Abstract:
A device positionable on a vascular structure for stimulating the vascular structure to elicit a physiologic response. The device includes a base having generally opposed inner and outer surfaces and a hydrophilic material presented on at least a portion of the inner surface presenting a lubricious surface for selectively positioning the device on the vascular structure. The device further includes an electrode structure presented with the base to provide stimulation to the vascular structure, wherein the base and electrodes are configured to conform to at least a portion of the vascular structure to maintain an intimate vascular structure-electrode interface.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to implantable devices for treating and managing cardiovascular and renal disorders. More particularly, the present invention relates to hydrophilic coatings for implantable vessel stimulation devices enabling efficient device placement and effective vessel-device interfaces while facilitating the inhibition of inflammatory responses and thrombus and fibrosis formation at implantation sites. 
         [0003]    Hypertension (high blood pressure) is a major cardiovascular disease estimated to affect millions people annually in the United Sates alone. Hypertension occurs when the body&#39;s smaller blood vessels constrict causing an increase in blood pressure. Because the blood vessels constrict, the heart generally must work harder to maintain blood flow at the higher pressures. Although the body can tolerate shorter periods of increased blood pressure, sustained hypertension can eventually result in damage to the kidneys, brain, eyes, and other tissues. The elevated blood pressure can also damage the lining of the blood vessels, accelerating atherosclerosis and increasing the likelihood of a blood clot forming that can lead to a heart attack and/or stroke. Sustained high blood pressure can also result in an enlarged and damaged heart that can lead to heart failure. Heart failure is the final common expression of a variety of cardiovascular disorders, including ischemic heart disease, and is characterized by an inability of the heart to pump enough blood to meet the body&#39;s needs. 
         [0004]    Heart failure often results in the activation of a number of body systems to compensate for the heart&#39;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, in addition to the activation of multiple other neurohormonal responses. Generally, 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. It also 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 heart failure. 
         [0005]    The wall of the carotid sinus, a structure at the bifurcation of the common carotid arteries, contains stretch receptors (baroreceptors) 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 control of the sympathetic nervous system. 
         [0006]    Electrical stimulation of the carotid sinus (baropacing) has been used to treat high blood pressure and angina by reducing blood pressure and the workload of the heart. For example, U.S. Pat. No. 6,073,048 to Kieval et al. discloses systems and devices for activating baroreceptors, indicating an increase in blood pressure and signaling the brain to reduce the body&#39;s blood pressure and level of sympathetic nervous system and neurohormonal activation and increase parasympathetic nervous system activation. 
         [0007]    Baroreceptor activation devices can be positioned either within the carotid artery (intravascular) or external to the carotid arteries (extravascular). When intravascular, the activation devices can be placed inside a vessel, such as near the baroreceptors at the carotid sinus where the carotid artery bifurcates into an external carotid artery and an internal carotid artery. Care generally must be taken when placing any device intravascularly, as interaction between the device and vascular lumen can present potential for damage to the device and or the inner walls of the vascular lumen. 
         [0008]    When using extravascular baroreceptor activation devices, the devices can be placed on or about an exterior portion of a vessel and selectively positioned near the baroreceptors, such as at the carotid sinus where the carotid artery bifurcates into an external carotid artery and an internal carotid artery. As with intravascular activation devices, care generally must be taken when placing an extravascular activation device near the baroreceptors at the carotid sinus, as any friction between the device and vascular wall can present potential for damage to the device and or the outer wall of a vascular lumen, and may cause constrictions or turbulence within the vessel. 
         [0009]    Moreover, the functionality of the device can depend upon the inner surface of the device being effectively coupled and in good contact with the exterior vascular surface, such that effective mechanical, electrical, thermal, chemical, biological, or other activation of the wall or structure in the wall can occur. However, when extravascular devices are implanted in the body and placed or about a vascular structure, an immune response can cause an inflammatory response followed by encapsulation of the internal surface of the device with tissue. When this type of response occurs, the mechanical, electrical, thermal, chemical, or biological characteristics of the vessel-electrode interface can degrade causing the device to fail or function ineffectively. 
         [0010]    Further, tissue building up on the exterior of the device can potentially contract the device on the artery, for example, can cause a false parameter indicative of the need to modify the baroreflex system activity. For example, in a baroreceptor activation device, this can then lead the control system to generate a control signal activating the baroreceptor activation device to induce a baroreceptor signal that is perceived by the brain to be apparent excessive blood pressure. 
         [0011]    Therefore, it would be desirable to produce an improved implantable vessel stimulation device overcoming deficiencies with existing designs. 
         [0012]    2. Description of the Background Art 
         [0013]    Certain types of implantable baroreceptor activation devices are designed to be placed over an artery or vessel (extravascular). For example, particular implantable conductive baroreceptor activation device structures (e.g., electrodes) can be wrapped around a carotid sinus or other vascular structure. Examples of such electrodes are disclosed in U.S. Patent Publication No. 2003/0060857, U.S. Patent Publication No. 2004/0010303, U.S. Patent Publication No. 2006/0004430, and U.S. Patent Publication No. 2006/0111626. The electrode structures can be held in place on or about the carotid artery, for example, proximate a baroreceptor to enable baroreceptor stimulation to induce the baroreflex to control hypertension or other conditions. 
       BRIEF SUMMARY OF THE INVENTION 
       [0014]    The vessel stimulation methods according to the various embodiments of the present invention generally include directing stimulation to a vessel wall for the purposes of eliciting a physiologic response. The method can include providing a device having a base structure having a hydrophilic material presented therewith and an electrode structure thereon. The method further can include selectively positioning the device on a vessel wall, extending the base structure around at least a portion thereof, and activating, deactivating, or otherwise modulating the device to provide stimulation to the vessel wall with the electrode for the purposes of eliciting a physiologic response. The method can also include determining an effective position for providing stimulation to the vessel wall before or during selectively positioning the device on the vessel wall. The determination step can include applying an electrical stimulus and observing a response. 
         [0015]    In various embodiments as described herein, the step of providing stimulation to the vessel wall can be for purposes of eliciting a baroreflex response. Specifically, the vessel wall can include one or more baroreceptors therein, wherein the step of selectively positioning the device on the vessel wall comprises determining the location of the one or more baroreceptors and effecting movement of the device such that the device is proximate the one or more baroreceptors. The step of activating, deactivating, or otherwise modulating the device can be used to provide stimulation to the vascular structure for purposes of eliciting the baroreflex response by activating a baroreceptor or nerves emanating therefrom. 
