Patent ID: 12186568

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG.1shows an exemplary embodiment of a system8including a pressure regulator/pacemaker/implantable cardio-defibrillator (ICD) with specialized leads going into a patient's heart90, e.g., for practicing the exemplary systems and methods described elsewhere herein. In the embodiment shown inFIG.1, the system8includes a controller40including a housing42sized and/or otherwise designed to be implanted within the patient's body. The housing42of the controller40is connected to several leads10,20,30that are designed to be implanted into the patient's heart90.

For example, as shown, a first lead10may include a proximal end12coupled to the housing42and a second end sized for introduction into the patient's heart90, e.g., into the right atrium92. The first lead10may have a distal end19carrying a sensor and/or electrode18for sensing electrical activity (depolarizations) and/or pacing the right atrium92, as programmed. In addition, the distal end19of the first lead10may include one or more features, e.g., a screw tip or other anchor (not shown) on its distal tip for securing the distal end19relative to the right atrium92or left atrium96. One or more wires or other conductors may extend from the distal end16to the proximal end12to communicate the signals from the sensor18to the controller40.

Similarly, a second lead20may include a proximal end22coupled to the housing42and a second end sized for introduction into the patient's heart90, e.g., into the right atrium92through the coronary sinus97or other vein of the heart90. The second lead20may include a sensor or electrode27designed to sense or measure pressure in the left atrium96. In addition, the second lead20may include a distal end29carrying an additional sensor or electrode28for sensing or measuring pressure located within the distal coronary sinus97, which may be reflective of left ventricle98pressures. Similar to the first lead10, the second lead20may include one or more features, e.g., a screw tip or other anchor (not shown), on the distal tip to secure the distal end29within the patient's heart90, e.g., within the coronary sinus97, similar to pacing leads. Alternatively, the first and second leads may be provided on a single device with a branch distal end (not shown), similar to embodiments described in the applications incorporated by reference herein.

Additionally, there may be a third lead30with a proximal end32to couple the lead30to the housing42. The third lead30may include a second end sized for introduction into the patient's heart90, e.g., into the right atrium92, through the tricuspid valve93and into the right ventricle94. The third lead30includes a distal end, which may include an electrode and/or sensor38designed to sense electrical activity or deliver electrical energy to stimulate the right ventricle96.

Similar to the first lead10and second lead20, the third lead30may include one or more features, e.g., a screw tip or other anchor (not shown), on the distal tip to secure the distal end within the patient's heart90, e.g., into the wall of the right ventricle94, similar to typically used pacing leads. The third lead30may sense and pace electrical activity occurring in the right ventricle94. In addition, the third lead30may include electrodes34and35designed to sense electrical capacitance at several points in time throughout the cardiac cycle to estimate the stroke volume of the right ventricle94. For example, changes in impedance throughout the cardiac cycle may be used to estimate volume changes in the right ventricle. Even with drift in electrical signals over time, these measurements can determine changes in volume changes which may be used to guide the pressure gradient or regurgitant volume.

In addition, the third lead30may include a tube-like structure36, designed to permit controlled flow to travel from the right ventricle94to the right atrium92. The regurgitating flow traveling through the tube decreases the forward flow through the pulmonary artery, and ultimately the left atrium96and left ventricle98. This tube-like structure may include one or more flow sensors, e.g., a rotating sensor, magnetic flux sensors, and/or other flow sensors such that retrograde flow may be measured. By combining volume changes in the right ventricle and retrograde flow measurements, stroke volume (and therefore cardiac output) may be estimated, especially relative changes in stroke volume. Alternatively, sensors measuring oxygen saturation or directly measuring flow, e.g., through the pulmonary artery95, may be included to estimate stroke volume of the right ventricle94.

In some embodiments, measuring changes in flow in response to changes in a pressure gradient or regurgitant volume, optimal heart rate and/or regurgitant volume may be estimated. In other embodiments, pressure waveforms from pressure sensors from the right ventricle94and/or the pulmonary artery96may be analyzed to better estimate left-sided filling pressures, e.g., the end diastolic filling pressure of the left ventricle98. The pressure waveforms may by analyzed by identifying the pulmonary artery systolic, diastolic, and/or mean pressure in order to estimate left-sided filling pressures.

