Patent Application
20200315653
The present disclosure pertains to medical devices, and methods for manufacturing and using medical devices. More particularly, the disclosure is directed to devices and methods for removing occlusive material from a body lumen. Further, the disclosure is directed to an atherectomy device for forming a passageway through an occlusion of a body lumen, such as a blood vessel.
Many patients suffer from occluded arteries and other blood vessels which restrict blood flow. Occlusions can be partial occlusions that reduce blood flow through the occluded portion of a blood vessel or total occlusions (e.g., chronic total occlusions) that substantially block blood flow through the occluded blood vessel. In some cases a stent may be placed in the area of a treated occlusion. However, restenosis may occur in the stent, further occluding the vessel and restricting blood flow. Revascularization techniques include using a variety of devices to pass through the occlusion to create or enlarge an opening through the occlusion. Atherectomy is one technique in which a catheter having a cutting element thereon is advanced through the occlusion to form or enlarge a pathway through the occlusion. A need remains for alternative atherectomy devices to facilitate crossing an occlusion.
This disclosure provides design, material, manufacturing method, and use alternatives for medical devices. For example, an atherectomy system includes an atherectomy burr and a drive mechanism that is adapted to rotatably actuate the atherectomy burr. A controller is adapted to regulate operation of the drive mechanism and to calculate an estimated load torque at the atherectomy burr based upon at least one of an angular velocity of the atherectomy system and an angular acceleration of the atherectomy system. The controller is further adapted to stop or reverse the drive mechanism when the estimated load torque at the atherectomy burr exceeds a torque threshold.
Alternatively or additionally, the controller may be adapted to determine an angular position of the atherectomy system.
Alternatively or additionally, the controller may be adapted to determine an angular velocity of the atherectomy system by determining a first derivative with respect to time of the angular position.
Alternatively or additionally, the controller may be adapted to determine an angular acceleration of the atherectomy system by determining a second derivative with respect to time of the angular position.
Alternatively or additionally, the controller may be adapted to calculate the estimated load torque Tload at the atherectomy burr in accordance with equation (1):
T
load
=K
T
*i−C
D
*{dot over (θ)}−I*{umlaut over (θ)} (1),
where
Alternatively or additionally, i may be a measured or calculated value.
Alternatively or additionally, CD may be a constant.
Alternatively or additionally, CD may be a calculated value.
Alternatively or additionally, the drive mechanism may include a drive cable that is coupled with the atherectomy burr and a drive motor that is adapted to rotate the drive cable.
As another example, an atherectomy system includes a drive mechanism that is adapted to rotatably actuate an atherectomy burr and a controller that is adapted to regulate operation of the drive mechanism. The controller is adapted to calculate an estimated load torque at the atherectomy burr Tload in accordance with equation (2):
T
load
=T
motor
−T
drag
−I*{umlaut over (θ)} (2),
where
Alternatively or additionally, Tmotor may be calculated by the controller in accordance with equation (3):
T
motor
=K
T
*i (3),
where
Alternatively or additionally, i may be a measured or calculated value.
Alternatively or additionally, Tdrag may be calculated by the controller in accordance with equation (4):
T
drag
=C
D*{dot over (θ)} (4),
where
Alternatively or additionally, CD may be a constant.
Alternatively or additionally, CD may be a time varying value.
Alternatively or additionally, when running at steady state, Tmotor is substantially equal to Tdrag, and thus at steady state Tload may be calculated by the controller in accordance with equation (5):
T
load
=−I*{umlaut over (θ)} (5).
Alternatively or additionally, the drive mechanism may include a drive cable that is coupled with the atherectomy burr and a drive motor that is adapted to rotate the drive cable.
As another example, an atherectomy system includes a drive mechanism that is adapted to rotatably actuate an atherectomy burr and a controller that is adapted to regulate operation of the drive mechanism. The controller is adapted to stop or reverse the drive mechanism when an estimated torque value Tload exceeds a torque threshold. When the atherectomy system is at steady state, the controller is adapted to calculate Tload in accordance with equation (5):
T
load
=−I*{umlaut over (θ)} (5),
where
T
load
=K
T
*i−C
D
*{dot over (θ)}−I*{umlaut over (θ)} (1),
where
Alternatively or additionally, the drive mechanism may be adapted to accelerate the atherectomy burr to full speed in less than 2 seconds.
