The drawings illustrate the design and utility of preferred embodiments of the present invention, in which similar elements are referred to by common reference numerals. In order to better appreciate how the above-recited and other advantages of the present inventions are obtained, a more particular description of the present inventions briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
Referring to
In the illustrated embodiment, the external device 14 is a handheld battery operated unit. Because the sensing device 12 is intended to be implanted deep within the tissue of the patient, the external device 14 and sensing device 12 are designed to communicate with each other using acoustic energy (e.g., at a relatively low frequency of 40 KHz), and in particular, by transmitting and receiving acoustic energy through the tissue. Thus, the external device 14 may be placed in direct contact with the patient's skin to communicate with the implanted sensing device 12.
The external device 14 may transmit acoustic energy to control or operate the sensing device 12, and receive acoustic energy to acquire the sensed physiological information from the sensing device 12. For example, the external device 14 may activate and deactivate the sensing device 12 (i.e., alternately placing it in an “active mode” and “dormant mode”). The external device may also transmit acoustic energy to charge the sensing device 12.
Thus, the implanted sensing device 12 may be activated on demand by the external device 14, sample the intended physiological parameter, and wirelessly transmit the physiological information to the external device 14. The external device 14 may then process the physiological information. For example, if the measured physiological parameter is absolute pressure, the external device 14 may calculate a gauge blood pressure value by subtracting the barometric pressure (measured by a barometric pressure sensor on the external device 14 or received from a remote site) from the measured absolute pressure.
The external device 14 may include a memory (not shown) for storing the recorded and processed physiological information readings and a display (not shown) for conveying the readings to a healthcare worker. The external device 14 may be optionally configured such that it can be connected to a personal computer (PC)-based clinic to enable downloading of the sensed physiological information.
Further details describing means for acoustically communicating between implanted devices and external devices are set forth in U.S. Patent No. 7,024,248, which is expressly incorporated herein by reference. Alternatively, other forms of wireless communications, e.g., electromagnetic or magnetic, can be used to communicate between the sensing device 12 and the external device 14. Notably, because the sensing device 12 is designed to be implanted during a surgical procedure, its size can be larger, thereby enabling wireless communication through the deep tissue using these alternative communications means. In alternative embodiments, the sensing device 12 may wirelessly communicate with other implantable devices, as described in U.S. patent application Ser. No. 10/413,428, entitled “Apparatus and Methods Using Telemetry for Intrabody Communications,” which is expressly incorporated herein by reference.
It should be appreciated that the implantation of the sensing device 12 into a patient will obviate the need to post-operatively monitor critical parameters using a catheter or tube. For example, the sensing device 12 can be implanted within the pulmonary artery or the left or right branch thereof to measure the full pulmonary artery pressure waveform of the patient after being transferred from the ICU to a regular hospital ward and to monitor such patient for the recovery period (typically 4 weeks) after being discharged from the hospital. The pulmonary pressure waveform can then be used to estimate stroke volume and cardiac output. Thus, it can be appreciated that the need for a right heart catheter (RHC) to perform the same function may be obviated by the use of the sensing device 12. Since many patients undergoing cardiac surgery continue to suffer from chronic heart disease, such as congestive heart failure (CHF), the chronically implanted sensing device 12 may also aid in optimizing the treatment for CHF in years to come. In optional embodiments, the physiological information measured by the sensing device 12 can be used to optimize the performance of one or more implanted therapeutic devices, as described in U.S. patent application Ser. No. 11/373,005, entitled “A Body Attachable Unit in Wireless Communication with Implantable Devices,” which is expressly incorporated herein by reference.
The sensing device 12 may also be configured, such that it measures other physiological parameters. For example, the sensing device 12 may measure blood flow, temperature, oxygen level, glucose level, electrical impedance, pH, and the like. More than one sensing device 12 may be implanted within a blood vessel to monitor at least one physiological parameter. For example, simultaneous pressure measurement using diagnostic devices 12 that measure pressure may be spaced along the longitudinal axis within the lumen of the blood vessel, thereby allowing calculation of blood flow (cardiac output) and blood flow velocity.
