Patent Application
20080051671
The present invention relates generally to the field of intravascular filter monitoring. More specifically, the present invention pertains to devices and methods for monitoring the flow of blood through an embolic protection filter.
Intravascular devices such as embolic protection filters are generally placed with the lumen of a blood vessel or artery to filter embolic debris dislodged during a therapeutic procedure such as percutaneous transluminal coronary angioplasty (PTCA), percutaneous extraction atherectomy, or stent delivery. To filter the dislodged embolic debris, an embolic protection filter can be placed distally of the therapeutic device (e.g. an angioplasty or atherectomy catheter) and deployed within the patient's vessel or artery. Over time, the embolic protection filter may become occluded with the embolic debris, necessitating the removal and/or replacement of the filter from the vessel.
Although many techniques have been developed to monitor the flow of blood through a patient's body, real-time monitoring of blood flow through an embolic protection filter can often prove difficult. For example, in a fluoroscopic monitoring technique, a contrast material is periodically injected into a vein or artery at pre-determined intervals throughout the course of a therapeutic procedure. The contrast media, which is visible under a fluoroscopic monitor, can be utilized to monitor the flow of blood through the vasculature, to determine the patency of a specific artery or vessel, and to assess the severity of the lesion or stenosis.
One particular issue associated with fluoroscopic monitoring, however, is the ability to readily monitor the flow of blood through an embolic protection filter. Since fluoroscopic monitoring may require as much as several minutes to perform, such techniques are not well suited for real-time monitoring of blood flow through an embolic protection filter.
The present invention relates generally to the field of intravascular filter monitoring. In an exemplary embodiment, an apparatus for monitoring blood flow across an intravascular device comprises an elongated member having a proximal end and a distal end, an intravascular device disposed about the elongated member proximal the distal end thereof, a first sensor adapted to measure blood flow or pressure proximal the intravascular device, and a second sensor adapted to measure blood flow or pressure distal the intravascular device. A control unit located outside of the patient's body may be used to determine the pressure drop across the intravascular device.
The following description should be read with reference to the drawings, in which like elements in different drawings are numbered in like fashion. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. Although examples of construction, dimensions, materials and manufacturing processes are illustrated for the various elements, those skilled in the art will recognize that many of the examples provided have suitable alternatives that may be utilized.
In certain embodiments of the present invention, elongated member 10 may comprise a guidewire or filterwire adapted to permit an intravascular device such as an angioplasty catheter or embolic protection filter to slide thereon. In other implementations, elongated member 10 may form part of a catheter that can be advanced along a separate wire disposed within the patient's vasculature. For example, elongated member 10 may form part of an angioplasty catheter having an angioplasty balloon adapted to perform a therapeutic procedure such as percutaneous transluminal coronary angioplasty (PTCA).
In the exemplary embodiment shown in
Elongated member 10 may also include a polymeric coating to facilitate advancement through the tortuous vasculature, and to reduce tissue damage in the patient. Examples of suitable polymeric coatings include polyacrylic acid, polycaprolactone, polycarboxylic acid, polyamide, polyvinyl ether, polyurethane, polytetrafluoroethylene, and polyorthoesters. Polyacrylic acid is commercially available from Boston Scientific Corporation of Natick, Mass. under the trade name HYDROPASS.
Attached to a distal portion of elongated member 10 is an embolic protection filter 18. One type of embolic protection filter 18 includes a support hoop 20 forming a mouth or opening 22 for collecting embolie debris. As shown in
A filter membrane 24 attached to the support hoop 20 is adapted to filter embolic debris contained within vessel V. Filter membrane 24 may comprise a braided wire mesh formed of a metallic material such as stainless steel, platinum, or nickel-titanium alloy (Nitinol). Alternatively, filter membrane 24 may comprise a microporous membrane made from a polymeric material such as polypropylene (PP), polyurethane, polyethylene terapthlalate, polyether-ether ketone (PEEK), polyether block amide (PEBA), polyamide (nylon), polyvinylchloride (PVC), polytetrafluoroethylene (PTFE) or any mixture, blend or combination thereof.
Elongated member 10 further includes a first sensor 26 coupled to the elongated member 10 proximal the embolic protection filter 18, and a second sensor 28 coupled to the elongated member 10 distal the embolic protection filter 18. The first and second sensors 26, 28 are configured to respond to changes in blood flow or pressure at locations 30 and 32 within vessel V, and output a corresponding electrical signal to a control unit 42 located outside the patient's body.
The first and second sensors 26, 28 each include a transducer capable of producing an electrical signal in response to fluidic pressure within vessel V. As shown in greater detail in
A metallic bonding pad 36 may be used to connect each transducer element 34 to a set of leads 38, 40 disposed in part within the inner lumen 16 of elongated member 10.
Connection of the leads 38, 40 to the bonding pads 36 may be accomplished by any suitable attachment mechanism, including soldering, welding or crimping. As shown in
In another exemplary embodiment in accordance with the present invention, the first and second sensors 26, 28 may comprise ultrasonic transducers adapted to measure the flow of blood using ultrasonic waves or pulses. A first ultrasonic transceiver is operatively coupled to the outside of elongated member 10 proximal the embolic protection filter 18. A second ultrasonic transceiver is operatively coupled to the elongated member 10 distal the embolic protection filter 18. As with the previous embodiment, several leads 38, 40 may be used to connect the first and second ultrasonic sensors to the control unit 42 located outside the patient's body.
