Flow-sensing vascular implants

Abstract

The vascular treatment device 10 includes a stent 2 having a tube with an inner surface 3 defining a central lumen 5, the stent being configured to be placed at a treatment site within an associated patient's blood vessel, and at least one sensor 12 attached to or embedded in the inner surface of the stent.

Description

[Technical field]

[0001] The following relates generally to vascular stent technology, blood flow sensing technology, pressure sensing technology, temperature sensing technology, stenosis sensing technology, and related technologies. [Background technology]

[0002] The development of vascular disease, both arterial and vascular, often results in a lifelong chronic condition for the patient, requiring continuous monitoring. Recurrence of disease symptoms, such as plaque buildup resulting in narrowing of the vessel lumen (called stenosis), is common and usually results in additional invasive treatment. Early detection of recurrent stenosis is important to minimize the severity of any medical intervention, which reduces procedural risk to the patient and preserves future treatment options. Current monitoring and detection techniques, including symptom observation, external ultrasound, and intravascular fluoroscopy, have various limitations, including lack of location specificity, limited anatomical access, procedural risk, and cost.

[0003] A common treatment for patients suffering from stenosis is to receive a stent to restore adequate blood flow through the stenosed vascular region affected by the disease. Stent restenosis due to the accumulation of plaque or other coagulated material inside the stent is a common occurrence, considering the underlying biological and lifestyle conditions that contribute to the disease. Indeed, the nature of the stent as a foreign and sometimes non-biological material in the body may increase the likelihood of stenosis accumulation in the stent.

[0004] Restenosis is most frequently detected by the recurrence of symptoms (pain, swelling, discoloration) reported by the patient. This form of detection is not only untimely, as significant disease progression is required to trigger the onset of symptoms, but also provides little information regarding the location of the disease. Symptoms may result from restenosis of a previously treated vessel segment, or from the development of stenosis in a previously healthy vessel segment.

[0005] Ankle-brachial blood pressure comparison, or tissue oxygenation measurement, are other non-invasive, scalable detection techniques. However, they also lack specific information regarding the location of the disease. For example, ankle-brachial blood pressure comparison can simply indicate the presence of at least one stenosis area somewhere between the ankle and brachial blood pressure measurement locations.

[0006] Other detection modalities, such as external ultrasound (US) or intravascular fluoroscopy, can detect restenosis before the onset of symptoms and provide location specificity, but cost, procedural risks, and limited anatomical access (i.e., external US is not effective in detecting stenosis in the pelvic vasculature, for example) make these techniques unsuitable for frontline detection. Summary of the Invention [Problem to be solved by the invention]

[0007] The following discloses specific improvements that overcome these and other problems. [Means for solving the problem]

[0008] In some embodiments disclosed herein, a vascular treatment device includes a stent having a tube with an inner surface defining a central lumen, the stent being configured to be placed at a treatment site within an associated patient's blood vessel, and at least one sensor attached to or embedded in the inner surface of the stent.

[0009] In some embodiments disclosed herein, a vascular treatment device includes a stent having a tube with an inner surface defining a central lumen, the stent configured to be placed at a treatment site within a blood vessel of an associated patient, and at least one pressure sensor attached or embedded to the inner surface of the stent, the at least one pressure sensor configured to obtain at least one blood pressure measurement including blood flow resistance.

[0010] In some embodiments disclosed herein, a vascular treatment method includes receiving blood flow resistance measurements caused by a stent placed in a blood vessel based on at least one measurement using one or more sensors, repeating the blood flow resistance measurements over successive sessions to generate a blood flow resistance versus time curve, assessing restenosis in the stent based on the blood flow resistance versus time curve, and outputting an indication of the restenosis assessment on a display device.

[0011] One advantage is that it provides real-time, non-invasive monitoring of blood flow through a previously implanted stent.

[0012] Another advantage resides in providing the treating physician with localization information that is key to early detection of disease progression and planning further treatment.

[0013] Another advantage is in monitoring and preventing restenosis in a stent implanted in a patient.

[0014] Another advantage resides in reducing the need for imaging of potential restenosis in patients.

[0015] A given embodiment may provide none, one, two, more, or all of the aforementioned advantages, and / or other advantages that will become apparent to those of ordinary skill in the art upon reading and understanding this disclosure.

[0016] The disclosure may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting the disclosure. [Brief description of the drawings]

[0017] [Figure 1] 1 illustrates a schematic diagram of a vascular treatment device according to the present disclosure. [Diagram 2] 2 shows an alternative embodiment of the device of FIG. 1; [Diagram 3] 2 shows an alternative embodiment of the device of FIG. 1; [Figure 4] 2 illustrates diagrammatically how the device of FIG. 1 can be used to perform a vascular treatment method; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A concern with stents is the possibility of restenosis occurring in the stent. Typically, this is monitored by techniques such as Doppler ultrasound imaging. However, stents can interfere with ultrasound image quality, and detection of material buildup on the stent by external imaging is difficult. Intravascular ultrasound imaging may provide higher image quality, but at the expense of performing a follow-up invasive intravascular procedure on the patient.

[0019] The following discloses an alternative approach in which a sensor is embedded in the stent and remains in the patient along with the stent to provide monitoring of any restenosis.

[0020] In one contemplated embodiment, a passive pressure sensor is used. Such a sensor is passive in that it can be advantageously very miniaturized, for example on the order of microns in size, and is charged and operated using an externally applied magnetic field. In one particular implementation, two such sensors are placed at the upstream and downstream ends of the stent, respectively. The pressure difference between the two sensors provides a metric of the flow resistance presented by the stent. In one approach, sensor readings are taken immediately after the stent is placed and at subsequent intervals, such as at follow-up physician visits. Restenosis then manifests as a gradually increasing flow resistance over time. In some examples, when multiple tents are placed in a vessel, the pressure gradient between the stents can be determined. In other examples, pressure measurements can be measured at the site of the stent, and pressure measurements can be made with cuffs at different sites, and the resulting pressure difference can be measured to determine stenosis. In another example, external Doppler ultrasound blood flow (Q) can be measured in combination with pressure gradient (ΔP) measurements at the stent. The actual resistance R can be calculated as R=ΔP / Q.

[0021] This type of sensor can detect restenosis in another way: as overgrowth of biological material accumulates on the inner wall of the stent and on the pressure sensor, the overgrowth can impose a force (corresponding to pressure) on the sensor. An increase in the measured "pressure" corresponds to an increase in restenosis. One suitable approach is to measure sensor readings in various clinical study subjects to determine which trend line in pressure readings (or pressure difference readings in two-sensor embodiments) over time corresponds to significant restenosis.

[0022] To enable measurement of the pressure of blood within the stent lumen (or to detect restenosis due to forces exerted by biological material overgrowth), a pressure sensor is suitably placed inside the stent, i.e., on the wall of the stent lumen. Note that pressure or flow measurement, as used herein, does not necessarily mean measurement in standard pressure or flow units, but more generally encompasses metrics measured by a sensor placed with the stent that correlate to pressure and / or flow.

[0023] Although a completely passive sensor is advantageous, the use of one or more active flow sensors within the stent is also contemplated. For example, sensors including a storage capacitor for inductively powering the sensor for measurement are contemplated.

[0024] In another approach, the implanted sensor can be a temperature sensor and the patient (or other subject) can be injected with chilled saline or contrast solution, and uptake of the chilled saline fluid into the blood vessel containing the stent is then detected by a temperature shift measured by the implanted temperature sensor, where the time delayed uptake is expected to correspond to an increase in the flow resistance of the stent and therefore restenosis. In another example, the patient can breathe (cold) air and the phase delay between a first "warm" temperature blood measurement and a second "cold" temperature blood measurement can be analyzed.

[0025] If the sensor is radiopaque (or has a radiopaque coating), it can also provide a marker for locating the stent in imaging during stent placement, thus replacing traditional fluoroscopic markers and thus not increasing the number of components of the stent.

[0026] The disclosed approach is suitable for use with any type of stent, including but not limited to self-expanding nitinol stents.

[0027] Stents and other vascular implants may also incorporate tabs or rings or other geometric extensions into their structure to provide improved visibility when viewed under fluoroscopy. One alternative embodiment contemplates replacing these features completely or partially with sensing elements. Elements located at either end, both ends, or along the length of the implant can measure a physiologically meaningful parameter (e.g., pressure) at a specific location within the region of the implant. Changes in that parameter can then be used to detect early onset of disease progression (e.g., changes in blood flow indicate restenosis). Additionally or alternatively, sensors providing position information can be included in the stent and used to detect compression, expansion, or breakage / failure of the implanted stent. Sensors located inside the stent, for example attached or embedded on the inner surface of the stent, are suitably in direct line with the blood and thus the blood-stent interface. This can measure tissue overgrowth on the inner stent surface, predict loss of patency, and even facilitate earlier intervention to improve stent patency.

[0028] With reference to FIGURE 1, an exemplary vascular treatment (i.e., thrombectomy or atherectomy) apparatus 1 is shown generally. As shown in FIGURE 1, apparatus 1 includes a treatment apparatus 10 having a vascular treatment device 2 (e.g., a self-expanding stent, a self-expanding filter, etc.) that is implanted into a blood vessel V. In some examples, stent 2 comprises a self-expanding Nitinol stent. Stent 2 comprises a tube having an inner surface 3 that defines a central lumen 5. Stent 2 is positioned at a treatment site within blood vessel V of an associated patient.

[0029] Delivery of the stent 2 into the blood vessel V may be accomplished, for example, using a catheter or other intravascular device (not shown) that is inserted into the vessel through an incision and moved to the treatment site where the stent 2 is deployed. For this purpose, various known stent delivery device systems can be used. After deploying the stent 2 into the vessel V, the intravascular device is withdrawn, leaving the deployed stent in place. In the case of a self-expanding (e.g., Nitinol) stent, stent delivery typically involves compressing the stent into a recess at or near the tip of the intravascular device and releasing the stent by pushing the stent out of the recess using an appropriate mechanism (e.g., wire drive or cable drive) of the intravascular device. In another approach, a stent (which may or may not be self-expanding in this approach) is deployed and an inflatable balloon at or near the tip of the interventional device is placed inside the deployed stent and inflated to expand the stent and push it into the wall of the blood vessel V. Typically, the stent 2 is a hollow tube that functions to increase the vessel diameter to relieve the stenosis. However, it is contemplated that the stent 2 may optionally include other features (not shown), such as a filter disposed inside the central lumen 5 of the stent, or a one-way valve, such as a bicuspid or tricuspid valve, disposed inside the central lumen 5 of the stent for use in inhibiting reversal of blood flow. Such one-way valves are sometimes included in the veins of the legs, for example, to combat blood pooling in the feet or legs. The term stent as used herein is intended to encompass such variations.

[0030] As shown in Figure 1, the self-expanding stent 2 can include one or more radiopaque markers 4 (two of which are shown in Figure 1, although any suitable number of markers can be used). The radiopaque markers 4 can take any form, such as a radiopaque coating applied to some or all of the wires or other materials that make up the stent 2, and / or separate radiopaque marker elements attached to the stent, such as by metallurgical bonding. Such radiopaque markers 4 provide visibility of the stent 2 in a medical imaging modality (not shown), such as x-ray or computed tomography (CT), which can be used to provide visualization of the stent delivery process for placing the stent 2 within a blood vessel V using an endovascular procedure as described above.

[0031] At least one sensor 12 is attached to or embedded in the inner surface 3 of the stent 2. In one example embodiment, the at least one sensor 12 comprises a temperature sensor configured to measure the temperature of blood flowing through the central lumen 5 of the stent 2. In another example embodiment, the at least one sensor 12 comprises a fluid flow resistance sensor configured to measure the blood flow resistance of the stent 2 disposed at the treatment site in the blood vessel V. In some embodiments, such a fluid flow sensor may comprise two pressure sensors spaced apart along the axis of the central lumen 5 of the stent 2 to measure a metric of fluid flow resistance as a measured pressure difference. In some examples, the at least one sensor 12 comprises an active sensor including a storage capacitor configured to inductively provide power to the at least one sensor 12. In other examples, the at least one sensor 12 comprises a passive sensor excited by an externally applied magnetic field provided by an associated magnetic source 6. In another example, instead of a radiopaque marker 4, the at least one sensor 12 may be coated with a radiopaque coating.

[0032] 1 further illustrates an electronic processing device 18, such as a workstation computer, or more generally, a computer. The electronic processing device 18 may also include a server computer or multiple server computers, for example, interconnected to form a server cluster, cloud computing resources, etc., to perform more complex computational tasks. The electronic processing device 18 includes typical components such as an electronic processor 20 (e.g., a microprocessor), at least one user input device (e.g., a mouse, keyboard, trackball, etc.) 22, and a display device 24 (e.g., an LCD display, a plasma display, a cathode ray tube display, etc.). In some embodiments, the display device 24 can be a separate component from the electronic processing device 18, or may include two or more displays.

[0033] The electronic processor 20 is operatively connected to one or more non-transitory storage media 26. The non-transitory storage media 26 may include, by way of non-limiting illustrative example, one or more of a magnetic disk, RAID, or other magnetic storage medium, a solid state drive, a flash drive, an electronically erasable read-only memory (EEROM) or other electronic memory, an optical disk or other optical storage device, various combinations thereof, such as a network storage device, an internal hard drive of the electronic processing device 18, various combinations thereof. It should be understood that any reference herein to a non-transitory medium or medium 26 should be broadly interpreted to encompass a single medium or multiple media of the same or different types. Similarly, the electronic processor 20 may be embodied as a single electronic processor or as two or more electronic processors. The non-transitory storage medium 26 stores instructions executable by at least one electronic processor 20. The instructions include instructions for generating a visualization of a graphical user interface (GUI) 28 for display on the display device 24.

[0034] The electronic processing device 18 is programmed (i.e., stored in the non-transitory storage medium 26) to determine, based on measurements obtained from the at least one sensor 12, whether the blood flow resistance measured by the at least one sensor 12 is below a predetermined fluid flow resistance threshold. An indication 29 of blood flow resistance below the predetermined fluid flow resistance threshold can be output to the display device 24.

[0035] 1 shows two sensors 12, any suitable number of sensors 12 may be implemented. In some embodiments, the sensor 12 includes one or more pressure sensors 12 configured to measure the blood flow resistance caused by the stent 2 based on at least one pressure measurement obtained by the pressure sensor 12. For example, the sensor 12 may include a first pressure sensor 12 and a second pressure sensor 12 disposed at spaced apart positions along the central axis of the central lumen 5. Such a spaced apart arrangement allows for the measurement of the blood flow resistance as a pressure difference between the readings of the two pressure sensors 12. As previously mentioned, this blood flow resistance is not necessarily provided in standard units of blood flow resistance, but is a quantitative metric of the blood flow resistance.

[0036] In another example, as shown in FIG. 2, each sensor 12 includes a first and a second permanent magnet 14. In one example, the first and second permanent magnets 14 can be connected by a coupler 16. By varying the distance, for example by a pressure-sensing membrane, pressure and / or temperature can be measured. In another example, the first and second permanent magnets 14 are disposed at opposite ends of the stent 2. One of the first and second permanent magnets 14 is fixed to the stent 2, and the other of the first and second permanent magnets 14 is configured to vibrate relative to the fixed magnet.

[0037] Measurements of the stent placed at the treatment site can be obtained from at least one sensor element by inducing at least one resonant rotational vibration of the permanent magnet with an externally applied magnetic field. Some suitable sensors of this passive dual magnet type are described in U.S. Patent Publication No. 2021 / 0244305 A1 to Gleich et al., which is incorporated herein by reference in its entirety. In one design of this type, each sensor 12 includes two permanent magnets 14 connected by an elastic coupler 16 located inside a container (not shown) fixed (e.g., embedded) to the inner surface 3 of the stent 2. One magnet is held in a fixed position and the other is free to vibrate by rotational motion. (In another embodiment, both magnets may be free to vibrate). The vibration occurs at a resonant frequency that is a function of the distance between the magnets 14, which can be changed as a function of the pressure or temperature measured by the sensor 12. The vibration resonant frequency can be sensed remotely by measuring the magnetic field generated by the magnetic source 6. The magnetic field is changed by the vibration of the free magnets 14. The magnetic source 6 may be located outside the patient's body (typically near or on the patient's skin in close proximity to the internal location of the stent 2), making this measurement completely non-invasive.