One or more pressure sensors may be placed at desired locations, e.g., in the left atrium, on the interatrial septum, or in the coronary sinus97(with occlusion to optimize pressure recordings), in order to estimate left-sided filling pressures. In addition or alternatively, one or more pressure sensors may be placed in the right atrium92, right ventricle94, right ventricular outflow track, or pulmonary artery95. By combining flow measurements with pressure sensors within the blood system prior to the lungs, filling pressures from the left atrium and/or left ventricle98may be estimated. The waveform analysis may include absolute pressures and/or the slope or change in pressure (tao) during the cardiac cycle.

FIG.2shows a simplified functional block diagram of one embodiment of the components located within and connected to the controller40. The components include a control processor51, which receives input information from various components in order to determine the function of the different components to treat the patient. The control processor51is connected to a memory component52, pressure sensors (17,27,28, and37), regurgitation control circuitry54, pacing circuitry55, stroke volume sensing circuitry56, and a telemetry interface57. The pacing circuitry55connects to the electrodes, for example, electrodes18and38. These connections allow for multiple capacities to sense electrical activity (such as myocardial depolarizations), deliver pacing stimulations, and/or deliver defibrillation or cardioversion shocks. The regurgitation control circuitry is connected to a motor70or pump71to affect blood flow36. The stroke volume sensing circuitry is connected to electrodes, for example electrodes34and35. These electrodes sense change in impedance values at periods of the cardiac cycle to estimate stroke volume. Optionally, the control processor51is connected to a telemetry interface57. The telemetry interface may wirelessly send and receive data from an external programmer62which is coupled to a display module64in order to facilitate communication between the control processor51and other aspects of the system external to the patient.

FIG.3shows an exemplary embodiment of a lead30including a regurgitant component that may be implanted within a patient's heart90, e.g., to control flow of blood from the right ventricle94to the right atrium92. In this embodiment, the lead30carries a tube device36designed to be placed across the tricuspid valve leaflets93to provide controllable regurgitation between the right ventricle and the right atrium (not shown). In an exemplary embodiment, the tube device36has an inner tubular core72defining a lumen or passage capable of transmitting blood from the right ventricle94to the right atrium92. The tube device36is connected to a motor70able to change the size of the inner core72by changing the size or orientation of an annular outer body74of the tube surrounding the inner core72. Alternatively, the tube device36may communicate with a micropump (not shown), e.g., within the controller40, able to pump a liquid or gas substance into the outer body74of the tube. The tube device36is connected to the controller40for controlling operation of the tube device36, and is mounted on the lead30proximally to the pacing lead38, e.g., secured in the apex of the right ventricle94. By adjusting the size of the inner core72, the controller40is able to control the amount of regurgitated blood traveling from the right ventricle94to the right atrium92. This blood flow shunts blood away from the pulmonary artery95; and ultimately will decrease the pressure in the left atrium96and left ventricle98.

In another embodiment, the regurgitation component may be pressure sensitive. For example, when the pressure within the right ventricle exceeds a certain pressure, the regurgitant component permits blood to regurgitate from the right ventricle to the right atrium. This mechanism prevents pulmonary pressures from exceeding a certain value. Furthermore, in another embodiment, this system may not require a processor or controller. For example, the regurgitation component may mechanical deform in response to a high pressure gradient between two areas, such as, the right atrium and right ventricle.

In an exemplary embodiment, the tube device36may be an annular balloon device formed from desired materials. For example, the material may be comprised of fabric material, such as polyester, nylon, or polypropylene. In other embodiments, the material may be made of stainless steel, nitinol, titanium, cobalt alloys, cobalt-chromium-nickel allows, MP35N, polymeric material, or any other suitable biocompatible material. The regurgitant member may be self-expanding, balloon expanding, or a shape-memory material. In another embodiment, aspects of the device may be made from tubing or wire. In yet another embodiment, the regurgitant component may be made of porcine or donor material, such as mammalian veins or heart valves. In other embodiments, the regurgitant component may include elastomeric materials, such as silicone or perfluorocarbon elastomers.

