WO2012015954A1

WO2012015954A1 - Transvascular wireless sensor system

Info

Publication number: WO2012015954A1
Application number: PCT/US2011/045581
Authority: WO
Inventors: Peter Hinchliffe; Harry Rowland; Michael Nagy; Reed Prior
Original assignee: Endotronix, Inc.
Priority date: 2010-07-27
Filing date: 2011-07-27
Publication date: 2012-02-02

Abstract

The present invention is a communication system for communicating with an implantable device. The communication system comprises an implantable device, an implantable electronic unit and a remote antenna, wherein the remote antenna extends from the implantable electronic unit on wire leads. In one embodiment, the implantable device may be a sensor. In another embodiment, the implantable electronic unit may communicate wirelessly with the implantable device through a remote antenna.

Description

TITLE

TRANSVASCULAR WIRELESS SENSOR SYSTEM

FIELD OF THE INVENTION

[0001] This application relates to a transvascular wireless sensor system that includes an implantable pressure sensor device capable of sensing pulmonary artery pressure, and an implantable reader device adjacent to the sensor that can interrogate the sensor automatically for readings.

BACKGROUND

[0002] For many people with heart conditions, pulmonary artery pressure ("PA pressure") is a key metric for prevention diagnosis and treatment. PA pressure is generated by the right ventricle ejecting blood into the pulmonary circulation, which acts as a resistance to the output from the right ventricle. As the heart relaxes, blood continues to flow from the pulmonary artery into the pulmonary circulation. The smaller arteries and arterioles serve as the chief resistance vessels, and through changes in their diameter, regulate vascular resistance. In hemodynamic terms, the mean PA pressure can be described as PA pressure=(CO x PVR) +PVP, where CO is cardiac output, PVR is pulmonary vascular resistance, and PVP is pulmonary venous pressure. PA pressure has been found to be particularly useful in the early prediction of congestive heart failure, allowing intervention before the onset of symptoms requiring hospitalization. To obtain an accurate reading, PA pressure must be measured within the pulmonary artery. This is because its value is different from blood pressure elsewhere in the circulatory system, and there is no known way to ascertain it other than by reading it directly inside or very near the vessels adjoining the pulmonary artery. Therefore, an implantable device must be used to measure PA pressure accurately.

[0003] The present and generally considered the most accurate way to measure PA pressure is by a Swan-Ganz catheter. A Swan-Ganz catheter is introduced through a large vein— often the internal jugular, subclavian, or femoral veins. From this entry site, it is threaded, often with the aid of fluoroscopy, through the right atrium of the heart, the right ventricle, and subsequently into the pulmonary artery. The Swan-Ganz catheter has two lumens and is equipped with an inflatable balloon at the tip, which facilitates its placement into the pulmonary artery through the flow of blood. The balloon, when inflated, causes the catheter to "wedge" in a small pulmonary blood vessel. So wedged, the catheter can provide an indirect measurement of the pressure in the left atrium of the heart, showing a mean pressure, in addition to a, x, v, and y waves which have implications for status of the left atria and the mitral valve. Left ventricular end diastolic pressure is measured separately, with a catheter that has directly crossed the aortic valve and is well positioned in the left ventricle. Left ventricular end diastolic pressure reflects fluid status of the individual in addition to heart health. However, this can only be implemented in-patient in a catheter lab, and does not allow at-home or outpatient PAP monitoring.

[0004] Examples of existing, presently available, implantable devices include cardiac resynchronization therapy (CRT) devices, implantable cardiac defibrillators (ICDs), cardiac resynchronization therapy devices with defibrillator built in (CRT-D) devices, ventricular assist devices (VADs), and others (collectively, "CRT-D"). In general, these devices consist of a battery-powered electronics unit implanted in the chest and away from the heart. One or more wires emerge from the electronics unit. These wires penetrate a vein or artery and connect to sensors or stimulating electrodes which are positioned in various locations in or near the heart. Some of these systems, such as CRT devices, ICDs, CRT-Ds, and VADs do not measure PA pressure. Other systems that measure PA pressure, such as an external impedance measurement device, do not measure it at the accuracy of the Swan-Ganz catheter. While other systems that measure PA pressure, such as an implantable ultrasound-powered sensor, require a patient to apply impedance matching gel to their skin each time a measurement is taken.

[0005] Figure 1 illustrates a typical implantable CRT-D device. Three leads 56, 57, 58 extend from the electronics module 50 to the right atrium 42, right ventricle 43 and through the coronary sinus 59 to the left ventricle 60. When the device is also used to defibrillate, or shock, the heart leads also possess a coil at their tips 61, 62, 63.

[0006] Other attempts by third parties to measure PA pressure with minimum inconvenience to patients exist. For example, a wireless, batteryless, implantable PA pressure sensor from CardioMEMS Inc., places the sensor into the pulmonary artery with a Swann-Ganz-like catheter system and a large, table mounted external reader unit interrogates the sensor wirelessly. However, it requires an external reader unit as well as patient compliance to take daily readings and upload them.

[0007] A wired implantable trans-septal version under development by St. Jude Medical Inc. resembles a miniaturized CRT device, with battery-powered electronics contained in a module implanted subcutaneously in the pectoral area, and a wired lead extending into the superior vena cava, then through the atrial septum and into the left atrium. Besides the standalone unit, a version of this device can be integrated into the electronics module of an existing implanted CRT-D device, sharing a common battery, and possibly other functions such as processor, memory, and wireless data transfer. However, it requires a longer lead to extend into the left atrium, which must penetrate the septal wall, causing undue trauma and possibly leading to further complications. A similar wired version that resides in the pulmonary artery was disclosed by Transoma Medical, Inc. However, this requires a permanent lead that crosses both the tricuspid and pulmonary valves, possibly leading to trauma or undue stress.

[0008] An implantable ultrasound-powered sensor under development at the Boston Scientific Corporation contains a pressure sensor, a custom ASIC with memory, and a piezoelectric transducer. The implant is placed in the pulmonary artery and an external unit stimulates the transducer with ultrasound energy to acquire a reading. The ASIC takes the reading and actuates the transducer to transmit, via ultrasound, the readings back to the reader unit. However, the implantable ultrasound-powered sensor requires patient action to carry out a measurement. As part of the process, the patient must apply an impedance-matching gel to his or her skin surface at the point of contact, each time a measurement is taken, and then clean it off of himself or herself and the reader unit.

[0009] An external impedance measurement device by Corventis, Inc attempts to calculate PA pressure noninvasively using external leads taped to the skin. It measures changes in body impedance and infers several physiological parameters, including PA pressure. However, this method is highly susceptible to error based on bodily impedance changes resulting from a number of variables that exist below, on, and above the skin. Additionally, it requires the patient to wear leads and carry an external reader unit to acquire readings. [0010] RF powered far-field solutions, such as the TSM35 by Millar Instruments, Inc. and Telemetry Research, Ltd., contain a battery which is charged by a large external coil. The battery powers an internal pressure sensor, an A/D converter, and a digital transmitter, which sends a far-field RF signal to a base station outside the body. However, these solutions require relatively high power to operate their implants, severely limiting battery life and/or requiring a very long charging time. Additionally, their implants are often large and rigid compared with other solutions and with present state of the art electronics would be impossible to deploy in the pulmonary artery volume.

[0011] It would be beneficial to have a device capable of providing accurate measurements of PA pressure in an out-patient, in-home setting which requires minimum patient action and which may be readily integrable with existing CRT-D devices.

SUMMARY OF INVENTION

[0012] The present invention is a communication system for communicating with an implantable device. In one embodiment, a communication system comprises an implantable device, an implantable electronic unit and a remote antenna, wherein the remote antenna extends from said implantable electronic unit on wire leads. In another embodiment, the implantable device may be a sensor such as, but not limited to, a pressure sensor, a temperature sensor, a pH sensor, a glucose sensor, an acceleration sensor, a mechanical stress and strain sensor, and any combination of these. In another embodiment, the implantable electronic unit may communicate wirelessly with the implantable device through a remote antenna.

[0013] In another embodiment the implantable electronic unit comprises a reader and a power module. In another embodiment the power module may be powered by a battery. [0014] In another embodiment, the implantable device may be implanted in a blood vessel such as, but not limited to, the right middle lobe pulmonary artery. The implantable electronic unit may implanted in a subcutaneous thoracic cavity and the remote antenna may be implanted subcutaneously or may be implanted in the superior vena cava.

[0015] In one embodiment, the remote antenna may transmit stimulating signals to the implantable device. The remote antenna may also receive reflected signals from the implantable device

[0016] In another embodiment, the remote antenna may communicate with the implantable device using RF frequency. The communication may be completed with inductive coupling and may use a fixed transmit frequency.

[0017] A method for communicating with an implanted device, the method comprising the steps of implanting an implantable device, implanting an implantable electronic unit, implanting a remote antenna on wire leads near the implantable device, connecting the wire leads to the implantable electronic unit and then communicating wirelessly with the implanted device via the implantable electronic unit and the remote antenna. In one embodiment the implantable device is a sensor such as, but not limited to, a pressure sensor, a temperature sensor, a pH sensor, a glucose sensor, an acceleration sensor, a mechanical stress and strain sensor, and any combination of these.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Preferred embodiments of the present disclosure are described herein with reference to the drawings wherein: [0019] Figure 1 illustrates an anatomical view illustrating a typical CRT-D device presently in use.

[0020] Figure 2 illustrates an anatomical view illustrating the proposed transvascular wireless PA pressure sensor being implanted.

[0021] Figure 3 illustrates an anatomical view illustrating a transvascular antenna unfolding sail.

[0022] Figure 4 illustrates an anatomical view illustrating a transvascular antenna with a coil in a stent-like tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings. It is to be understood that other embodiments may be utilized and structural and functional changes may be made without departing from the respective scope of the invention.

[0024] Figure 2 illustrates a sensor 10 implanted into the right middle lobe pulmonary artery, using a simple, low-risk, and low-cost catheter-based approach. The sensor 10 is shown inside the right middle lobe pulmonary artery 46. In one embodiment, a delivery system 14 inside a sheath 20 is delivered from the axillary vein 48 down the superior vena cava 47, into the right atrium 42, then into the right ventricle 43, afterwards into the pulmonary artery 44, then into the right pulmonary artery 45, and finally into the right middle lobe artery 46. In one embodiment, after delivery, the sheath 20 and delivery system 14 are retracted, and the sensor 10 remains behind as a permanent or semi-permanent implant.

[0025] Figure 3 illustrates a reader electronic unit 50 with a battery powered module that is placed in a pocket 53 that is typically in the upper left pectoral. Extending from the electronics unit 50 is a pair of wires 55, typically twisted or attached together in a ribbon 52 or by any other means. The wires 55 typically terminate in a remote antenna 51, such as, for example, a coil antenna. This remote antenna 51 may transmit stimulating signals to, and receive a reflected signal from, the sensor 10. The reader may interrogate the implanted sensor using near-field inductive coupling as identified in U.S. Patent Application Nos. 12/419,326 and 12/727,306 that are assigned to Endotronix, Inc. and are incorporated by reference in their entirety.

[0026] Both the sensor 10 and the remote antenna 51 may be implanted noninvasively using catheter-based methods consistent with the method illustrated in Figure 2. The sensor 10 may reside in the right pulmonary artery 45, at or near the first trifurcation or in the right middle lobe pulmonary artery 46. The remote antenna 51 may reside in the superior vena cava, several millimeters away from the sensor 10. However, the sensor 10 and remote antenna 51 may also be placed in other locations in or near the heart as desired or needed. The remote antenna 51 and sensor 10 may communicate by way of, but such communication is not limited to, a coupled RF magnetic field, through the walls of the pulmonary artery and superior vena cava. In another embodiment, the remote antenna may be implanted subcutaneously

[0027] The general form of the sensor 10 may as described in U.S. Patent Application Nos.

12/419,326 and 12/727,306 that are assigned to Endotronix, Inc. and are incorporated by reference in their entirety. To maximize inductive coupling the coil antennae of the reader electronic unit 50 and the sensor 10 may be substantially parallel to one another, and placed as near as possible to one another, so their coil areas overlap as much as possible. Normally, about

100% area overlap is achieved by making the reader antenna coil much larger than that of the sensor 10, and locating the implant coil completely within the reader antenna coil's circumference. Both the reader antenna and the sensor may be provided with radio opaque markings that indicate the rotational orientation of the coils, and it is preferred the catheter delivery systems allow the implanting surgeon to position them - rotationally or translationally - precisely during deployment. Once deployed, both implants can remain in their position and orientation throughout the useful lifetime of the device. Additionally, it is preferred both the sensor and antenna are resistant to clotting, thrombus formation, and must not interfere with nor be affected by other medical equipment such as magnetic resonance imaging, electrocardiogram, the implantable cardioverter-defibrillator, cardiac resynchronization therapy, etc.

[0028] As for the antenna, it is preferred that it is catheter deployable, meaning that in its initial state it is fit into a small cylindrical volume by ways including, but not limited to, being folded or rolled to minimize its size during deployment. Upon deployment, the antenna can then expand to a shape that maximizes coil area for optimum inductive coupling with the implant. One possible means for accomplishing this is to fabricate the antenna as a flex circuit on coated polyimide, PTFE, or other medically compatible materials. Upon deployment, a frame of nitinol or other supporting wires unfold to open the antenna into a flat sheet, similar to a sail. Another possible means is to incorporate the flexible antenna into a cylinder or partial cylinder that expands to rest circumferentially against the vessel wall, similar to a stent. (See Figure 4.) In another embodiment the antenna coil could reside in the wall of a stent type structure 52 as shown in Figure 4. In one embodiment, the communication between the electronics unit and the sensor is accomplished using a fixed transmit frequency.

[0029] In one embodiment, the electronic module may be integrated into a CRT, ICD, VAS, CRT-D or other similar devices. In another embodiment, advantages may be gained by integrating the functionality of the PA pressure sensor with a CRT-D device. Thus providing both a standalone implantable sensor, for patients without a CRT-D device and an implantable sensor that is incorporated into an existing CRT-D device.

[0030] To facilitate catheter-based implantation, the embodiment disclosed above places a sensor in a region of the pulmonary artery directly under the superior vena cava. However, the sensor can detect the pulmonary artery pressure from a wide range of locations including, but not limited to, within the pulmonary artery, right atrium, and nearby vessels. The reader antenna, likewise, may be placed in other vessels or areas besides the superior vena cava, as long as it is near the sensor and/or is oriented where the coils are parallel. Examples may include, but are not limited to, the right atrium and ascending aorta.

[0031] The embodiment disclosed above places the antenna inside an adjacent or nearby blood vessel. However, it may also be possible to place the antenna in another subcutaneous location outside the blood vessel. Examples may include, but are not limited to, in the body cavity, or between muscles or tissue linings.

[0032] The embodiment disclosed above makes reference to the "burst and listen" RF communication method disclosed in U.S. Patent Application Nos. 12/419,326 and 12/727,306 that are assigned to Endotronix, Inc. and are incorporated by reference in their entirety. However, the transvascular RF coupling concept is valid for any power or data communication requiring near-field wireless coupling, RF or otherwise. These include swept-frequency, grid dip, phase matching, battery or capacitor charging, digital PWM, other digital methods, ultrasound, and optical methods.

[0033] The transvascular concept of placing the transmitter and receiver in separate areas may also be useful in other applications where it is desired to communicate data or transfer energy across locations within the body without wired connection. The transvascular concept may also be useful where it is advantageous to place the transmitters and receivers of these systems inside blood vessels to detect parameters, stimulate body functions or actuate body functions. Placing sensors or antennas inside of vessels permits the use of catheter-based techniques, which continue to gain wide acceptance and enjoy technological advances. In this variation, the wireless implant may be used to stimulate rather than to sense, but the concept of transvascular power transfer is the same.

[0034] Besides sensing PA pressure, there are other applications for the concept of a standalone wireless sensor or a noninvasively implanted antenna on a wire, which connects to an electronics unit in a more benign location. For example, there may be advantages to a remote antenna/sensor system for measuring intra cranial pressure in brain sinuses, bladder pressures, lung pressures, stomach pressures, etc. It may also be advantageous in sensing other parameters such as, but not limited to, chemical, temperature, oxygen level, PH, glucose level, acceleration, mechanical stress and strain, etc. In any situation where a blood vessel passes near the sensor location, a catheter-implanted antenna could be placed to gain an accurate near-field reading. Likewise with wireless actuators.

Claims

CLAIMS Having thus described the invention, we claim:

1. A communication system for communicating with an implantable device comprising;

an implantable device;

an implantable electronic unit; and

a remote antenna, wherein said remote antenna extends from said implantable electronic unit on wire leads.

2. The communication system of claim 1 wherein said implantable device is a sensor.

3. The communication system of claim 1 wherein said implantable electronic unit communicates wirelessly with said implantable device through said remote antenna.

4. The communication system of claim 1 wherein said implantable electronic unit comprises;

a reader; and

a power module.

5. The communication system of claim 1 wherein said remote antenna transmits stimulating signals to said implantable device and receives reflected signals from said implantable device.

6. The communication system of claim 1 wherein said remote antenna communicates with said implantable device using RF frequency.

7. The communication system of claim 6 wherein said communication is completed with inductive coupling.

8. The communication system of claim 6 wherein said communication uses a fixed transmit frequency.

9. The communication system of claim 1 wherein said implantable device is substantially parallel to said implantable electronic unit.

10. The communication system of claim 1 wherein said remote antenna is placed near said implantable device.

11. The communication system of claim 1 wherein said implantable device comprises an implant coil and said implantable electronic unit comprises an antenna coil.

12. The communication system of claim 11 wherein said implant coil is positioned within the circumference of said antenna coil.

13. The communication system of claim 1 wherein said implantable device is implanted in a blood vessel.

14. The communication system of claim 1 wherein said remote antenna is catheter deployable.

15. The communication system of claim 1 wherein said implantable device is implanted in the right middle lobe pulmonary artery, said implantable electronic unit is implanted in a subcutaneous thoracic cavity, and said remote antenna is implanted in the superior vena cava.

16. The communication system of claim 2 wherein said implantable sensor is a pressure sensor.

17. The communication system of claim 1 wherein said remote antenna is implanted subcutaneously.

18. The communication system of claim 1 wherein said implantable electronic unit is integrated into a CRT, ICD, VAD or CRT-D device.

19. A method for communicating with an implanted device, the method comprising the steps of: implanting an implantable device;

implanting an implantable electronic unit;

implanting a remote antenna on wire leads near said implantable device;

connecting said wire leads to said implantable electronic unit; and

communicating wirelessly with said implanted device through said implantable electronic unit and said remote antenna.

20. The method of claim 19 wherein said implantable device is a sensor.