DEVICES AND METHODS FOR TREATMENT OF HEART FAILURE VIA ELECTRICAL MODULATION OF A SPLANCHNIC NERVE

Abstract

Disclosed herein is a device, and method for treating heart failure by electrically modulating a splanchnic nerve with an implantable device.

Claims

1. A method of selecting a patient for a greater splachnic nerve blocking procedure to treat heart failure or symptoms associated with heart failure in the patient, comprising: evaluating the patient's splachnic vascular capacitance and determining whether or not the splachnic vascular capacitance is below normal; if the evaluated splachnic vascular capacitance is below normal, identifying a target greater splachnic nerve for a blocking procedure, wherein identifying the target greater splachnic nerve comprises temporarily blocking the identified greater splachnic nerve and measuring a physiological response to determine if the temporarily blocking produced a desired clinical result; if the temporary blocking produced the desired clinical result, performing the blocking procedure on the identified greater splachnic nerve.

2. The method of claim 1, wherein the evaluating step comprises performing at least one of an orthostatic stress test, a fluid challenge, an exercise test, and a drug challenge.

3. The method of claim 1, wherein the temporarily blocking step comprises electrically stimulating a greater splachnic nerve.

4. The method of claim 1, wherein performing the blocking procedure on the identified greater splachnic nerve comprises performing the blocking procedure with an implanted device.

5. A nerve cuff adapted to deliver blocking therapy and further adapted to confirm the the blocking therapy, comprising: a cuff sized and configured to be positioned around a greater splanchnic nerve; at least first, second, and third blocking therepy electrodes secured to the cuff and axially spaced from one another; at least one confirmation and stimulation electrode secured to the cuff and axially spaced from the first, second and third blocking therepy electrodes.

6. The nerve cuff of claim 5, wherein a distance between adjacent pairs of the first, second, and third blocking therepy electrodes is 1 to 2 mm.

7. The nerve cuff of claim 5, wherein the at least one confirmation and stimulation electrode comprises first and second confirmation and stimulation electrodes.

8. The nerve cuff of claim 7, wherein a distance between the first and second confirmation and stimulation electrodes is 2-3 mm.

9. A method of using the nerve cuff in claim 5, comprising: delivering blocking therepy with the first, second, and third blocking therepy electrodes to the greater splanchnic nerve; ceasing the delivery of blocking therepy; subsequent to the cessation step, stimulating the greater splachnic nerve with the at least one confirmation and stimulation electrode; and recording extracellular action potentials resulting from the stimulating step with at least one of the first, second, and third blocking therepy electrodes.

10. A method of increasing exercise capacity in a patient by blocking a greater splanchnic nerve, comprising: detecting that a patient has started to exercise; and after detecting that the patient has started to exercise and in response to the detection, delivering blocking therapy to a greater splanchnic nerve to increase the exercise capacity in a patient.

11. The method of claim 10, wherein delivering the blocking therapy comprising deliverying the blocking therepy with an implanted nerve cuff secured to the greater splanchnic nerve.

12. The method of claiim 10, further comprising assessing the effectiveness of the blocking therapy.

13. The method of claim 12, further comprising monitoring therapy effectiveness by measuring physiological signals.

14. A method of treating heart failure or symptoms associated with heart failure in a human patient, comprising: in a patient with heart failure or symptoms associated with heart failure; surgically accessing at least one thoracic nerve and optionally deflating the lung proximate to that nerve; and affixing an implantable neuromodulation device for applying nerve blocking therapy to said at least one nerve, said device comprising a stimulus producer for producing a nerve stimulus, and a delivery member for delivering stimulus to said nerve, wherein said stimulus has parameters able to cause a reversible blockage to the nerve conduction along the at least one thoracic nerve.

15. The method of claim 14, wherein the implantable neuromodulation device is affixed using a surgically implantable nerve cuff.

16. The method of claim 14, wherein said nerve is a greater splanchnic nerve, and at least one of a left greater splanchnic nerve and a right greater splanchnic nerve.

17. The method of claim 14, wherein surgically accessing is selected from the group consisting of transthoracic, transabdominal, percutaneous, access or any combination thereof.

18. A method of treating heart failure or symptoms associated with heart failure in a human patient, comprising: in a patient with heart failure or symptoms associated with heart failure, thoracoscopically accessing at least one greater splanchnic nerve and optionally deflating the lung proximate to that nerve, affixing an implantable neuromodulation device with a nerve cuff to said at least one nerve, said device further comprising a pulse generator, a detection member for detecting at least one physiological parameter, and at least one lead for delivering stimulus to said nerve through said nerve cuff, wherein said stimulus has parameters able to cause a reversible blockage to the nerve conduction along the at least one greater splanchnic nerve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Other advantages of the disclosure are made apparent in the following descriptions taken in conjunction with the provided drawings wherein are set forth, by way of illustration and example, certain exemplary embodiments of the present disclosure wherein:

[0039] FIG. 1 is an anatomical representation of the supply of sympathetic nerve fibers to organs of the human body.

[0040] FIG. 2 is a flow diagram showing the mechanisms of decompensated heart failure

[0041] FIG. 3 is a partial flow diagram showing the role of splanchnic compartment in blood volume distribution in heart failure.

[0042] FIG. 4 is a partial flow diagram showing the role of the therapeutic effects of disclosure to heart failure.

[0043] FIG. 5 is a graphical representation of pathophysiology of acute decompensated heart failure.

[0044] FIGS. 6A, 6B and 6C are representations of the electrical current in different cuff electrodes.

[0045] FIGS. 7A and 7B illustrate factors that determine minimal electrical blocking parameter.

[0046] FIG. 8 is a schematic diagram of patient lying in the lateral decubitus position having one camera port in the fifth intercostal space at the mid-axillary line and one instrument port placed at the anterior axillary line.