[0038] In another example, as shown in FIG. 3, the sensor 12 includes a first sensor element 30 of dual magnet type having first and second magnets 32 connected by an elastic coupler 34 attached or embedded at a first location on the inner surface 3 of the stent 2. A second sensor element 36 of dual magnet type includes first and second permanent magnets 38 connected by an elastic coupler 40 attached or embedded at a second location on the inner surface 3 of the stent 2. The second location is spaced apart from the first location along the central axis of the central lumen 5 of the stent 2. The pressure difference between the readings of the two sensors 30 and 36 serves as a metric of fluid flow resistance, as follows: restenosis in the stent 2 is expected to result in an increase in flow resistance - thus an increase in the measured pressure difference over time correlates with an increase in restenosis in the stent 2. In this approach, to allow the two pressure sensors 30 and 36 to be read independently, they can optionally be designed to vibrate at different resonant frequencies. This can be done, for example, by making the mass and / or magnetization of the elastic coupler 16 and / or the two permanent magnets 14 different from the two pressure sensors 30 and 36 .

[0039] At each visit, a frequency sweep of the frequency of the magnetic field generated by the magnetic source 6 is applied to identify the resonant frequency of each of the two dual magnet pressure sensors 12. To assess restenosis over time, in one suitable workflow, such measurements are performed at successive time intervals, for example at successive physician visits. The pressure difference (now a fluid flow metric) is measured at each such visit, thereby generating a fluid flow resistance vs. time curve over days, weeks, months, or years. Based on this curve, the physician can assess the extent of restenosis. This assessment may be based on a threshold value or on the rate of increase of flow resistance over time (i.e., the slope of the fluid flow resistance vs. time curve). Optionally, clinical trials can be used to calibrate the relationship between the extent of restenosis and the change in fluid flow resistance over time (or resistance gradient) measured using the sensors 30, 36. In another approach, in vitro bench testing can be performed to calibrate the relationship, for example using a porcine blood vessel with stent 2 implanted in it and a mechanical pump providing a flow of saline solution simulating blood flow.

[0040] These are merely examples and should not be construed as limiting. These examples may also use temperature readings measured by sensor 12 instead of pressure readings.

[0041] At least one electronic processor 20 is configured as described above to execute vascular treatment method or process 100. Non-transitory storage medium 26 stores instructions readable and executable by at least one electronic processor 20 to perform the disclosed operations, including executing vascular treatment method or process 100. In some examples, method 100 may be performed, at least in part, by cloud processing.

[0042] 4, with continued reference to Figures 1-3, an exemplary embodiment of a vascular treatment method 100 is illustrated generally as a flow chart. To begin method 100, a stent 2 is deployed within a patient's vessel V via a treatment device 10 at a treatment location within the vessel V.

[0043] In operation 102, a blood flow resistance measurement caused by a stent (2) placed in blood vessel V is measured by sensor 12 and received by electronic processing device 18. In operation 104, electronic processing device 18 determines whether the blood flow resistance is below a predetermined fluid flow resistance threshold. In operation 106, an indication 29 of blood flow resistance below the predetermined fluid flow resistance threshold is output on display device 24. As previously mentioned, other metrics can be used, such as the slope or other characteristics of the blood flow resistance versus time curve measured over successive physician visits.

[0044] The present disclosure has been described with reference to the preferred embodiment. Modifications and alterations may occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiments be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

1. A stent having a tube with an inner surface defining a central lumen, the stent being configured to be placed at a treatment site in the blood vessel of the relevant patient, At least one sensor attached to or embedded in the inner surface of the stent, A vascular treatment device having [a certain feature].

2. The vascular treatment apparatus according to claim 1, wherein the at least one sensor includes a fluid flow resistance sensor configured to measure blood flow resistance at the treatment site within the blood vessel.

3. Determine whether the blood flow resistance falls below a predetermined fluid flow resistance threshold. The system outputs an index of blood flow resistance that is below the predetermined fluid flow resistance threshold to the display device. The vascular treatment apparatus according to claim 2, further comprising an electronic processing device configured as described above.

4. The at least one sensor, The one or more pressure sensors are configured to measure the blood flow resistance caused by the stent based on at least one blood pressure measurement obtained by the one or more pressure sensors, A vascular treatment device according to claim 1, having the following features.