         [0016]    The baroreceptor active device according to various embodiments of the present invention is selectively positionable on a vascular structure for providing stimulation to the vascular structure for purposes of eliciting a baroreflex response. The device includes a base structure having inner and outer surfaces, typically on opposite sides of the base structure, and a hydrophilic material presented on at least a portion of the inner surface presenting a lubricious surface for selectively positioning the device on the vascular structure. The device further includes an electrode structure presented with the base structure operable to provide stimulation to the vascular structure, wherein the base structure and electrodes are configured to conform to at least a portion of the vascular structure to maintain an intimate vascular structure-electrode interface. 
         [0017]    In one embodiment, an anti-inflammatory agent can be presented with the hydrophilic material. In some embodiments, the base structure can include electrical insulation, such that the stimulation is directionally provided toward the vascular structure. In another embodiment, the base structure can further include hydrophilic material disposed on the outer surface of the base structure. In another embodiment, the base structure can further include a hydrophobic material presented intermediate the hydrophilic material and the inner surface. In yet another embodiment, the base structure can further include a hydrophobic material presented intermediate the hydrophilic material and the inner surface and hydrophilic material disposed on the outer surface of the base structure. In one embodiment, the vascular structure includes a portion of a carotid artery and the base structure has a length enabling the base structure to extend substantially around the portion of the carotid artery conforming thereto. 
         [0018]    The method of providing stimulation to the vascular structure for purposes of eliciting a baroreflex response according to the various embodiments includes providing an extravascular device comprising a base structure having a hydrophilic material presented therewith and an electrode structure thereon, selectively positioning the device on the vascular structure, extending the base structure around at least a portion of the vascular structure and optionally operably coupling the base structure thereto and selectively positioning and re-positioning the device on the vascular structure. The hydrophilic material can provide a lubricious surface for effecting movement of the device with respect to the vascular structure during positioning and re-positioning, and activating, deactivating, or otherwise modulating the device to provide stimulation to the vascular structure. 
         [0019]    In an embodiment, the method can also include determining an effective position for providing stimulation to the vascular structure before or during selectively positioning the device on the vascular structure. The step of determining an effective position can include applying an electrical stimulus and observing a response. 
         [0020]    In one embodiment, the device can include a belt mechanism comprising a strap and a buckle, wherein the step of operably coupling the base structure to the vascular structure comprising engaging the strap with the buckle such that the buckle retains at least a portion of the strap. The step of operably coupling the base structure to the vascular structure can also include suturing the base structure to the vascular structure. The base structure can include a hydrophobic material presented therewith enabling adhesion between the vascular structure and hydrophobic material. 
         [0021]    The vascular structure can be a carotid artery having baroreceptors therein, wherein the step of selectively positioning the device on the vascular structure includes determining the location of one or more baroreceptors by, for example, measuring the efficacy of a stimulation and effecting movement of the device such that the device is more optimally positioned relative to one or more baroreceptors. 
         [0022]    A method of selectively positioning a device on a vascular structure for providing stimulation to the vascular structure for purposes of eliciting a physiologic response according to the various embodiments can include providing a base structure having a hydrophilic material presented therewith and one or more electrodes thereon, selectively positioning the device on the vascular structure, wherein the hydrophilic material provides a lubricious surface between the base structure and the vascular structure during positioning, and extending the base structure around at least a portion of the vascular structure and optionally operably coupling the base structure thereto, and selectively re-positioning the device on the vascular structure. 
         [0023]    In an embodiment, the method can further include determining an effective position for providing stimulation to the vascular structure before or during selectively positioning or re-positioning the device on the vascular structure, said step of determining an effective position comprising applying an electrical stimulus and observing a response. 
         [0024]    In another embodiment, the device can include a belt mechanism having a strap and a buckle, the step of operably coupling the base structure to the vascular structure comprising engaging the strap with the buckle such that the buckle retains at least a portion of the strap and such that the strap can be selectively released to facilitate any re-positioning of the device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a schematic view of an upper torso of a human body depicting the major arteries and veins and associated anatomy; 
           [0026]      FIG. 2  is a cross-sectional schematic view of a carotid sinus and baroreceptors within a vascular wall of the carotid sinus; 
           [0027]      FIG. 3  is a schematic view of the baroreceptors within a vascular wall and a baroreflex system; 
           [0028]      FIG. 4  is a schematic view of an upper torso of a human body depicting an intravascular baroreceptor activation system and device disposed near baroreceptors within the vascular wall of the carotid sinus; 
           [0029]      FIG. 5  is a close-up view of the carotid sinus of  FIG. 4  depicting the intravascular baroreceptor activation device disposed proximate baroreceptors within the vascular wall at the bifurcation of the carotid artery; 
           [0030]      FIGS. 6   a - 6   d  are cross sectional views of various embodiments of the intravascular baroreceptor activation device of  FIG. 5 , depicting single or multi-layer coatings presented on an exterior surface thereof; 
           [0031]      FIG. 7  is a schematic view of an upper torso of a human body depicting an extravascular baroreceptor activation system and device disposed near baroreceptors within the vascular wall of the carotid sinus; 
           [0032]      FIG. 8  is a close-up view of the carotid sinus of  FIG. 7  depicting the extravascular baroreceptor activation device disposed proximate baroreceptors within the vascular wall proximate the bifurcation of the carotid artery; 
           [0033]      FIGS. 9-12  are schematic views of various embodiments of the extravascular electrode device disposed at the carotid sinus for extravascular electrical activation; 
           [0034]      FIGS. 13   a  and  13   b  are cross sectional views of wire electrode embodiments of the extravascular baroreceptor activation device of  FIGS. 9-12 , depicting single or multi-layer coatings presented on an exterior surface thereof; 
           [0035]      FIGS. 14   a  and  14   b  are cross sectional views of ribbon electrode embodiments of the extravascular baroreceptor activation device of  FIGS. 9-12 , depicting single or multi-layer coatings presented on an exterior surface thereof; 
           [0036]      FIGS. 15   a  and  15   b  are cross sectional views of foil electrode embodiments of the extravascular baroreceptor activation device of  FIGS. 9-12 , depicting single or multi-layer coatings presented on an exterior surface thereof; 
           [0037]      FIGS. 16-17  are schematic views of an extravascular electrode device disposed at the carotid sinus for extravascular electrical activation; 
           [0038]      FIGS. 18   a - 18   d  are cross-sectional views of electrode embodiments of an extravascular baroreceptor activation device, depicting single or multi-layer coatings on the inner and or outer surfaces of the extravascular baroreceptor activation device; 
           [0039]      FIG. 19  is a schematic view an extravascular electrical activation device and a tether disposed about the internal carotid artery and common carotid artery, respectively; 
           [0040]      FIG. 20  is an elevational view of an extravascular electrode according to a further embodiment; 
           [0041]      FIG. 21  is the extravascular electrode of  FIG. 20  coupled with the common carotid artery near the carotid bifurcation; 
           [0042]      FIG. 22  depicts the electrode of  FIG. 20  coupled with the internal carotid artery near the carotid artery bifurcation; 
           [0043]      FIG. 23  depicts the electrode of  FIG. 22 , wherein the carotid artery bifurcation has a different geometry; 
           [0044]      FIG. 24  depicts the extravascular electrode of  FIG. 20  further including a belt mechanism, wherein the electrode is coupled with the common carotid artery near the carotid artery bifurcation; and 
           [0045]      FIG. 25  depicts the extravascular electrode of  FIG. 20  further including an aperture and matching protrusion, wherein the electrode is coupled with the common carotid artery near the carotid artery bifurcation. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0046]    Referring to  FIG. 1 , an upper torso of a human body  40  is depicted with some of the major arteries and veins of the cardiovascular system. The left ventricle of the heart  42  pumps oxygenated blood up into the aortic arch  44 . The right subclavian artery  46 , the right common carotid artery  48 , the left common carotid artery  50 , and the left subclavian artery  52  branch off the aortic arch  44  proximal of the descending thoracic aorta  54 . A distinct vascular segment referred to as the brachiocephalic artery  56  connects the right subclavian artery  46  and the right common carotid artery  48  to the aortic arch  44 . The right common carotid artery  48  bifurcates into the right external carotid artery  58  and the right internal carotid artery  60  at the right carotid sinus  62 . The left carotid artery (not depicted) similarly bifurcates into the left external carotid artery and the left internal carotid artery at the left carotid sinus. 