In use, the first and second ultrasonic transceivers transmit an ultrasonic wave or pulse that can be subsequently received. As the wave travels from the source to the receiver, the velocity of the wave will either increase or decrease due to the Doppler effect resulting from the flow of blood through the vessel V. The velocity of the blood can then be determined by measuring the difference in travel time or the relative phase shift between the source (i.e. upstream) wave and the received (i.e. downstream) wave. As with any of the other techniques described herein, the pressure drop through the embolic protection filter can then be determined by comparing (i.e. subtracting) the respective values obtained from both the first and second transceivers to obtain a differential value representing the pressure drop through the embolic protection filter 18.
In yet another exemplary embodiment in accordance with the present invention, the first and second sensors 26, 28 may comprise microelectrical mechanical system (MEMS) sensors. Each MEMS sensor 26, 28 may be embedded at least in part within a grove 35 formed on the outer surface of the elongated member 10. An optional primer coating may be applied to the groove 35 to facilitate attachment of the MEMS sensor therein. If desired, a second coating (e.g. polyimide or silicon rubber) may also be applied to each sensor to insulate the sensor once placed within the groove.
In certain embodiments, the electrical signal outputted from each MEMS sensor may be transmitted through several leads operatively connected to a control unit located outside the patient's body. In other embodiments, the electrical signal outputted from each MEMS sensor may be wirelessly transmitted to an antennae located outside of the patient's body. In either embodiment, the control unit 42 is configured to receive the electrical signals from each MEMS sensor, and determine the pressure drop through the embolic protection filter 18.
While the exemplary embodiment of
To determine the pressure drop through the embolic protection filter 18, a control unit 42 may be used with any of the embodiments discussed herein. Control unit 42 includes a comparator circuit configured to take an electrical signal received from the first sensor 26, and compare that signal to an electrical signal received from the second sensor 28 to determine a differential value. From this differential value, a measure of the pressure drop through the embolic protection filter 18 can be obtained and outputted to a screen 48 located on the control unit 42.
Control unit 42 may further include a calibration device to calibrate the first and second sensors 26, 28, and reset the calibration device to zero-out the control unit 42 prior to the collection of embolic debris within the embolic protection filter 18. The calibration device can be utilized to selectively change the sensitivity of the first and/or second sensors 26, 28, and to compensate for environmental variables such as the size of the vessel, the location or position of the device within the vasculature, and the type of intravascular device employed. For example, if a resistive-type strain gauge is used, the calibration device can include a Wheatstone bridge circuit to balance the resistance of the gauge.
Control unit 42 may further optionally include a signaling device to notify the physician when the pressure drop within the embolic protection filter 18 has reached a pre-determined value. For example, control unit 42 may include an audible signal configured to sound when the pressure drop through the filter reaches a certain threshold value pre-determined by the operator. Control unit 42 may also include an LED or other visual indicator that can be actuated when the pressure drop through the embolic protection filter reaches a certain level.
A method in accordance with the present invention includes the steps of transluminally inserting the elongated member 10 into a vessel V and advancing the device to a desired location distal a lesion L. Once the elongated member 10 is in place, the embolic protection filter 18 can then be deployed within the vessel, as shown in
To monitor the flow of blood through the embolic protection filter 18, control unit 42 continuously and repeatedly receives and compares the signals received from the first and second sensors 26, 28 to obtain a differential value. This differential value is outputted to a screen 48 located on the control unit 42. As the embolic protection filter 18 becomes occluded with embolic debris dislodged during the therapeutic procedure, the flow of blood at second location 32 decreases in comparison to the flow of blood at first location 30. When the differential value measured by the control unit 42 reaches a certain threshold level, the signaling device can be actuated to notify the physician that the embolic protection filter l 8 may need to be removed and/or replaced.
Although the exemplary embodiment described with respect to
In use, the elongated member 110 can be inserted transluminally into a vessel and advanced to the site of the lesion L to perform an angioplasty procedure such as percutaneous transluminal coronary angioplasty (PTCA). Once positioned, the operator next calibrates the device while the balloon 52 is in the collapsed (i.e. unexpanded) position to obtain an initial reading from each of the sensors 126, 128. A control unit 142 similar to that described with respect to
Once the operator has positioned the apparatus adjacent the lesion L, and has obtained an initial (i.e. calibration) reading from each of the sensors 126, 128, the balloon 152 is then inflated within vessel V, forcing the lesion L to become dislodged from the vessel wall. As the balloon 152 is inflated, the pressure differential measured by the first and second sensors 126, 128 increases as a result of the occlusion within vessel V created by the balloon 152. This increase in pressure differential can be outputted to the screen 148 on the control unit 142 to provide the operator with feedback that the balloon 152 has been engaged within the vessel V. An alarm can be activated when the pressure differential has reached a certain pre-determined level, or when the second pressure sensor 128 measures a no-flow condition, indicating total occlusion within the vessel V.
Having thus described the several embodiments of the present invention, those of skill in the art will readily appreciate that other embodiments may be made and used which fall within the scope of the claims attached hereto. Numerous advantages of the invention covered by this document have been set forth in the foregoing description. It will 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 parts without exceeding the scope of the invention.
This application is a continuation application of U.S. application Ser. No. 10/306,288 filed Nov. 27, 2002.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10306288 | Nov 2002 | US |
| Child | 11929007 | Oct 2007 | US |