[0047] FIG. 9 is an axial cross section view of the upper thoracic region including one visualization port and two instrument ports accessing the paravertebral region where the thoracic splanchnic nerves lie.

[0048] FIG. 10 is a plot of aortic and ventricular pressure in response to electrical stimulation of a GSN in an animal study.

[0049] FIG. 11 is a schematic of the identification and exposure of the greater splanchnic nerve.

[0050] FIGS. 12A and 12B are schematic diagrams of nerve cuff configurations used to deliver blocking therapy.

[0051] FIG. 13 is a plot of mean arterial pressure over time showing response to stimulation of a blocked nerve.

[0052] FIG. 14 is a flowchart illustrating the steps from patient selection to permanent implantation.

[0053] FIG. 15 is a schematic diagram of IPG placement.

[0054] FIG. 16 is a functional block diagram that shows the components and the respective signal flow of components housed in an implantable pulse generator, or stimulus producer, for neuromodulation and cardiac electrical modulation.

[0055] FIG. 17 is a flowchart illustrating the steps for blocking therapy after exercise is detected.

[0056] FIG. 18 is a flowchart illustrating the steps for blocking therapy.

DETAILED DESCRIPTION

[0057] The present disclosure relates to medical devices and methods that offer treatment of heart disease, dysfunction and heart failure, particularly HFpEF through the mechanism of increased venous capacitance and relief of pulmonary congestion. The treatments are provided through electrical block of at least a portion of a splanchnic nerve (e.g., greater splanchnic nerve, lesser splanchnic nerve, least splanchnic nerve, splanchnic nerve roots, nerve fibers connected between the thoracic sympathetic trunk and celiac plexus) with a nerve cuff electrode implanted to impede or stop communication of a nerve signal along the blocked nerve, which can affect physiological responses that are directly or indirectly involved in the numerous factors of cardiovascular health.

[0058] FIG. 1 is an anatomical representation of the supply of sympathetic nerve fibers to organs of the human body. The SNS is part of the autonomic nervous system, which also includes the parasympathetic nervous system.

[0059] The SNS activates what is often termed the fight or flight response. Like other parts of the nervous system, the sympathetic nervous system operates through a series of interconnected neurons. Sympathetic neurons are frequently considered part of the peripheral nervous system, although there are many that lie within the central nervous system.

[0060] Sympathetic neurons of the spinal cord (which is part of the CNS) communicate with peripheral sympathetic neurons via a series of sympathetic ganglia. Within the ganglia, spinal cord sympathetic neurons join peripheral sympathetic neurons through chemical synapses. Spinal cord sympathetic neurons are therefore called presynaptic (or preganglionic) neurons, while peripheral sympathetic neurons are called postsynaptic (or postganglionic) neurons.

[0061] At synapses within the sympathetic ganglia, preganglionic sympathetic neurons release acetylcholine, a chemical messenger that binds and activates nicotinic acetylcholine receptors on postganglionic neurons. In response to this stimulus, postganglionic neurons principally release noradrenaline (norepinephrine). Prolonged activation can elicit the release of adrenaline from the adrenal medulla.

[0062] Once released, noradrenaline and adrenaline bind adrenergic receptors on peripheral tissues. Binding to adrenergic receptors causes the effects seen during the fight-or-flight response. These include pupil dilation, increased sweating, increased heart rate, and increased blood pressure.

[0063] Sympathetic nerves originate inside the vertebral column, toward the middle of the spinal cord in the intermediolateral cell column (or lateral horn), beginning at the first thoracic segment of the spinal cord and are thought to extend to the second or third lumbar segments. Because its cells begin in the thoracic and lumbar regions of the spinal cord, the SNS is said to have a thoracolumbar outflow. Thoracic splanchnic nerves (e.g., greater, lesser, or least splanchnic nerves), which synapse in the prevertebral ganglia are of particular interest for this disclosure.

[0064] FIG. 2 is a flow diagram showing the mechanisms of decompensated heart failure. It illustrates the role of sympathetic nerve activation 100 in the mobilization of venous reservoir 101 into the effective circulatory volume 102 leading to decompensation 103. Reversing, at least partially, by ablation of a greater splanchnic nerve, the sympathetic activation of splanchnic nerves is expected to relieve HF symptoms and reduce load on the failing heart.

[0065] A particular area of interest in the body is the splanchnic compartment, splanchnic vascular bed, or splanchnic reservoir, which include the vasculature of the visceral organs including the liver, spleen, small and large bowel, stomach as well as the pancreas. The splanchnic venous vascular bed serves as the major blood reservoir and can be affected by activation (e.g., stimulation) or deactivation (e.g., blocking or ablation) of splanchnic nerves and particularly of the greater splanchnic nerve (GSN) causing relaxation of veins, mobilization, release or uptake of venous blood from or to splanchnic vascular beds, respectively, and important changes in circulating blood volume.

[0066] The GSN may at least partially control splanchnic venous compliance and capacitance. Capacitance is reduced in CHF patients and particularly in some very hard to treat HFpEF patients as a part of overall elevated sympathetic state. The sympathetic fibers in the greater splanchnic nerve bundle that control contraction of splanchnic veins are the particular target of the proposed blocking therapy. In the context of this disclosure the GSN can mean right or left greater splanchnic nerve and electrical block and stimulation can be performed via an implanted nerve cuff electrode(s) or a bilateral treatment can be performed from nerve cuff electrodes implanted to access both right and left greater splanchnic nerves. The splanchnic congestion and high venous pressure is believed to adversely affect renal function and can be illustrated by hepatorenal syndrome that causes diuretic resistance. One theory is that the high portal vein pressure is sensed by mechanoreceptors in the portal venous system and signaled via neural reflex pathways to the kidney resulting in the retention of sodium and fluid. It is believed by inventors that the proposed block may at least partially reverse this phenomenon, improve renal function and enable diuretics to work (restore diuretic responsiveness).

