Lead guide
阅读说明:本技术 引线导向引导 (Lead guide ) 是由 M·G·T·克里斯蒂 R·A·德雷克 B·普鲁肖特哈曼 A·M·马勒威茨 于 2018-07-03 设计创作,主要内容包括:在一些实例中,一种医疗装置系统包括电极。所述医疗装置系统可以包括联接到所述电极的阻抗测量电路,所述阻抗测量电路可以被配置为产生指示接近所述电极的阻抗的阻抗信号。所述医疗装置系统可以包括处理电路,所述处理电路可以被配置为识别所述阻抗信号的第一频率分量和第二频率分量,并且基于所述第一频率分量和所述第二频率分量来提供所述电极在患者体内的位置的指示。(In some examples, a medical device system includes an electrode. The medical device system may include an impedance measurement circuit coupled to the electrode, the impedance measurement circuit may be configured to generate an impedance signal indicative of an impedance proximate the electrode. The medical device system may include processing circuitry that may be configured to identify first and second frequency components of the impedance signal and provide an indication of a location of the electrode within a patient's body based on the first and second frequency components.)
1. A medical device system, comprising:
an electrode;
an impedance measurement circuit coupled to the electrode, the impedance measurement circuit configured to generate an impedance signal indicative of an impedance proximate the electrode; and
a processing circuit configured to:
identifying a first frequency component and a second frequency component of the impedance signal; and is
Providing an indication of a position of the electrode within the patient based on the first frequency component and the second frequency component.
2. The medical device system of claim 1, further comprising an implantable medical lead, the electrode disposed on the implantable medical lead, and wherein a proximal end of the lead includes a connector that connects the lead to a medical device.
3. The medical device system of any of claims 1-2, wherein the processing circuitry is configured to determine a first characteristic of the first frequency component and a second characteristic of the second frequency component, wherein the processing circuitry is configured to provide the indication of the location of the electrode within the patient based on the first characteristic and the second characteristic.
4. The medical device system of any one of claims 1-3, wherein the processing circuitry is configured to determine a relationship between the first characteristic and the second characteristic, wherein the processing circuitry is configured to provide the indication of the location of the electrode within the patient based on the relationship between the first characteristic and the second characteristic.
5. The medical device system of any of claims 1-4, wherein the first frequency component corresponds to a systolic frequency, the first characteristic includes an amplitude of the first frequency component, the second frequency component corresponds to a respiratory frequency, and the second characteristic includes an amplitude of the second frequency component, and
wherein the processing circuit is configured to determine the magnitude of the first frequency component and the magnitude of the second frequency component.
6. The medical device system of any one of claims 1-5, wherein the first characteristic and the second characteristic include one of an amplitude, a frequency, a wavelength, or an intensity in Fourier space.
7. The medical device system of any of claims 1-6, wherein the relationship includes a ratio of the first characteristic to the second characteristic, and wherein the processing circuitry is configured to determine the ratio.
8. The medical device system of any of claims 1-7, wherein the first frequency component corresponds to a systolic frequency and the second frequency component corresponds to a respiratory frequency, and wherein the processing circuitry is configured to provide the indication of the location of the electrode within the patient relative to at least one of a heart or a lung of the patient.
9. The medical device system of any one of claims 1-8, wherein the processing circuitry is configured to provide an indication of: (a) the position of the electrode relative to at least one of: a sternum; a heart; a lung; or a portion of the heart or lung; and/or (b) an indication of at least one of: a relative cranial-caudal position of the electrode, a relative left-right lateral position of the electrode, or a relative ventral-dorsal position of the electrode.
10. The medical device system of any of claims 1-9, wherein the impedance measurement circuit is configured to generate the impedance signal, wherein the processing circuit is configured to identify the first frequency component and the second frequency component, and wherein the processing circuit is configured to periodically provide the indication of the location over time as the location varies.
11. The medical device system of any one of claims 1-10, wherein the electrode is positioned on an implant tool configured to be advanced into the substernal space of the patient, the implant tool defining a channel configured to receive a medical lead for implantation of the medical lead in the substernal space.
12. The medical device system of any one of claims 1-11, further comprising a plurality of electrodes disposed on the lead, wherein the impedance measurement circuit is configured to generate a plurality of impedance signals, each of the impedance signals indicative of an impedance proximate a respective electrode of the plurality of electrodes, the plurality of electrodes coupled to the impedance measurement circuit and including the electrode.
13. The medical device system of any of claims 1-12, wherein the processing circuit is configured to identify, for each of the plurality of impedance signals, the first frequency component and the second frequency component, and wherein the processing circuit is configured to provide, for at least one of the electrodes, an indication of the relative position of the electrode within the patient based on the first frequency component and the second frequency component of the respective impedance signal.
14. The medical device system of any of claims 1-13, wherein the processing circuit is configured to determine that the measurement of the impedance signal satisfies a criterion.
15. The medical device system of any of claims 1-14, wherein the processing circuit is configured to provide a warning indication to a user in response to determining that the measurement satisfies the criteria.
Technical Field
The present disclosure relates to medical devices, and more particularly, to techniques for implanting medical devices (e.g., implantable medical electrical leads).