         [0047]    From the aortic arch  44 , oxygenated blood flows into the common carotid arteries  48 ,  50  and the subclavian arteries  46 ,  52 . From the common carotid arteries  48 ,  50 , oxygenated blood circulates through the head and cerebral vasculature and oxygen depleted blood returns to the heart  42  by way of the jugular veins, of which only the right internal jugular vein  64  is depicted. From the subclavian arteries  46 ,  52 , oxygenated blood circulates through the upper peripheral vasculature and oxygen depleted blood returns to the heart  42  by way of the subclavian veins, of which only the right subclavian vein  66  is depicted. The heart  42  pumps the oxygen depleted blood through the pulmonary system where it is re-oxygenated. The re-oxygenated blood returns to the heart  42 , which pumps the re-oxygenated blood into the aortic arch  44  as described above. This cycle repeats. 
         [0048]    Referring to  FIGS. 2 and 3 , baroreceptors  68  are located within the arterial walls of the right and left common carotid arteries (near each of the right carotid sinus and left carotid sinus), arterial walls of the aortic arch, subclavian arteries, brachiocephalic artery, and other arteries and veins. The baroreceptors  68  located within the vascular walls of the right common carotid artery  48  near the right carotid sinus  62  will be described herein. Baroreceptors  68  are a type of stretch receptor used by the body to sense blood pressure. An increase in blood pressure causes the arterial wall  70  to stretch and a decrease in blood pressure causes the arterial wall  70  to return to its original size. Such a cycle is repeated with each beat of the heart. Because baroreceptors  68  are located within the arterial wall  70 , they are able to sense deformation of the adjacent tissue that is indicative of a change in blood pressure. The baroreceptors  68  located in the right carotid sinus  48 , the left carotid sinus, and the aortic arch play a significant role in sensing blood pressure that affects the baroreflex system. 
         [0049]    A schematic view of baroreceptors  68  disposed in a generic vascular wall  70  is depicted in  FIG. 3  with a schematic flow chart of the baroreflex system  72 . Baroreceptors  68  are generally profusely distributed within the vascular walls  70  of the major arteries discussed above to generally form an arbor  74 . The baroreceptor arbor  74  comprises a plurality of baroreceptors  68 , each of which can transmit baroreceptor signals to the brain  76  via a nerve  78 . The baroreceptors  68  are so profusely distributed and arborized within the vascular wall  70  that discrete baroreceptor arbors  74  can be generally indiscernible. Those skilled in the art will recognize that the baroreceptors  68  as depicted in  FIGS. 2 and 3  are schematic for illustration and discussion purposes. It will be understood that activation of the baroreflex response for purposes of the present invention can be accomplished by activating a baroreceptor, mechanoreceptors, pressoreceptors, other baroreceptor-like tissue, or nerves emanating therefrom or associated therewith. 
         [0050]    Baroreceptor signals are used to activate a number of body systems which collectively can be referred to as the baroreflex system  72 . Baroreceptors  68  are connected to the brain  76  via a nerve  78  and the nervous system  80 . Thus, the brain  76  is able to detect changes in blood pressure that is indicative of cardiac output  86 . If cardiac output  86  is insufficient to meet demand (i.e., the heart is unable to pump sufficient blood), the baroreflex system  72  activates a number of body systems, including the heart  42 , kidneys  82 , vessels  84 , and other organs/tissues. Such activation of the baroreflex system  72  generally corresponds to an increase in neurohormonal activity. Specifically, the baroreflex system  72  initiates a neurohormonal sequence that signals the heart  42  to increase heart rate and increase contraction force in order to increase cardiac output  86 , signals the kidneys  82  to increase blood volume by retaining sodium and water, and signals the vessels  84  to constrict to elevate blood pressure. The cardiac, renal and vascular responses increase blood pressure and cardiac output  86 , and thus increase the workload of the heart  42 . In a patient with heart failure, this further accelerates myocardial damage and exacerbates the heart failure state. 
         [0051]    Referring to  FIGS. 4 and 7 , baroreceptor activation systems  88  (FIG.  4 —intravascular  88 ′ and FIG.  7 —extravascular  88 ″) generally comprises a control system  92 , a baroreceptor activation device  90  (intravascular  90 ′ and/or extravascular  90 ″), and can comprise one or more sensors  93 . The sensors  93  can sense and/or monitor a parameter (e.g., cardiovascular function) indicative of the need to modify the baroreflex system and generates a signal indicative of the parameter. The control system  92  generates a control signal as a function of the received sensor signal. The control signal activates, deactivates or otherwise modulates the baroreceptor activation device  90 . Activation of the device  90  can result in activation of the baroreceptors  68  and/or nerves emanating therefrom. Alternatively, deactivation or modulation of the baroreceptor activation device  90  can cause or modify deactivation of the baroreceptors  68  and/or associated nerves. 
         [0052]    The baroreceptor activation device  90  can comprise one of a wide variety of devices utilizing mechanical, electrical, thermal, chemical, biological, or other means to activate baroreceptors  68 . Thus, when the sensor  93  detects a parameter indicative of the need to modify the baroreflex system  72  activity (e.g., excessive blood pressure), the control system  92  can generate a control signal to modulate the baroreceptor activation device  90  thereby inducing a baroreceptor signal that is perceived by the brain to be apparent excessive blood pressure. When the sensor  93  detects a parameter indicative of normal body function (e.g., normal blood pressure), the control system  92  generates a control signal to modulate (e.g., deactivate) the baroreceptor activation device  90 . 