[0067] FIG. 3 and FIG. 4 show some of the interactions between increases in sympathetic nervous system activity, including natural activity (e.g. rate of firing) of the GSN, and the storage of blood in the splanchnic bed. As illustrated by FIG. 3, increased central SNA 114, can manifest, at least partially, in the elevated activity of the GSN in all types of HF, resulting in a lower splanchnic capacitance and possibly stiffened, less-compliant splanchnic bed and regional effects including a decrease in the amount of blood stored in the splanchnic veins perfusing and surrounding the splanchnic organs (e.g., liver, spleen, pancreas, stomach, bowels) 110 and an increase in the amount of blood in central (and pulmonary) veins 112. The volume of blood in splanchnic veins or the splanchnic vascular bed 111 can be described as a venous reservoir, or unstressed volume and refers to the blood volume that does not contribute to the effective circulating volume and is therefore hidden from circulation or the hemodynamically hidden blood volume. The volume of blood in central veins 113 can be termed effective circulatory volume or stressed volume and refers to blood that is present mainly in the non-splanchnic veins and is one of the main determinants of preload to the heart and in CHF can contribute to venous congestion, high pulmonary circulation pressures and sensation of dyspnea.

[0068] Conversely, as illustrated by FIG. 4, decreased sympathetic nervous system activity or a splanchnic bed normalized with GSN blocking 120 may result in the compliance of the splanchnic bed, which may be relaxed or normalized from the stiff or contracted state. Blocking or inhibiting a target splanchnic nerve can result in a decrease of efferent sympathetic tone to smooth muscle in the walls of veins in the splanchnic vascular bed referred to as splanchnic venodilation resulting in an increase 121 in the volume of blood stored in the splanchnic bed 122 and a decrease 123 of volume of blood in the central veins 124 or in the overall decrease in sympathetic nervous system activity. Other effects of GSN blocking or inhibition may comprise reduction of pulmonary vascular pressure and pulmonary capillary wedge pressure that is index of left ventricular end-diastolic pressure, which are important measurable improvements in the treatment of HF. Understanding and utilizing these interactions are some of the primary aims of several embodiments disclosed herein. Specifically, the compliance and capacitance of splanchnic vasculature is desired to be increased.

[0069] FIG. 5 shows one possible clinical scenario in which the sympathetic hyperactivity of the greater splanchnic 126 nerve leads to the acceleration of fluid overload 127 and pulmonary venous congestion in a HFpEF patient. Preventable hospital admission of the HF patient is precipitated by the increase of pulmonary blood pressures in response to exercise that causes dyspnea upon exertion. This sensation can be partially explained by the patient's inability to buffer the sudden increase of venous blood volume and pressure caused by exercise that is transmitted to the pulmonary circulation and left atrium of the heart.

[0070] FIGS. 6A, 6B and 6C compares three different types of cuff electrodes including monopolar (FIG. 6A), bipolar (FIG. 6B), and tripolar (FIG. 6C). Electrical current paths of the compared types are shown. During high frequency biphasic stimulation (HFBS), when compared with a point electrode, the monopolar cuff electrode 130 (FIG. 6A) uses the electrical current more efficiently because the cuff limits the current flow 131 in a 2-dimensional space along a nerve. But, the electrical current coming into the monopolar cuff might not be equal on each end 132 and 133 of the cuff electrode 130, which could cause unintended stimulation at one end of the cuff. The current 131 on each side of the cuff is mainly determined by the tissue resistance on each side of the cuff and by the location of the remote reference electrode (not shown). In addition, although the reference electrode is located remotely, there is always a virtual anode 134 at each end of the cuff because the current always flows into the nerve at the cuff ends. For HFBS, the virtual anode is actually delivering HFBS at each end of the cuff causing an excitation or block depending on the stimulation intensity.

[0071] Similarly, a bipolar cuff electrode 135 (FIG. 6B) could produce a virtual anodal 136 or cathodal 137 electrode at each end of the cuff 135 depending on the tissue resistance within and around the cuff. For HFBS, these virtual electrodes could produce an unintended stimulation or blockade depending on stimulation intensity. The virtual electrodes 136 and 137 could produce variability and unpredictability in each clinical application because the tissue resistance in and around the cuff 135 could change with time. In acute animal experiments, this variability or unpredictability presented as variable blocking effects, i.e., sometimes the nerve was blocked but other times the nerve block failed depending on the blood or fluid accumulation in and around the cuff or the position of the nerve in the cuff

[0072] The tripolar cuff electrode 140 (FIG. 6C) effectively eliminates the virtual electrode problems (e.g., associated with a monopolar cuff or bipolar cuff) by connecting the two electrodes 142 at each end of the cuff thereby forcing the potentials at each end of the cuff to be equal (i.e., no electrical current 141 can flow outside the cuff). The tripolar cuff electrode may be an efficient minimal electrode cuff configuration because it maximally utilizes the current 141 for nerve stimulation when compared to the monopolar or bipolar cuff electrode. In order to fully utilize the efficiency, the inner diameter 143 of a tripolar cuff should closely fit the diameter of a nerve it is fitted to so that less current will flow in the space between the nerve and the electrode. The electrode spacing 144 should be 1 to 2 mm in general because the internodal distance of a nerve axon is about 100 times the axon diameter. For axons of 1 to 20 m in diameter, the internodal distances range from 0.1 mm to 2 mm. For electrical blocking of the target nerve (e.g., GSN, lesser splanchnic nerve, least splanchnic nerve, splanchnic nerve roots) that has an axon diameter less than 10 m, electrode spacing of 1 mm may be adequate.