Background
Implantable pulse generators have been used to provide electrical stimulation to organs, tissues, muscles, nerves, or other locations of a patient. An example of electrical stimulation is cardiac pacing. Cardiac pacing involves electrical stimulation of the heart when the heart's natural pacemaker or conduction system fails to provide synchronized atrial and ventricular contractions at an appropriate rate and interval to suit the patient's needs. Bradycardia pacing increases the rate at which a patient's heart contracts when the patient's heart beats too slowly to alleviate symptoms associated with bradycardia. Malignant tachyarrhythmias, such as Ventricular Fibrillation (VF), are uncoordinated contractions of the heart's ventricular myocardium and are the most common arrhythmias in patients with cardiac arrest. If this arrhythmia persists for more than a few seconds, cardiogenic shock can result and stop effective blood circulation. Sudden Cardiac Death (SCD) may therefore be a matter of minutes. Cardiac pacing may also provide electrical stimulation intended to suppress or convert tachyarrhythmias. This may alleviate symptoms and prevent or terminate arrhythmias that may lead to sudden cardiac death or require treatment with high voltage defibrillation or cardioversion shocks.
Conventional implantable pulse generators include a housing that encloses the pulse generator and other electronics and is implanted subcutaneously in the chest of the patient. The housing is connected to one or more implantable medical electrical leads. The electrical lead includes one or more electrodes on a distal portion of the lead that is implanted within the patient, such as inside the patient's heart (e.g., such that at least one electrode contacts the endocardium), within a vessel near the heart (e.g., within the coronary sinus), or attached to an outer surface of the heart (e.g., in the pericardium or epicardium).
Disclosure of Invention
This disclosure describes, among other things, systems and techniques for implanting an implantable medical electrical lead. One aspect of the present disclosure includes a method for guiding a guide during implantation of a lead in an extra-cardiovascular location in a patient. The extravascular location of the heart may include a subcutaneous and/or substernal location. The subcutaneous lead does not contact the heart closely but lies in the tissue or muscle plane between the skin and the sternum, and likewise, the substernal lead does not contact the heart closely but lies in the tissue or muscle plane between the sternum and the heart.
Due to the distance between the heart and the electrodes of one or more leads implanted in the patient, to achieve better pacing, sensing or defibrillation, the pacing/sensing electrodes and defibrillation coil electrodes should be placed in the tissue plane such that the electrodes are directly above or near the surface of the heart contour. For example, one or more electrodes for delivering pacing pulses should be positioned in the carrier above the approximate center of the chamber to pace to produce the lowest pacing capture threshold for pacing. Also, the electrode or electrodes used for sensing the cardiac electrical activity of the heart should be located above the approximate center of the chamber to be sensed to obtain an optimal sensing signal. For shock purposes, the defibrillation coil electrode is preferably disposed over the approximate center of the chamber to be shocked.
By providing guidance to a user (e.g., a physician) during an implantation procedure, guiding a lead to such a desired location as described herein may be improved. The systems and techniques described herein include determining a position of a lead relative to one or more organs or other anatomical structures of a patient. For example, the relative position of the electrodes on the lead within the patient may indicate the position of the lead relative to the patient's heart or lungs. Medical device system may be basedAn indication of the relative position of the electrodes (e.g., placed on the substernal implantable electrical stimulation lead) with respect to the heart and lungs of the patient is provided in the impedance signal indicative of the impedance proximate the electrodes. By using the systems and techniques described herein, leads may be placed with greater accuracy, reliability, and repeatability (e.g., from patient to patient). The guide system may improve the function of the lead, for example, by providing more or better information about the substernal space during guidance and placement of the lead within the patient. By using impedance information about the substernal space (e.g., including impedance information from the carrier signal between the two electrodes), guidance and placement of the substernal implantable electrical stimulation lead may be performed more safely and more efficiently. In addition, the systems and techniques described herein may be used in other anatomical spaces, such as within the heart or near other organs. For example, the medical device systems described herein may be used with a left ventricular lead implant, e.g., to provide impedance mapping functionality, with an Electrocardiographic (ECG) band during medical diagnosis or treatment to provide more information, or with another mapping system (e.g., Cardiolnsight (available from Medtronicplc, dublin, ireland)TMA non-invasive 3D mapping system).
In one example, the present disclosure is directed to a method for indicating a relative position of an electrode within a patient, the method comprising: generating, by an impedance measurement circuit coupled to the electrode, an impedance signal indicative of an impedance proximate the electrode; identifying, by a processing circuit, a first frequency component and a second frequency component of an impedance signal; providing, by the processing circuit and based on the first frequency component and the second frequency component, an indication to a user of a relative position of the electrode within the patient.
In one example, the present disclosure relates to a medical device system comprising: an electrode; and an impedance measurement circuit coupled to the electrode, the impedance measurement circuit configured to generate an impedance signal indicative of an impedance proximate the electrode; a processing circuit configured to identify a first frequency component and a second frequency component of an impedance signal; and providing an indication of the relative position of the electrode within the patient based on the first frequency component and the second frequency component.
In one example, the present disclosure is directed to a medical device system comprising: an electrode; and an impedance measurement circuit coupled to the electrode, the impedance measurement circuit configured to generate an impedance signal indicative of an impedance of the proximal end of the electrode; a processing circuit configured to: identifying a first frequency component of the impedance signal corresponding to a systolic frequency and a second frequency component of the impedance signal corresponding to a respiratory frequency; determining a first amplitude of the first frequency component and a second amplitude of the second frequency component; determining a relationship between the first amplitude and the second amplitude; and providing an indication of the relative position of the electrodes within the patient's body based on the relationship.
This summary is intended to provide an overview of the subject matter described in this disclosure. The figures and the description below are not intended to provide an exclusive or exhaustive explanation of the systems, apparatuses, and methods described in detail in the figures and the description below. Further details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the statements provided below.
Drawings
Fig. 1A-1C are front, side, and top conceptual views, respectively, illustrating an example medical device system in conjunction with a patient.
Fig. 2 is a functional block diagram depicting an example of a guidance system.
Fig. 3 is a functional block diagram showing an example configuration of a transport system.
Fig. 4 is a partial perspective view showing a portion of the technique of implanting a lead.
Fig. 5A is a partial perspective view showing a portion of the technique of implanting a lead.
Fig. 5B is a perspective view showing a portion of the wire feed system.
Fig. 6 and 7 are flow diagrams depicting methods of implanting leads according to some examples of the present disclosure.
Fig. 8A and 8B illustrate examples of substernal spatial locations within a patient.
Fig. 8C depicts a graph including examples of impedance signals for different positions in the substernal space of a patient.
Fig. 9A-9D illustrate an example of a lead placed in the substernal space.
10A-10E illustrate examples of techniques for determining the relative position of electrodes within a patient.
The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.
Detailed Description
In this disclosure, techniques, systems, devices, components, assemblies, and methods are described for guiding a lead to a target delivery site, for example, within a substernal space. For delivery to the substernal space, the lead may be delivered through a surgical incision made in the skin or tissue near or below the xiphoid process (also referred to as "subxiphoid") to create an access point to the substernal space and advanced to a desired location within the substernal space with the aid of a guide system. The entry point may also be formed at the notch connecting the xiphoid process with the sternum. In other instances, the substernal space may also be accessed through the manubrium. By using the systems and techniques described herein, the lead may be safely guided to the substernal space or other target location, and more optimal lead placement may be achieved.
In general, a medical device system may include one or more electrodes, such as electrodes placed on a lead or, for example, a housing electrode. The impedance measurement circuit may use two or more electrodes to generate an impedance signal between them. In some examples, the impedance signal indicates an impedance proximate to one of the electrodes. In the example of a lead having four electrodes, an impedance signal may be generated for each electrode with a respective four carriers between each of the four electrodes and the tubular electrode. In one example, the impedance signal may indicate an impedance proximate to an electrode on the lead, including when the electrode on the lead is a cathode or when the electrode on the lead is an anode.
In one example, an impedance signal may be generated between any two electrodes, e.g., between two electrodes on the same lead. In this way, the impedance signal may be indicative of, for example, the impedance proximate the cathode. In one example, the electrodes used for impedance measurement may be unipolar, although unipolar may not be required. For example, a monopolar configuration with the electrode located on the lead or delivery tool may be used, and the position of the electrode may be changed with implantation of the lead or delivery tool. In one example, different sized electrodes (e.g., can-shaped or patch-shaped) may be used. In one example, tissue proximate to a smaller electrode forming the carrier may drive the impedance signal.
In some instances, a high frequency carrier signal may be injected between an electrode, such as a coil electrode and a case electrode, and the resulting impedance signal may be indicative of the impedance proximate to the lead electrode. The high frequency signal may comprise a frequency of about 0.1Hz to about 1MHz, for example about 4Hz to about 100 kHz. In other examples, other types of signals may be injected through the same electrode or other electrodes to facilitate impedance measurements.
When the lead is implanted in a patient, the impedance signal may change as the position of the electrodes on the lead changes. By using the systems and techniques described herein, the relative position of the leads can be determined without fluorescence imaging information. In some instances, the systems and techniques described herein may be compatible with fluoroscopic imaging, but such imaging may not be needed to safely position the lead in place in the substernal space.
The impedance signal may contain one or more frequency components. For example, the first frequency component of the impedance signal corresponds to a cardiac contraction frequency and the second frequency component of the impedance signal corresponds to a respiratory frequency. The processing circuitry may identify such frequency components or other components of the impedance signal. The processing circuitry provides an indication to a user of the relative position of the electrodes based on the first and second frequency components. For example, when the lead is implanted, the techniques described herein make it possible to indicate the relative distance to the heart and lungs of the patient or the relative position of the lead within the patient, e.g., based on the first and second frequency components. In this manner, the appropriate position of the lead may be determined based on the electrode configuration on the lead and the anatomy of the patient. In one example, the systems and techniques described herein include detecting a change in the position of a lead, such as detecting migration of the lead after the implantation procedure is completed. In some examples, the processing circuitry provides an indication of the relative position of the electrodes to the user based on other components of the impedance signal, such as higher order frequency components (e.g., harmonics of the first or second frequency components).