         [0053]    The baroreceptor activation device  90  can indirectly activate one or more baroreceptors  68  by stretching or otherwise deforming the vascular wall  70  surrounding the baroreceptors  68 . In other embodiments, the baroreceptor activation device  90  can directly activate one or more baroreceptors  68  by changing the electrical, thermal, or chemical environment or potential across the baroreceptors  68 . Changing the electrical, thermal, or chemical potential across the tissue surrounding the baroreceptors  68  can also cause the surrounding tissue to stretch or otherwise deform, thus mechanically activating the baroreceptors  68  in addition to electrically, thermally, or chemically activating the baroreceptors  68 . 
         [0054]    The baroreceptor activation devices  90  described below (intravascular  90 ′ and extravascular  90 ″) can generally be suitable for implantation, and are preferably implanted using a minimally invasive percutaneous translumenal approach and/or a minimally invasive surgical approach, depending on whether the device is disposed intravascular, extravascular, or within the vascular wall. 
         [0055]    The baroreceptor activation device  90  can be positioned anywhere baroreceptors  68  affecting the baroreflex system  72  are numerous, such as in the heart  42 , in the aortic arch  44 , in the common carotid arteries  48 ,  50  near the carotid sinus, in the subclavian arteries  46 ,  52 , or in the brachiocephalic artery  56  or other arteries or veins. The baroreceptor activation device  90  can be implanted such that the device  90  is positioned immediately adjacent the baroreceptors  68 . The baroreceptor activation device  90  can be implanted near the right carotid sinus  62  and/or the left carotid sinus and/or the aortic arch  44 , where baroreceptors  68  have a significant impact on the baroreflex system  72 . For purposes of illustration only, the present embodiments are described with reference to baroreceptor activation device  90  positioned near the carotid sinus  62  in the right carotid artery  48 . 
         [0056]    Referring to  FIGS. 4 and 5 , an intravascular baroreceptor activation system  88 ′ is depicted. The intravascular baroreceptor activation system  88 ′ generally comprises an intravascular baroreceptor activation device  90 ′, a control system  92 , a sensor  93 , and a lead or line  94  operably coupling the baroreceptor activation device  90 ′ and control system  92 . The intravascular baroreceptor activation device  90 ′ can comprise, for example, an internal inflatable balloon, an internal deformable coil, or an internal conductive structure (e.g., an electrode). The internal inflatable balloon and internal deformable coil can indirectly activate baroreceptors  68  by stretching or otherwise deforming the vascular wall  70 . For example, upon inflation or deflation, the balloon can expand or return to its relaxed geometry such that the baroreceptors  68  and/or the vascular wall  70  are deformed or returned to its nominal state, respectively. With respect to the coil, upon activation or removal of the electrical current, the structure geometry can be changed such that the baroreceptors  68  and/or the vascular wall  70  are removed from or returned to their nominal state. Thus, by selectively changing the balloon or coil structure, the baroreceptors  68  adjacent thereto can be selectively activated or deactivated so that a baroreceptor signal can be induced to effect a change in the baroreflex system of a patient. 
         [0057]    The baroreceptor activation device  90 ′ can also be in the form of an intravascular electrically conductive structure (e.g., electrode). The electrode  90 ′ can serve the dual purpose of maintaining lumen patency while delivering electrical stimuli. To this end, the electrode  90 ′ can be implanted utilizing conventional intravascular stent and filter delivery techniques. The electrode  90 ′ can comprise a geometry enabling blood perfusion therethrough. The electrode  90 ′ can comprise electrically conductive material, which can be selectively insulated to establish contact with the inside surface of the vascular wall at desired locations, and limit extraneous electrical contact with blood flowing through the vessel and other tissues. 
         [0058]    The electrode  90 ′ can be connected to an electric lead  94 , which is operably connected to the control system  92 . By selectively activating, deactivating, or otherwise modulating the electrical control signal transmitted to the electrode  90 ′, electrical energy can be delivered to the vascular wall  70  to activate the baroreceptors  68 . As discussed previously, activation of the baroreceptors  68  can occur directly or indirectly. In particular, the electrical signal delivered to the vascular wall  70  by the electrode  90 ′ can cause the vascular wall  70  to stretch or otherwise deform thereby indirectly activating the baroreceptors  68  disposed therein. Alternatively, the electrical signals delivered to the vascular wall  70  by the electrode  90 ′ can directly activate the baroreceptors  68  and/or associated nerves. In either case, the electrical signal is delivered to the vascular wall  70  adjacent to the baroreceptors  68 . The electrode  90 ′ can also delivery thermal energy in addition to or in lieu of electrical energy by utilizing a semi-conductive material having a higher resistance such that the electrode  90 ′ resistively generates heat upon application of electrical energy. 
         [0059]    Various further embodiments are contemplated for the electrode  90 ′, including its design, implanted location, and method of electrical activation. These embodiments are described in detail in U.S. Patent Publication No. 2003/0060857, which is incorporated herein by reference in its entirety. 
         [0060]    Referring to  FIGS. 6   a - 6   d,  exemplary cross sections of the intravascular baroreceptor activation device  90 ′ are depicted. As stated, those skilled in the art will recognize that other cross-sectional electrode  90 ′ geometries enabling blood perfusion therethrough can be used. For example, the electrodes  90 ′ can comprise oval wire, rectangular ribbon, or foil formed of an electrically conductive and radiopaque material such as platinum or platinum iridium. 
         [0061]    The intravascular baroreceptor activation devices  90 ′ can comprise a core  98  and one or more single and/or multi-layer coatings disposed thereon. Such coatings can include hydrophilic and hydrophobic coatings  97 ,  98 , respectively. Examples of hydrophilic coatings for use with the intravascular baroreceptor activation device electrode are described in U.S. Pat. Nos. 7,056,533 and 6,706,408 and U.S. Patent Publication No 2003/0215649A1, all of which are incorporated herein by reference in their entirety. Examples of hydrophobic coatings for use with the intravascular baroreceptor activation device electrodes are described in U.S. Pat. No. 7,041,088 and U.S. Patent Publication No. 2006/0105018. 
         [0062]    As described above, the intravascular baroreceptor activation device  90 ′ can be implanted utilizing conventional intravascular stent and filter delivery techniques. Hydrophilic coatings  97  on the exterior surface of the intravascular baroreceptor activation device  90 ′ can provide a lubricious surface, reducing the amount of friction as the electrode  90 ′ is inserted into the artery and as the position of the device is adjusted. This can inhibit any damage to the artery and device  90 ′ during insertion. 