[0073] Computational modeling results suggest that the minimum frequency needed to block nerve activity is determined by potassium channel kinetics. Since it is also known that at lower temperatures ion channel kinetics become slower, the minimal blocking frequency must decrease with temperature. FIG. 7A demonstrates how changes in temperature affect the minimum electrical frequency required to block axonal conduction for a nerve having an Axon diameter of 10 m. Thus, the minimum blocking frequency should be at least 6 kHz due to the temperature of the human body (37 C.). The minimum stimulation intensity needed to block the nerve (i.e., the block threshold) increases with increasing frequency for axons of different diameter (5 to 20 m), see FIG. 7B.

[0074] A non-limiting example of placing a therapy delivery device on a target site of the splanchnic nerves is described. FIG. 8 is a schematic illustration of a view looking down on a patient 81 that is positioned in a lateral decubitus position. Flexion of the table allows some separation of the ribs by dropping the patient's hips and therefore increasing the intercostal space 82 to work through. The ipsilateral arm is abducted on an arm holder. Rotating the table anteriorly and using reverse Trendelenburg positioning further maximizes the exposure to the superior paravertebral area by allowing the soon to be deflated lung 87 (FIG. 9) to fall away from the apical posterior chest wall 88.

[0075] The following procedure is an example and it is understood that a skilled thoracic surgeon can modify and improve it. The procedure begins by placing patient under general anesthesia and intubated via a double lumen endotracheal tube. The double lumen endotracheal tube permits ventilation of one lung 89 and collapse of the other lung 87 on the side of the thorax that is to be operated upon without using carbon dioxide insuflation. One incision is made in the midaxillary line seventh intercostal space that is identified as port 204. Port 204 can be used for various reasons, but it is preferred that port 204 is used as a telescopic video port, which may provide video assistance during the procedure. While under endoscopic observation, a second incision is made in the fifth intercostal space at the anterior axillary line that is identified as port 206. Port 206 is preferably used as an instrument channel. A third incision is made at the posterior axillary line in the sixth intercostal space that is identified as port 202. Port 202 is preferably used as a second instrument channel. Additional ports (or fewer) can be made as needed.

[0076] FIG. 9 is a schematic diagram of a transverse cross section of the surgical site. The surgical exposure of an area of interest 207 and preparation of the relevant portion of the GSN for treatment is described. Visualization during the procedure may be provided by a camera introduced via a port, e.g., port 204. After the lung 87 is collapsed, and if necessary, retracted down by a fanning instrument via one of the instrument ports (e.g., port 202), the pleural cavity 208 is inspected. The entire intrathoracic sympathetic chain (not shown) can be visualized under the parietal pleura. The greater splanchnic nerve (not shown) can be visualized through the parietal pleura from its first root to the diaphragmatic recess. Before making an incision, identification of the GSN can be confirmed. A needle or hook electrode can be introduced through one of the instrument ports and manipulated to penetrate the parietal pleura proximate to the GSN. After obtaining the desired position proximate to the GSN, the hook electrode is connected to an external electrical stimulator to deliver a stimulation signal and monitor physiological response to confirm GSN stimulation.

[0077] FIG. 10 illustrates a response to stimulation 146 of a GSN at a level just above the diaphragm in an animal experiment performed by the authors. The recognizable waveforms of increased aortic and left ventricular pressure reflect the physiologic response to electrical stimulation of the GSN. Similar increases were observed in central venous pressure, right atrial pressure and pulmonary artery pressure that can be measured and monitored in real time in any well-equipped modern catheterization laboratory by a trained cardiologist or surgeon.

[0078] After confirmation of GSN identification, the GSN 45 may be exposed and dissected from the fascia. FIG. 11 is a diagram showing exposure of a GSN 45. A pleural incision 70 from the level of T7 to the diaphragm 52 along the medial aspect of the GSN 45 is shown (FIG. 11). Electrocautery should not be used near the nerve, nerve branches or the cuff electrode. Dissection of the pleura 70 and tissue on both sides of the target nerve should be performed using fine instruments. The optimal location for implantation of the cuff electrode is as close the diaphragm 52 as possible. Prior to implanting a nerve cuff electrode, the diameter 161 of the GSN should be determined. A vessel loop of a known size should be used to estimate nerve diameter. It is possible to have cuffs of several diameters available to improve the cuff fit on the nerve.

[0079] In one embodiment, a nerve cuff electrode is tripolar in configuration. It is envisioned that more than 3 electrodes can be advantageous in some embodiments. The nerve cuff diameter will be approximately the same diameter as the nerve to optimize nerve to electrode contact but minimize nerve damage. Additionally, the nerve cuff assembly may include additional cuffs (with or without electrical contacts), proximal and/or distal to the active nerve cuff. The additional cuffs may be used to serve as strain relief for the active cuff electrode and aid in maintaining alignment of the active nerve cuff

[0080] A cuff 191 can be equipped with additional electrodes for nerve recording designed to pick up extracellular potentials that propagate along axons 190 (See FIGS. 12A and 12B). With the electrode connected to a suitable recording amplifier that can be part of the embedded electronics of the IPG (e.g., signal conditioning circuit and DAQ, see FIG. 16), a signal can be recorded whenever an action potential propagates along the nerve. The amplitude V of the recorded potential is a function of the extracellular action current amplitude, its wavelength and the length of the nerve portion that is between electrodes. Nerve potentials can be recorded if a length of nerve is encompassed by an insulating cuff with electrodes placed inside the cuff. The amplitude of the recorded signal depends non-linearly on the length of the insulated portion. To obtain maximal signal amplitudes the length of a nerve cuff should approximate wavelength to the extent possible. Since a GSN in humans can be dissected and cuffed at 2 to 4 cm of length, it is feasible. There is no further advantage to having the cuff length exceed wavelength. For large myelinated axons, optimal length ranges between 30 and 40 mm. As a rule, adequate signals are recorded during behavioral tasks when the cuff length is about 10 times greater than the cuff inside diameter. An essential prerequisite for recording nerve activity is to use an insulating cuff comprising an electrically insulating layer 192. A cuff wall permeable to electric current or an incompletely sealed cuff will allow nerve currents to leak out and, additionally, signals generated by structures outside the cuff by electromyographic (EMG) noise originating from nearby muscles and heart ECG may leak into the cuff and contaminate the recordings with unwanted noise. Therefore, cuff-recording electrodes will not be able to resolve nerve potentials from the noise unless the cuff is well sealed along its entire length.

