Patent Application
20190167122
This disclosure relates to medical devices and, in particular, to sensors for endovascular assemblies for improving vascular compliance of a vessel.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Endovascular devices are commonly used in vascular passages when the vascular passageway becomes stiff and loses compliance. When a vascular passageway loses compliance due to, for example, age, congestive heart failure, or atherosclerosis, the vascular passageway stiffens and loses compliance, causing the heart to exert more force to effect the same volume of blood into the vascular passage. It is desirable to have a sensor system associated with endovascular devices to monitor blood flow within the vascular passageway and provide information to adjust parameters of implanted endovascular devices.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
In one embodiment, a system for monitoring the flow of blood within an endoluminal passage is provided comprising a medical device and a sensor. The medical device is implantable within the endoluminal passage and includes a shaft and an expandable segment coupled to the shaft. The expandable segment is movable between a first state and a second state. Movement of the expandable segment is responsive to a change in the fluid pressure external to the expandable segment. The sensor is positioned on the medical device and is adapted to collect information associated with the state of the expandable segment.
In another embodiment, a system for monitoring the flow of blood within an endoluminal passage is provided including a medical device and a plurality of sensors. The medical device is implantable within an endoluminal passage and includes a shaft and a plurality of expandable segments coupled to the shaft. The plurality of expandable segments are arranged linearly along the shaft. Each of the expandable segments is movable between a first state and a second state. Movement of the expandable segments is responsive to a change in fluid pressure external to the expandable segment. The plurality of sensors are positioned on the medical device and are configured to collect information associated with the states of the plurality of expandable segments.
In yet another embodiment, a method of determining a characteristic of the flow of blood within an endoluminal passage is provided, including implanting a medical device within an endoluminal passage and transmitting a signal generated by a sensor. The medical device includes a shaft, an expandable segment coupled to the shaft, and a sensor positioned on the medical device. The expandable segment is movable between an expanded state and a compressed state. Movement of the expandable segment is responsive to a change in the flow of blood within the endoluminal passage over the expandable segment. The signal is generated by the sensor responsive to the flow of blood in the endoluminal passage over the medical device.
The embodiments may be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale. Moreover, in the figures, like-referenced numerals designate corresponding parts throughout the different views.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
In some examples, a medical device may be placed in the vascular passageway and manually inflated and deflated using a pump which coordinates inflation with the heartbeat of the patient. This configuration can be useful to assist the heart when the patient is stationary, such as when they are asleep or interred at a treatment facility. However, such a device cannot be used without the pumping assembly and therefore restricts the movement of the patient.
In treating particularly serious conditions, such as when a medical device is placed in a non-compliant aorta, frequent or constant monitoring of the blood flow within the endovascular passage may be necessary to ensure the health of the patient.
A system for monitoring the flow of blood within an endoluminal passage is provided comprising a medical device and a sensor. The medical device is implantable within the endoluminal passage and includes a shaft and an expandable segment coupled to the shaft. The expandable segment is movable between a first state and a second state. Movement of the expandable segment is responsive to a change in the fluid pressure external to the expandable segment. The sensor is positioned on the medical device and is adapted to collect information associated with the state of the expandable segment.
One interesting feature of the systems and methods described below may be that the expandable segment and a reservoir portion are configured to provide a passive gradient of flow through the medical device, passively working with the heartbeat of the patient to inflate and deflate the expandable segment with the proper timing, thereby reducing stress on the heart muscles. The lack of an active pump may grant increased freedom of movement to a patient utilizing the medical device.
Another interesting feature of the systems and methods described below may be that the sensor on the medical device may be able to detect and transmit information to the patient and/or physician indicating the status of the blood flow within the endoluminal passage. If the blood flow is non-optimal, the patient may be informed as quickly as possible, allowing the operating parameters of the medical device to be quickly adjusted and avoiding harm to the patient. Furthermore, other aspects of the medical care of the patient may be altered in response to information gathered in the operation of the medical device within the endoluminal passage, such as prescription or alteration of drugs to avoid heart failure.
Yet another interesting feature of the systems and method described below may be that the sensor on the medical device may require no power source located outside the body to gather and transmit data. Such a configuration may grant significant mobility to the patient. In some situations, current may be selectively induced through the sensor remotely from outside the body, ensuring that the patient need not be connected to any wires in order to gather and transmit data.
