| Automatic baroreflex modulation based on cardiac activity -> Monitor Keywords |
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Automatic baroreflex modulation based on cardiac activityRelated Patent Categories: Surgery: Light, Thermal, And Electrical Application, Light, Thermal, And Electrical Application, Electrical Therapeutic Systems, Hypertension TreatingAutomatic baroreflex modulation based on cardiac activity description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070021799, Automatic baroreflex modulation based on cardiac activity. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCES TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. patent application Ser. No. 10/402,911 (Attorney Docket No.: 021433-000410US), filed on Mar. 27, 2003, which (1) is a continuation-in-part of U.S. patent application Ser. No. 09/963,777 (Attorney Docket No.: 021433-000120US), filed on Sep. 26, 2001, which is a continuation-in-part of U.S. patent application Ser. No. 09/671,850 (Attorney Docket No.: 021433-000100US), filed on Sep. 27, 2000, now issued as U.S. Pat. No. 6,522,926; and (ii) claims the benefit of U.S. Provisional Patent Application No. 60/368,222 (Attorney Docket No.: 021433-000400US), filed on Mar. 27, 2002, the disclosures of each of the above being hereby incorporated by reference in their entirety. The parent application for this application has incorporated by reference the disclosures of the following U.S. patent applications: U.S. patent application Ser. No. 09/964,079 (Attorney Docket No.: 021433-000110US), filed on Sep. 26, 2001, now issued as U.S. Pat. No. 6,985,774, and U.S. patent application Ser. No. 09/963,991 (Attorney Docket No.: 021433-000130US), filed on Sep. 26, 2001, now issued as U.S. Pat. No. 6,850,801, now issued as U.S. Pat. No. 6,850,801, the disclosures of which are also effectively incorporated by reference herein. BACKGROUND OF THE INVENTION Field of the Invention [0002] The present invention generally relates to medical devices and methods of use for the treatment and/or management of cardiovascular and renal disorders. Specifically, the present invention relates to devices and methods for controlling the baroreflex system for the treatment and/or management of cardiovascular and renal disorders and their underlying causes and conditions. [0003] Cardiovascular disease is a major contributor to patient illness and mortality. It also is a primary driver of health care expenditure, costing more than $326 billion each year in the United States. Hypertension, or high blood pressure, is a major cardiovascular disorder that is estimated to affect over 50 million people in the United Sates alone. Of those with hypertension, it is reported that fewer than 30% have their blood pressure under control. Hypertension is a leading cause of heart failure and stroke. It is the primary cause of death in over 42,000 patients per year and is listed as a primary or contributing cause of death in over 200,000 patients per year in the U.S. Accordingly, hypertension is a serious health problem demanding significant research and development for the treatment thereof. [0004] Hypertension occurs when the body's smaller blood vessels (arterioles) constrict, causing an increase in blood pressure. Because the blood vessels constrict, the heart must work harder to maintain blood flow at the higher pressures. Although the body may tolerate short periods of increased blood pressure, sustained hypertension may eventually result in damage to multiple body organs, including the kidneys, brain, eyes and other tissues, causing a variety of maladies associated therewith. The elevated blood pressure may also damage the lining of the blood vessels, accelerating the process of atherosclerosis and increasing the likelihood that a blood clot may develop. This could lead to a heart attack and/or stroke. Sustained high blood pressure may eventually result in an enlarged and damaged heart (hypertrophy), which may lead to heart failure. [0005] Heart failure is the final common expression of a variety of cardiovascular disorders, including ischemic heart disease. It is characterized by an inability of the heart to pump enough blood to meet the body's needs and results in fatigue, reduced exercise capacity and poor survival. It is estimated that approximately 5,000,000 people in the United States suffer from heart failure, directly leading to 39,000 deaths per year and contributing to another 225,000 deaths per year. It is also estimated that greater than 400,000 new cases of heart failure are diagnosed each year. Heart failure accounts for over 900,000 hospital admissions annually, and is the most common discharge diagnosis in patients over the age of 65 years. It has been reported that the cost of treating heart failure in the United States exceeds $20 billion annually. Accordingly, heart failure is also a serious health problem demanding significant research and development for the treatment and/or management thereof. [0006] Heart failure results in the activation of a number of body systems to compensate for the heart's inability to pump sufficient blood. Many of these responses are mediated by an increase in the level of activation of the sympathetic nervous system, as well as by activation of multiple other neurohormonal responses. Generally speaking, this sympathetic nervous system activation signals the heart to increase heart rate and force of contraction to increase the cardiac output; it signals the kidneys to expand the blood volume by retaining sodium and water; and it signals the arterioles to constrict to elevate the blood pressure. The cardiac, renal and vascular responses increase the workload of the heart, further accelerating myocardial damage and exacerbating the heart failure state. Accordingly, it is desirable to reduce the level of sympathetic nervous