[0081] A possible side-effect of the HFBS therapy includes undesired stimulation of muscle and pain nerves, for example, intercostal nerves and innervated fascia. In one embodiment, an isolating material may be inserted between the dissected nerve and the intercostal space. The isolating material serves to limit undesired stimulation, thus limiting possible pain associated with HFBS.

[0082] Another possible side-effect of HFBS may be a result of the initial nerve excitation during HFBS (or onset phenomenon). The mechanism by which HFBS provides its blocking action is believed to be through constantly activated potassium channels. HFBS generates an initial action potential because the potassium channel is not yet activated at the beginning of the HFBS. A possible means to limit onset phenomenon is to use a cascade of electrodes to create block of different strengths or gradually incremental partial blocks. The length of GSN available for implantation of the cuff electrode is approximately 3 to 4 cm long. Based on this, a nerve cuff with 5 to 12 or more electrodes is possible. In one embodiment, a 3 to 4 cm nerve cuff with 5 to 12 active electrodes is implanted on the GSN. Gradual HFBS of different strengths could be created. Each block could reduce conduction and onset would only come from the virtual electrodes at the edges of the cuff. The virtual electrodes proximate to the cuff edges would have less intensity, thus limiting possible side-effects from the onset phenomenon, especially on the afferent edge of the nerve where pain fibers may be a concern

[0083] Regardless of the modality of nerve block, embodiments of a device and method may further be configured to assist the blocking procedure with a means to confirm safety and efficacy prior to and following blocking. A means to confirm technical efficacy may comprise identification of a target nerve before blocking and absence of a target nerve signal transmission following the blocking. A means to confirm procedural efficacy may comprise temporarily blocking a target nerve to assess if a resulting physiologic response is representative of a desired clinical effect of the procedure.

[0084] Confirmation of efficacy may be assessed manually by a practitioner by observing the parameter measurements in real time. Alternatively, confirmation may be assessed automatically by the computerized system console that takes input from the physiologic monitoring equipment and compares it to a stimulation signal profile. Confirmation may also be performed by the software embedded in the IPG. Automatic changes to the block parameters (e.g. current intensity) can be made by software based on the results. Confirmation may include stimulation of the nerve proximate to the block and measurement of nerve activity distal to the block. Recording of nerve signals from nerve cuff electrodes is known.

[0085] Confirmation of blocking therapy effectiveness may be accomplished using nerve cuff designs shown in FIGS. 12A and 12B. One exemplary embodiment is illustrated in FIG. 12A. A nerve 190 (e.g., GSN) positioned inside a cuff 191 having four active electrodes is shown. The electrodes are embedded (or affixed) to an insulating material 192 (elastomeric cuff). The electrodes are numbered 1, 2, 3, and 4. This configuration provides a means to deliver electrical nerve blocking therapy and tests the effectiveness of the nerve block by recording stimulation-induced extracellular action potentials post-block. Electrodes 2, 3, and 4 may be used to deliver blocking therapy. An example of inter-electrode distance, d, between the electrodes to provide blocking therapy is 1 to 2 mm. The effects of the electrical blocking therapy is expected to last seconds to minutes after the blocking signal ends. During the post-block period, electrodes 2, 3 and 4 may be used to record extracellular action potentials generated by the proximal electrode 1 in a tri-polar recording configuration that promotes cancelation of common noise. Electrodes 2, 3, and 4 may be switched from delivering a high frequency block to recording extracellular potentials using embedded electronics such as an embodiment of an electrode configuration switch shown in FIG. 16. The DAQ and signal conditioning circuitry (FIG. 16) may provide for acquisition of the extracellular potential as well as filtering and amplification needed for recording. The stimulation via proximal electrode 1 is unipolar with the return electrode in a remote location (e.g., the IPG case). The electrodes may be connected to the IPG using wired connections (see wire 193). The connections provide communication between the nerve 190 and IPG for delivery of HFBS, recording, and nerve stimulation.

[0086] In another exemplary embodiment, a nerve cuff 195 has 5 active electrodes (FIG. 12B). In this example, the high frequency block therapy is delivered via electrodes 3, 4, and 5 in a tripolar configuration with electrode 4 acting as a cathode. During the post-block period, electrodes 3, 4, and 5 are used to record the stimulation-induced extracellular action potential. The proximal stimulus may be delivered via proximal electrodes 1 and 2 where the stimulus is bipolar. An example of the inter-electrode distance, d, between the bipolar stimulation electrodes is 2 to 3 mm.

[0087] To facilitate a clinically effective procedure, an embodiment may involve confirming that a patient will experience the desired physiologic effect of blocking before final implantation. This may be achieved by electrically blocking the nerve temporarily and observing a physiologic response (e.g., hemodynamic effect). If potential clinical success is assessed to have a physiologic response as desired then permanent implantation may proceed. Conversely, if the physiologic response to temporary blocking is not as desired a physician may decide to not proceed with implantation. Another option is to access the contralateral GSN and evaluate the clinically efficacy.