The medical device 10 may include a shaft (46 in
The expandable segment 20 may be any portion of the medical device 10 which inflates and deflates to control blood flow in the endoluminal passage 14 to increase blood pressure within the endoluminal passage 14. Examples of the expandable segment 20 may include a balloon, a bladder, or a sac. The expandable segment 20 may extend longitudinally along the shaft 46 from a first end 22 to a second end 24. As shown in
The reservoir portion 26 may be any component capable of receiving and storing fluid outside of the expandable segment 20. Examples of the reservoir portion 26 may include a tube, a sac, an inflatable balloon, or some other container. The reservoir portion 26 may receive fluid from the expandable segment 20 from a tether 42 extending between the expandable segment 20 and the reservoir portion 26. The tether 42 may be any object which couples together and provides fluid communication between the reservoir portion 26 and the expandable segment 20. Examples of the tether 42 may include a tube, a catheter, or a sheath. The tether 42 may be an extension of the shaft 46.
The reservoir portion 26, expandable segment 20, and tether 42 may form a closed fluid system. All of the reservoir portion 26, expandable segment 20, and tether 42 may be filled with a fluid having a density which is less than the density of blood within the endoluminal passage 14. This closed fluid system provides a pumping mechanism when blood flows through the endoluminal passage 14. While the expandable segment 20 is inflated within the endoluminal passage 14, the cross-sectional area that it takes up within the endoluminal passage 14 simulates the changing size of a healthy, compliant endovascular passage 14 and increases the resting pressure of blood within the endoluminal passage 14. The pumping of blood into the endovascular passage 14 by the left ventricle 16 may create a pressure wave which travels downstream from the left ventricle 16. Within this pressure wave, blood flowing through the endoluminal passage 14 may apply increased pressure sequentially from the first end 22 to the second end 24 of the expandable segment 20. Blood flow over a portion of the expandable segment 20 may deflate a portion of the expandable segment 20, causing fluid within the expandable segment 20 to flow into the reservoir portion 26. As the fluid enters the reservoir portion 26, the pressure within the reservoir portion 26 may increase. The increased pressure within the reservoir portion 26 may provide a passive force on the fluid to flow back into the expandable segment 20 as the pressure wave travels past the expandable segment 20 and the pressure of the blood flow diminishes over the expandable segment 20.
The reservoir portion 26 may include a container 28 which may have a fixed volume or which may be inflatable. The container 28 may be made of any material capable of retaining the fluid delivered from the expandable segment 20, such as rubber or a polymer. The reservoir portion 26 may be located within the endoluminal passage 14, inside the body of the patient 12 but outside the endoluminal passage 14, or outside the body of the patient 12 altogether. In some embodiments, the reservoir portion 26 may be located within or directly alongside the expandable segment 20. In such arrangements, a tether 42 may not be needed. In some embodiments, the reservoir portion 26 may include a port 58 coupled to the container 28. The port 58 may extend through the skin 18 of the patient 12. The port 58 may be used to add fluid to the closed fluid system of the expandable segment 20, the reservoir portion 26, and the tether 42, or may be used to remove fluid from the closed fluid system. Adjusting the amount of fluid within the closed fluid system may control the range pressures within the expandable segment 20 and the range of inflation or deflation that the expandable segment 20 experiences.
The medical device 10 may also include a mounting element 40 which fixes the position of the expandable segment 20 within the endoluminal passage 14. The mounting element 40 may be any object which is expandable to grip the walls of the endoluminal passage 14. Examples of the mounting element 440 may include a self-expanding stent portion or barbs. The mounting element 40 may be arranged anywhere along the length of the shaft 46 or expandable segment 20, such as, for example, at the first end 22 and the second end 24 of the expandable segment 20. In some embodiments, the expandable segment 20 may include a mounting element 40 proximate to the first end 22 of the expandable segment 20 to prevent downstream movement of expandable segment 20 as blood flows through the endoluminal passage 14. In other embodiments, the expandable segment 20 may include an additional mounting element 40 proximate the second end 24 of the expandable segment 20 to better fix the position of the expandable segment 20 within the endoluminal passage 14.