system activation in order to stop or at least minimize this vicious cycle and thereby treat or manage the heart failure. [0007] A number of drug treatments have been proposed for the management of hypertension, heart failure and other cardiovascular disorders. These include vasodilators to reduce the blood pressure and ease the workload of the heart, diuretics to reduce fluid overload, inhibitors and blocking agents of the body's neurohormonal responses, and other medicaments. [0008] Various surgical procedures have also been proposed for these maladies. For example, heart transplantation has been proposed for patients who suffer from severe, refractory heart failure. Alternatively, an implantable medical device such as a ventricular assist device (VAD) may be implanted in the chest to increase the pumping action of the heart. Alternatively, an intra-aortic balloon pump (IABP) may be used for maintaining heart function for short periods of time, but typically no longer than one month. Other surgical procedures are available as well. [0009] It has been known for decades that the wall of the carotid sinus, a structure at the bifurcation of the common carotid arteries, contains stretch receptors (baroreceptors) that are sensitive to the blood pressure. These receptors send signals via the carotid sinus nerve to the brain, which in turn regulates the cardiovascular system to maintain normal blood pressure (the baroreflex), in part through activation of the sympathetic nervous system. Electrical stimulation of the carotid sinus nerve (baropacing) has previously been proposed to reduce blood pressure and the workload of the heart in the treatment of high blood pressure and angina. For example, U.S. Pat. No. 6,073,048 to Kieval et al. discloses a baroreflex modulation system and method for stimulating the baroreflex arc based on various cardiovascular and pulmonary parameters. [0010] Although each of these alternative approaches is beneficial in some ways, each of the therapies has its own disadvantages. For example, drug therapy is often incompletely effective. Some patients may be unresponsive (refractory) to medical therapy. Drugs often have unwanted side effects and may need to be given in complex regimens. These and other factors contribute to poor patient compliance with medical therapy. Drug therapy may also be expensive, adding to the health care costs associated with these disorders. Likewise, surgical approaches are very costly, may be associated with significant patient morbidity and mortality and may not alter the natural history of the disease. Baropacing also has not gained acceptance. Several problems with electrical carotid sinus nerve stimulation have been reported in the medical literature. These include the invasiveness of the surgical procedure to implant the nerve electrodes, and postoperative pain in the jaw, throat, face and head during stimulation. In addition, it has been noted that high voltages sometimes required for nerve stimulation may damage the carotid sinus nerves. Accordingly, there continues to be a substantial and long felt need for new devices and methods for treating and/or managing high blood pressure, heart failure and their associated cardiovascular and nervous system disorders. [0011] U.S. Pat. No. 6,522,926, signed to the Assignee of the present application, describes a number of systems and methods intended to activate baroreceptors in the carotid sinus and elsewhere in order to induce the baroreflex. Numerous specific approaches are described, including the use of coil electrodes placed over the exterior of the carotid sinus near the carotid bifurcation. While such electrode designs offer substantial promise, there is room for improvement in a number of specific design areas. For example, it would be desirable to provide designs which permit electrode structures to be closely and conformably secured over the exterior of a carotid sinus or other blood vessels so that efficient activation of the underlying baroreceptors can be achieved. It would be further desirable to provide specific electrode structures which can be variably positioned at different locations over the carotid sinus wall or elsewhere. At least some of these objectives will be met by these inventions described hereinbelow. BRIEF SUMMARY OF THE INVENTION [0012] To address hypertension, heart failure and their associated cardiovascular and nervous system disorders, the present invention provides a number of devices, systems and methods by which the blood pressure, nervous system activity, and neurohormonal activity may be selectively and controllably regulated by activating baroreceptors. By selectively and controllably activating baroreceptors, the present invention reduces excessive blood pressure, sympathetic nervous system activation and neurohormonal activation, thereby minimizing their deleterious effects on the heart, vasculature and other organs and tissues. [0013] The present invention provides systems and methods for treating a patient by inducing a baroreceptor signal to effect a change in the baroreflex system (e.g., reduced heart rate, reduced blood pressure, etc.). The baroreceptor signal is activated or otherwise modified by selectively activating baroreceptors. To accomplish this, the system and method of the present invention utilize a baroreceptor activation device positioned near a baroreceptor in the carotid sinus, aortic arch, heart, common carotid arteries, subclavian arteries, and/or brachiocephalic artery. Preferably, the baroreceptor activation device is located in the right and/or left carotid sinus (near the bifurcation of the common carotid artery) and/or the aortic arch. By way of example, not limitation, the present invention is described with reference to the carotid sinus location. [0014] Generally speaking, the baroreceptor activation