The sensing device 12 may alternatively include a microphone for recording breathing sounds, which may be useful for diagnosis of diseases (e.g., detecting edema of congestive heart failure (CHF) patients, as described in U.S. Pat. No. 7,035,684, which is expressly incorporated herein by reference. The microphone may also be used to analyze the performance of mechanical and bio-prosthetic heart valves, including failure detection, hemodynamic analysis, and thrombus formation over the heart valve, as described in Lanning & Shandas, “Medical & Biological Engineering & Computing,” July 2003, Volume 41, issue 4, pp. 416-424. The microphone is preferably operated in the frequency range of 100 Hz-10 KHz, and more preferably in the frequency range of less than 1 KHz. In this case, the sensing device 12 may be implanted in any of the blood vessels close to the valve.
The sensing device 12 may also be implanted in the chambers of the heart. For example, in the case where the sensing device 12 measures pressure, it may be implanted within the left ventricle or the left atrium of the patient to monitor the left ventricle end diastolic pressure or its surrogates (e.g., pulmonary artery diastolic pressure or right atrium pressure). Monitoring this parameter for the long term can be extremely important for the optimal treatment of heart diseases. In the case where the sensing device 12 records sound, it may be secured close to the valve within the heart chambers, or be secured to the valve itself, so that the functioning of the valve can be analyzed. The sensing device 12 may be implanted proximally or distally to the valve, or two of the diagnostic devices 12 may be respectively implanted proximally and distally to the valve.
Having generally described the sensing device 12, its specific structure will now be described with reference to
The sensing device 12 comprises a plurality of components, including a sensor 16, acoustic transducer 18, energy storage device 20, acoustic switch 22, and control/processing unit 24, all housed within a casing 26. The casing 26 is composed of a suitable biocompatible material, such as titanium, and is hermetically sealed to isolate the components from the environment outside of the sensing device 12. Further details regarding the construction of casings for implantable devices are described in U.S. Pat. No. 6,764,446, which is expressly incorporated herein by reference. As shown in
The sensor 16 may be any desired biosensor that generates a signal proportional to a measured physiological parameter that may be processed and wirelessly transmitted from the control/processing unit 24 to the external device via the acoustic transducer 18. In the illustrated embodiment, the sensor 16 is preferably a pressure sensor, but may be any other suitable sensor capable of measuring physiological parameters, such as those previously set forth.
The acoustic transducer 18 includes one or more piezoelectric elements configured for transmitting and receiving acoustic signals. In particular, the acoustic transducer 18 generates an electrical signal proportional to the magnitude of acoustic energy received by the acoustic transducer 18, which electrical signal is conveyed to the control/processing unit 24. Similarly, the acoustic transducer 18 generates an acoustic signal proportional to the magnitude of the electrical energy conveyed from the control/processing unit 24 to the acoustic transducer 18. Further details regarding the construction of acoustic transducers for implantable devices are described in U.S. Pat. No. 6,140,740, which is expressly incorporated herein by reference.
The energy storage device 20 may be any of a variety of known devices, such as an energy exchanger, a battery and/or a capacitor. Preferably, the energy storage device 20 is capable of storing electrical energy substantially indefinitely unless actively discharged. In the illustrated embodiment, the energy storage device 20 is located adjacent the rear side of the printed circuit board 28. The energy storage device 20 includes a terminal 30 that contacts a corresponding terminal 32 on the printed circuit board 28, so that the energy storage device 20 can supply the remaining components with power.
The acoustic switch 22 is coupled between the energy storage device 20 and the control/processing unit 24 to minimize the standby current from the energy storage device 20, thereby significantly extending the operable life span of the sensing device 12. In particular, the acoustic switch 22 is activated upon acoustic excitation of the acoustic transducer 18 by an acoustic activation signal transmitted by the external device 14 to allow current flow from the energy storage device 20 to the control/processing unit 24. Thus, the acoustic switch 22 allows the sensing device 12 to operate in two modes, a “sleep” or “dormant” mode when the sensing device 12 is not in use, i.e., when the acoustic switch 22 is open and no electrical energy is delivered from the energy storage device 20 to the control/processing unit 24, and an “active” mode, when the acoustic switch 22 is closed and electrical energy is delivered from the energy storage device 20 to the control/processing unit 24. Further details regarding the construction and function of acoustic switches are disclosed in U.S. Pat. No. 6,628,989, which is expressly incorporated herein by reference.
