS duration being below the QRS duration threshold. The method300may return to block308in response to the QRS duration exceeding the QRS duration threshold to test a different implant location.

One or more pacing electrodes of the IMD, or implantable lead, may be implanted at the selected implant location in block312. In some embodiments, the guiding element may be retracted from the side lumen after implanting at least one pacing electrode of the IMD.

FIG. 7is a flow diagram that illustrates one example of a method of choosing the implant location based on the QRS duration and/or pacing threshold corresponding to potential implant locations in block310(FIG. 6). In general, more than one implant location may be monitored and tested. The implant location may be selected based on a narrowest QRS duration corresponding to the particular implant location. In some embodiments, the QRS duration may be monitored as the guide element is advanced to one or more depths in the myocardium. Multiple electrodes may also be used to test different depths in the myocardium without repositioning the guiding element.

The QRS duration and the pacing threshold corresponding to each potential implant location may be monitored in block320. Any suitable technique may be used to the monitor the QRS duration. In some embodiments, an electrode apparatus operably coupled to the patient may be configured to monitor QRS duration in response pacing the potential implant location.

The QRS duration for each implant location may be compared to a QRS duration threshold. The method310may continue to block324in response to not more than one potential implant location corresponding to a QRS duration below the QRS duration threshold. The method310may continue to block326in response to more than one potential implant location corresponding to a QRS duration exceeding the QRS duration threshold.

The implant location with the lowest QRS duration threshold may be selected in block324. The location with the lowest QRS duration threshold may be determined by directly measuring the implant location or indirectly. In some embodiments, the guide element may be advanced deeper into the myocardium until a wider QRS duration is detected at a particular potential implant location. The wider QRS duration may exceed a QRS duration threshold. The guide element may be retracted proximally from the particular potential implant location to a less deep implant location. The selected implant location may be determined as being proximal to the potential implant location associated with a narrower QRS duration than detected at the particular potential implant location.

If more than one potential implant location has a narrowest QRS duration, more than one of the potential implant locations may be in the conduction system of the heart. The implant location may be selected based on a corresponding pacing threshold below a below a target value in block326.

While the present disclosure is not so limited, an appreciation of various aspects of the disclosure will be gained through a discussion of the specific examples and illustrative embodiments provided below. Various modifications of the examples and illustrative embodiments, as well as additional embodiments of the disclosure, will become apparent herein.

An implantable medical system comprising:an implantable catheter advanceable into a coronary sinus of a patient's heart, the catheter comprising a sheath body extending between a proximal portion and a distal portion, the catheter comprising a side lumen and an angled opening proximal to the distal portion in fluid communication with the side lumen, wherein the side lumen and the angled opening define a deflection angle;a guide element receivable in the side lumen, the guide element extending from a proximal portion to a distal portion, wherein the distal portion includes at least one testing electrode, wherein the guide element is advanceable through the angled opening to be deflected laterally away from the catheter at the deflection angle to position the at least one testing electrode in a myocardium of the patient's heart when the distal portion of the catheter is positioned in the coronary sinus; andan implantable lead receivable in the side lumen, the lead comprising a lead body extending from a proximal portion to a distal portion, wherein the implantable lead comprises an anchoring element disposed along the lead body and at least one pacing electrode disposed along the distal portion, wherein the lead is advanceable through the angled opening to be deflected laterally away from the catheter at the deflection angle to implant the at least one pacing electrode in the myocardium to pace a conduction system of the patient's heart.

The system according to Example 1, wherein the anchoring element is positioned proximal to the at least one pacing electrode.

The system according to Example 1, wherein the anchoring element is integrally formed with the at least one pacing electrode.

The system according to any preceding Example, wherein the anchoring element comprises a helical structure configured to engage the coronary sinus vessel wall of the patient.

The system according to any preceding Example, wherein the lead is a bipolar lead comprising two or more pacing electrodes including the at least one second electrode.

The system according to any preceding Example, wherein the sheath body comprises a tapered tip portion distal to the angled opening.

The system according to Example 6, wherein the sheath body comprises an ultrasound visible tip portion extending distal to the tapered tip portion.

The system according to any preceding Example, wherein the guide element and the lead are separately advanceable or retractable relative to one another.

The system according to any preceding Example, wherein the guide element is advanceable through a lead lumen of the lead to a potential implant location.

A delivery system for an implantable medical device, the system comprising:an implantable catheter advanceable into a coronary sinus of a patient's heart, the catheter extending between a proximal portion and a distal portion, the catheter comprising a side lumen and an angled opening proximal to the distal portion in fluid communication with the side lumen, wherein the side lumen and the angled opening define a deflection angle;a guide element receivable in the side lumen, the guide element extending from a proximal portion to a distal portion, wherein the distal portion includes at least one testing electrode, wherein the guide element is advanceable through the angled opening to be deflected laterally away from the catheter at the deflection angle to position the at least one testing electrode in a myocardium of the patient's heart when the distal portion of the catheter is positioned in the coronary sinus;an implantable lead receivable in the side lumen, the lead comprising a lead body extending from a proximal portion to a distal portion, wherein the implantable lead comprises an anchoring element disposed along the lead body and at least one pacing electrode disposed along the distal portion, wherein the lead is advanceable through the angled opening to be deflected laterally away from the catheter at the deflection angle to implant the at least one pacing electrode in the myocardium to pace a conduction system of the patient's heart; andan electrical analyzer operably coupled to the at least one testing electrode, the electrical analyzer configured to provide pacing pulses to a potential implant location when the at least one testing electrode is positioned in the myocardium of the patient's heart and the distal portion of the catheter is positioned in the coronary sinus.

