Patent Grant
11419513
The present invention generally relates to the field of vascular monitoring. In particular, the present invention is directed to wireless vascular monitoring implants, systems, methods, software and anchoring structures therefore. More specifically, embodiments disclosed herein relate to fluid volume sensing in the inferior vena cava (IVC) using wireless, remotely or automatically actuatable implants for monitoring or management of blood volume.
Others have attempted to develop vascular monitoring devices and techniques, including those directed at monitoring vessel arterial or venous pressure or vessel lumen dimensions. However, many such existing systems are catheter based (not wireless) and thus can only be utilized in a clinical setting for limited periods of times, and may carry risks associated with extended catheterization. For a wireless solution, the complexity of deployment, fixation and the interrelationship of those factors with detection and communication have led to, at best, inconsistent results with such previously developed devices and techniques.
Existing wireless systems focus on pressure measurements, which in the IVC can be less responsive to patient fluid state than IVC dimension measurements. However, systems designed to measure vessel dimensions also have a number of drawbacks with respect to monitoring in the IVC. Electrical impedance-based systems require electrodes that are specifically placed in opposition across the width of the vessel. Such devices present special difficulties when attempting to monitor IVC dimensions due to the fact that the IVC does not expand and contract symmetrically as do most other vessels where monitoring may be desired. Precise positioning of such position-dependent sensors is a problem that has not yet been adequately addressed. IVC monitoring presents a further challenge arising from the physiology of the IVC. The IVC wall is relatively compliant compared to other vessels and thus can be more easily distorted by forces applied by implants to maintain their position within the vessel. Thus devices that may perform satisfactorily in other vessels may not necessarily be capable of precise monitoring in the IVC due to distortions created by force of the implant acting on the IVC wall. As such, new developments in this field are desirable in order to provide doctors and patients with reliable and affordable wireless vascular monitoring implementation, particularly in the critical area of heart failure monitoring.
Embodiments disclosed herein comprise wireless vascular monitoring devices, circuits, methodologies, and related techniques for use in assisting healthcare professionals in predicting, preventing, and diagnosing various conditions whose indicators may include vascular fluid status. Using embodiments disclosed, metrics including, for example, relative fluid status, fluid responsiveness, fluid tolerance, or heart rate may be accurately estimated.
In one implementation, the present disclosure is directed to a wireless implanted sensor system. The sensor system includes a wireless sensor implant configured to be implanted in a patient, the sensor implant comprising a first coil formed around a first axis and a wearable antenna configured to be wrapped around a patient to form a second coil around a second axis with the second axis substantially aligned with the first axis when on the patient; the second coil producing an electromagnetic field around the second coil and along the second axis when energized; wherein the electromagnetic field passes through the first coil along the first axis, thereby producing a current in the first coil resulting in a signal produced by the first coil being receivable by the second coil of the wearable antenna.
In another implementation, the present disclosure is directed to a patient wearable antenna adapted to energize and receive a sensing signal from a sensor implant. The patient wearable antenna includes a substrate with first and second ends sized to extend around the patient's waist or torso, configured to accommodate a range of patient girths with the first and second ends coming together; a closure disposed on at least one of the first and second ends of the substrate configured to secure the substrate around the patient's waist or torso; and a core wire disposed on or in the substrate forming a circumferential electrical loop around the patient's waist or torso when the substrate is disposed around the patient's waist or torso, the core wire, when energized by an electrical current delivered thereto, generates an electromagnetic field along a first axis substantially aligned with the patient's cranial-caudal axis.
In yet another implementation, the present disclosure is directed to a patient wearable antenna adapted to energize and receive a sensing signal from an implant having a coil formed around a first axis. The patient wearable antenna includes a substrate with first and second ends sized to extend around the patient, configured to accommodate a range of patient sizes with the first and second ends coming together; a closure disposed on at least one of the first and second ends of the substrate configured to secure the base layer around the patient; a core wire disposed on or in the substrate sized to form a fixed length circumferential electrical loop around the patient and, when disposed around the patient and energized by an electrical current delivered thereto, generates an electromagnetic field around a second axis extending through a center of the electrical loop around the patient and substantially aligned with the first axis; and a control system wirelessly communicating with the core wire, the control system including a transmit/receive switch to switch the core wire between a transmit mode configured to transmit an energizing signal to the implant and a receive mode configured to receive a signal from the implant.
In still another implementation, the present disclosure is directed to a method for detecting a signal from a resonant circuit implanted within a patient wherein the resonant circuit comprises a coil formed around a first axis. The method includes placing an antenna coil formed around a second axis on a patient with the second axis substantially aligned with the first axis of the implant coil; energizing the antenna coil on the patient to direct the magnetic field at the resonant circuit coil in an orientation configured to energize the resonant circuit and produce a responsive sensing signal therefrom; and receiving the responsive signal at the antenna coil.
These and other aspects and features of non-limiting embodiments of the present disclosure will become apparent to those skilled in the art upon review of the following description of specific non-limiting embodiments of the invention in conjunction with the accompanying drawings.
For the purpose of illustrating the disclosure, the drawings show aspects of one or more embodiments of the disclosure. However, it should be understood that the present disclosure is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:
Aspects of the present disclosure are directed to wireless, resonant circuit-based vascular monitoring (“RC-WVM”) implants, systems, methods, and software, including excitation and feedback monitoring (“EFM”) circuits that can be used to energize an RC-WVM implant with an excitation signal and receive characteristic feedback signals produced by the RC-WVM implant. By automatically or manually analyzing the feedback produced by the RC-WVM implant, it is possible to assist healthcare professionals in predicting, preventing, and diagnosing various heart-related, kidney-related, or vascular-related health conditions. For example, the feedback produced by the RC-WVM implant at a particular time can be compared to feedback produced by the RC-WVM implant at other times and/or feedback produced by a baseline RC-WVM implant in order to understand vessel geometry and therefore estimate relative fluid status, fluid responsiveness, fluid tolerance, heart rate, respiration rate and/or other metrics. One or more of these estimations can be generated automatically or manually in order to monitor the status of a patient and provide feedback to a healthcare professional and/or the patient in case of any anomalies or relevant trends.
System Overview
The unique physiology of the IVC presents some distinctive challenges in attempting to detect and interpret changes in its dimensions arising from changes in patient fluid state. For example, the IVC wall in a typical monitoring region (i.e., between the hepatic and renal veins) is relatively compliant compared to other vessels, which means that changes in vessel volume can result in different relative distance changes between the anterior-posterior walls as compared to the lateral-medial walls. Thus, it is quite typical that changes in fluid volume will lead to paradoxical changes in the geometry and motion of the vessel; that is, as the blood volume reduces the IVC tends to get smaller and collapses with respiration, and as the blood volume increases the IVC tends to get larger and the collapse with respiration is reduced. Systems and implants disclosed herein are uniquely configured to compensate for and interpret such paradoxical changes.
As shown in
RC-WVM implants 12 generally comprise a variable inductance, constant capacitance, resonant L-C circuit formed as a resiliently collapsible coil structure, which, when positioned at a monitoring position within the patient's IVC, moves with the IVC wall as it expands and contracts due to changes in fluid volume. The variable inductance is provided by the coil structure of the implant such that the inductance changes when the dimensions of the coil change with the IVC wall movement. The capacitive element of the circuit may be provided by a discrete capacitor or specifically designed inherent capacitance of the implant structure itself. Embodiments of RC-WVM implant 12 also may be provided with anchoring and isolation means inherently designed into the implant structure, or with distinct additional such structures, to ensure that the implant is securely and properly positioned in the IVC without unduly distorting the vessel wall so as to distort or otherwise negatively impact measurements determined by the implant. In general, RC-WVM implants 12 are configured to at least substantially permanently implant themselves in the vascular lumen wall where placed upon deployment and do not require a physical connection (for communications, power or otherwise) to devices outside the patient's body after implantation. “Substantially permanently implanted” as used herein means that in normal usage the implant will, throughout its useful, operational life, remain implanted in the vascular lumen wall and may to varying degrees become integrated into the vascular lumen wall by tissue ingrowth, but the implant may be intentionally removed as medically dictated by an intravascular interventional or surgical removal procedure specifically undertaken for the purpose of removing the implant. Details of alternative embodiments of implant 12, shown in
Control system 14 comprises, for example, functional modules for signal generation, signal processing and power supply (generally comprising the EFM circuits and indicated as module 20) and communications module 22 to facilitate communication and data transfer to various remote systems 18 through data links 26 and optionally other local or cloud-based networks 28. Details of alternative embodiments of control system 14, modules 20 and 22, and elements of alternative EFM circuits are described below and illustrated in
Antenna module 16 is connected to control system 14 by power and communication link 24, which may be a wired or wireless connection. Antenna module 16 creates an appropriately shaped and oriented magnetic field around RC-WVM implant 12 based on signals provided by the EFM circuitry of control system 14. The magnetic field energizes the L-C circuit of RC-WVM implant 12 causing it to produce a “ring-back” signal indicative of its inductance value at that moment. Because the inductance value is dependent on the geometry of the implant, which changes as mentioned above based on dimensional changes of the IVC in response to fluid state heart rate etc., the ring-back signal can be interpreted by control system 14 to provide information as to the IVC geometry and therefore fluid state. Antenna module 16 thus also provides a receive function/antenna as well as a transmit function/antenna. In some embodiments the transmit and receive functionality are performed by a single antenna, in others each function is performed by a separate antenna. Antenna module 16 is schematically depicted in
The variable inductance L-C circuit produces a resonant frequency that varies as the inductance is varied. With the implant securely fixed at a known monitoring position in the IVC, changes in geometry or dimension of the IVC cause a change in configuration of the variable inductor, which in turn cause changes in the resonant frequency of the circuit. These changes in the resonant frequency can be correlated to changes in the vessel geometry or dimension by the RC-WVM control and communication system. Thus, not only should the implant be securely positioned at a monitoring position, but also, at least a variable coil/inductor portion of the implant should have a predetermined resilience and geometry. Thus, in general, the variable inductor is specifically configured to change shape and inductance in proportion to a change in the vessel geometry. In some embodiments, an anchoring and isolation means will comprise appropriately selected and configured shape and compliance in the sensor coil structure of the implant so as to move with the vessel wall while maintaining position. Such embodiments may or may not include additional anchoring features as discussed in more detail below. Alternatively, an anchoring and isolation means may comprise a separate structure spaced and/or mechanically isolated from a variable inductor coil structure such that the anchoring function is physically and/or functionally separated from the measuring/monitoring function such that any distortion or constraint on the vessel caused by the anchor is sufficiently distant and/or isolated from the variable inductor so as not to unduly affect measurements.
RC-WVM implant 12 as a variable inductor is configured to be remotely energized by an electric field delivered by one or more transmit coils within the antenna module positioned external to the patient. When energized, the L-C circuit produces a resonant frequency which is then detected by one or more receive coils of the antenna module. Because the resonant frequency is dependent upon the inductance of the variable inductor, changes in geometry or dimension of the inductor caused by changes in geometry or dimension of the vessel wall cause changes in the resonant frequency. The detected resonant frequency is then analyzed by the RC-WVM control and communication system to determine the change in the vessel geometry or dimension. Information derived from the detected resonant frequency is processed by various signal processing techniques as described herein and may be transmitted to various remote devices such as a healthcare provider system or patient system to provide status, or in appropriate instances, alerts or modifications in treatment. In order to facilitate measurement of the detected resonant frequency, it may be desirable to provide designs with a relatively higher Q factor, i.e. resonant circuit configurations that maintain signal/energy for relatively longer periods, especially when operating at lower frequencies. For example, to realize advantages of designs employing Litz wire as further described herein, it may be desirable to operate in a resonant frequency range of below 5 MHz, typically between about 1 MHz and 3 MHz, in which case resonant circuit configuration with a Q factor of at least about 50 or greater may be desired.
An Example of a Complete System Embodiment
Details of one possible embodiment of a complete, exemplary system 10 are discussed hereinafter with reference to
In a further alternative embodiment, implant 12a is configured to ensure strut sections 38 are straight strut sections between crown sections 40. Straight strut sections can provide an advantage of the strut section always being in contact with the vessel wall over its entire length, irrespective of the size of vessel into which it is deployed. When the sensor construct frame is formed, for example, by laser cutting the construct from a nitinol tube, the straight configuration of the straight strut sections can be achieved by shape-setting the strut sections to maintain the desired straight configuration.
With reference also to
As shown in
The overall structure of RC-WVM implants 12 presents a balance of electrical and mechanical requirements. For example, an ideal electrical sensor is as close to a solenoid as possible with strut lengths as short as possible and ideally zero, whereas mechanical considerations of deployment and stability dictate that implant strut lengths be at least as long as the diameter of the vessel into which it is to be deployed to avoid deployment in the wrong orientation and maintain stability. Dimensions of elements of RC-WVM implant 12a are identified by letters A-F in
Another alternative structure for RC-WVM implant 12 is illustrated by RC-WVM implant 12b as shown in
Unlike implant 12a, frame 66 of implant 12b is non-continuous so as to not complete an electrical loop within the implant as this would negatively impact the performance. Any overlapping ends of frame 66 are separated with an insulating material such as heat shrink tubing, an insulating epoxy or reflowed polymer. RC-WVM implant 12b (may or) may not include anchors. Instead, the implant is configured to have a compliance/resilience to permit it to move with changes in the IVC wall geometry or dimension while maintaining its position with minimal distortion of the natural movement of the IVC wall. This configuration can be achieved by appropriate selection of materials, surface features and dimensions. For example, the strut section length of the frame must balance considerations of electrical performance versus stability, wherein shorter strut section length may tend to improve electrical performance but longer strut section length may increase stability.
In order to energize RC-WVM implant 12 and receive the signal back from the implant, antenna module 16 will functionally include a transmit and a receive antenna (or multiple antennas). Antenna module 16 thus may be provided with physically distinct transmit and receive antennas, or, as in the presently described exemplary system 10, provided by a single antenna that is switched between transmit and receive modes. Antenna belt 16b, shown
In terms of mechanical construction, antenna belt 16b generally comprises stretchable web section 72 and buckle 74 with a connection for power and data link 24. In one embodiment, in order for the size of the antenna belt 16b to accommodate patients of different girths (e.g., a patient girth range of about 700-1200 cm), a multi-layer construction made up of a combination of high-stretch and low-stretch materials may be employed. In such an embodiment, base layer 76 is a combination of high-stretch sections 76a and low-stretch section 76b, which are joined such as by stitching. Outer layer 78, with substantially the same profile as base layer 76, may be comprised entirely of the high-stretch material, which may be a 3D mesh fabric. Within each section, antenna core wire 82 is provided in a serpentine configuration with an overall length sufficient to accommodate the total stretch of the section. Core wire 82 should not itself stretch. Thus, the stretchability of the fabric layers is paired with the core wire total length to meet the desired girth accommodation for a particular belt design. Outer layer 78 is joined along the edges to base layer 76. Stitching covered by binding material 80 is one suitable means for joining the two layers. The layers may be further bonded together by a heat fusible bonding material placed between the layers. End portions 81 of web section 72 are configured for attachment to buckle 74.
Core wire 82, which forms the antenna element, is disposed between the layers and provided with an extendable, serpentine configuration so that it may expand and contract with the stretch of the belt. A mid-section 84 of core wire 82, which corresponds to low-stretch section 76b, has a greater width. This section, intended to be placed in the middle of the patient's back with antenna belt 16b worn approximately at chest level at the bottom of the rib cage, provides greatest sensitivity for reading the signal from RC-WVM implant 12. As one possible example, core wire 82 may be made up of 300 strands of twisted 46 AWG copper wire with a total length in the range of approximately 0.5-3 m. For an antenna belt configured to stretch to accommodate patient girths in the range of about 700 to 1200 mm, the total length of core wire 82 may be approximately 2 m. In some embodiments, it may be preferable to place the antenna belt more caudally, with the height approximately at the height of the patient's elbows when standing.
Many ways of providing a workable buckle for such an antenna belt may be derived by persons of ordinary skill based on the teachings contained herein. Factors to be considered in designing such a buckle include physical security, ease of manipulation by persons with reduced dexterity and protection from electrical shock by inadvertent contact with the electrical connectors. As an example, buckle 74 is comprised of two buckle halves, inner half 74a and outer half 74b as shown in
Electrical connection of core wire 82 may be provided by recessed connector pins disposed on opposed connector halves 88a and 88b. Connection of power and data link 24 may be provided, for example, through a coaxial RF cable with coaxial connectors (e.g., SMA plugs) on buckle 74 and control system 14. As just one possible example, a convenient length for the power and data link, using a conventional, 50 Ohm coax cable, is about 3 m.
As mentioned above, use of a single coil antenna as in antenna belt 16b requires switching the antenna between transmit and receive modes. Such switching is executed within control system 14, an example of which is schematically depicted as control system 14a in
As with any RF coil antenna system, the antenna and system must be matched and tuned for optimum performance. Values for inductance, capacitance and resistance and their interrelationship should be carefully considered. For example, the coil inductance determines the tuning capacitance while the coil resistance (including the tuning capacitance) determines the matching capacitance and inductance. Given the relatively low power of the disclosed systems, special attention is given to these aspects to ensure that an adequately readable signal is generated by RC-WVM implant 12 upon actuation by the driving magnetic field. With an adjustable girth belt such as antenna belt 16b (or with different size antenna belts), additional considerations are presented because of the variable or different lengths of antenna coil controlled by the control system. To address these considerations, separate tuning-matching circuits 94, 96 (
Using conventional coax cable for RF-power transmission, as is described above in one embodiment of power and data link 24, optimal RF power transfer between the antenna and the control system is achieved when the system and antenna impedances are matched to 50 Ohm real resistance. However, in the embodiment described above, resistance of antenna belt 16b is generally far below 50 Ohm. Transformation circuits, as part of tuning-matching circuits 94, 96 can be used to transform the antenna resistance to 50 Ohm. In the case of antenna belt 16b it has been found a parallel capacitor transformation circuit is efficient for this purpose.
In one example of tuning using the system components heretofore described, a series capacitor was used, which, in conjunction with a matching capacitor, forms the total resonance. Using measured values as set forth below in Table II, a target resonance frequency was computed at 2.6 MHz based on the inductance and capacitance. Considering the inductance variation with stretching of antenna belt 16b at 2.6 MHz, the resonance frequency was measured to vary only from about 2.5 MHz to about 2.6 MHz for change in length between 1200 mm and 700 mm circumferences of antenna belt 16b, respectively. Considering the resistance of 11.1 Ohm, the Q-factor of the cable/belt assembly computes to be 3. Such a low Q-factor translates to a full width of the pulse at half maximum of 600 kHz. This is far less than the variation of the resonance frequency due to stretching of the belt from 700 mm to 1200 mm circumference. Tuning values for antenna belt 16b were thus determined at 2.6 MHz with Cmatch=2.2 nF and Ctune=2.2 nF.
While it could be expected that a variable length antenna, such as included in antenna belt 16b might present difficulties in tuning and maintaining the antenna tuning as the length changed, it was discovered that with the present configuration this was not the case. As described above, by intentionally employing a cable for power and data link 24 that has a relatively large inductance compared to the antenna inductance, the proportional change in the inductance due to changes in belt diameter are small enough not to degrade performance.
Referring again to
In an alternative implementation, control system 14 excites antenna module 16 at a pre-determined frequency that is within an expected bandwidth of the paired RC-WVM implant 12. The system then detects the response from the paired RC-WVM implant and determines the implant natural frequency. Control system 14 then adjusts the excitation frequency to match the natural frequency of the paired implant and continues to excite at this frequency for a complete reading cycle. As will be appreciated by persons of ordinary skill, frequency determination and adjustment as described for this embodiment may be implemented via software using digital signal processing and analysis.
In another alternative implementation, each individual RF burst comprises a continuous frequency sweep over a predefined range of frequencies equal to the potential bandwidth of the implant (
In a further alternative implementation, the excitation comprises a transitory frequency sweep over a set of discrete frequency values covering the potential bandwidth of the paired RC-WVM implant 12. The frequency is sequentially incremented for each RF burst and the RMS value of the RC-WVM implant response is evaluated after each increment. Control system 14 then establishes the frequency that produces the maximum amplitude in RC-WVM implant response and continues exciting the paired RC-WVM implant at that frequency until a drop of a predefined magnitude is detected and the frequency sweep is re-started.
In yet another implementation, the excitation signal is composed of a pre-defined set of frequencies, wherein each remain constant. Control system 14 excites antenna module 16 (and hence the paired implant) by applying equal amplitude at all frequency components. The system detects the response from the paired implant and determines its natural frequency. Control system 14 then adjusts the relative amplitude of the excitation frequency set to maximize the amplitude of the excitation frequency that is closest to the natural frequency of the paired implant. The amplitude of the other frequencies are optimized to maximize the response of the paired implant while meeting the requirements of electro-magnetic emissions and transmission bandwidth limitations.
In another implementation, direct digital synthesizer (DDS) 98, may be provided as a multi-channel DDS system to generate a simultaneous pre-defined number of discrete frequencies belonging to the estimated operational bandwidth of the paired RC-WVM implant 12 as shown in
In yet another implementation, signal generator module 20a can be configured to provide pulse shaping as illustrated in
Referring again to
As a means of noise reduction, the response signal of the implant 12 is observed a predefined number of times (e.g., 256), and the average response is then computed. This approach greatly contributes to increasing the signal-to-noise ratio of the detected signal.
The average response is then transmitted to an external interface device 18 (e.g., laptop computer) by means of communications module 118. Different approaches can be taken for this. In one embodiment, the communication is performed using the UART interface from the microcontroller and external hardware is employed to convert from UART to USB. In a second embodiment, a microcontroller with USB driving capabilities is employed, and in this case connection with the external interface device is achieved by simply using a USB cable. In yet another implementation, the communication between the microcontroller and the external interface device is wireless (e.g. via Bluetooth).
The system is to be powered by a low voltage power supply unit (PSU), consisting of a AC-DC converter with insulation between mains input and output providing a minimum of 2 Means of Patient Protection (MOPP) as per Clause 8 of IEC 60601-1:2005+AMD1:2012. In this way, the power supply provides protection from electrocution to the user. The PSU is able to accommodate a wide range of mains voltages (e.g., from 90 to 264 VAC) and mains frequencies (e.g., 47 to 63 Hz) to allow operation of the system in different countries with different mains specifications.
Control system 14a as described above utilizes a software-based frequency detection. Thus, in terms of signal transmission, once the excitation frequency is optimized, system 10 employing control system 14a with signal generator module 20a operates in open loop mode, i.e., frequency or frequencies and amplitude of the transmit signal are not affected by RC-WVM implant 12 response. On the receive side, using amplifier-receiver module 20b, control system 14a detects the response signal from RC-WVM implant 12 and such signal is digitized using a high-speed data converter. The raw digitized data is subsequently transferred to a processing unit (e.g., laptop computer or other equipment microcontroller) and digital signal analysis techniques (e.g. Fast Fourier Transform) are applied to establish the frequency content of the signal. Thus, one advantage of using these software-based techniques is that phased-lock loop (PLL) circuits or similar circuits are not used or required in control system 14a.
A further component of the overall RC-WVM system as described herein is the RC-WVM implant delivery system.
In one deployment option, an RC-WVM implant may be inserted from a peripheral vein such as the femoral or iliac vein into the IVC to be positioned at a monitoring location between the hepatic and renal veins. It will be understood that the implant also may be introduced from other venous locations. Depending on implant configuration, when placed in the IVC for fluid status monitoring, specific orientation of RC-WVM implant 12 may be required to optimize communication with the belt reader antenna coil. To facilitate desired placement or positioning, the length and diameter of RC-WVM implant 12 may be designed so that it gradually expands (“flowers”) as it is held in position with the pusher 126 and the sheath 124 is withdrawn, as schematically illustrated in
Systems as described herein have been evaluated in pre-clinical testing using RC-WVM implant 12a (as in
The ability of RC-WVM implant 12 (in this case, implant 12a) to detect IVC area changes as a result of fluid loading is demonstrated in
These output signals thus demonstrate the detection of modulation of the IVC with respiration. In particular, it will be appreciated that embodiments of the present invention can thus provide an unexpectedly powerful diagnostic tool, not only capable of identifying gross trends in IVC geometry variations, but also capable of discriminating in real-time between changes in IVC geometry arising from respiration and cardiac function.