         [0063]    The hydrophilic coating  97  can also present a biocompatible and anti-thrombogenic surface inhibiting the formation of scar material and thromboses on or near the surface of the intravascular baroreceptor activation device  90 ′. By inhibiting such formation, effective blood perfusion through the device  90 ′ can be maximized and any turbulent blood flow at bifurcation of the carotid artery  62  and through the device  90 ′ can be reduced. 
         [0064]    In addition, inhibition of thromboses or scar material formation on an intravascular baroreceptor activation electrode  90 ′ can maximize the functionality of the electrode  90 ′ by not affecting the vessel-electrode interface. As stated, the functionality of the electrode  90 ′ can depend upon the electrode surface being in good contact with the internal surface of the carotid arteries, such that effective electrical activation of the baroreceptors can occur. By inhibiting or limiting the inflammatory response, and therefore limiting encapsulation of the device  90 ′ with scarring and/or thromboses, effective vessel-electrode interfacing can be accomplished and/or maintained. 
         [0065]    A hydrophobic coating  98  can also be provided on the intravascular baroreceptor activation device between the exterior surface thereof and the hydrophilic coating. The hydrophilic coating adjacent the lumen of the vessel can enable ease of insertion into position within the artery, while the hydrophobic layer can enable the promotion of long term adhesion once the intravascular baroreceptor activation device is properly positioned. 
         [0066]    Anti-inflammatory agents can also be included in one or more of the hydrophilic and/or hydrophobic coatings (e.g., steroid eluting electrodes), such as those described in U.S. Pat. No. 4,711,251, U.S. Pat. No. 5,522,874, and U.S. Pat. No. 4,972,848, all of which are incorporated herein by reference in their entirety. Such agents can reduce tissue inflammation at the chronic interface between the device (e.g., electrodes)  90 ′ and the vascular wall tissue, thereby increasing the efficiency of stimulus transfer, reducing power consumption, and maintaining activation efficiency. 
         [0067]    Referring to  FIGS. 6   a  and  6   b,  a hydrophilic coating  96  is disposed on the core  98  of the device  90 ′. In this embodiment, the hydrophilic coating  96  can provide a lubricious surface, reducing the amount of friction as the device  90 ′ is positioned in the artery. This can inhibit any damage to the artery and device  90 ′ during placement. The hydrophilic coating  96  can also inhibit the formation of thromboses or scar material on the inner lumen of the artery or outer surface of the device. 
         [0068]    Referring to  FIGS. 6   c  and  6   d,  a hydrophobic coating  97  can be disposed intermediate the hydrophilic coating  96  and the core  98 . In this embodiment, the hydrophilic coating  96  can provide a lubricious surface, reducing the amount of friction as the device  90 ′ is positioned in the artery. This can inhibit any damage to the artery and device  90 ′ during placement. The hydrophobic layer  97  can enable the promotion of long term adhesion once the intravascular baroreceptor activation device  90 ′ is properly positioned. 
         [0069]    Referring to  FIGS. 7 and 8 , an extravascular baroreceptor activation system  88 ″ generally comprises an extravascular baroreceptor activation device  90 ″, a control system  92 , a sensor  93 , and a lead or line  94  operably coupling the baroreceptor activation device  90 ″ and control system  92 . An extravascular baroreceptor activation device  90 ″ can comprise, for example, an external pressure cuff, an external deformable coil, an external flow regulator, a transducer, a fluid delivery device, a magnetic device, an external conductive structure (e.g., an electrode), or an external Peltier device. As with the intravascular baroreceptor activation device  90 ″, by selectively activating, deactivating, or otherwise modulating the extravascular baroreceptor activation device  90 ″, a baroreceptor signal can be induced to effect a change in the baroreflex system of a patient. 
         [0070]    Referring to  FIGS. 9-12 ,  16 , and  17 , various embodiments of the extravascular baroreceptor activation device  90 ″ in the form of electrodes disposed at the carotid artery  48  are depicted. The location of the carotid sinus  62  can be identified by a landmark sinus bulge  63 , which is typically located on the internal carotid artery  60  just distal of the bifurcation of the common carotid artery  48  into the external carotid artery  58  and the internal carotid artery  60 . The carotid sinus  62 , and in particular the sinus bulge  63  of the carotid sinus  62 , can contain a relatively high density of baroreceptors  68  in the vascular wall  70 . For this reason, it can be desirable to position the extravascular electrode activation device  90 ″ on and/or around the sinus bulge  63  to maximize baroreceptor  68  responsiveness and to minimize extraneous tissue stimulation. 
         [0071]    The electrodes  90 ″ are depicted schematically for purposes of illustrating various positions of the electrodes  90 ″ on and/or around the carotid sinus  62  and the sinus bulge  63 . In each of the embodiments, the electrodes  90 ″ can be monopolar, bipolar, or tripolar (anode-cathode-anode or cathode-anode-cathode sets). In addition to the embodiments depicted and described herein, further extravascular electrode  90 ″ designs are described in U.S. Patent Publication No. 2003/0060857, U.S. Patent Publication No. 2004/0010303, U.S. Patent Publication No. 2006/0004430, U.S. Patent Publication No. 2006/0111626, and co-pending U.S. Patent Application No. 60/805,707, entitled “IMPLANTABLE ELECTRODE ASSEMBLY UTILIZING A BELT MECHANISM FOR SUTURELESS ATTACHMENT,” all of which are incorporated by reference in their entirety. 
         [0072]    Referring to  FIG. 9 , specifically, the extravascular electrical activation devices  90 ″ can extend around a portion or the entire circumference of the carotid sinus  62  in a circular fashion. In  FIG. 10 , the electrodes  102  of the extravascular electrical activation device  90 ″ extend around a portion or the entire circumference of the carotid sinus  62  in a generally helical fashion. In the helical arrangement, the electrodes  102  can wrap around the sinus  62  any number of times to establish the desired contact and coverage. In the arrangement as depicted in  FIG. 11 , a single pair of electrodes  102  or multiple pairs of electrodes  102  can wrap around the sinus  62  multiple times to establish further contact and coverage. 
         [0073]    The electrode pairs  102  can extend from a point proximal of the sinus  62  or bulge  63  to a point distal of the sinus  62  or bulge  63  to ensure activation of baroreceptors  68  throughout the sinus  62  region. The electrodes  102  can be connected to a single channel or multiple channels. The plurality of electrode pairs  102  can be selectively activated for purposes of targeting a specific area of the sinus  62  to increase baroreceptor  68  responsiveness, or for purposes of reducing the exposure of tissue areas to activation to maintain baroreceptor  68  responsiveness during a long term. 
         [0074]    In  FIG. 12 , the electrodes  102  extend around the entire circumference of the sinus  62  in a criss-cross fashion. The criss-cross arrangement of the electrodes  102  enables contact with both the internal and external carotid arteries  58 ,  60  around the carotid sinus  62 . 