In other examples, the processing circuitry may determine a state of the patient or a state of an organ of the patient, such as a change in fluid content in tissue within the chest cavity of the patient, a change in a contribution of the heart to the impedance signal, or a change in heart rate. The lung contribution to the impedance signal may be due to, for example, a shift in the position of the lead in the substernal space or a change in the patient's posture following the implantation procedure. In some examples, the processing circuitry may determine the presence of air pockets or evaluate air pockets around the electrodes. The impedance signal may be modulated by saline infused into the patient or by vacuum use during implantation. In some instances, the use of a vacuum during surgery may minimize the opportunity to introduce air into the implantation space.
The processing circuit may determine a characteristic of the first frequency component. The characteristic of the first frequency component may be referred to as a first characteristic. Likewise, the processing circuit may determine a characteristic of the second frequency component, and the characteristic of the second frequency component may be referred to as a second characteristic. The first and second characteristics, which may be referred to individually or collectively as "characteristics," may correspond to an amplitude, frequency, wavelength, power or intensity, another signal characteristic, or any combination thereof, in fourier space. In some instances, the characteristic is based on or determined by the function. In some examples, the characteristic is determined based on or by a hardware filter, a software filter, or a combination of both. The processing circuitry may provide an indication of the relative position of the electrode within the patient based on the first characteristic and the second characteristic.
The processing circuit may determine a relationship between the first characteristic and the second characteristic. In one example, the relationship is a ratio. In another example, the relationship is a function and may include a weighting factor. The first characteristic may correspond to an amplitude of a systolic frequency component (e.g., a first frequency component) of the impedance signal. The second characteristic may correspond to an amplitude of a respiratory frequency component (e.g., a second frequency component) of the impedance signal. In this example, the relationship is a ratio of the second characteristic to the first characteristic (e.g., a ratio of respiratory impedance to cardiac impedance). In one example, the relationship may be a ratio of the first characteristic to the second characteristic. By using the relationship between the first and second characteristics, the system may provide a relative position of the electrodes. Thus, when the ratio is relatively large, it may indicate that the corresponding electrode is closer to the patient's lungs than to the patient's heart. When the ratio is relatively small, it may indicate that the corresponding electrode is closer to the patient's heart than to the patient's lungs. In this way, for example, the defibrillation electrodes can be safely guided into place in the substernal space.
In one example, when the ratio is relatively large, the ratio may be greater than a previously measured ratio (e.g., time relativity). As such, the guidance system may indicate that the lead (e.g., an electrode on the lead) is getting closer to the patient's lungs over time, which may indicate that the lead is moving away from the patient's heart over time.
In one example, a relatively large ratio may refer to a ratio that is greater than a threshold (e.g., 0.9, 1.0, 1.1, or another value). For example, the ratio may be greater than 1 when the second characteristic corresponding to the amplitude of the respiratory frequency component is greater than the first characteristic corresponding to the amplitude of the systolic frequency component. Thus, this may indicate that the electrode is closer to the lung than the heart. In a similar manner, a relatively small ratio that is less than a threshold (e.g., 1.0, 0.6, 0.4, or another value) may indicate that the electrode is closer to the heart than the lungs.
In one example, a relatively large ratio may refer to a relationship between a plurality of ratios (e.g., to a plurality of ratios corresponding to a respective plurality of electrodes).
Thus, a relatively larger ratio may be greater than another ratio (e.g., as in fig. 10D for electrode 118B relative to the other electrodes).
In general, the processing circuitry may use more than one ratio value (e.g., ratio over time, ratio threshold, multiple ratios of multiple electrodes) to provide an indication of relative position. Relative position may refer to the position of an electrode relative to one or more organs, tissues, bones, etc. For example, the relative position of the electrodes may include or refer to at least one of the sternum, the heart, the lungs, or a portion of the heart or lungs of the patient with respect to the patient. In one example, the relevant position may additionally or alternatively include or refer to at least one of a relative cranial-caudal position of the electrode, a relative left-right lateral position of the electrode, or a relative ventral-dorsal position of the electrode. As the relative position changes (e.g., such as during an implantation procedure), one or more indications may be provided over time (e.g., periodically or continuously). As described herein, information regarding the relative position of the leads or electrodes may supplement information from other sources, such as an imaging system. In some examples, the indication of the relative position of the electrodes or leads includes information on the map, e.g., providing an impedance map to assist in guidance and lead placement. In one example, the indication may comprise an alarm, which may include, for example, a sound, light, or pop-up window displayed to the user on the display. The indication may comprise one or more types of indications, and may comprise information from other sources, such as medical imaging information or pre-loaded patient anatomy. In one example, such impedance mapping may be achieved using different combinations of electrodes, such as signals between defibrillation electrodes, pacing electrodes, or sensing electrodes, between housing or housing electrodes, or any combination thereof. In some examples, the indication includes a relative distance of the electrode or lead to the patient's heart and lungs,
in some instances, using the relationship between the first characteristic and the second characteristic, the system may provide an indication that the electrode is properly positioned. For example, the techniques and guidance systems described herein may determine satisfactory positioning within the substernal space. In some instances, this may not require determining the relative positions of the electrodes. For example, the processing circuitry may determine that the relationship between the first and second characteristics meets a criterion or a set of criteria, such as a threshold or a threshold range of values. In one example, a satisfactory ratio of respiratory to cardiac amplitude may be used (e.g., using the values described herein). In one example, the techniques and systems described herein may determine an electrode carrier based on the relationships (e.g., ratios) described herein.