Alternative Patient Care Systems Based on RC-WVM Implants Disclosed Herein
Antenna module 16 may be configured to communicate via wireless or wired connection 24 with control system 14, as elsewhere described herein. Data and information collected by control system 14 may be communicated ultimately to a healthcare provider device 131 via hard wired links such as telephone or local area networks 132 or through Internet or cloud-based systems 133. Personal communication devices 134, such as smart phones or tablets, also may be used for communication with, or as alternatives to, other communications devices and modes described herein. Healthcare provider device 131 may be configured with an appropriate user interface, processing and communications modules for data input and handling, communications and processing, as well as treatment and control modules, which may include treatment algorithms as described herein for determining treatment protocols based on collected IVC diameter or area measurements, and systems for automated remote control of treatment devices based on determined treatment protocols as elsewhere described herein. Examples of such treatment devices include, but are not limited to, dialysis machine 135 and drug delivery devices 136. Examples of treatments include, when measured dimensions fall within the hypovolemic warning zone, administration of fluids or vaso-constricting drugs, and when measured dimensions fall within the hypervolemic warning zone, dialysis or administration of diuretics or vasodilating drugs.
IVC physical dimension data and/or fluid volume state information derived therefrom may also be communicated directly to the patient themselves, along with therapy advice based on this data and using pre-determined algorithms/implanted medical devices. Communications protocols throughout the system may include bidirectional communications to permit a healthcare provider (or other appropriately trained operator at another point in the system) to alter overall monitoring protocols executed at the monitoring device or, for example, to request additional queries by the monitoring device outside the current operational protocol.
Other embodiments include systems for patient self-directed therapy, for example with IVC volume metrics data utilized directly by the patient with or without clinician overview, e.g., for self-administration of drugs or other therapies. Such systems may also be implemented for home dialysis and/or peritoneal dialysis. Wireless communication between the IVC monitor and the patient's or healthcare provider's cell phone or computer would allow continuous or periodic transmission of IVC data and the use of software applications to provide alarms or reminders, graphically present trends, suggest patient actions, drug dosage options, or treatment system settings, and allow communication with physicians.
In response to a prompt from system 10b to take a reading, the patient would position him/herself with respect to or on antenna module 16 as appropriate to communicate with selected RC-WVM 12. A user interface of control system 14, or, in one possible alternative, personal communication device 134 may provide sequential prompts and/or instructions to the patient.
Varying levels of response may be generated by home system 137 depending on IVC measurements received from RC WVM implant 12 and as may be interpreted in light of other patient data (D). Minimal responses may be provided if the patient fluid status is within acceptable ranges and no action is required. Mid-level responses may include warnings or to contact healthcare providers or prompts for medication administration or changes in home drug delivery, or home dialysis. Consistently out-of-range or increasing readings would prompt response escalation to clinical intervention. Patient treatment protocols, in general, may be based on the applicable standards of care for disease state management as informed by diagnostic information reported by RC-WVM implant 12 and system 10. Specific examples of treatment protocols designed to take advantage of the unique capabilities of RC-WVM implant 12 are provided in Applicant's co-pending international application no. PCT/US2017/046204, filed Aug. 10, 2017, entitled “Systems And Methods For Patient Fluid Management”, which is incorporated by reference herein. When home dialysis or drug delivery is prompted, it may be controlled directly in a closed-loop system as described above or may be controlled by the patient with prompts from the system. Patient data (D) and IVC measurements from RC-WVM implant 12 also may be communicated continuously or periodically by system 10b to cloud storage 133 and further communicated to a remote patient management system 138. Functionality for system 10b may be largely contained in home system 137 or in patient management system 138 or appropriately distributed across the network. Optionally, patient-related data including sensor results and patient health and fluid states also may be communicated to or accessible by a hospital network 140. System 10b also may receive patient-related data, including for example, medical records related to past therapies and medical history.
When a patient condition is recognized by system 10b as outside acceptable limits, an alert may be generated by physician alert system 139. Information supporting the alert condition may be communicated, for example, through patient management system 138 to physician alert system 139. Physician alert system 139 may reside at a healthcare provider office and/or may include a mobile link accessible by the healthcare provider remotely to permit communication 142 between the healthcare provider and the patient. Communication 142 between healthcare provider and patient may be network, Internet or telephone-based and may include email, SMS (text) messaging or telephone/voice communication. Physician alert system 139 allows the healthcare provider to review logs of IVC measurements and medication changes over time and make decisions regarding therapy titration, and in critical cases, hospital admissions, remote from the patient.
Exemplary system embodiments 10a and 10b are each illustrated, respectively, in
As mentioned above, various care algorithms may be developed based on systems 10a and 10b. For example, in one scenario, a first, home-care algorithm governs interactions in the home system including periodic IVC diameter/area measurements using RC-WVM implant 12 and dictates whether to maintain current therapies or to change therapies within the scope of home-care team capabilities. As long as IVC volume metrics stay within predefined limits, the first, home-care algorithm continues to govern monitoring and treatment. However, if monitored parameters, for example IVC volume metrics, exceed the predefined limits, then an alert is generated that engages a second, healthcare-provider algorithm. Such an alert may be generated internally by home system 137, or may be generated in patient management system 138 (or physician alert system 139) based on monitored data communicated by home system 137 and received by the other systems either periodically or on a continuous basis. In one embodiment, an alert is received initially by a physician's assistant or heart failure nurse who can triage the situation through patient management system 138 locally or remotely. At this initial level the assistant or nurse may elect to generate a message for communication 142 to the patient through the network related to modulation of therapy or other parameters such as level of physical activity. However, if triage indicates the alert to represent a more critical event, the physician may be alerted through physician alert system 139. Multiple layers of care and review based on measured IVC volume metrics are thus provided to efficiently manage patient fluid status and where possible avoid hospitalizations.
RC-WVM Implant Design Considerations and Alternative Implant Embodiments
It will be appreciated that the measurement of dimensional changes in the IVC presents unique considerations and requirements arising from the unique anatomy of the IVC. For example, the IVC is a relatively low pressure, thin-walled vessel, which changes not simply its diameter, but its overall shape (cross-sectional profile) in correspondence to blood volume and pressure changes. Rather than dilating and constricting symmetrically around its circumference, the IVC expands and collapses primarily in the anterior-posterior direction, going from a relatively circular cross-section at higher volumes to a flattened oval-shaped cross-section at lower volumes. Thus embodiments of RC-WVM implants 12 must monitor this asymmetrical, low-pressure collapse and expansion in the A-P direction without excessive radial constraint, yet must also engage the vessel walls with sufficient force to anchor the implant securely and prevent migration. Accordingly, RC-WVM implant 12 must be capable of collapsing with the vessel in the A-P direction from a generally circular cross-section to an oval or flattened cross-section without excessive distortion of the vessel's natural shape. These requirements are achieved according to various embodiments described herein by appropriate selection of material compliance and configuration such that the coil measurement section of RC-WVM implant 12 is maintained in contact against the IVC wall without undue radial pressure that may cause distortion thereof. For example, RC-WVM implants 12 according to embodiments described herein may exert a radial force in the range of about 0.05N-0.3N at 50% compression. In another alternative, potentially increased security of positioning may be achieved without compromising measurement response by physically separating anchoring and measurement sections so as to move possible distortions of the vessel wall due to anchoring a sufficient distance spaced from the measurement section so as not to affect measurements.
RC-WVM implants 12 as described may be configured in various structures such as collapsible loops or tubes of formed wire with resilient sinusoidal or “Z-shaped” bends, or as more complex collapsible shapes with more resilient regions such as “spines” joined by relatively less resilient regions such as “ears.” Each structure is configured based on size, shape and materials to maintain its position and orientation through biasing between resilient elements of the implant to ensure contact with the vessel walls. Additionally or alternatively, anchors, surface textures, barbs, scales, pin-like spikes or other securement means may be placed on the structure to more securely engage the vessel wall. Coatings or coverings also may be used to encourage tissue in-growth. In some embodiments it may be preferable to configure specific portions of the structure, for example the coil spines, as the position-maintaining engagement portion in order to reduce any effect of the biasing force on movement of the vessel walls as sensed at the coil ears, or vice-versa. In yet other embodiments, separate anchoring structures may be coupled to a coil-measurement portion of the implant. Such anchoring structures may comprise hooks, expandable tubular elements, or other tissue-engaging elements which engage the vessel upstream or downstream of the coil portion so as to minimize any interference with the natural expansion or contraction of the vessel in the area of the coil itself. Sensing modalities and positioning is described in more detail below.
When RC-WVM implant 12 is energized it must generate a signal of sufficient strength to be received wirelessly by an external system. In the case of a variable induction circuit, the coil which transmits the signal to the external receiver must maintain a tubular shape or central antenna orifice of sufficient size, even when the vessel is collapsed, such that its inductance is sufficient to generate a field strong enough to be detected by an external antenna. Thus, in some embodiments, it may be desirable that the variable inductor have a collapsing portion which deforms with the expansion and collapse of the vessel, and a non-collapsing portion which deforms relatively little as the vessel collapses and expands. In this way, a substantial portion of the coil remains open even when the vessel is collapsed. In other embodiments, the coil may be configured to deform in a first plane containing the anterior-posterior axis while deflecting relatively little in a second orthogonal plane containing the medial-lateral axis. In still other embodiments, a first inductive coil may be provided to expand and collapse with the vessel, and a separate transmit coil, which deforms substantially less, provided to transmit the signal to the external receiver. In some cases the transmit coil also may be used as an anchoring portion of the implant.
Turning to specific alternative RC-WVM implant embodiments disclosed herein, a first exemplary alternative embodiment is RC-WVM implant 12c, shown in
As the IVC changes shape, the longitudinal wires may move closer together or farther apart, and coil ears 150 may also move closer together or farther apart, thereby changing the inductance of the coil. The ears may be separated by about 1 cm to about 5 cm at the apex of the curved ends of the ears. RC-WVM implant 12c, as adapted for an average IVC size, may be about 2.5 cm to 10 cm long. It may be appreciated that as the IVC collapses in the anterior-posterior direction, coil ears 150 deform inwardly thereby changing the inductance of the coil. However, the central region of the coil remains relatively un-deformed and maintains sufficient size that the inductance of the coil is high enough to produce a field sufficiently strong for external detection. Capacitor portion 144 in this embodiment includes discrete capacitor 152 to complete the L-C circuit. Capacitor portion 144 may be alternatively located in a number of locations, such as distal to coil ears 150, or along one of spines 148.
As described above, the IVC in a typical monitoring region between the hepatic and renal veins is relatively compliant, and tends to collapse into a non-circular oval-shaped cross-section, which is wider in the medial-lateral direction than it is in the anterior-posterior direction. A feature of “dog-bone” style implant such as RC-WVM implant 12c is that spines 148 create more stiffness in the plane of the central region of the coil which causes the device to rotationally auto-orient around the longitudinal axis of the vessel with the two spines along the medial and lateral walls, and coil ears 150 flaring anteriorly and posteriorly. Typically, a RC-WVM implant 12 thusly configured will assume an unbiased implanted configuration in which the distance between the spines preferably corresponds to the natural medial-lateral dimension of the IVC at current blood volume such that the implant does not distort the vessel from its natural shape. In one alternative, overall the diameter of RC-WVM implant 12 may be somewhat oversized as compared to the vessel diameter at its secured location so it is always relatively biased outward against the vessel walls. In such a case, when the IVC collapses, the A-P dimension reduces and the M-L dimension increases, although the M-L increase is generally much less than the A-P collapse, the oversizing maintains vessel wall contact and secure positioning. As elsewhere discussed, resiliency of the coil/wires forming the implant must be selected in this case also so as to move with the vessel without distorting measurements based on vessel wall movement.
A further alternative embodiment of RC-WVM implant 12 is the “x-bow” shaped implant 12d, shown in
Similar to “dog-bone”-shaped RC-WVM implant 12c, “x-bow”-shaped RC-WVM implant 12d deforms with the vessel walls in the anterior-posterior direction while having relatively little deformation in the medial lateral direction. RC-WVM implant 12d is thus able to deform with the IVC as it collapses but retains an open coil shape in the medial-lateral direction to maintain a high level of inductance, thus being capable of producing a field of sufficient strength to be detected by an external receiver.
In other embodiments, a tether or stent-like structure may be used to anchor RC-WVM implant 12 in a predetermined location while allowing it to very gently press against the walls of the vessel desired to be monitored. An important issue that must be taken into consideration is the fact that implants in veins or arteries can modify the flexibility or resiliency of the vein or artery to the point that changes in the shape of the veins or arteries that may be expected to be measurable using such implants may not take place or may be severely attenuated due to the shape of, function of, or vascular response to the implant. Accordingly, it is important that the implant have sufficient stiffness to anchor itself in the vessel while simultaneously allowing natural expansion and contraction of the vessel walls at the location(s) where the implant is measuring vessel dimension. In the implants described above, for example, the wall-engaging ears of the coils must have sufficient compliance/flexibility and resilience to move in and out with the vessel walls without excessive distortion or attenuation of the natural wall motion.
As shown in
In another RC-WVM implant 12 alternative embodiment, an “x-bow”-shaped RC-WVM implant similar to RC-WVM implant 12d shown in
Other embodiments of RC-WVM implant 12 may be adapted to balance the anchoring and measuring requirements by providing separate, longitudinally spaced measurement and anchor sections. Such embodiments split the anchoring and measurement into two discrete regions longitudinally separated from each other a sufficient distance that the anchoring section does not distort or constrain the vessel in the region being measured. The radial force characteristics of the measurement and anchoring sections will determine the spacing required, in certain embodiments, where the radial force of both sections is relatively low, the spacing can be reduced to as little as 5 mm. Examples of RC-WVM implant embodiments with separate measurement and anchor sections are shown in
As mentioned, embodiments of RC-WVM implant 12 with separate anchor and measurement sections also may employ the anchor section as an antenna coil. RC-WVM implant 12h, shown in
A further alternative embodiment for RC-WVM implant 12 involves the use of two capacitors to “double tune” the device. One example of such an embodiment is RC-WVM implant 12i, shown in
In any embodiment of RC-WVM implant 12 described herein, it may be advantageous to form the coil portion of the implant with multi-stranded wire or cable comprising a plurality of separately insulated strands wound or braided together to optimize the performance with high frequency alternating current. In some embodiments, the electrically conductive wire or wires used in the implant may comprise Litz wire in which the separately insulated strands of wire are braided or wound together in a particular prescribed pattern to optimize AC current transmission by optimizing for the high frequency “skin effect”. The individual wire insulation could be PTFE, polyester, polyurethane, nylon, or polyimide, among others. An additional insulated jacket may be provided around the entire multi-stranded wire or cable in order to provide electrical insulation from blood, which could otherwise render the implant suboptimal or unreliable under some circumstances, and to bind the Litz wire to the frame. Such additional insulation may be provided in the form of PET (polyethylene terephthalate), ETFE, FEP, PE/PP, TPE, polyurethane, silicone, polyimide, or other material, and may be provided on the wires of an RC-WVM implant and/or to encase RC-WVM implant 12 in its entirety. Due to the use of high frequency electromagnetic signals, more, or different, insulation may need to be provided for the electrical portions of RC-WVM implant 12 than may be required for other types of implants or electrical devices.