         [0075]    Referring to  FIGS. 13   a,    13   b,    14   a,    14   b,    15   a,  and  15   b,  various exemplary cross sections of the extravascular baroreceptor activation devices  90 ″ of  FIGS. 9-12  are depicted. The electrodes  102  can comprise round wire ( FIGS. 13   a  and  13   b ), rectangular ribbon ( FIGS. 14   a  and  14   b ), or foil ( FIGS. 15   a  and  15   b ), formed of an electrically conductive material, that can also be radiopaque, such as platinum or platinum iridium. Those skilled in the art will recognize that other cross-sectional electrode  90 ″ geometries can be used. 
         [0076]    The extravascular baroreceptor activation electrodes  102  can comprise a core  102  and one or more single and/or multi-layer coatings disposed thereon. Such coatings can include hydrophilic coatings  103  and hydrophobic coatings  105 . Hydrophilic coatings  103  on the surface of the electrodes  102  can provide a lubricious surface, reducing the amount of friction as the electrode  90 ″ is positioned onto the artery proximate the baroreceptors. This can inhibit any damage to the artery and device  90 ″ during implantation. 
         [0077]    The hydrophilic coating  103  can also present a biocompatible surface that facilitates the inhibition of the formation of scar material on or near the surface of the extravascular baroreceptor activation device  90 ″. Reducing or inhibiting such formation on an extravascular baroreceptor activation electrode  90 ″ can maximize the functionality of the baroreceptor activation device  90 ″ by not affecting the vessel-electrode interface. As discussed above, the functionality of the electrode  90 ″ can depend upon the electrode  90 ″ being in good contact with the internal surface of the vessel, such as the carotid arteries, in order that effective electrical activation of the baroreceptors can occur so that a baroreceptor signal can be induced to effect a change in the baroreflex system of a patient. By reducing or inhibiting the inflammatory response, and therefore encapsulation of the device  90 ″ with scarring and/or thromboses, a more effective vessel-electrode interface can be accomplished and/or maintained. 
         [0078]    A hydrophobic coating  105  can also be provided on the electrode  102  of the extravascular baroreceptor activation device  90 ″ between the exterior surface of the core  101  and the hydrophilic coating  103 . In this embodiment, the hydrophilic coating  103  adjacent the interior surface of the vessel can enable ease of positioning onto position in the artery. The hydrophobic layer  105  intermediate the core  101  and the hydrophilic coating  103  can enable the promotion of long term adhesion once the intravascular baroreceptor activation device  90 ″ is properly positioned. 
         [0079]    Anti-inflammatory agents can be included in one or more of the hydrophilic and/or hydrophobic coatings (e.g., steroid eluting electrodes), such as those described in U.S. Pat. No. 4,711,251, U.S. Pat. No. 5,522,874, and U.S. Pat. No. 4,972,848, all of which are incorporated herein by reference in their entirety. Such agents can reduce tissue inflammation at the chronic interface between the device  90 ″ (e.g., electrodes) and the vascular wall tissue, thereby increasing the efficiency of stimulus transfer, reducing power consumption, and maintaining activation efficiency. 
         [0080]    Referring to  FIGS. 16-17 , the extravascular electrical activation devices  90 ″ are depicted to include a substrate or base structure  100 , which can encapsulate or support the electrode pairs  102  and can provide a means for attachment to the sinus as described in more detail hereinafter. 
         [0081]    Referring to  FIGS. 18   a - 18   d,  various exemplary cross sections of the extravascular baroreceptor activation device  90 ″ of  FIGS. 16-17  are depicted. Each embodiment of the extravascular baroreceptor activation device  90 ″ can comprise a base  100  and at least one of a hydrophilic coating  104  and/or a hydrophobic coating  106  on an interior surface  110  and/or exterior surface  108  thereof. Examples of hydrophilic coatings  104  for use with the extravascular electrode activation device  90 ″ are described in U.S. Pat. Nos. 7,056,533 and 6,706,408 and U.S. Patent Publication No 2003/0215649A1, all of which are incorporated herein by reference in their entirety. Examples of hydrophobic coatings for use with the extravascular electrode activation device  90 ″ are described in U.S. Pat. No. 7,041,088 and U.S. Patent Publication No. 2006/0105018. 
         [0082]    Referring to  FIG. 18   a,  a hydrophilic coating  104  is disposed on the exterior surface  108  of the base  100 . A hydrophobic coating  106  is disposed on the interior surface  110  of the base. A second hydrophilic coating  104  is then disposed on the hydrophobic coating  106 . In this embodiment, the hydrophilic coating  104  on the hydrophobic coating  106  can provide a lubricious surface, reducing the amount of friction as the device  90 ″ is positioned on the artery. This can inhibit any damage to the artery and device  90 ″ during placement. The hydrophobic layer  106  can enable the promotion of long term adhesion once the extravascular baroreceptor activation device  90 ″ is properly positioned. The hydrophilic coating  104  on the exterior surface  108  of the electrode  102  can reduce or inhibit the formation of scar material on the exterior of the artery or interior surface of the electrode that otherwise could contract the electrode on the artery causing a false parameter indicative of the need to modify the baroreflex system activity causing the control system to generate a control signal activating the baroreceptor activation device to induce a baroreceptor signal that is perceived by the brain to be apparent excessive blood pressure. 
         [0083]    Referring to  FIG. 18   b,  a hydrophilic coating  104  is disposed on the exterior surface  108 . In this embodiment, the hydrophilic coating  104  adjacent the exterior surface of the vessel can provide a lubricious surface, reducing the amount of friction as the device  90 ″ is positioned on the artery. This can inhibit any damage to the artery and device  90 ″ during placement. 
         [0084]    Referring to  FIG. 18   c,  a hydrophobic coating  106  is disposed on the interior surface  110 . A second hydrophilic coating  104  is then disposed on the hydrophobic coating  106 . In this embodiment, the hydrophilic coating  104  on the hydrophobic coating  106  adjacent the exterior surface of the vessel can provide a lubricious surface, reducing the amount of friction as the device  90 ″ is positioned on the artery. This can inhibit any damage to the artery and device  90 ″ during placement. The hydrophobic layer  106  can enable the promotion of long term adhesion once the extravascular baroreceptor activation device  90 ″ is properly positioned. 
         [0085]    Referring to  FIG. 18   d,  hydrophobic coatings  106  are disposed on the interior and exterior surfaces  110 ,  108 . Hydrophilic coatings  104  are then disposed on the hydrophobic coating  106 . 
         [0086]    The base  100  in the various embodiments can comprise insulative properties, or insulation, such that the stimulation is directionally provided toward the vascular structure. 