Alternatively or additionally, the drive mechanism may include a drive motor having a power rating of at least about 60 watts.
The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures, and Detailed Description, which follow, more particularly exemplify these embodiments.
The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:
While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.
For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.
All numeric values are herein assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.
The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).
As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.
Many patients suffer from occluded arteries, other blood vessels, and/or occluded ducts or other body lumens which may restrict bodily fluid (e.g. blood, bile, etc.) flow. Occlusions can be partial occlusions that reduce blood flow through the occluded portion of a blood vessel or total occlusions (e.g., chronic total occlusions) that substantially block blood flow through the occluded blood vessel. Revascularization techniques include using a variety of devices to pass through the occlusion to create or enlarge an opening through the occlusion. Atherectomy is one technique in which a catheter having a cutting element thereon is advanced through the occlusion to form or enlarge a pathway through the occlusion. Ideally, the cutting element excises the occlusion without damaging the surrounding vessel wall and/or a previously implanted stent where restenosis has occurred. However, in some instances the cutting element may be manipulated and/or advanced such that it contacts the vessel wall and/or the stent. Therefore, it may be desirable to utilize materials and/or design an atherectomy device that can excise an occlusion without damaging the surrounding vessel and/or a previously implanted stent where restenosis has occurred. Additionally, it may be desirable that a cutting element be useful in removing hard occlusive material, such as calcified material, as well as softer occlusive material. The methods and systems disclosed herein may be designed to overcome at least some of the limitations of previous atherectomy devices while effectively excising occlusive material. For example, some of the devices and methods disclosed herein may include cutting elements with unique cutting surface geometries and/or designs.
In some cases, the feedback loop 54 may include a reference block for determining a speed reference and a Proportional Integral Derivative (PID) controller that is operably coupled to the reference block for receiving the speed reference, the PID controller adapted to utilize the speed reference, a Proportional (P) gain value, an Integral (I) gain value and a Derivative (D) gain value in determining the control effort signal. In some cases, the feedback loop 54 may be adapted to add an offset value to a reference signal provided to the reference loop 54 in order to accurately hold speed of the drive motor 22 during a no-load situation. In some instances, for example if the atherectomy burr 14 becomes stuck, the control system 52 may be further adapted to increase the torque provided by the drive motor 22 until a torque threshold is reached for a brief period of time, and to subsequently direct the drive motor 22 to reverse at a slow speed in order to unwind energy in the drive mechanism.
The drive circuitry 308 receives an input from a feedback portion 310. In some cases, the feedback portion 310 begins with a reference input 312 from a reference schedule block 314, which provides the reference input 312 to a PID controller 316. In some cases, the reference schedule block 314 may be configured to accept additional inputs, such as from a user and/or from additional sensors not illustrated. As an example, if the device has been running for too long of a period of time, the reference schedule block 314 may reduce the speed reference in order to prevent overheating. A PID controller is a controller that includes a (P) proportional portion, an (I) integral portion and a (D) derivative portion. The PID controller 316 outputs a control effort value or reference current 318 to the drive circuitry 308. A motor state estimation block 320 receives a current/voltage signal 322 and a motor position signal 323 from the drive circuitry 308 and receives state feedback 324 from the PID controller 316. The motor state estimation block 320 provides a state feedback signal 325 back to the PID controller 316.
The motor state estimation block 320 outputs a speed value 326 back to the reference schedule block 314. While the feedback from the motor state estimation block 320 to the reference schedule block 314 is shown as being a speed value, in some cases the feedback may additionally or alternatively include one or more of position, torque, voltage or current, and in some cases may include the derivative or integral of any of these values. In some cases, the motor state estimation block 320 may instead receive a signal 323 that represents speed, instead of position (as illustrated). The motor position signal 323 may be an indication of relative rotational position of an output shaft of the motor 302, and thus an indication of relative rotational position of the load 306, which if tracked over time may provide an indication of speed.
In some cases, the drive circuitry 308 and the feedback loop 310 may in combination be considered as forming a controller 350 that is adapted to determine an estimated torque at the atherectomy burr (the load 306 as shown in
If the estimated torque at the load 306 becomes too high, this may be an indication that the burr is getting stuck. In order to protect against possible damage to the drive cable 304, and to protect against possible injury to the patient, the atherectomy system 300 may be adapted to stop or even reverse operation of the atherectomy system 300 if the estimated torque meets or exceeds a predetermined torque threshold. It will be appreciated that the actual value of the predetermined torque threshold may vary, depending on the mechanics of the atherectomy system 300, but may be set at a level low enough to prevent damage and injury, but not set so low as to engender too many false alarms caused by minor and/or temporary torque increases that are not caused by the load 306 becoming stuck. For example, the instantaneous torque may vary by small amounts as the atherectomy system 300 progresses through the patient's vasculature.