In some embodiments, nitinol frame such as frames 244 and 246, shown in
Laser cut frame 246, as shown in
The number of turns of wire used to form a coil portion of RC-WVM implant 12 embodiments may be optimized to provide enough conductive material to allow the use of lower capacitance value capacitors in order to enable the use of a physically smaller capacitor, thereby minimizing implant size. The preferred number of turns will depend on various factors including the diameter of the coil, the size and number of strands of wire or cable, the strength of the field produced by the transmit antenna, the sensitivity of the receive antenna, the Q value of the capacitor, and other factors. Such coils could have anywhere from 1 to 10 or more turns (each turn being a complete 360 degree loop of the wire around the frame), and preferably have at least 2 such turns. For example, Litz wire used in an RC-WVM implant 12 embodiment may have 180 strands of 46 AWG (0.04 mm wire), but could include anywhere from 1 to 1000 strands, and the strands could be about 0.01 to 0.4 mm in diameter.
Alternative System Embodiments, Components and Modules
Alternative embodiments 16c and 16d for antenna module 16 are illustrated, respectively, in
Systems as described herein have been evaluated in pre-clinical testing using RC-WVM implant 12c as shown in
The raw voltage signal in
Further alternative examples of configurations and components for control system 14 and antenna module 16 are shown in
In some embodiments, where a single antenna-coil may be used for both the transmit and receive signals, antenna module 16 includes a switching mechanism to alternate between transmission and reception, thereby eliminating interference between the transmitted signal and the received signal. Examples of such switches are the passive and active diode switches shown in
Advantageously, this allows simultaneous transmission and reception of fields to/from the implant to maximize signal strength and duration, and potentially eliminate complex switching for alternating between transmission and reception. Notably, in some implementations, single or plural circular or other-shaped transmit and/or receive coils may be used, the transmit and receive coils may be disposed in the same plane or different planes, and the area enclosed by the transmit coil may be larger or smaller than the area enclosed by the receive coil. The transmit and receive coils may be formed using copper tape or wire or could be implemented as a portion of a printed circuit board.
The transmit and receive coils used for exciting RC-WVM implant 12 and receiving the implant ring-back signal in response to that excitation, respectively, should be tuned (matched and centered) on the particular RC-WVM implant's L-C circuit resonant frequency range. In exemplary embodiments, a signal generator may be used to generate a sine wave burst of 3 to 10 cycles at 20 Vpp with a frequency selected to maximize the response of the RC-WVM implant L-C circuit. The signal generator may transmit a burst at whatever rate provides a clinically adequate measurement of the variation in the vessel dimensions; this could be every millisecond, every ten milliseconds, or every tenth of a second. It will be understood that a variety of waveforms may be used including pulse, sinusoidal, square, double sine wave, and others so long as the waveform contains the spectral component corresponding to the resonant frequency of the implant. Geometric decoupling, damping, detuning, and/or switching may be used to prevent the transmit pulse signals from being picked up by the receive coil while the transmit coil is transmitting.
RC-WVM Embodiments with On-Board Power and Electronics and Related Control Systems
In some situations it may be desirable to remove the necessity for external transmit and receive antennas, increase the communications distance of the RC-WVM implant and/or communicate with another implanted monitor/device.
In one alternative, as exemplified by
In another alternative, as exemplified in
Illustrative examples of wireless implants 12q and 12r employing on-board electronics systems are shown in
Another advantage of on-board electronics systems, such as system 392, is that the on-board system may be used to determine the resonant frequency and transmit a signal to a sub-cutaneous cardiac monitor/device (such as Medtronic LINQ or Biotronik BioMonitor). The subcutaneous cardiac monitor/device may be preexisting in the patient or may be implanted along with the RC-WVM implant. This architecture allows the device to potentially take multiple readings at pre-set time points or as indicated by triggers such as an accelerometer.
In yet a further alternative embodiment, when utilized with an on-board power supply as a part of an on-board electronics system, such as systems 380 or 392) wireless implants such as implants 12q, 12r, or other configurations disclosed herein, may be configured as a variable inductor without the necessity to include a specifically matched capacitance to create a tuned resonant circuit. In this case, the on-board electronics system applies a current to the implant sensor coil and then measures changes in inductance as a result of the coil-changing geometry in response to movement of the vascular lumen wall at the monitoring location where the implant is positioned. Signals based on the varying inductance measurements can then be transmitted by a communications module of the on-board electronics system, again, without the necessity of specially tuned antennas. Implants employing direct, variable inductance instead of a resonant circuit with a variable resonant frequency may be mechanically constructed as elsewhere described herein with respect to the exemplary embodiments of RC-WVM implants 12, except that a specific capacitance or capacitor to produce a resonant circuit is not required.
Hardware and Software Examples for Computer-Implemented Components
It is to be noted that any one or more of the aspects and embodiments described herein, such as, for example, related to communications, monitoring, control or signal processing, may be conveniently implemented using one or more machines (e.g., one or more computing devices that are utilized as a user computing device for an electronic document, one or more server devices, such as a document server, etc.) programmed according to the teachings of the present specification, as will be apparent to those of ordinary skill. Appropriate software coding can readily be prepared by skilled programmers based on the teachings of the present disclosure, as will be apparent to those of ordinary skill in the software art. Aspects and implementations discussed above employing software and/or software modules may also include appropriate hardware for assisting in the implementation of the machine executable instructions of the software and/or software module. In general, the term “module” as used herein refers to a structure comprising a software or firmware implemented set of instructions for performing a stated module function, and, unless otherwise indicated, a non-transitory memory or storage device containing the instruction set, which memory or storage may be local or remote with respect to an associated processor. A module as such may also include a processor and/or other hardware devices as may be described necessary to execute the instruction set and perform the stated function of the module.
Such software may be a computer program product that employs a machine-readable storage medium. A machine-readable storage medium may be any medium that is capable of storing and/or encoding a sequence of instructions in a non-transitory manner for execution by a machine (e.g., a computing device) and that causes the machine to perform any one of the methodologies and/or embodiments described herein. Examples of a machine-readable storage medium include, but are not limited to, a magnetic disk, an optical disc (e.g., CD, CD-R, DVD, DVD-R, etc.), a magneto-optical disk, a read-only memory “ROM” device, a random access memory “RAM” device, a magnetic card, an optical card, a solid-state memory device, an EPROM, an EEPROM, and any combinations thereof. A machine-readable medium, as used herein, is intended to include a single medium as well as a collection of physically separate media, such as, for example, a collection of compact discs or one or more hard disk drives in combination with a computer memory. As used herein, a machine-readable storage medium does not include transitory forms of signal transmission.
Such software may also include information (e.g., data) carried as a data signal on a data carrier, such as a carrier wave. For example, machine-executable information may be included as a data-carrying signal embodied in a data carrier in which the signal encodes a sequence of instruction, or portion thereof, for execution by a machine (e.g., a computing device) and any related information (e.g., data structures and data) that causes the machine to perform any one of the methodologies and/or embodiments described herein.
Examples of a computing device include, but are not limited to, an electronic book reading device, a computer workstation, a terminal computer, a server computer, a handheld device (e.g., a tablet computer, a smartphone, smart watch, etc.), a web appliance, a network router, a network switch, a network bridge, any machine capable of executing a sequence of instructions that specify an action to be taken by that machine, and any combinations thereof.
Memory 508 may include various components (e.g., machine-readable media) including, but not limited to, a random access memory component, a read only component, and any combinations thereof. In one example, a basic input/output system 516 (BIOS), including basic routines that help to transfer information between elements within control system 14, 500, such as during start-up, may be stored in memory 508. Memory 508 may also include (e.g., stored on one or more machine-readable media) instructions (e.g., software) 520 embodying any one or more of the aspects and/or methodologies of the present disclosure. In another example, memory 508 may further include any number of program modules including, but not limited to, an operating system, one or more application programs, other program modules, program data, and any combinations thereof.
Exemplary control system 500 may also include a storage device 524. Examples of a storage device (e.g., storage device 524) include, but are not limited to, a hard disk drive, a magnetic disk drive, an optical disc drive in combination with an optical medium, a solid-state memory device, and any combinations thereof. Storage device 524 may be connected to bus 512 by an appropriate interface (not shown). Example interfaces include, but are not limited to, SCSI, advanced technology attachment (ATA), serial ATA, universal serial bus (USB), IEEE 1394 (FIREWIRE), and any combinations thereof. In one example, storage device 524 (or one or more components thereof) may be removably interfaced with control system 500 (e.g., via an external port connector (not shown)). Particularly, storage device 524 and an associated machine-readable medium 528 may provide nonvolatile and/or volatile storage of machine-readable instructions, data structures, program modules, and/or other data for RC-WVM control and communication system 500. In one example, software 520 may reside, completely or partially, within machine-readable medium 528. In another example, software 520 may reside, completely or partially, within processor 504.