In some instances, the impedance signal may be used to determine an absolute impedance. For example, the absolute impedance, which may be combined with a ratio, may be used to determine the location of the lead (e.g., relative location in an air pocket of the implanted space, determining internal or external to the pericardial sac, or other location information).
Other information may be determined from the impedance signal. For example, the impedance signal morphology may contain information about the relative distance between the components of the medical device system and the organ, or other information about the organ, such as respiration rate, heart rate, thoracic impedance, or edema status within the patient. The information may be used to determine the relative position of the lead within the patient, or to inform the appropriate patient treatment parameters. In some instances, such information may be used for ongoing therapy or ongoing monitoring (e.g., ongoing respiratory monitoring). In some instances, the processing circuitry may use this information to monitor the lead after implantation, e.g., to determine a change in the position of the implanted lead. In some instances, the processing circuitry may use such information to determine changes in the patient's anatomy, changes in lead properties, such as lead integrity, or changes in the electrode-tissue interface.
In one example, information determined from the impedance signal (e.g., relative position of the electrodes, appropriate position, signal characteristics, or other information) may be used to determine an electrode carrier for therapy or sensing. The information may be used, for example, to determine a plurality of carriers available from a plurality of electrodes. The processing circuitry described herein may determine such a carrier.
The lead may be implanted with the delivery system. The delivery system may include an implantation tool. For example, the implantation tool comprises an elongated tool, a sheath, and a handle. In some examples, the implantation tool includes one or more electrodes, for example on the elongate tool, the sheath, or both. By using the systems and techniques described herein with a delivery system, a lead can be placed such that the therapy vehicle between a defibrillation electrode on the lead and a housing or cartridge electrode substantially spans the ventricle of the heart. In some instances, the lead may be implanted in a position substantially centered under the patient's sternum. In other examples, the lead may be implanted such that it is laterally offset from the center of the sternum. The implantation tool may define a channel configured to receive a medical lead for implanting the medical lead in the substernal space.
In some examples, the delivery system may include one or more electrodes, for example on a distal portion of the elongate tool or on a distal portion of the sheath, such as described with respect to fig. 5B. One or more electrodes on the implantation tool may be located elsewhere, such as at the proximal portion of the sheath. One or more electrodes on the implantation tool may be used to generate the impedance signal. The impedance signal generated using the one or more electrodes on the implantation tool may be used in the same or similar manner as the impedance signal of the one or more electrodes on the medical lead. By using the techniques described herein, an implantation tool can be guided to an appropriate location within a patient to allow for more efficient implantation of a lead.
In some examples, the lead or tool includes a plurality of electrodes. In this way, the impedance measurement circuit may generate a plurality of impedance signals, each signal indicative of an impedance proximate to a respective one of the plurality of electrodes. The first and second frequency components may be identified for each of the plurality of impedance signals by the processing circuitry. Providing an indication of the relative position of the lead within the patient may be based on the first and second frequency components of the plurality of impedance signals.
In some examples, the processing circuitry provides an indication of the relative position of one or more of the plurality of electrodes. In some examples, the indication of the relative position of one of the plurality of electrodes is based on the relative position of at least one other of the plurality of electrodes. That is, for each of the plurality of electrodes, a ratio between the first characteristic and the second characteristic may be compared to another ratio of one or more other electrodes of the plurality of electrodes. The indication of the relative position of the electrodes may be based on the result of the comparison.
Fig. 1A-1C are front, side, and top schematic views, respectively, illustrating an example of a medical device system 100 (also referred to as "
In the illustrated example, the
However, these techniques may be applicable to other cardiac systems, including cardiac pacemaker systems, cardiac resynchronization therapy defibrillator (CRT-D) systems, cardioverter systems, or combinations thereof, as well as other stimulation and/or sensing systems, such as neurostimulation systems. Furthermore, although described primarily in the context of implanting leads, the techniques may be applicable to the implantation of other devices, such as leadless implantable stimulators that include electrodes on their housings.
Additionally, the
In general, a system (e.g., system 100) may include one or more medical devices, leads, external devices, or other components configured for the techniques described herein. In the example shown, the
The ICD110 may also be configured to provide a signal, such as a high frequency carrier signal, between the two electrodes of the
In one example, the ICD110 may comprise all or a portion of a guidance system. A guide system may be used to guide and
ICD110 is implanted subcutaneously or submuscularly to the left side of
In general, the "substernal space" may refer to the area defined by the lower surface between
In the present disclosure, the term "extrapericardial" space may refer to the area around the outer surface of the heart, but not within the pericardial sac or cavity. The region defined as the extra-pericardial space includes the space, tissue, bone, or other anatomical features around and near the periphery of the pericardium.