Alternatively or optionally, the sensing device 12 may be configured as a passive device, as described in U.S. Pat. Nos. 5,704,352 and 6,855,115, or the sensing device 12 may be wirelessly charged by transferring energy (e.g., ultrasound, electromagnetic, or magnetic energy) from the external device to the sensing device 12, as described in U.S. Pat. No. 6,475,170, all of which are expressly incorporated herein by reference. In addition, the energy storage device 20 may be capable of being charged from an external source, and in particular, from acoustic energy transmitted to the sensing device 12 from the external device 14.
The control/processing unit 24 may include circuitry for activating or controlling the sensor 16 and for receiving signals from the sensor 16. In particular, under control of the control/processing unit 24, the physiological parameters may be measured and the resulting physiological information transmitted from the sensing device 12 to the external device 14 continuously or periodically until the sensing device 12 is deactivated, or for a fixed predetermined time, as will be appreciated by those skilled in the art.
The control/processing unit 24 may also include memory for storing information, e.g., data received from the sensor 16, and/or commands for use internally. The control/processing unit 24 may include an oscillator or other circuitry for wirelessly transmitting acoustic signals to the external device via the acoustic transducer 18, signal detection circuitry for wirelessly receiving acoustic signals from the external device via the acoustic transducer 18, and/or a processor for analyzing, interpreting, and/or processing the received signals. The control/processing unit 24 may include a processor for analyzing, interpreting, and/or processing the signals received by the sensor 16 or from the external device.
The casing 26 has at least one face 34 that is substantially flexible for transmitting pressure to the sensor 16 and acoustic transducer 18. The volume between the flexible face 34 and the printed circuit board 28 is preferably filled with an uncompressible liquid that is preferably chemically inert and has a low thermal expansion. The flexible face 34 of the casing 26 is preferably composed of a metal membrane with a thickness of 1-250 microns. The casing 26 further comprises a pair of eyelets 36 through which sutures can be threaded to facilitate affixation of the sensing device 12 within the patient, as will be described in further detail below.
Further details on the structure of a wireless device capable of sensing pressure can be found in U.S. patent application Ser. No. 09/888,272, entitled “Implantable Pressure Sensors and Methods for Making and Using Them,” which is expressly incorporated herein by reference.
Having described the function and structure of the implantable system 10, methods of implanting the sensing device 12 within a patient will now be described. These methods contemplate delivering the sensing device 12 as an adjunct to a surgical procedure for repair or placing an anatomical structure within the patient. In this manner, the same opening formed within the patient as a necessary step in the surgical procedure is used to deliver the sensing device 12 therethrough. Thus, even though the sensing device 12 may ultimately be implanted within a blood vessel leading one of ordinary skill in the art to believe that the means for delivery should be a catheterization procedure, the sensing device 12 will actually be delivered through the surgical opening and into the blood vessel. Thus, it can be appreciated that no additional access opening need be formed through the skin of the patient to implant the sensing device 12. In addition, because a catheterization procedure is not performed to effect implantation of the sensing device 12, the size of the sensing device 12 may be larger and will only be constrained by the size of the blood vessel in which the sensing device 12 is intended to be implanted.
Referring now to
In the illustrated method, this is accomplished by first making a cut C through the wall of the pulmonary artery PA to expose the lumen L (shown in
In an alternative method, a delivery device may be used to introduce the sensing device 12 into the pulmonary artery PA. For example, the sensing device 12 can be loaded into an introducer cannula 42, as shown in
The introducer cannula 42 is preferably made of a thin-walled plastic tube, although a metal tube, such as one composed of stainless steel, can be used. The distal tip of the introducer cannula 42 may be soft in order to prevent or minimize injury to the vessel wall, but in alternative embodiments, may be rigid to facilitate its introduction through the vessel wall. The cannula 42 includes two opposing prongs 44 that function to hold and maintain the sensing device 12 within the cannula 42. Other suitable means for holding the sensing device 12 can also be used.