[0088] To confirm this notion FIG. 13 illustrates an experiment where the hemodynamic response to a greater splanchnic nerve stimulation and block with locally injected lidocaine, a nerve blocking agent, was tested in an animal. Time on the X-axis is in minutes. The Y-axis represents mean arterial blood pressure in mmHg. The first arrow 157 from the left indicates the time of injection of lidocaine. The second arrow 158 indicates the time of application of electrical stimulation to the greater splanchnic nerve proximal to the blocked area of the nerve. The term proximal as used herein with reference to a relative position on a nerve denotes a location nearer to a point of origin, such as brain, spinal cord, sympathetic chain or a midline of the body and where the term distal is used to denote a location further away from the point of origin and closer to the innervated peripheral organ such as splanchnic vascular beds, liver and spleen. Following the first stimulation 158 proximal to the nerve block 157, no or very little physiologic response is observed on arterial blood pressure, or other physiologic parameters that are omitted on this graph for simplicity. The third arrow 159 illustrates electrical stimulation of the greater splanchnic nerve for 30 seconds applied distal to the lidocaine blocked area. The physiologic response manifests by increase of mean arterial blood pressure and other hemodynamic parameters as described in this application.

[0089] It is noted that MAP monitoring as mentioned above is an example and hemodynamic monitoring does not necessarily need to be invasive monitoring and may be accomplished with a less invasive monitoring of blood pressure, for example using a Nexfin or ClearSight device (Edwards) for continuous monitoring of hemodynamics commonly used in hospitals. The ClearSight system quickly connects to the patient by wrapping an inflatable cuff around the finger. The ClearSight system provides noninvasive access to automatic, up-to-the-minute hemodynamic information including: SV, CO, SVR, or Continuous Blood Pressure (cBP). Such a monitoring device may be hooked up to a computerized console to communicate physiologic response to the computer, which may determine stimulation or blocking parameters based on the physiologic responses.

[0090] FIG. 14 is a flowchart that illustrates an example of a process from patient selection to permanent device implantation for blocking of the GSN to treat heart failure. One means for the selection of patients 165 suitable for GSN blocking may include evaluation of splanchnic vascular capacitance. An orthostatic stress test (tilt table test), fluid challenge, exercise test or an appropriate drug challenge can help distinguish low vascular compliance from normal. Orthostatic stress causes blood shifts from the stressed volume to the unstressed volume. In healthy patients, to compensate for the shift, sympathetic tone increases resulting in splanchnic vasoconstriction and rapid mobilization of blood from the unstressed compartment to the active circulation. The hemodynamic response to tilt in chronic CHF is atypical; as there is significantly less peripheral pooling in the upright posture indicating diminished splanchnic vascular capacitance. Acute oral or intravenous fluid challenge is another test to assess splanchnic vascular capacitance. A fluid challenge could test the capacitance by measuring the effects of a fluid bolus on cardiac filling and pulmonary pressures. Patients with low capacitance of the splanchnic venous reservoir will be unable to compensate for the hemodynamic effect of the fluid bolus. Patients with HF, HFPEF and patients with increased SNA will be more likely to respond to the fluid challenge with a disproportional rise in cardiac filing pressure and other related and measurable physiologic parameters. This response could indicate that the patient might be a candidate for GSN ablation therapy. After the patient is identified as a candidate for blocking therapy, the process of identifying the appropriate nerve target 166 is implemented as the first step in the implantation procedure. FIG. 10 illustrates a physiological response to electrical stimulation to identify a target nerve (GSN). After nerve target identification and selection, one means of confirmation of procedural efficacy 167 is to temporarily block the nerve target and evaluate 168 whether the physiological response is consistent with the desired clinical effect. After nerve target identification has been confirmed and procedural efficacy has been confirmed permanent implant 169 be initiated. Confirmation of the technical efficacy or success of the blocking procedure may be accomplished by delivering electrical stimulation proximal to the location of block where a physiological response was elicited prior to electrical block. Absence or attenuation of responses will indicate technical success of the blocking therapy (see FIG. 13). If the blocking therapy is a success, no further action is needed. If the blocking is not successful, the clinician may opt to provide additional blocking 170 therapy at the same site or repeat the procedure of identifying additional nerve targets (e.g., contralateral GSN) and providing blocking therapy as described previously.

[0091] In one exemplary embodiment, as illustrated in FIG. 15 a portable and implantable device 175 with lead wires 176 is adapted to terminate at a nerve cuff electrode 177 implanted around a target GSN 45. The lead 176 is tunneled from the nerve cuff 177 implanted around the GSN 45 to the subcutaneous IPG 178 implant site that can be on the patient's abdomen, flank or back. Another lead 179 or leads may be implanted in the heart 180 via the veins of cardiovascular system. The nerves are accessed as described in FIGS. 8, 9, and 11.

[0092] The pulse generator 178 for electrical nerve stimulation in an embodiment is implantable and programmable. Programmable pulse generators can employ conventional microprocessors and other standard electrical components. The pulse generators envisioned for use in the present embodiments are able to generate charge balanced, biphasic pulses. The biphasic pulse is repeated continuously to produce the blocking stimulus waveform. The pulse rate will vary depending on the duration of each phase, but will be in the range of 0.5 Hz up to 10 kHz. When the stimulus is delivered at the appropriate rate, typically around 6 kHz, the nerve membrane is rendered incapable of transmitting an action potential. The amplitude of the signal can vary between 0 and 20 mA. This type of conduction block is immediately reversible by ceasing the application of the waveform.

[0093] In a further embodiment, it is envisioned that the device and IPG can both receive and transmit signals. For example, it is envisioned that signals could be transmitted from the device to an external programmer or display. Likewise, it is envisioned in a further embodiment that patient or clinician input could be received by the device to modulate the generated pulse, as needed. The pulse generator can be battery operated or operated by a radiofrequency device. Because the IPG, components, and power source of the device may be implanted, it is envisioned that the device is hermetically sealed.

[0094] A schematic of the implantable pulse generator (IPG) that may be part of a system embodiment is shown in FIG. 16, which also shows various functional components of an implantable device 175. The components are typically contained in a case 215, which can be electrically conductive and connected to the internal electronics of the IPG, which is often referred to as the can, housing, encasing, or case electrode, and may be programmably selected to act as the return electrode for unipolar operational modes. The case 215 may further be used as a return electrode alone, or in combination with, one or more electrodes for stimulating or blocking purposes. The case may also be used as one of the sensors in determination of lead impedance, for example. The case 215 may be made of a conductive metal, such as titanium, and the implantable device hermetically sealed and leak rate tested.

[0095] The case further includes a connector (not shown, e.g., a header or a connector block, made of polyurethane or other suitable material), having a plurality of terminals shown schematically with the names of the leads to which they are connected shown next to the terminals, including: a nerve lead terminal 216, a cardiac lead terminal 217, and a physiological sensor terminal 218 for physiological sensors e.g., a blood pressure probe. The electrical connection from the connector to the circuitry through the hermetically sealed case are typically realized utilizing feedthroughs made of an electrical conductor, such as platinum.

[0096] The implantable device 175 may include a programmable microcontroller 219 that controls various operations of the implantable neurostimulator device, including physiological monitoring, nerve blocking therapy, electroneurogram sensing, and cardiac sensing and stimulation therapy. Electroneurogram sensing can be realized using the same cuff electrodes that are used for stimulation and blocking (FIGS. 12A and 12B). The microcontroller includes a microprocessor or equivalent control circuitry, RAM or ROM memory, logic and timing circuitry, state machine circuitry, and I/O circuitry.

[0097] The implantable device further includes a high frequency blocking module 220, neurostimulation pulse generator 221, as well as an optional cardiac pulse generator 222 that generate electrical stimulation or blocking pulses for delivery by the neural lead 176 and cardiac lead(s) 179 via an electrode configuration switch. The cardiac function of the device may be atrial or ventricular. The electrode configuration switch 223 may include multiple switches for connecting the desired electrodes to the appropriate I/0 circuits, thereby providing complete electrode programmability. Accordingly, the switch, in response to a control signal from the microcontroller 219, determines the polarity of the stimulation pulses (e.g., unipolar, bipolar, etc.) by selectively closing the appropriate combination of switches. The cardiac pulse generator 222 is capable of delivering a single electric pulse that excites myocardium and generates an entire heart muscle contraction (cardiac capture) and the neurostimulation pulse generator 221 is capable of delivering trains of pulses that selectively excite an approximate nerve creating series of action potentials in the nerve fibers. The high frequency blocking 220 is capable of delivering trains of pulses that selectively block the nerve creating temporary blocking of nerve conduction.

[0098] The pulse generators and high frequency block module are controlled by the microcontroller via appropriate control signals used to trigger or inhibit the electrical pulses. The microcontroller is illustrated as including timing control circuitry 224 to control the timing of the electrical pulses (e.g., electrical nerve blocking frequency, neural stimulation frequency, cardiac pacing rate, etc.). The timing control circuitry 224 may also be used for the timing of the high frequency block therapy, nerve stimulation periods (duty cycles, pulse widths), cardiac refractory periods, noise detection windows, etc.

[0099] In another embodiment, GSN activity may be monitored to control or modulate blocking therapy. GSN activity may be used as a measure of therapy efficacy or as an indication for initiating therapy. Signal conditioning circuits may be selectively coupled to the nerve lead 216 through the switch 223 to detect the presence of greater splanchnic nerve activity. The signal conditioning circuits and may include dedicated sense amplifiers, multiplexed amplifiers, or shared amplifiers. Each sensing circuit may employ one or more low power precision amplifiers with programmable gain or automatic gain control, bandpass filtering, and a threshold detection circuit to selectively sense the nerve signal of interest.

[0100] In another embodiment, GSN activity may be monitored to control or modulate blocking therapy. The DAQ module may be used to acquire the electroneurograms. The electroneurograms may be saved to memory and sent to an external system for signal processing. Some processing, such as stimulus artifact reduction, may be performed by the signal conditioning circuit of the IPG. The external system my employ one or more sense amplifiers, multiplexed amplifiers, or shared amplifiers. Each sensing circuit may employ one or more low power precision amplifiers with programmable gain or automatic gain control, bandpass filtering, and a threshold detection circuit to selectively sense the nerve signal of interest. After processing, the telemetry circuit can receive information used to control or modulate blocking therapy.

[0101] The operating parameters of the implantable device may be non-invasively programmed into the memory 225 through a telemetry circuit 226 in telemetric communication via a communication link with the external device, such as a clinician programmer or a patient interface 227. In addition to telemetric communication, communication may also be achieved using radio frequency or RF (circuitry not shown). The microcontroller can activate the telemetry circuit with a control signal. The telemetry circuit allows the status information relating to the operation of the device, as contained in the microcontroller 219 or memory 225, to be sent to the external device through the established communication link. The telemetry may be operated on demand by a physician, a care provider who is not a physician, or the patient.

[0102] The device additionally includes a battery 228 that provides operating power to all of the components shown in FIG. 16. The battery is capable of operating at low current drains for long periods of time. The battery 228 also desirably has predictable discharge characteristics so that elective replacement time can be detected. The device can further include magnet detection circuitry (not shown), coupled to the microcontroller 219, to detect when a magnet is placed over the device. A magnet may be used by a clinician to perform various test functions of the exemplary device or to signal the microcontroller that a wand of an external programmer is in place to receive or transmit data to the microcontroller through the telemetry circuits. Communication between the device and external devices (clinician programmer, patient interface, sensors, etc.) may also be performed wirelessly using RF communication protocols.