The
In other examples, lead 102 may be implanted in other extra-cardiovascular locations. For example,
Although referred to herein as "defibrillation electrodes" and "sensing electrodes," electrodes 106, 108 may correspond to devices other than ICD110, for example. In some instances, a "defibrillation electrode" as used herein may include a coil electrode that may pace or sense in some cases. In some instances, a "sensing electrode" as used herein may include a ring, tip, segmented, or hemispherical electrode that may pace in some cases.
The leads 102 may be configured in different sizes and shapes, for example, may be suitable for the purpose (e.g., different patients or different treatments). In some examples, the distal portion of the
In one example, the electrode arrangement on the
The systems and techniques described herein may be implemented using different types of leads (e.g., as described above or other lead shapes, lead configurations, etc.), including leads designed for different types of therapy (e.g., defibrillation, cardiac pacing, spinal cord stimulation, or brain stimulation). The systems and techniques described herein may be implemented using, for example, a delivery system (e.g., a sheath or elongate tool) or other device that may be inserted into a patient (e.g., a substernal space of a patient).
In general, for example,
In some instances, the
The
The user may program or update therapy parameters for defining a therapy, or perform any other activity with respect to the
Fig. 2 is a functional block diagram illustrating an example of a
The
The
The
The memory 206 includes computer readable instructions that, when executed by the
The
Generally, a rapid or significant change in impedance (e.g., a sudden significant increase or decrease) may indicate that further action may be required by the physician. For example, a decrease in the value of the measured impedance signal during implantation may indicate that the electrode has encountered an air pocket in the substernal space. In one example, a change in the value of the impedance signal measured during the implantation procedure may indicate that the lead has approached, has contacted, or has entered the pericardial space. In one example, a sudden change in impedance may indicate that the electrode is disposed on or has been in contact with a lead, for example, on the heart or lungs. In response to a sudden change in the measured impedance signal, the
In one example, the
In some instances, multiple criteria may be used. For example, the
The
In some examples, the
Fig. 3 is a functional block diagram illustrating an example configuration of a conveying
Fig. 4 is a partial perspective view showing a portion of a technique of implanting a lead. For example, with respect to the
Fig. 5A is a partial perspective view showing a portion of a technique for implanting a lead (e.g., lead 102). For example, an elongate tool 302 (not shown) within
The
Fig. 5B is a perspective view illustrating a portion of the
Once
Some implant systems may not include a sheath, but may include a tool coupled to and adjacent to the distal end of the lead and used to push the distal end to a desired location. In this case, either the tool (if there is an electrode) or the lead wire may be connected to the impedance circuit in the guidance system.
In some examples, the
The
In some examples,
Fig. 6 is a flow chart depicting a method of implanting a lead in accordance with some examples of the present disclosure. As described herein, this example method may be performed in part by a clinician and in part by any one or more devices implementing a guidance system. According to this example method, the clinician creates an entry point into the substernal space, such as an
In one example, a
A
In this way, for example, a user may receive an indication of the relative position of the lead within the patient prior to removing the
In some examples, the
in some instances, the indication may be a confirmation that the
In some instances, the indication provided by the guidance system to the user may be an indication that includes feedback, such as real-time feedback to the user. For example, real-time feedback may indicate that the lead is more properly placed in the cranium. Another example of an indication includes an alarm, suggesting that the lead is too close to the organ, such as whether the impedance meets or exceeds a threshold, or whether the ratio of respiratory impedance to cardiac impedance meets or exceeds a threshold.
FIG. 7 illustrates an example method for providing an indication of the relative position of electrodes. As described herein, the example method may be performed by any one or more devices implementing the
Each of the first frequency component and the second frequency component may have different characteristics at a particular time. For example, the frequency components may have different frequencies, different amplitudes, different wavelengths, or other differences. The characteristics may change as the electrodes move within the substernal space, and may also change due to changes in the patient's physiological state. The
The
In some instances, after generating the impedance signal, filtering may be performed, for example, by the processing circuit. A fourier transform may be performed on the impedance signal, impedance peaks may be identified, filters may be applied, or other processing techniques may be used. In some examples, a 10 hz low pass filter is applied, and then a fourier transform is performed.
In some examples, the first frequency component includes a value of about 0.15 hertz to about 0.45 hertz, such as about 0.3 hertz (e.g., about 18 breaths per minute). In some examples, the second frequency component includes a value of about 0.66 hertz to about 1.66 hertz, such as about 1.0 hertz (e.g., about 60 heartbeats per minute). In this way, the first and second frequency components may be distinguished to determine a relationship therebetween.
In general, the systems and techniques described herein may be used with other types of leads instead of or in addition to implanted leads. By supplementing the delivery process of the lead using the systems and techniques herein, safer tunneling of the lead and delivery system may be achieved. In other examples, the systems and techniques may be used as diagnostic tools for respiratory or cardiac monitoring (e.g., EKG monitoring, for example).