         [0087]    From the foregoing discussion with reference to  FIGS. 9-12 ,  16 , and  17 , one skilled in the art will recognize that numerous arrangements can be used for the electrodes of the extravascular activation device. In each of the examples above, the electrodes are generally wrapped around a portion of the carotid structure, requiring deformation of the electrodes from their relaxed geometry (e.g., straight). To reduce such deformation, the electrodes and/or the base can comprise a relaxed geometry substantially conformable to the shape of the carotid anatomy at the point of attachment. In other words, the electrodes and the base structure or backing can be pre-shaped to generally conform to the vessel anatomy in a substantially relaxed state. Alternatively, the electrodes can have a geometry and/or orientation that reduce the amount of electrode strain. Optionally, the base can comprise elasticity or otherwise be stretchable to facilitate wrapping of and conforming to the carotid sinus or other vascular structure. 
         [0088]      FIG. 19  schematically depicts an extravascular electrical activation device  90 ″ including a support collar or anchor  112 . In this embodiment, the activation device  90 ″ is wrapped around or otherwise coupled to the internal carotid artery  60  at the carotid sinus  62 , and the support collar  112  is wrapped around or otherwise coupled to the common carotid artery  48 . The activation device  90 ″ is connected to the support collar  112  by cables  114 , which act as a loose tether. With this arrangement, the collar  112  isolates the activation device  90 ″ from movements and forces transmitted by the cables  114  proximal of the support collar  112 , such as can be encountered by movement of the control system  92 . As an alternative to support collar  112 , a strain relief (not depicted) can be connected to the base of the activation device  90 ″ at the juncture between the cables  112  and the base  100 . With either approach, the position of the device  90 ″ relative to the carotid anatomy can be better maintained despite movements of other parts of the system. 
         [0089]    In this embodiment, the base  100  of the activation device can comprise molded tube, a tubular extrusion, or a sheet of material wrapped into a tube shape utilizing a suture flap with sutures  116  as depicted. The base  100  can be formed of a flexible and biocompatible material such as silicone, which can be reinforced with a flexible material such as polyester fabric available under the trade name Dacron® to form a composite structure. The inside diameter of the base  100  can correspond to the outside diameter of the carotid artery at the location of implantation, for example 6 to 8 mm. The wall thickness of the base  100  can be very thin to maintain flexibility and a low profile, for example less than 1 mm. If the device  90 ″ is to be disposed about a sinus bulge  62 , a correspondingly shaped bulge can be formed into the base  100  for added support and assistance in positioning. 
         [0090]    The electrodes  102  (depicted in phantom lines) can comprise round wire, rectangular ribbon, or foil, formed of an electrically conductive and radiopaque material such as platinum or platinum iridium. The electrodes  102  can be molded into the base  100  or adhesively connected to the inside diameter thereof, leaving a portion of the electrode  102  exposed for electrical connection to carotid tissues. The electrodes  102  can encompass less than the entire inside circumference (e.g., 300°) of the base  100  to avoid shorting. The electrodes  102  can have any of the shapes and arrangements described previously. 
         [0091]    The support collar  112  can be formed similarly to base  100 . For example, the support collar  112  can comprise molded tube, a tubular extrusion, or a sheet of material wrapped into a tube shape utilizing a suture flap with sutures  116  as depicted. The support collar  112  can be formed of a flexible and biocompatible material such as silicone, which can be reinforced to form a composite structure. The cables  114  are secured to the support collar  112 , leaving slack in the cables  114  between the support collar  112  and the activation device 
         [0092]    Those skilled in the art will recognize that it can be desirable to secure the activation device  90 ″ to the vascular wall  70  using sutures or other fixation means. For example, sutures can be used to maintain the position of the electrical activation device  90 ″ relative to the carotid anatomy (or other vascular site containing sites to be activated). Such sutures can be connected to base  100 , and pass through all or a portion of the vascular wall  70 . For example, the sutures can be threaded through the base structure, through the adventitia of the vascular wall, and tied. If the base  100  comprises a patch or otherwise partially surrounds the carotid anatomy, the corners and/or ends of the base  100  can be sutured, with additional sutures evenly distributed therebetween. In order to minimize the propagation of a hole or a tear through the base structure, a reinforcement material such as polyester fabric can be embedded in the silicone material. In addition to sutures, other fixation means can be employed such as, for example, staples or a biocompatible adhesive. 
         [0093]    The inner surfaces of the extravascular baroreceptor activation device  90 ″ and/or the collar can comprise a hydrophilic coating and/or hydrophobic coating thereon. The hydrophilic coatings on the interior surface of the extravascular baroreceptor activation device  90 ″ and/or the collar can provide a lubricious surface, reducing the amount of friction as the device  90 ″ and/or the collar are positioned on the artery. This can inhibit any damage to the artery, device  90 ″, and collar during placement. The coating can also provide a biocompatible surface inhibiting the formation of scar material on the exterior of the artery or interior surface of the electrode  90 ″ and collar that otherwise could contract the electrode and the collar on the artery causing a false parameter indicative of the need to modify the baroreflex system activity causing the control system to generate a control signal activating the baroreceptor activation device to induce a baroreceptor signal that is perceived by the brain to be apparent excessive blood pressure. 
         [0094]    In addition, by inhibiting the formation of scar material on the electrode, the functionality of the activation device  90 ″ can be maximized by optimizing the electrical characteristics of the vessel-electrode interface. As has been described, when using externally positioned electrodes, the functionality of the device can depend upon the inner surface of the device being in good contact with the exterior surface of the carotid arteries, such that effective activation of the baroreceptors can occur. 
         [0095]    The hydrophobic coating can also be provided to enable the promotion of long term adhesion of the extravascular activation device  90 ″ and/or the collar  112  once they are properly positioned. 
         [0096]    Referring now to  FIGS. 20-25 , a further electrode embodiment is depicted. Electrode  90 ″ comprises a base  100 , which can be elastic and formed silicone or other elastomeric material, having an electrode-carrying surface  118  and a plurality of attachment tabs  120  extending from the electrode-carrying surface  118 . The attachment tabs  120  can be formed from the same material as the electrode-carrying surface  118  or formed from other elastomeric materials. In the latter case, the base  100  will be molded, stretched, or otherwise assembled from the various pieces. In the illustrated embodiment, the attachment tabs  120  are formed integrally with the remainder of the base  100 , i.e., being cut from a single sheet of the elastomeric material. 
         [0097]    The geometry of the electrode  90 ″, and in particular the geometry of the base  100 , is selected to enable a number of different attachment modes to the blood vessel. In particular, the geometry of the device of  FIG. 20  is intended to enable attachment to various locations on the carotid arteries at or near the carotid sinus  62  and the bifurcation of the common carotid  48  into internal and external carotid arteries  58 ,  60 . 