When using the cannula 42 to facilitate implantation of the sensing device 12, a suture 38 with needles 40 can be threaded through the two eyelets 36 of the sensing device 12, as previously discussed with respect to
In an alternative method illustrated in
Referring now to
In
In
Although the previous implantation techniques introduce the sensing device 12 through a cut formed in the vessel wall of the pulmonary artery, an alternative implantation method may be employed without cutting the vessel wall of the pulmonary artery while still taking advantage of the surgical procedure performed on the heart. In particular, access to the pulmonary artery PA may be provided through the wall of the heart H, as illustrated in
As shown in
After the distal end of the catheter 56 is properly located within the pulmonary artery PA, the sensing device 12 can be affixed to the vessel wall. In the illustrated method, one or more of the eyelets 36 of the sensing device 12 are disposed outside of the catheter 56. In this case, the eyelet 56 can be flapped from the outside of the pulmonary artery PA. That is, the sensing device 12 is positioned at the desired implantation site and placed against the vessel wall, and because the low blood pressure vessel wall is relatively thin, it will deform, thereby allowing the physician to feel the contour of the sensing device 12, including the eyelets 36. The sensing device 12 can then be affixed to the vessel wall via the eyelets 36 using a suture 38 and needle 40 in a standard manner, as illustrated in
The method described with respect to
For example, the sensing device 12 may initially be implanted within the pulmonary artery PA in the manner described with respect to
As another example, the bypass cannula can initially be introduced through the heart wall into the right atrium RA, the heart arrested, and then the cannula connected to the heart-lung machine to bypass the blood. The surgical procedure can then be performed to repair or replace an anatomical structure within the heart, after which the cannula can be exchanged with the delivery catheter 56, and the heart restarted. The sensing device 12 may then be implanted within the pulmonary artery PA in the manner described with respect to
While the sensing device 12 has been illustrated and described as being implanted within the pulmonary artery PA, it should be appreciated that the sensing device 12 can be implanted in other blood vessels of the patient's body, e.g., the vena cava, pulmonary vein, coronary sinus, aorta, sub-clavian artery, iliac artery, and carotid artery. While the inventive method lends itself well to the implantation of the sensing device 12 in blood vessels, it should be appreciated that the sensing device 12 can be implanted as an adjunct to surgery in other anatomical vessels, such as the esophagus, intestine, trachea, bronchial tubes, etc. In addition, the sensing device 12 can be implanted as an adjunct to surgery in anatomical cavities besides vessels, such as heart chambers (right atrium, right ventricle, left atrium, left ventricle, or the septum between the chambers), stomach, etc. In addition, while the afore-described implantation techniques take particular advantage of open surgical procedures, the sensing device 12 can be implanted as an adjunct to other types of surgical procedures, such as minimally invasive thoracoscopy typically used for CABG or repairing/replacing a heart valve or used for the treatment of other diseases, such as lung cancer. Lastly, while the present implantation techniques have been described with respect to wireless sensing devices, the same implantation techniques can be utilizes to implant wireless therapeutic devices (e.g., a drug releasing device or neuro-stimulator for treating arrhythmia, pain, or neurological disturbances or for stimulating the gastrointestinal system or urinary system) within the anatomical vessels or cavities of patients.
Although particular embodiments of the present invention have been shown and described, it should be understood that the above discussion is not intended to limit the present invention to these embodiments. It will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention. Thus, the present invention is intended to cover alternatives, modifications, and equivalents that may fall within the spirit and scope of the present invention as defined by the claims.
This application claims the benefit under 35 U.S.C. § 119 to U.S. Provisional Application Ser. No. 60/803,023, filed on May 23, 2006, which is incorporated herein by reference.
Number | Date | Country | |
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60803023 | May 2006 | US |