Exemplary control system 500 may also optionally include an input device 532. In one example, a user of control system 500 may enter commands and/or other information into the via input device 532. Examples of an input device 532 include, but are not limited to, frequency adjust 288 (
A user may also input commands and/or other information to exemplary control system 500 via storage device 524 (e.g., a removable disk drive, a flash drive, etc.) and/or network interface device 540. A network interface device, such as network interface device 540, may be utilized for connecting control system 500 to one or more of a variety of networks, such as network or cloud 28, and one or more remote devices 18 connected thereto. Examples of a network interface device include, but are not limited to, a network interface card (e.g., a mobile network interface card, a LAN card), a modem, and any combination thereof. Examples of a network include, but are not limited to, a wide area network (e.g., the Internet, an enterprise network), a local area network (e.g., a network associated with an office, a building, a campus or other relatively small geographic space), a telephone network, a data network associated with a telephone/voice provider (e.g., a mobile communications provider data and/or voice network), a direct connection between two computing devices, and any combinations thereof. A network, such as network 28, may employ a wired and/or a wireless mode of communication. In general, any network topology may be used. Information (e.g., data, software 520, etc.) may be communicated to and/or control system 500 via network interface device 540.
Exemplary control system 500 may further include display adapter 552 for communicating a displayable image to a display device, such as display device 536. Examples of a display device include, but are not limited to, LCD frequency display 292 (
Disclosure Summary
The present disclosure describes plural embodiments of implantable wireless monitoring sensors configured to sense changes in a dimension of a body lumen within which the sensor is implanted, as well as systems and methods employing such sensors. Aspects of disclosed sensors, systems and methods include one or more of the following, which may be combined in multiple different combinations as described herein.
For example, wireless sensor implants may be optionally configured with any of the following aspects of resilient sensor constructs, coils, variable inductance or resonance, anchor elements or electrical characteristics:
Wireless Implant sensors or resilient sensor construct configurations based on one of the above frame related aspects and one of the above coil related aspects to provide one of a variable inductance or a resonant circuit employing variable inductance and fixed capacitance, optionally with one of the above anchor element aspects may take any of the following configurations:
Systems and methods employing any of the above listed wireless sensor implants or resilient sensor constructs may further include any of the following antennas and/or deployment systems:
Turning to specific alternative RC-WVM implant embodiments disclosed herein, a first exemplary alternative embodiment is RC-WVM implant 12s, shown in
RC-WVM implant 12s utilizes PTFE coated gold Litz wire 42s wound on nitinol wire frame 44s. PTFE has good heat resistance to withstand manufacturing processes while also being biocompatible. The overall configuration of implant 12s includes strut sections 38 and crown sections 40 substantially as described above. Alternatively, anchors 48s are secured adjacent crown sections 40 as described below. Sections of heat shrink tubing 61s are used to help ensure compression of reflow material and may be removed in a later assembly step. A section of heat-shrink tubing 60s may be used to cover and insulate capacitor 46s, which in one embodiment may be a 47 nF capacitor, or heat shrink tubing also may be removed as mentioned above.
Capacitor 46s may be comprised of any suitable structure to provide the desired capacitance, in one embodiment 47 nF, as mentioned. For example, the desired capacitance may be achieved with a specifically sized gap, different terminal materials (e.g., leads, etc.), overlapping wires, or it could be a gap in a tube with a certain dielectric value. In an exemplary embodiment as illustrated, surface mount capacitor 46s is soldered between the two terminals 56s, formed through the joining of the 300 strands of Litz wire 42s. Other electrical attachments such as crimped, or attached directly to the terminals of the cap brazed with no solder may also be employed. The capacitor section is then encapsulated using a reflow process comprising positioning polymer reflow tube 59s over the capacitor, connection and terminals, followed by heat-shrink tubing 60s positioned over the reflow tube. Reflow tube 59s and heat shrink tube 60s are placed over the Litz wire/nitinol frame assembly before the capacitor before the capacitor is soldered in place (
Details of alternative anchors 48s are shown in
Anchor 48s may be formed by laser cutting a pattern from a nitinol tube and shape setting the anchor barbs via a heat treatment process. Other embodiments can be formed using wire of various materials, shape set or bent using a standard process, or laser cut from other metals or bioabsorbable polymers. External surfaces of anchors may utilize different shapes of anchors or different surface finishes to engage the vessel wall and prevent migration of the implant. The overall length of anchors 48s that extend beyond crowns sections 40 of implant 12s is selected to facilitate the expansion of the implant upon deployment from delivery system 122 (
Attachment section 49s may be formed using a tube laser cutting process to produce a spiral section of a tube. As indicated in
After placement of the anchor on the implant strut, polymeric reflow tube 59s is positioned over this assembly and further heat shrink tube 61s placed over this. Heat is then applied to melt the polymer tube and shrink the heat shrink tube, thus forcing the polymer between spacing in the spiral of the anchor section and thereby reinforcing the fixation of the anchor to the implant assembly. Reflow tube 59s also may be sized with a slight interference fit between the outer surface of the implant assembly and the inner surface of the anchor attachment section to provide some fixation, both longitudinal and rotational, during assembly. The spacing between the spirals is designed to allow the reflow material to flow into the spaces and form a bond. The width of the spirals is designed to allow the spiral section to be manipulated into position during assembly, while still providing sufficient rigidity when fully assembled. The thickness of the section is minimized to reduce the overall profile of the implant. One advantage of attachment section 49s employing a spiral portion as means of attachment is that it permits attachment of the anchor to any wire-based implant, including insulated wire implants without disturbing or penetrating the insulation layer. The spiral portion as described distributes the attachment force across space of the insulation layer to avoid compromise of the layer and the spaces between the spiral facilitate bonding attachment. Another advantage of attachment using a spiral portion as described is that the aspect ratio of the spiral section may be selected so as to allow the spiral to be slightly unwound to permit placement of the anchor in the middle of the implant strut section without needing to thread it over the end past the capacitor terminals. Alternative embodiments of attachment section 49s may employ other shapes, such as a T-shape rather than the spiral section, to prevent rotation and detachment from the sensor. Further alternatives may also include the replacement of polymer reflow tube 59s with just heat-shrink that could be left in place, or use an adhesive or other bonding technology.
As shown in
Isolation section 53s is designed to isolate or reduce transmission of mechanical motion of anchor section 51s from or to attachment section 49s and thus to the implant, to allow the implant to move freely and at least substantially free of distortions resulting from contact of the anchor section with the vessel wall. Isolation section 53s thus may comprise a narrow cross-section area to provide flexibility while keeping thickness constant to provide adequate support. Fillets/curves surfaces as shown are maintained to avoid stress concentrations that could lead to fatigue or unwanted tissue damage. Alternative embodiments of isolation section 53s may include varying tube thickness to provide more flexibility or varying the cross-section in a non-mirrored fashion to provide preferential flexibility in one direction.
Implant repositionability or even recapture with the deployment system can be facilitated through the addition of recapture features in the distal end of the anchor and the pusher tip, exemplary embodiments of which are shown in
While anchors 48s are shown in
In other alternative embodiments, as illustrated in
As best seen in detail in
Attachment arm 658 may contain a saw tooth-like configuration as shown in
In some embodiments, for example as shown in
In other embodiments, the decoupling split 666 of the anchor frame may be located elsewhere on the frame and, in such cases, preferably structurally reinforced by bridging with an additional metallic or polymeric component that provides sufficient structural integrity to the anchor frame while maintaining the discontinuous configuration. Alternatively, a continuous anchor frame structure may be devised by carefully selecting the amount of metallic material of the frame and shape of the frame to minimize or control interference with the RC-WVM implant signal such that it may be otherwise compensated for in signal processing.