The system according to Example 10, further comprising an electrode apparatus operably coupled to the patient, the electrode apparatus configured to monitor QRS duration in response pacing the potential implant location.

The system according to Example 10 or 11, comprising an implantable controller operably coupled to the at least one second electrode, the anchoring element, or both, the implantable controller configured to provide pacing pulses to a selected implant location.

The system according to any Example 10 to 12, further comprising an interventricular ultrasound (IVUS) system configured to monitor the position of the distal portion of the catheter.

A method comprising:advancing a catheter into a coronary sinus of a patient's heart, the catheter comprising a sheath body extending between a proximal portion and a distal portion, the catheter comprising a side lumen and an angled opening proximal to the distal portion in fluid communication with the side lumen;orienting the angled opening toward a wall of the coronary sinus proximate to a conduction system of the patient's heart;advancing a guide element including at least one testing electrode through the side lumen and the angled opening, the guide element extending from a proximal portion to a distal portion, wherein the angled opening is configured to deflect the guide element laterally away from the catheter to position the at least one testing electrode in a myocardium of the patient's heart;pacing one or more potential implant locations using the at least one testing electrode positioned in the myocardium;monitoring QRS duration corresponding to each potential implant location in response to pacing the one or more potential implant locations; andimplanting at least one pacing electrode of an implantable lead at a selected implant location of the potential implant locations based on a corresponding QRS duration below a duration threshold.

The method according to Example 14, further comprising retracting the guiding element from the side lumen after implanting the at least one pacing electrode.

The method according to Example 14 or 15, further comprising determining the selected implant location based on a corresponding narrowest QRS duration.

The method according to any Example 14 to 16, wherein monitoring QRS duration comprises monitoring the QRS duration as the guide element is advanced to one or more depths in the myocardium.

The method according to any Example 14 to 17, further comprising:advancing the guide element deeper into the myocardium until a wider QRS duration is detected at a particular potential implant location;retracting the guide element proximally from the particular potential implant location; anddetermining the selected implant location proximal to the potential implant location associated with a narrower QRS duration than detected at the particular potential implant location.

The method according to any Example 14 to 18, further comprising:monitoring pacing threshold corresponding to each potential implant location in response to pacing the one or more potential implant locations using the at least one testing electrode; andin response to identifying more than one of the potential implant locations having a corresponding QRS duration below the duration threshold, determining the selected implant location based on a corresponding pacing threshold below a below a target value.

The method according to any Example 14 to 19, further comprising monitoring advancement of the catheter using an intraventricular ultrasound (IVUS) system.

All references and publications cited herein are expressly incorporated herein by reference in their entirety for all purposes, except to the extent any aspect directly contradicts this disclosure.

Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims may be understood as being modified either by the term “exactly” or “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein or, for example, within typical ranges of experimental error.

The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range. Herein, the terms “up to” or “no greater than” a number (e.g., up to 50) includes the number (e.g., 50), and the term “no less than” a number (e.g., no less than 5) includes the number (e.g., 5).

Terms related to orientation, such as “proximal” and “distal,” are used to describe relative positions of components and are not meant to limit the absolute orientation of the embodiments contemplated.

The terms “coupled” or “connected” refer to elements being attached to each other either directly (in direct contact with each other) or indirectly (having one or more elements between and attaching the two elements). Either term may be replaced to “couplable” or “connectable” to describe that the elements are configured to be coupled or connected. In addition, either term may be modified by “operatively” and “operably,” which may be used interchangeably, to describe that the coupling or connection is configured to allow the components to interact to carry out functionality.

As used herein, the term “configured to” may be used interchangeably with the terms “adapted to” or “structured to” unless the content of this disclosure clearly dictates otherwise.

The singular forms “a,” “an,” and “the” encompass embodiments having plural referents unless its context clearly dictates otherwise.

The term “or” is generally employed in its inclusive sense, for example, to mean “and/or” unless the context clearly dictates otherwise. The term “and/or” means one or all of the listed elements or a combination of at least two of the listed elements.

The phrases “at least one of,” “comprises at least one of,” and “one or more of” followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

In general, the terms “aspect” and “embodiment” may be used interchangeably to describe one or more examples of the present disclosure. Reference to “one embodiment,” “an embodiment,” “certain embodiments,” or “some embodiments,” etc., means that a particular feature, configuration, composition, or characteristic described in connection with the embodiment (or aspect) is included in at least one embodiment of the disclosure. Thus, the appearances of such phrases in various places throughout are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, configurations, compositions, or characteristics may be combined in any suitable manner in one or more embodiments.