         [0098]    A number of reinforcement regions  122  are attached to different locations on the base  100  to enable suturing, clipping, stapling, or other fastening of the attachment tabs  120  to each other and/or the electrode-carrying surface  118  of the base  100 . In an embodiment intended for attachment at or around the carotid sinus  62 , a first reinforcement strip  124  is provided over a first end  126  of the base  100  opposite to a second end  128  which carries the attachment tabs  120 . Pairs of reinforcement strips  130  and are provided on each of the axially aligned attachment tabs  120   a,  while similar pairs of reinforcement strips  130  are provided on each of the transversely angled attachment tabs  120   b.  In the illustrated embodiment, all attachment tabs  120  will be provided on one side of the base  100 , preferably emanating from adjacent corners of the rectangular electrode-carrying surface  118 . 
         [0099]    The structure of electrode  90 ″ enables the surgeon to implant the electrode  90 ″ so that the electrodes  102  (which can be stretchable, flat-coil electrodes) are located at a location relative to the target baroreceptors. The preferred location can be determined, for example, as described in U.S. Pat. No. 6,850,801, which is incorporated herein by reference in its entirety. 
         [0100]    Once the selected location for the electrodes  102  of the electrode assembly  90 ″ is determined, the surgeon can position the base  100  so that the electrodes  102  are located appropriately relative to the underlying tissue. Thus, the electrodes  102  can be positioned over the common carotid artery CC as depicted in  FIGS. 21 ,  24 , and  25 , or over the internal carotid artery IC, as depicted in  FIGS. 22-23 . In  FIG. 21 , the assembly can be attached by stretching the base  100  and axially aligned attachment tabs  120   a  over the exterior of the common carotid artery CC. The reinforcement tabs  122   a  can then be secured to the reinforcement strip  126 , either by suturing, stapling, fastening, gluing, welding, or other known mechanisms. Attachment tabs  120   b  can be cut off at their bases. 
         [0101]    In other cases, the bulge of the carotid sinus  62  and the baroreceptors can be located differently with respect to the carotid bifurcation. For example, as depicted in  FIGS. 22-23 , the receptors can be located further up the internal carotid artery IC so that the placement of electrode  90 ″ over the exterior of the common carotid artery CC as depicted in  FIG. 21  will generally not be as effective. The electrode  90 ″, however, can still be successfully attached by utilizing the transversely angled attachment tabs  120   b  rather than the central or axial tabs  120   a.  As depicted in  FIG. 22 , the lower tab  120   b ′ is wrapped around the common carotid artery CC, while the upper attachment tab  120   b ″ is wrapped around the internal carotid artery IC. The axial attachment tabs  120   a  will usually be cut off, although either of them could in some instances also be wrapped around the internal carotid artery IC. Again, the tabs  120   b  used can be stretched and attached to reinforcement strip  126 , as generally described above. 
         [0102]    Referring to  FIG. 23 , in instances where the carotid bifurcation has less of an angle, the assembly can be attached using the upper axial attachment tab  120   a ′ and be lower transversely angled attachment tab  120   b ′. Attachment tabs  120   a ″,  120   b ″ can be cut off. The elastic nature of the base  100  and the stretchable nature of the electrodes  102  enable the desired conformance and secure mounting of the electrode  90 ″ over the carotid sinus  62 . Those skilled in the art will recognize that these and/or similar structures can also be useful for mounting electrodes at other locations in the vascular system. 
         [0103]    Referring to  FIGS. 24 and 25 , mechanisms can be included on the device  90 ″ to facilitate the electrode attachment to the carotid artery. For example, in  FIG. 24 , a loop or slot  124  can be included on the rectangular electrode-carrying surface  118 . Once the preferred location for the electrodes  102  of the electrode assembly  90 ″ is determined, the surgeon can position the base  100  so that the electrodes  102  are located appropriately relative to the underlying baroreceptors. Thus, the electrodes  102  can be positioned over the common carotid artery CC, the assembly can be attached by stretching the base  100  and axially aligned attachment tabs  120   a  over the exterior of the common carotid artery CC. The axially aligned attachment tabs  120   a  can then be looped through the loop or slot  124 . Attachment tabs  120   b  can be cut off at their bases. 
         [0104]    Referring to  FIG. 25 , an aperture  126  and projection  128  can be included on the rectangular electrode-carrying surface  118 . Once the preferred location for the electrodes  102  of the electrode assembly  90 ″ is determined, the surgeon can position the base  100  so that the electrodes  102  are located appropriately relative to the underlying baroreceptors. Thus, the electrodes  102  can be positioned over the common carotid artery CC, the assembly can be attached by stretching the base  100  and axially aligned attachment tabs  120   a  over the exterior of the common carotid artery CC. The aperture  126  and projection  128  on the axially aligned attachment tabs  120   a  can then be coupled. Attachment tabs  120   b  can be cut off at their bases. 
         [0105]    As discussed above, the inner surfaces of the extravascular baroreceptor activation device  90 ″ can comprise a hydrophilic coating and/or hydrophobic coating thereon. The hydrophilic coatings on the interior surface of the extravascular baroreceptor activation device  90 ″ and/or the collar can provide a lubricious surface, reducing the amount of friction as the device  90 ″ and/or the collar are positioned on the artery. This can inhibit any damage to the artery, device  90 ′, and collar during placement. The coating can also provide a biocompatible surface inhibiting the formation of scar material on the exterior of the artery or interior surface of the electrode  90 ″ and collar, which otherwise could contract the electrode and the collar on the artery causing a false parameter indicative of the need to modify the baroreflex system activity causing the control system to generate a control signal activating the baroreceptor activation device to induce a baroreceptor signal that is perceived by the brain to be apparent excessive blood pressure. 
         [0106]    The hydrophobic coating can also be provided to enable the promotion of long term adhesion of the extravascular baroreceptor activation device  90 ″ once it is properly positioned. 
         [0107]    In addition, by inhibiting the formation of scar material on the electrode, the functionality of the baroreceptor activation device  90 ″ can be maximized by optimizing the electrical characteristics of the vessel-electrode interface. As has been described, when using externally positioned electrodes, the functionality of the device can depend upon the inner surface of the device being in good contact with the exterior surface of the carotid arteries, such that effective activation of the baroreceptors can occur. 
         [0108]    Although the devices herein have been described with reference to particular embodiments, one skilled in the art will recognize that changes can be made in form and detail. Specifically, while the devices and methods herein have been depicted and described with reference to activating, deactivating, or otherwise modulating a device to provide stimulation to a vascular structure for purposes of eliciting a baroreflex response, those skilled in the art will recognize that the methods and devices herein can be used for other types of stimulation directed to a vessel wall for the purposes of eliciting a physiologic response. Therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive. Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein.