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IMPLANTABLE AND RECHARGEABLE
This application relates generally to implantable medical devices and, more particularly, to implantable and rechargeable neural stimulators.
The automatic nervous system (ANS) regulates "involuntary" organs. The ANS includes the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system is affiliated with stress and the "fight or 15 flight response" to emergencies. The parasympathetic nervous system is affiliated with relaxation and the "rest and digest response." The ANS maintains normal internal function and works with the somatic nervous system. Autonomic balance reflects the relationship between parasympathetic 20 and sympathetic activity. A change in autonomic balance is reflected in changes in heart rate, heart rhythm, contractility, remodeling, inflammation and blood pressure. Changes in autonomic balance can also be seen in other physiological changes, such as changes in abdominal pain, appetite, 25 stamina, emotions, personality, muscle tone, sleep, and allergies, for example.
Neural stimulation therapy has been proposed for a variety of reasons. Reduced autonomic balance (increase in sympathetic and decrease in parasympathetic cardiac tone) during 30 heart failure has been shown to be associated with left ventricular dysfunction and increased mortality. Research also indicates that increasing parasympathetic tone and reducing sympathetic tone may protect the myocardium from further remodeling and predisposition to fatal arrhythmias following 35 myocardial infarction. Direct stimulation of the vagal parasympathetic fibers has been shown to reduce heart rate via the sympathetic nervous system. In addition, some research indicates that chronic stimulation of the vagus nerve may be of protective myocardial benefit following cardiac ischemic 40 insult. Neural stimulation also has been proposed to alleviate pain and as a therapy for hypertension.
It can be difficult to anticipate the amount of energy needed for neural stimulation. For effective therapy, it may be necessary to stimulate neural targets intermittently or continu- 45 ously. Also, high current levels may be effective for a larger area, or lower levels may be effective for a smaller area. A flexible power management system is needed to improve neural stimulation devices.
One aspect of the present subject matter relates to an implantable medical device. An embodiment of the device comprises a rechargeable power supply adapted to be 55 recharged through an ultrasound signal, a neural stimulator connected to the rechargeable power supply, and a controller connected to the rechargeable power supply. The neural stimulator is adapted to generate a neural stimulation signal for delivery to a neural stimulation target through an elec- 60 trode. The controller is further connected to the neural stimulator to control the neural stimulator according to a neural stimulation protocol. Other aspects are provided herein.
An embodiment of the implantable medical device comprises a structure, a rechargeable battery connected to the 65 structure, a transducer adapted to charge the rechargeable battery using ultrasound energy, a sensor electrically con
nected to the rechargeable battery, a neural stimulator electrically connected to the rechargeable battery, and a controller electrically connected to the rechargeable battery and adapted to communicate with the sensor and the neural stimulator. The structure is selected from a group of structures consisting of: a structure adapted to be chronically implanted within a vessel, and a structure adapted to be subcutaneously implanted using a hypodermic needle.
One aspect of the present subject matter relates to a system. An embodiment of the system comprises at least two implantable medical devices, where each device being adapted to be chronically implanted into a vessel. Each device includes a rechargeable battery and an ultrasound transducer connected to the battery and adapted to recharge the battery using an ultrasound signal, a neural stimulator adapted to be powered by the battery, a sensor adapted to be powered by the battery, a controller electrically connected to a neural stimulator and the pressure sensor, and a communication module adapted to be powered by the battery and to transmit and receive ultrasound communication signals to another implantable medical device.
One aspect of the present subject matter relates to a method of operating an implantable medical device with a pressure sensor and a neural stimulator chronically implanted in a vessel. According to an embodiment of the method, a pressure is sensed within the vessel using the pressure sensor, a neural target is stimulated using the neural stimulator, a power supply is recharged using ultrasound signals.
This Summary is an overview of some of the teachings of the present application and not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description and appended claims. Other aspects will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which are not to be taken in a limiting sense. The scope of the present invention is defined by the appended claims and their equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of one embodiment of a chronically-implanted device.
FIG. 2 illustrates an embodiment where the device implanted subcutaneously using a hypodermic needle.
FIG. 3 illustrates an embodiment where a chronicallyimplanted device, in the form of a stent, is placed within a vessel and where the device includes an encapsulated electronics platform.
FIG. 4 illustrates one embodiment of a chronically-implanted device in the form of a stent that includes an encapsulated electronics platform.
FIG. 5 illustrates one embodiment of a chronically-implanted device in the form of a stent that includes two encapsulated electronics platforms.
FIG. 6 illustrates an embodiment of a chronically-implanted device having a cylindrical or radially-oriented anode and cathode.
FIG. 7 illustrates an embodiment of a chronically-implanted device having a longitudinally-oriented anode and cathode.
FIG. 8 illustrates an embodiment where the chronicallyimplanted device is powered by a small rechargeable battery adapted to be recharged using ultrasound waves from an ultrasound power source.
FIG. 9 illustrates a system embodiment where two implantable neural stimulation devices are adapted to communicate with each other.
FIG. 10 illustrates a system including an implantable medical device (IMD) and a programmer, according to various 5 embodiments of the present subject matter.
FIG. 11 illustrates an embodiment where an implantable medical device network includes a planet and a plurality of satellites formed by the chronically-implanted device.