[0103] The device further includes an impedance measuring circuit 229 that is enabled by the microcontroller via a control signal. The impedance measuring circuit is used for many purposes, including: lead impedance surveillance during acute and chronic phases for proper lead positioning or dislodgement; detecting operable electrodes and automatically switching to an operable pair if dislodgement occurs; measuring respiration rate, tidal volume or minute ventilation; measuring thoracic impedance; detecting when the device has been implanted; measuring cardiac stroke volume and systolic and diastolic volume of blood in the heart; and so forth. The impedance measuring circuit may be coupled to the switch so that any desired electrode may be used.

[0104] In one configuration, the accelerometer output signal from the activity/position sensor is bandpass-filtered, rectified, and integrated at regular timed intervals. A processed accelerometer signal can be used as a raw activity signal. The device derives an activity measurement based on the raw activity signal at intervals timed according to the cardiac cycle or at other suitable time intervals. The activity signal alone can be used to indicate whether a patient is active or resting. The activity measurement can further be used to determine an activity variance parameter. A large activity variance signal is indicative of a prolonged exercise state. Low activity and activity variance signals are indicative of a prolonged resting or inactivity state. The activity variance can be monitored during day and night periods set by the telemetry for the geographic area and time zone to detect the low variance in the measurement corresponding to the sleep state.

[0105] In one embodiment as shown in FIG. 17, the activity signal is used to provide responsive therapy. Patients with HFpEF experience exercise limitations that have a tremendous effect on quality of life. Upon detection of exercise 235, therapy is initiated 236 to increase exercise capacity in these patients. Patients may also initiate therapy prior to exercise. The efficacy of therapy 237 can be derived from the calculation of the activity variance parameter described above. The activity variance is compared over time to indicate exercise time (or exercise capacity) to create a measure of therapy efficacy. Once blocking therapy is initiated 236, the effectiveness of the block may be determined (see FIGS. 12A and 12B). If block is not effective, parameters will be changed until successful blocking is confirmed. Once the blocking is confirmed, physiological sensors will be monitored to determine therapy effectiveness 234. The signal conditioning and DAQ 230 modules in the IPG (FIG. 16) will be used to acquire the physiological signal 238 used to determine therapy effectiveness (Physiological Sensor Module, FIG. 16). High frequency block parameters may be adjusted based on detection from physiological sensors.

[0106] Another embodiment of the disclosure uses an accelerometer 239 to monitor position and provide therapy in response to positional conditions. CHF patients may experience fluid back-up in the lungs that results in difficulty breathing at rest or when lying in bed. This results in altered sleep patterns, such as sleeping in an upright position. This significantly reduces sleep quality and results in deterioration of health and quality of life. The accelerometer signal will be used to detect sleeping in upright positions that are indicative of congestion. Detection of altered sleeping patterns will trigger blocking therapy to relieve lung congestion leading to improved sleep quality. The accelerometer signal will be used to detect exercise 235 such as walking or walking up the stairs and activate therapy in HFpEF patients that experience dyspnea from exertion due to elevation of pulmonary blood pressure in response to exercise induced mobilization of splanchnic venous blood into the circulating volume (FIG. 17).

[0107] Another embodiment of the disclosure comprises a detection device, a detection algorithm, a treatment device and a treatment algorithm (FIG. 16). The detection and input of a variety of health and heart health indicators (including venous capacitance, unstressed volume, effective circulatory volume, pulmonary pressure, dyspnea, as well as other factors described herein, etc.) is envisioned to help determine the ranges in which the nerve block is initiated, continued or terminated. These inputs, along with the use of additional algorithms are envisioned to help streamline the application of the present therapies. It is important and envisioned that these algorithms are not only accurate and effective for starting, continuing and stopping the generated signal, but also that the system is tolerant of random or isolated stimuli that do not require treatment. Further an algorithm may incorporate information such as a feedback signal, sensor input, or programmable input which may affect its output. In a further embodiment, said device may be configured to receive signals from sensors including fluid or blood pressure (BP) sensor and adjust accordingly to modulate and deliver modified therapy, as needed or desired. Sensors are envisioned to be comprised within the device or separate from the device. Furthermore, it is also envisioned that specifically the leads of the device may also comprises a detector capable of sensing values (e.g., blood pressure, heart rate, cardiac output, acceleration, fluid imbalance, fluid impedance, etc.) and fine tuning delivery of the nerve block to reduce venous congestion.

[0108] While automatic detection followed by the delivery of therapy is envisioned to optimize the ease and convenience and minimize risk of user error during operation, patient-initiated therapy is also envisioned wherein the patient experiences shortness of breath or other symptoms and initiates the therapy 244 for a set amount of time until benefit is achieved. In addition, it is envisioned that the device may be remotely activated and controlled, in coordination or independent of any sensors/algorithms, in such a way that a user, emergency medical personnel or medical practitioner could perform a manual override and operation as required. One embodiment of operation of an implantable system provides for blocking therapy initiation by a clinician, a patient, programmed treatment algorithm, or via sensor activation based on a detection algorithm (see FIG. 18). After therapy is initiated 240, blocking effectiveness is assessed 241. If blocking is not successful, high frequency blocking parameters will be adjusted until blocking is successful. Once blocking success is determined, therapy effectiveness may be assessed 242 by monitoring physiological sensors 243. High frequency blocking parameters may be modified to improve therapy effectiveness. In addition, a programmer or patient programmer can be used to remotely change stimulation parameters as required. For example, maximum allowed stimulation energy may be reduced based on pain sensation by the patient or increased based on medical tests.

[0109] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.