device may be activated, deactivated or otherwise modulated to activate one or more baroreceptors and induce a baroreceptor signal or a change in the baroreceptor signal to thereby effect a change in the baroreflex system. The baroreceptor activation device may be activated, deactivated, or otherwise modulated continuously, periodically, or episodically. The baroreceptor activation device may comprise a wide variety of devices which utilize electrodes to directly or indirectly activate the baroreceptor. The baroreceptor may be activated directly, or activated indirectly via the adjacent vascular tissue. The baroreceptor activation device will be positioned outside the vascular wall. To maximize therapeutic efficacy, mapping methods may be employed to precisely locate or position the baroreceptor activation device. [0015] The present invention is directed particularly at electrical means and methods to activate baroreceptors, and various electrode designs are provided. The electrode designs may be particularly suitable for connection to the carotid arteries at or near the carotid sinus, and may be designed to minimize extraneous tissue stimulation. While being particularly suitable for use on the carotid arteries at or near the carotid sinus, the electrode structures and assemblies of the present invention will also find use for external placement and securement of electrodes about other arteries, and in some cases veins, having baroreceptor and other electrically activated receptors therein. [0016] In a first aspect of the present invention, a baroreceptor activation device or other electrode useful for a carotid sinus or other blood vessel comprises a base having one or more electrodes connected to the base. The base has a length sufficient to extend around at least a substantial portion of the circumference of a blood vessel, usually an artery, more usually a carotid artery at or near the carotid sinus. By "substantial portion," it is meant that the base will extend over at least 25% of the vessel circumference, usually at least 50%, more usually at least 66%, and often at least 75% or over the entire circumference. Usually, the base is sufficiently elastic to conform to said circumference or portion thereof when placed therearound. The electrode connected to the base is oriented at least partly in the circumferential direction and is sufficiently stretchable to both conform to the shape of the carotid sinus when the base is conformed thereover and accommodate changes in the shape and size of the sinus as they vary over time with heart pulse and other factors, including body movement which causes the blood vessel circumference to change. [0017] Usually, at least two electrodes will be positioned circumferentially and adjacent to each other on the base. The electrode(s) may extend over the entire length of the base, but in some cases will extend over less than 75% of the circumferential length of the base, often being less than 50% of the circumferential length, and sometimes less than 25% of the circumferential length. Thus, the electrode structures may cover from a small portion up to the entire circumferential length of the carotid artery or other blood vessel. Usually, the circumferential length of the elongate electrodes will cover at least 10% of the circumference of the blood vessel, typically being at least 25%, often at least 50%, 75%, or the entire length. The base will usually have first and second ends, wherein the ends are adapted to be joined, and will have sufficient structural integrity to grasp the carotid sinus. [0018] In a further aspect of the present invention, an extravascular electrode assembly comprises an elastic base and a stretchable electrode. The elastic base is adapted to be conformably attached over the outside of a target blood vessel, such as a carotid artery at or near the carotid sinus, and the stretchable electrode is secured over the elastic base and capable of expanding and contracting together with the base. In this way, the electrode assembly is conformable to the exterior of the carotid sinus or other blood vessel. Preferably, the elastic base is planar, typically comprising an elastomeric sheet. While the sheet may be reinforced, the reinforcement will be arranged so that the sheet remains elastic and stretchable, at least in the circumferential direction, so that the base and electrode assembly may be placed and conformed over the exterior of the blood vessel. Suitable elastomeric sheets may be composed of silicone, latex, and the like. [0019] To assist in mounting the extravascular electrode over the carotid sinus or other blood vessel, the assembly will usually include two or more attachment tabs extending from the elastomeric sheet at locations which allow the tabs to overlap the elastic base and/or be directly attached to the blood vessel wall when the base is wrapped around or otherwise secured over a blood vessel. In this way, the tabs may be fastened to secure the backing over the blood vessel. [0020] Preferred stretchable electrodes comprise elongated coils, where the coils may stretch and shorten in a spring-like manner. In particularly preferred embodiments, the elongated coils will be flattened over at least a portion of their lengths, where the flattened portion is oriented in parallel to the elastic base. The flattened coil provides improved electrical contact when placed against the exterior of the carotid sinus or other blood vessel. Continue reading about Automatic baroreflex modulation based on cardiac activity... Full patent description for Automatic baroreflex modulation based on cardiac activity Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Automatic baroreflex modulation based on cardiac activity patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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