5. The at least one sensor, A first pressure sensor and a second pressure sensor are positioned at intervals along the central axis of the central lumen. A vascular treatment device according to claim 1, having the following features.

6. The at least one sensor includes at least one sensor element having first and second permanent magnets connected by an elastic coupler, The measurement values ​​of the stent placed at the treatment site can be obtained from the at least one sensor element by inducing at least one resonant rotational vibration of the permanent magnet using an externally applied magnetic field. The vascular treatment device according to claim 1.

7. The at least one sensor element having first and second permanent magnets connected by an elastic coupler, A first sensor element having first and second permanent magnets connected by elastic couplers attached to or embedded at a first position on the inner surface of the stent, A second sensor element having first and second permanent magnets connected by an elastic coupler attached to or embedded in a second position on the inner surface of the stent, Includes, The second position is spaced apart from the first position along the central axis of the central lumen of the stent. The vascular treatment device according to claim 6.

8. The vascular treatment apparatus according to claim 1, wherein the at least one sensor is a passive sensor that is excited by an externally applied magnetic field supplied by an associated magnetic source.

9. The vascular treatment apparatus according to claim 1, wherein the at least one sensor is an active sensor comprising a storage capacitor configured to inductively supply power to the at least one sensor.

10. The vascular treatment device according to claim 1, wherein the at least one sensor is a temperature sensor configured to measure the temperature of the blood flowing through the central lumen of the stent.

11. The at least one sensor, A first temperature sensor and a second temperature sensor are positioned at intervals along the central axis of the central lumen. A vascular treatment device according to claim 10, having the following features.

12. The vascular treatment device according to claim 1, wherein the stent includes a self-expanding nitinol stent.

13. A stent having a tube with an inner surface defining a central lumen, the stent being configured to be placed at a treatment site in the blood vessel of the relevant patient, At least one pressure sensor attached to or embedded in the inner surface of the stent, the at least one pressure sensor configured to acquire at least one pressure measurement value including blood flow resistance, A vascular treatment device having [a certain feature].

14. Determine whether the blood flow resistance falls below a predetermined fluid flow resistance threshold. The system outputs an index of blood flow resistance that is below the predetermined fluid flow resistance threshold to the display device. The vascular treatment apparatus according to claim 13, further comprising an electronic processing device configured as described above.

15. The at least one pressure sensor, A first pressure sensor and a second pressure sensor are positioned at intervals along the central axis of the central lumen. A vascular treatment device according to claim 13, having the following features.

16. The at least one pressure sensor includes at least one pressure sensor element having first and second permanent magnets connected by an elastic coupler, The measurement values ​​of the stent placed at the treatment site can be obtained from the at least one sensor pressure element by inducing at least one resonant rotational vibration of the permanent magnet using an externally applied magnetic field. The vascular treatment device according to claim 13.

17. The at least one pressure sensor element having first and second permanent magnets connected by an elastic coupler, A first pressure sensor element having first and second permanent magnets connected by elastic couplers attached to or embedded at a first position on the inner surface of the stent, A second pressure sensor element having first and second permanent magnets connected by an elastic coupler attached to or embedded at a second position on the inner surface of the stent, Includes, The second position is spaced apart from the first position along the central axis of the central lumen of the stent. The vascular treatment device according to claim 16.

18. The at least one pressure sensor, A passive sensor excited by an externally applied magnetic field supplied by an associated magnetic source. An active sensor including a storage capacitor configured to inductively supply power to at least one of the sensors, The vascular treatment device according to claim 6, having one of the following.

19. The stent includes one or more radiopaque markers, The electronic processing device is programmed to perform image analysis based on changes in the configuration of one or more radiopaque markers in a continuous sequence of images of the stent acquired during the procedure of placing the stent into the blood vessel. The vascular treatment device according to claim 13.

20. The steps include receiving a blood flow resistance measurement caused by a stent placed in a blood vessel based on at least one measurement from one or more sensors, To generate a blood flow resistance versus time curve, the process involves repeating blood flow resistance measurements over consecutive sessions, A step of evaluating restenosis in the stent based on the blood flow resistance versus time curve, The steps include outputting an index for evaluating restenosis to a display device, A vascular treatment method having the following characteristics.

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