Accordingly, the controller 350 may be adapted to calculate an estimated torque at the load 306 and to compare the estimated torque at the load 306 to the torque threshold. If the estimated torque meets or exceeds the torque threshold, the atherectomy system 300 may stop or even reverse the drive mechanism (the drive motor 302 and the drive cable 304, for example). In some instances, the atherectomy system 300 may be adapted to calculate an estimated torque at the load 306 based upon at least one of an angular velocity of the atherectomy system 300 and an angular acceleration of the atherectomy system 300.
In some instances, the controller 350 may be adapted to determine an angular position of the atherectomy system 300. This may mean determining an angular position of the motor 302, or that of the cable 304. It will be appreciated that the controller 350 may be adapted to determine an angular velocity of the atherectomy system 300 by determining a first derivative with respect to time of the angular position. The controller 350 may be adapted to determine an angular acceleration of the atherectomy system 300 by determining a second derivative with respect to time of the angular position. In some instances, for example, the controller 350 may be adapted to calculate an estimated torque at the load 306, indicated by Tload, in accordance with equation (1):
T
load
=K
T
*i−C
D
*{dot over (θ)}−I*{umlaut over (θ)} (1),
where
In some cases, the drive motor current i may be a measured or calculated value. In some cases, the drive motor current i may be estimated within the motor state estimation block 320. For example, the reference current 318 may be fed into the motor state estimation block 320 via a path 319, and the motor state estimation block 320 may predict the drive motor current i more rapidly than the drive motor current i could be measured. In some instances, the coefficient of friction CD may be a constant. In some cases, CD may be a calculated value or even a time-varying value. In some cases, CD may be a factor of one or more of an amount of current being commanded, system speed, and the age (total run time of the system). The controller 350 may calculate CD based on one or more of these factors, for example. In some cases, the controller 350 may include a lookup table, for example, that provides particular values for CD for each of a number of rotational speed ranges. This is just an example. {dot over (θ)} represents the angular velocity of the atherectomy system 300, and as indicated may be determined by taking a first derivative, with respect to time, of the angular position of the atherectomy system 300. {umlaut over (θ)} represents the angular acceleration of the atherectomy system 300, and as indicated may be determined by taking a second derivative, with respect to time, of the angular position of the atherectomy system 300. The inertia of the system 1 may be easily calculated based on the mass and geometry of the system.
In some cases, the controller 350 may be adapted to calculate an estimated torque at the load 306 in accordance with equation (2):
T
load
=T
motor
−T
drag
−I*{umlaut over (θ)} (2),
where
In some cases, the controller 350 may be adapted to calculate the estimated motor torque Tmotor in accordance with equation (3) and may calculate the estimated drag torque Tdrag is calculated by the controller in accordance with equation (4):
T
motor
=K
T
*i (3).
T
drag
=C
D*{dot over (θ)} (4).
It will be appreciated that in some cases, that when the atherectomy system 300 is running at steady state, and thus is not accelerating, that Tmotor may be considered as being substantially equal to Tdrag, and thus at steady state Tload may be calculated by the controller 350 in accordance with equation (5):
T
load
=I*{umlaut over (θ)} (5).
Accordingly, and in some cases when the atherectomy system 300 is at steady state, the controller 350 may be adapted to calculate Tload in accordance with equation (5):
T
load
=−I*{umlaut over (θ)} (5)
and when the atherectomy system 300 is accelerating, the controller 350 may be adapted to calculate Tload in accordance with equation (1):
T
load
=K
T
*i−C
D
*{dot over (θ)}−I*{umlaut over (θ)} (1).
It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the disclosure. This may include, to the extent that it is appropriate, the use of any of the features of one example embodiment being used in other embodiments. The invention's scope is, of course, defined in the language in which the appended claims are expressed.
This application claims the benefit of priority under 35 U.S.C. § 119 to U.S. Provisional Application Ser. No. 62/830,990 filed Apr. 8, 2019, the entirety of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62830990 | Apr 2019 | US |