Fig. 8A and 8B show examples of substernal spatial locations within a patient. Fig. 8A is a medical image of the substernal
Fig. 9A-9D illustrate an example of a lead placed in a substernal spatial location in a pig model with
Fig. 10A shows a bar graph of the minimum impedance 120 (left), average impedance 122 (middle), and maximum impedance 124 (right) of the carrier between the
Fig. 10B shows a bar graph of the minimum impedance 120 (left), average impedance 122 (center) and maximum impedance 124 (right) of the carrier between the
Fig. 10C shows a bar graph of the ratio of respiratory impedance to cardiac impedance for four carriers (e.g., 116A to the left cartridge, 116B to the second cartridge from the left, 118A to the third cartridge from the left, and 118B to the right cartridge). Fig. 10C corresponds to the cranial position of the lead in fig. 9A and 9B, and the
Fig. 10E shows a graph of impedance ratios versus medical imaging measurements for various electrode positions. As described herein, the impedance ratio (X-axis) of
In one example, the
By using the techniques and systems described herein, lead performance may be improved because the lead may be placed in a more desirable location for therapeutic stimulation. Treatments such as defibrillation or anti-tachycardia pacing may be improved, as well as sensing capabilities and battery life. The indication of the relative position of the electrodes may be used to avoid being too close to the organ, for example in terms of electrical proximity (e.g., based on an impedance signal). Furthermore, a better map of the substernal space may be provided to a user, such as a physician, via the impedance information.
The following numbered clauses are illustrative of one or more aspects of the present disclosure.
Clause 1: in one example, a method comprises: generating, by an impedance measurement circuit coupled to an electrode, an impedance signal indicative of an impedance proximate to the electrode; identifying, by a processing circuit, a first frequency component and a second frequency component of an impedance signal; providing, by the processing circuitry and based on the first frequency component and the second frequency component, an indication to a user of a location of the electrode within the patient.
Clause 2: in some examples of the method of clause 1, the method further comprises determining, by the processing circuit, a first characteristic of the first frequency component and a second characteristic of the second frequency component, wherein providing the indication of the location of the electrode within the patient comprises providing the indication of the location of the electrode within the patient based on the first characteristic and the second characteristic.
Clause 3: in some examples of the method of clause 2, the method further comprises determining, by the processing circuit, a relationship between the first characteristic and the second characteristic, wherein providing the indication of the location of the electrode within the patient comprises providing the indication of the location of the electrode within the patient based on the relationship between the first characteristic and the second characteristic.
Clause 4: in some examples of the method of clause 3, the relationship comprises a ratio of the first characteristic to the second characteristic.
Clause 5: in some examples of the method of clauses 2 or 3, the first frequency component corresponds to a systolic frequency, the first characteristic comprises an amplitude of the first frequency component, the second frequency component corresponds to a respiratory frequency, and the second characteristic comprises an amplitude of the second frequency component.
Clause 6: in some examples of the method of any of clauses 2, 3 or 5, the first characteristic and the second characteristic comprise at least one of an amplitude, a frequency, a wavelength, a power in fourier space, or an intensity in fourier space.
Clause 7: in some examples of the methods of any of clauses 1-6, the first frequency component corresponds to a systolic frequency and the second frequency component corresponds to a respiratory frequency, and wherein providing the indication of the position of the electrode within the patient includes providing an indication of the position of the electrode relative to at least one of the heart or lungs of the patient.
Clause 8: in some examples of the method of any of clauses 1-7, the method further comprises: providing an indication of the position of the electrode comprises: providing an indication of a position of the electrode relative to at least one of: a sternum; a heart; a lung; or a portion of the heart or lung.
Clause 9: in some examples of the methods of any of clauses 1-8, providing an indication of the location of the electrode within the patient's body comprises providing an indication of at least one of: the relative cranial-caudal position of the electrode, the relative left-right lateral position of the electrode, or the relative ventral-dorsal position of the electrode.
Clause 10: in some examples of the method of any of clauses 1-9, the method further comprises generating an impedance signal, identifying the first frequency component and the second frequency component, and periodically providing a location indication over time as the location changes.
Clause 11: in some examples of the method of any of clauses 1-10, the method further comprises: generating, by an impedance measurement circuit, a plurality of impedance signals, each impedance signal indicative of an impedance proximate to a respective one of a plurality of electrodes coupled to the impedance measurement circuit and including an electrode; identifying, by the processing circuit and for each of the plurality of impedance signals, first and second frequency components; and providing, by the processing circuitry and for the at least one electrode, an indication of the position of the electrode within the patient's body based on the first and second frequency components of the respective impedance signal.
Clause 12: in some examples of the method of clause 11, providing an indication of a location of at least one of the plurality of electrodes within the patient's body comprises providing an indication of a location of at least one of the plurality of electrodes based on a location of at least one other of the plurality of electrodes.
Clause 13: in some examples of the method of clause 11 or
Clause 14: in some examples of the method of any of clauses 1-13, the range of frequency values of the first frequency component includes a value of about 0.15 hertz to about 0.45 hertz and the range of frequency values of the second frequency component includes a value of about 0.66 hertz to about 1.66 hertz.
Clause 15: in some examples of the methods of any of clauses 1-14, providing the indication of the location of the electrode within the patient's body comprises determining the location of the electrode without fluorescence imaging information.
Clause 16: in some examples of the method of any of clauses 1-15, the electrode is located on a medical lead configured to be implanted within the substernal space of the patient.