In some embodiments, anchor frame 650 may be attached to the RC-WVM sensor section and loaded in the deployment system with the orientation of the anchor frame exposed first during deployment. In this case, pusher 126 of delivery system 122 bears on crown sections 40 of the sensor section (see, e.g.,
Once an RC-WVM implant employing anchor frame 650 is deployed within a vessel, barbs 656 engage with the vessel wall in various orientations to prevent movement of the device.
In another example, as shown in
Various orientations and configurations of anchor barbs 656 may be provided in different embodiments as illustrated in
In other embodiments, examples of which are shown in
As described above, it may be desirable to configure anchor frame 650 so that it does not form a coil that could interfere with the RC-WVM implant signal. One solution, as described above is split 666. In other embodiments, for example where other design considerations may make a discontinuous structure less preferable such that anchor frame wire is mechanically and electrically joined (e.g. a crimped joint), the terminations of the wire ends where joined and in contact with each other may be electrically insulated so as to not form coil capable of coupling with a magnetic field. An example of such insulation is a polymer coating. In other embodiments, for example, where the anchor frame may be formed of nitinol laser cut tubing, for which a mechanical joint or bond may be required, the terminations of the nitinol frame can be physically and electrically separated by use of a non-conducting bonding agent such as a polymer, epoxy or ceramic material.
As previously discussed, the radial force exerted by the RC-WVM implant should be such that the sensor section moves with the natural motion of the IVC as it expands and contracts due to changes in fluid volume. Anchor frame 650 is configured to exert an outward radial force that is sufficient to ensure engagement of anchor barbs 656 into the vessel wall to help prevent migration along the vessel without interference with motion and electrical performance of the RC-WVM sensor section. Thus, the radial force exerted by anchor frame 650 typically may be equal to or higher than that exerted by the sensor section of the RC-WVM implant, so as to provide migration resistance while substantially isolated by isolation section 659 from the lower radial force sensor section, which, is configured to permit natural expansion and contraction of the IVC in response to varying fluid status.
Isolation section 659 allows attachment between the sensor section and anchor frame, but also permits the sensor section and anchor frame to act independently of each other. Thus, the RC-WVM sensor section can contract and expand at the monitoring location within the vessel independently of anchor frame expansion and contraction at the anchoring location in the vessel. One design consideration in selecting the configuration of the anchor frame is that the radial force exerted by the anchor frame should be sufficient to prevent migration of the RC-WVM implant, but low enough so as to not stent or prop open the vessel.
The configuration of anchor frame 650a in
In another alternative embodiment, the anchor frame may be configured so as to intentionally fracture and self-separate from the sensor section over time. In this embodiment, connection points between the anchor frame and sensor section, for example in isolation section 659, are designed to deliberately fracture. The purpose of the deliberate fracture is to completely isolate the anchor frame from the sensor section after fracture. In such an embodiment, the anchor frame would secure the RC-WVM implant against migration when first deployed in the vessel. Over time, as the sensor section embeds into the tissue, the risk of migration diminishes. As a result, the anchor frame's function is no longer required. This embodiment allows for disconnection of the anchor frame from the device once it is no longer required without the need for surgical intervention.
The material and design of the isolation sections 659 may be selected to provide for different time periods for fracture to occur. For example, the geometry, design, movement and material of the sensor section, isolation section and anchor frame can be tuned for a fatigue induced fracture to occur after/within a given time due to fatigue. Alternatively, fracture can be induced by external means. For example ultra sound/RF may be used to induce fracture by breaking down the material or bond between the anchor frame and sensor section at a pre-set frequency or energy. In a further alternative embodiment, chemically induced fracture of isolation sections 659 may be achieved with, for example, a biodegradable polymer such as PLA, PCL, PLGA, PLG or other as the bond/connection between the anchor frame and RC-WVM implant frame. Chemically induced fracture takes advantage of the material properties of biodegradable polymers, which can degrade at controlled rates including such as of pH, temperature, microorganisms present, and water etc.
In another alternative embodiment, anchor frame 650 may be made of a bioabsorbable/biodegradable material such as commonly used for bioabsorbable stents. Similar to other embodiments of the anchor frame, the purpose of a bioabsorbable anchor frame is to help prevent migration. Once again, as the sensor section embeds into the tissue over time, the risk of migration diminishes. As a result, the anchor frame's function is no longer required. The material and design of a bioabsorbable anchor frame may be selected for different time periods for absorption.
The foregoing has been a detailed description of illustrative embodiments of the invention. It is noted that in the present specification and claims appended hereto, conjunctive language such as is used in the phrases “at least one of X, Y and Z” and “one or more of X, Y, and Z,” unless specifically stated or indicated otherwise, shall be taken to mean that each item in the conjunctive list can be present in any number exclusive of every other item in the list or in any number in combination with any or all other item(s) in the conjunctive list, each of which may also be present in any number. Applying this general rule, the conjunctive phrases in the foregoing examples in which the conjunctive list consists of X, Y, and Z shall each encompass: one or more of X; one or more of Y; one or more of Z; one or more of X and one or more of Y; one or more of Y and one or more of Z; one or more of X and one or more of Z; and one or more of X, one or more of Y and one or more of Z.
Various modifications and additions can be made without departing from the spirit and scope of this invention. Features of each of the various embodiments described above may be combined with features of other described embodiments as appropriate in order to provide a multiplicity of feature combinations in associated new embodiments. Furthermore, while the foregoing describes a number of separate embodiments, what has been described herein is merely illustrative of the application of the principles of the present invention. Additionally, although particular methods herein may be illustrated and/or described as being performed in a specific order, the ordering is highly variable within ordinary skill to achieve aspects of the present disclosure. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this invention.
Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present invention.
This application is a continuation of U.S. Nonprovisional application Ser. No. 17/018,194, filed Sep. 11, 2020; which application was a continuation of PCT/US2019/034657, filed May 30, 2019, which international application claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 62/678,237, filed May 30, 2018, and titled “Wireless Resonant Circuit and Variable Inductance Vascular Monitoring Implants and Anchoring Structures Therefore”. U.S. Nonprovisional application Ser. No. 17/018,194 was also a continuation-in-part of U.S. Nonprovisional patent application Ser. No. 16/177,183, filed on Oct. 31, 2018, now U.S. patent Ser. No. 10/806,352, issued Oct. 20, 2020, and titled “Wireless Vascular Monitoring Implants”. U.S. Nonprovisional patent application Ser. No. 16/177,183 was a continuation application of PCT/US17/63749, filed Nov. 29, 2017, and which international application claims the benefit of priority of U.S. Provisional Application No. 62/534,329 filed Jul. 19, 2017, and U.S. Provisional Application No. 62/427,631, filed Nov. 29, 2016; U.S. Nonprovisional patent application Ser. No. 16/177,183 also was a continuation-in-part of PCT/US2017/046204, filed Aug. 10, 2017, which international application claims the benefit of priority to U.S. Provisional Patent Application No. 62/373,436, filed Aug. 11, 2016. Each of these applications is incorporated by reference herein in its entirety.
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| Number | Date | Country |
|---|---|---|
| 2986252 | Jul 2018 | EP |
| 2473529 | Mar 2011 | GB |
| 2011234884 | Nov 2011 | JP |
| 201501512 | Oct 2015 | WO |
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| Entry |
|---|
| ISR Report and Written Opinion dated Dec. 30, 2020, in connection with PCT/EP2020/067713 filed on Jun. 24, 2020. |
| Number | Date | Country | |
|---|---|---|---|
| 20210401305 A1 | Dec 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62678237 | May 2018 | US | |
| 62534329 | Jul 2017 | US | |
| 62427631 | Nov 2016 | US | |
| 62373436 | Aug 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17018194 | Sep 2020 | US |
| Child | 17469624 | US | |
| Parent | PCT/US2019/034657 | May 2019 | US |
| Child | 17018194 | US | |
| Parent | PCT/US2017/063749 | Nov 2017 | US |
| Child | 16177183 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16177183 | Oct 2018 | US |
| Child | PCT/US2019/034657 | US | |
| Parent | PCT/US2017/046204 | Aug 2017 | US |
| Child | PCT/US2017/063749 | US |