The electrodes 36 may be located anywhere along the medical device 10 within the endoluminal passage 14. For example, the electrodes 36 may be located on the surface (52 in
In order to operate, the electrodes 36 may require an electrical current source. The electrical current source may be any device which is configured to provide a flow of electrons to the electrodes 36. The electrical current source may provide an alternating current or a direct current. In some embodiments, the electric current should not result in heating or stimulation of tissue of the patient 12. For example, an alternating current at a frequency of about 1 kHz may be used to prevent electrical stimulation of tissue. Examples of the electrical current source may be a battery (44 in
The induction coil 30 may be electrically coupled to the electrodes by a pair of wires 32, 34 which form a circuit with the electrodes 36. The first wire 32 may deliver current the induction coil 30 to the first electrode 36 and the second wire 34 may return current from the second electrode 36. The wires 32, 34 may be made of any material suitable to conduct electricity, such as copper or gold. In some embodiments, the induction coil 30 may be coupled to the reservoir portion 26. In such embodiments, the wires 32, 34, may run through or along the reservoir portion 26 and tether 42 to reach the shaft 46. The wires 32, 34 may run along or through the shaft 46 to reach the electrodes 36.
Other sensors may be used instead of or alongside the electrodes 36 to sense the inflated state of the expandable segment 20.
As shown in
In some embodiments, the electrical current source for the electrodes 36 may be the battery 44, as shown in
The medical device 10 may further include one or more piezoelectric sensors 48. The piezoelectric sensor 48 may be any material which may release an electric charge in response to mechanical stress. Examples of the piezoelectric sensor 48 may include a ceramic material, a crystal, or a biological material. The piezoelectric sensor 48 may be positioned on the expandable segment 20 to detect whether the expandable segment 20 is inflating or deflating. For example, the piezoelectric sensor 48 may be bonded to the surface 52 of the expandable segment 20 exposed to the endoluminal passage 14 or within the interior 38 of the expandable segment 20. Alternatively, the piezoelectric sensor 48 may be embedded within the surface 52 of the expandable segment 20. When the expandable segment 20 inflates or deflates, the surface 52 of the expandable segment 20 may expand or contract, causing the piezoelectric sensor 48 to also expand or contract. Compression or expansion of the piezoelectric sensor 48 may release a charge which can be used to power a transmitter 50 electrically coupled to the piezoelectric sensor 48 to transmit a signal. The signal generated by the piezoelectric sensor 48 may be received by a receiver (not shown) to indicate to the operator the status of the expandable segment 20. The transmitter 50 may be physically coupled to the piezoelectric sensor 48 or may be positioned elsewhere in the medical device, such as the shaft 46, and only electrically coupled the piezoelectric sensor 48. The transmitter 50 may be electrically powered only by the piezoelectric sensor 48 or may be powered by a different electrical current source, such as the battery 44.
As shown in
Alternatively, in some embodiments, the inductor capacitor sensor 54 may be electrically coupled to a transmitter 50 to transmit a signal indicating the capacitance of the inductor capacitor sensor 54. The signal generated by the inductor capacitor sensor 54 may be received by the receiver to indicate to the operator the status of the expandable segment 20. The transmitter 50 may be physically coupled to the inductor capacitor sensor 54 or may be positioned elsewhere in the medical device, such as the shaft 46, and only electrically coupled to the inductor capacitor sensor 54. The transmitter 50 may be electrically powered by a different electrical current source, such as the battery 44.
As shown in
The electrical current generated within the inductor capacitor sensor 54 may be generated from a variety of sources. For example, a stationary magnet may be arranged within the medical device 10 near the coils of the inductor capacitor sensor 54 to allow expansion or compression of the coils within the magnetic field of the magnet to generate the electrical current. Alternatively, a rotating or otherwise moving magnet could generate a magnetic field which could induce the electrical current within the inductor capacitor sensor 54. The electrical current could also be provided to the inductor capacitor sensor 54 directly through a power source such as the battery 44.
Another possible embodiment may include metallic markings 66 coupled to the surface 52 of the expandable segment 20. The metallic markings 66 may be located on the outside of the surface 52, within the interior 38 of the expandable segment 20, or embedded within the surface 52 of the expandable segment. The metallic markings 66 may be any metal having a density higher than the other materials of the expandable segment 20. Metallic markings 66 may be used to determine the state of the expandable segment 20 under a variety of visualization techniques including ultrasound and x-ray. Non-ferrous metals may be used in the metal markings 66 to allow visualization under magnetic resonance imaging.
The medical device may also include shaft markings 64 on the surface of or imbedded within the shaft 46 of the medical device 10. The shaft markings 64 may be of the same type as the markings 66 on the expandable segment 20. When visualized, a distance 68 between the shaft markings 64 and the markings 66 on the expandable segment 20 may be used to measure the inflated or deflated state of the expandable segment 20.