Clause 17: in some examples of the method of any of clauses 1-16, the electrode is located on an implant tool configured for advancement into the substernal space of the patient, the implant tool defining a channel configured to receive a medical lead for implanting the medical lead in the substernal space.
Clause 18: in some examples of the method of any of clauses 1-17, the method further comprises determining, by the processing circuit, that the measurement of the impedance signal satisfies the criterion.
Clause 19: in some examples of the method of any of clauses 1-18, the method further comprises: in response to determining that the measurement satisfies the criterion, a warning indication is provided to the user by the processing circuit.
Clause 20: in some examples, a medical device system includes: an electrode; an impedance measurement circuit coupled to the electrode, the impedance measurement circuit configured to generate an impedance signal indicative of an impedance proximate the electrode; and processing circuitry configured to: identifying a first frequency component and a second frequency component of the impedance signal; and providing an indication of the position of the electrode within the patient based on the first frequency component and the second frequency component.
Clause 21: in some examples of the medical device system of
Clause 22: in some examples of the medical device system of
Clause 23: in some examples of the medical device system of
Clause 24: in some examples of the medical device system of
clause 25: in some examples of the medical device system of any of clauses 22-24, the first characteristic and the second characteristic comprise one of an amplitude, a frequency, a wavelength, or an intensity in fourier space.
Clause 26: in some examples of the medical device system of clause 23, the relationship comprises a ratio of the first characteristic to the second characteristic, and wherein the processing circuitry is configured to determine the ratio.
Clause 27: in some examples of the medical device system of any of clauses 20-26, the first frequency component corresponds to a systolic frequency and the second frequency component corresponds to a respiratory frequency, and wherein the processing circuitry is configured to provide an indication of a location of the electrode within the patient's body relative to at least one of the patient's heart or lungs.
Clause 28: in some examples of the medical device system of any of clauses 20-27, the processing circuitry is configured to provide an indication of a position of the electrode relative to at least one of: a sternum; a heart; a lung; or a portion of the heart or lung.
Clause 29: in some examples of the medical device system of any of clauses 20-28, the processing circuitry is configured to provide an indication of at least one of: the relative cranial-caudal position of the electrode, the relative left-right lateral position of the electrode, or the relative ventral-dorsal position of the electrode.
Clause 30: in some examples of the medical device system of any of clauses 20-29, the impedance measurement circuit is configured to generate the impedance signal, wherein the processing circuit is configured to identify the first and second frequency components, and wherein the processing circuit is configured to periodically provide the location indication over time as the location changes.
Clause 31: in some examples of the medical device system of any of clauses 20-30, the processing circuit is configured to provide an indication of a location of the electrode within the patient's body without fluorescence imaging information.
Clause 32: in some examples of the medical device system of any of clauses 20-31, the electrode is located on an implant tool configured for advancement into the substernal space of the patient, the implant tool defining a channel configured to receive a medical lead for implanting the medical lead in the substernal space.
Clause 33: in some examples of the medical device system of any of clauses 20-32, the medical device system further comprises a lead, wherein the electrode is disposed on the lead, and wherein a proximal end of the lead comprises a connector for connecting the lead to the medical device.
Clause 34: in some examples of the medical device system of clause 33, the medical device system further comprises a plurality of electrodes disposed on the lead, wherein the impedance measurement circuit is configured to generate a plurality of impedance signals, each of the impedance signals being indicative of an impedance proximate to a respective electrode of the plurality of electrodes, the plurality of electrodes being coupled to the impedance measurement circuit and comprising the electrode.
Clause 35: in some examples of the medical device system of clause 34, the processing circuitry is configured to identify first and second frequency components for each of the plurality of impedance signals, and wherein the processing circuitry is configured to provide, for at least one electrode, an indication of the relative position of the electrode within the patient's body based on the first and second frequency components of the respective impedance signal.
Clause 36: in some examples of the medical device system of any of clauses 20-35, the processing circuit is configured to determine that the measurement of the impedance signal satisfies the criterion.
Clause 37: in some examples of the medical device system of clause 36, the processing circuitry is configured to provide a warning indication to the user in response to determining that the measurement satisfies the criteria.
Clause 38: in some examples, a medical device system includes: an electrode; an impedance measurement circuit coupled to the electrode, the impedance measurement circuit configured to generate an impedance signal indicative of an impedance proximate the electrode; a processing circuit configured to: identifying a first frequency component of the impedance signal corresponding to a systolic frequency and a second frequency component of the impedance signal corresponding to a respiratory frequency; determining a first amplitude of the first frequency component and a second amplitude of the second frequency component; determining a relationship between the first amplitude and the second amplitude; and providing an indication of the position of the electrode within the patient based on the relationship.
Clause 39: in some examples of the medical device system of clause 38, the relationship comprises a ratio of the second amplitude to the first amplitude.
Clause 40: in some examples of the medical device system of clauses 38 or 39, the medical device system further comprises a user interface configured to provide an indication that the electrode is closer to the patient's lung than the patient's heart when the ratio is relatively large and configured to provide an indication that the electrode is closer to the patient's heart than the patient's lung when the ratio is relatively small.
Clause 41: in some examples of the method of
Various examples have been described. These and other examples are within the scope of the following claims.
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