The following detailed description of the present subject matter refers to the accompanying drawings which show, by way of illustration, specific aspects and embodiments in 15 which the present subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present subject matter. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the 20 scope of the present subject matter. References to "an", "one", or "various" embodiments in this disclosure are not necessarily to the same embodiment, and such references contemplate more than one embodiment. The following detailed description is, therefore, not to be taken in a limiting 25 sense, and the scope is defined only by the appended claims, along with the full scope of legal equivalents to which such claims are entitled.
Embodiments of the present subject matter provide implantable and rechargeable neural stimulators. Ultrasound 30 energy can be used to recharge the stimulators. Some embodiments integrate a stimulator and a sensor in an implantable device, such that the device can autonomously provide stimulation therapy based on need. For example, a neural stimulator integrated with a pressure sensor can be activated when the 35 sensor senses a higher blood pressure in the vasculature. The pressure sensor can use micro-electrical mechanical systems (MEMS) technology, for example. The devices can be implanted either subcutaneously or in the vasculature depending in the sensor-stimulator pair application. 40 Examples of integrated sensors include sensors that can sense either electrical or physical physiologic parameters. These sensors can provide localized feedback for the neural stimulation. For example, a pressure sensor can sense high blood pressure and the stimulator can stimulate the appropriate 45 nerve to lower the blood pressure. Such a system can be integrated into a device with a small form factor with its own power supply, such that the device is physically capable of being implanted through a hypodermic needle or intravascularly fed into a vessel, for example. A stent-like anchoring 50 mechanism can be used in vasculature.
Embodiments also have the ability to wirelessly communicate other device(s), either inside or outside the body. Typically, such a system can communicate with another device within the body using ultrasound, which has minimal loss 55 within the body. Communications with external devices can be performed using ultrasound, or inductive or RF telemetry. The intra-body communication allows the neural stimulation therapy to be to be coordinated with other implantable neural stimulators or other implantable devices such as from a car- 60 diac rhythm management (CRM) device (e.g. pacemaker) also has such communication capability. Intrabody communication can significantly improve the efficacy of the neural stimulator, and the neural stimulation therapy.
The neural stimulator with integrated sensor can be chroni- 65 cally implanted to treat conditions such as hypertension and chronic pain. Some device embodiments have its own power
source, and some device embodiments are powered remotely. Diagnostic and therapy functions can be performed at fixed times or based at least in part on feedback received from the sensor.
Neural stimulation can be used to provide therapy for a variety of systemic abnormalities like hypertension. Hypertension is a cause of heart disease and other related cardiac co-morbidities. Hypertension occurs when blood vessels constrict. As a result, the heart works harder to maintain flow at a higher blood pressure, which can contribute to heart failure. A large segment of the general population, as well as a large segment of patients implanted with pacemakers or defibrillators, suffer from hypertension. The long term mortality as well as the quality of life can be improved for this population if blood pressure and hypertension can be reduced. Many patients who suffer from hypertension do not respond to treatment, such as treatments related to lifestyle changes and hypertension drugs. Hypertension generally relates to high blood pressure, such as a transitory or sustained elevation of systemic arterial blood pressure to a level that is likely to induce cardiovascular damage or other adverse consequences. Hypertension has been arbitrarily defined as a systolic blood pressure above 140 mm Hg or a diastolic blood pressure above 90 mm Hg. Hypertension occurs when blood vessels constrict. As a result, the heart works harder to maintain flow at a higher blood pressure. Consequences of uncontrolled hypertension include, but are not limited to, retinal vascular disease and stroke, left ventricular hypertrophy and failure, myocardial infarction, dissecting aneurysm, and renovascular disease.
The automatic nervous system (ANS) regulates "involuntary" organs, while the contraction of voluntary (skeletal) muscles is controlled by somatic motor nerves. Examples of involuntary organs include respiratory and digestive organs, and also include blood vessels and the heart. Often, the ANS functions in an involuntary, reflexive manner to regulate glands, to regulate muscles in the skin, eye, stomach, intestines and bladder, and to regulate cardiac muscle and the muscle around blood vessels, for example.
The ANS includes, but is not limited to, the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system is affiliated with stress and the "fight or flight response" to emergencies. Among other effects, the "fight or flight response" increases blood pressure and heart rate to increase skeletal muscle blood flow, and decreases digestion to provide the energy for "fighting or fleeing." The parasympathetic nervous system is affiliated with relaxation and the "rest and digest response" which, among other effects, decreases blood pressure and heart rate, and increases digestion to conserve energy. The ANS maintains normal internal function and works with the somatic nervous system.
The heart rate and force is increased when the sympathetic nervous system is stimulated, and is decreased when the sympathetic nervous system is inhibited (the parasympathetic nervous system is stimulated). An afferent nerve conveys impulses toward a nerve center, such as a vasomotor center which relates to nerves that dilate and constrict blood vessels to control the size of the blood vessels. An efferent nerve conveys impulses away from a nerve center.
A pressoreceptive region or field is capable of sensing changes in pressure, such as changes in blood pressure. Pressoreceptor regions are referred to herein as baroreceptors, which generally include any sensors of pressure changes. The baroreflex functions as a negative feedback system, and