The medical device 10 may include a second accelerometer 80 on the shaft 46 of the medical device 10. The second accelerometer 80 may be in the interior 38 of the expandable segment 20 on the outer surface of the shaft 46, or may be embedded within the shaft 46. The second accelerometer 80 may be arranged to measure acceleration of the shaft 46 which is transverse to the axis 82 defined by the shaft 46. The second accelerometer 80 may be used in conjunction with the first accelerometer 70 to provide a shaft-stabilized indication of the inflation or deflation of the expandable segment 20. For example, the medical device 10 as a whole, and the shaft 46 in particular, may move transversely within the endoluminal passage 14 due to blood flowing over the medical device 10 or movement of the patient. The acceleration information provided by the second accelerometer 80 coupled to the shaft 46 may be used as a control in determining the inflation or deflation of the expandable segment 20. For example, the transverse acceleration information provided by the second accelerometer 80 may be subtracted from the acceleration information provided by the first accelerometer 70. For improved accuracy, the first accelerometer 70 and the second accelerometer 80 may be transversely aligned with respect to each other.
In some embodiments, the light emitting source 74 may periodically or continuously emit light 78. The light 78 travels from the light emitting source 74 to the light sensor 76. A circuit containing the light emitting source 74 and the light sensor 76 may be used to measure the time elapsed between when the light 78 was emitted from the light emitting source 74 and when the light 78 was received by the light sensor 76. When the expandable segment 20 is fully inflated, the time necessary for the light 78 to travel from the light emitting source 74 to the light sensor 76 may be greater than the time necessary for the light 78 to travel from the light emitting source 74 to the light sensor 76 when the expandable segment 20 is deflated.
In another embodiment, the light sensor 76 may be a reflective material such as a mirror. In such a configuration, the light sensor 76 may not be connected to an electrical circuit. The light emitting source 74 may also have a sensor to detect when light is received. The light emitting source 74 may periodically or continuously emit light 78. The light 78 may travel through the interior 38 of the expandable segment 20 to reach the reflective light sensor 76. Upon reaching the reflective light sensor 76, the light 78 may reflect against the light sensor 76 and travel back to the light emitting source 74. The light emitting source 74 may receive the light 78 and calculated the travel time between the light emitting source 74 emitting the light 78 and the light emitting source 74 receiving the light 78. This information may be used to determine the degree of inflation of the expandable segment 20 and transmit this information outside the body 12.
Initially, the method of operations (100) may include implanting the medical device 10 within the endovascular passageway 14 (102). The medical device 10 may include the shaft 46, the expandable segment 20 coupled to the shaft 46, and the sensor 36, 48, 54 coupled to the medical device 10. The expandable segment 20 may be movable between an expanded state and a compressed state, responsive to a change in the blood flow within the endoluminal passage 14 over the expandable segment 20. The method of operations (100) also may include transmitting a signal generated by the sensor 36, 48, 54 (104).
The method (100) may also include electrically charging a circuit including the sensor 36, 48, 54, where the sensor 36, 48, 54 are the electrodes 36 positioned on the surface 52 of the expandable segment 20. The electrodes 36 may longitudinally or radially spaced apart on the surface of the expandable segment 20. The inflated or deflated state of the expandable segment 20 may be determined by measuring the impedance between the electrodes 36.
In some embodiments, the method (100) may also include imaging the endoluminal passage 14 before implanting the medical device 10 to determine a responsiveness of the endoluminal passage 14 to blood flow created by the left ventricle 16. By determining the responsiveness of the endoluminal passage 14, the sensor 36, 48, 54 may be calibrated to the specific endoluminal passage 14 such that when the medical device is implanted, the medical device 10 accurately measures the blood flow within the endoluminal passage and the state of the expandable segment 20.
In some embodiments, the method (100) may also include adjusting the fluid pressure of the medical device 10 based on the signal generated by the sensor 36, 48, 54. If the measurement indicates that the expandable segment 20 is not sufficiently deflating, fluid may be released from the medical device 10 through the port 58 to allow for adequate deflation. Alternatively, where the measurement indicates that the expandable segment 20 is not fully inflating at the resting pressure of the endoluminal passage 14, fluid may be added to the medical device 10 through the port 58 to allow for adequate inflation.
Additionally, the method (100) may also include adjusting a medication dose of a patient based upon information received by the sensor 36, 48, 54. For example, impending heart failure of a patient may be detected by changes in the fluid flowing over the medical device 10 positioned in the endoluminal passage 14.
In addition to the advantages that have been described, it is also possible that there are still other advantages that are not currently recognized but which may become apparent at a later time. While various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible. Accordingly, the embodiments described herein are examples, not the only possible embodiments and implementations.