FIG.4shows an additional exemplary embodiment of a lead30including a movable structure41that may be implanted within a patient's heart90, e.g., to control flow of blood from the right ventricle94to the right atrium92. This lead30may be connected to the pacing electrode38in the right ventricle94to pace the heart (e.g., to increase the heart rate). The lead30carries the movable structure41at a desired location, e.g., around the outside of the lead30. This movable structure41may be connected to a motor70, such that changes in shape and/or orientation of the movable structure41will affect or prevent leaflet coaptation from the tricuspid valve93. In an exemplary embodiment, the movable structure41may have several spindle-like structures made up of or coated with biocompatible material. For example, the motor70may be mounted on the lead30such that the motor70may move towards or away from the tip of the pacing lead38such that the spindles increase or decrease in diameter. Therefore, the motor70may cause radial expansion in order to induce regurgitation. In this and other configurations, the controller40may induce or control blood to regurgitate from the right ventricle94to the right atrium92.

Turning toFIG.5, an exemplary method is shown for determining optimal heart rate and/or regurgitant volume, e.g., using any of the systems described elsewhere herein. The controller of the system may operate the regurgitant volume and other components to enable the desired data to be acquired and calculations to be performed. Variations in heart rate and regurgitant volume are used in order to estimate the relationship between left-sided filling pressures and cardiac output. For example, at step910, heart rate and regurgitant volume may generate hemodynamic data at a given level of patient activity and intra-cardiac filling pressures.

At step912, the controller may then use the slope of this relationship to determine the optimal left-sided filling pressure and cardiac output. Optionally, at step914, an accelerometer implanted in the patient's body, e.g., within the housing42of the controller40shown inFIG.1, may be used to identify the patient's level of activity. For example, the controller40may acquire data from the accelerometer indicating that the patient is resting (e.g., no substantially signals from the accelerometer) or active.

In addition, at step916, the controller40may identify the current level of regurgitation, which may provide an estimate of the total body volume of the patient. In another embodiment, the device may measure if the patient is sleeping or has evidence of sleep apnea and change function based on the identification of said occurrence.

At step918, the controller40may also determine the maximum allowable left-sided filling pressure and minimum cardiac output allowable. These values may also be dependent on the level of patient activity and/or the total body blood volume. That is, when the patient is at an increased level of activity, the controller may accept a higher maximum of left-sided filling pressure.

Optionally, the device may determine or have pre-programmed levels of minimum allowable cardiac output (step920). For example, the device may identify a rise in total body volume when the cardiac output falls below this threshold. Therefore, the device may identify a level of cardiac output not sufficient to satisfy the demands of the body.

Similarly, the device may identify a left-sided filling pressure, e.g., the left ventricular end diastolic pressure, where the patient cannot maintain activity, or where the device measures a rapid increase in ventilation (step918). Therefore, the device may identify a certain LVEDP (or rapid change in LVEDP) that results in shortness of breath. Therefore, the device may have a programmed (or monitored or adjustable) LVEDP threshold such that the device does not allow this pressure to go higher. The device may set this LVEDP even if a higher pressure increases cardiac output. This setting may be useful because left-sided filling pressures may be more predictive of exercise capacity rather than cardiac output. Therefore, while the device may be limiting cardiac output, the reduction in left-sided filling pressures actually improve patient quality of life.

At step922, these values are then incorporated into an algorithm by the controller40. These values are then gradually adjusted (feedback loop) back to step910in order to identify the optimal settings to optimize patient hemodynamics and quality of life.

Once calibrated, regurgitant volume and heart rate may be anticipated based on patient activity and intra-cardiac pressures in order to optimize filling pressures and/or cardiac output. Over time, the decreased left atrium and left ventricle filling pressures may lead to beneficial myocardial remodeling. This may improve myocardial function and/or decrease arrhythmias and/or ectopic beats.

Turning toFIG.6, this figure illustrates an exemplary method of using the pressure/volume relationship to guide the heart rate and regurgitation components of the device. In response to changing volume status, heart rate, adrenergic level, and regurgitant volume, the device may monitor both estimated change in pressure and estimated change in stroke volume. In other embodiments, the device may attempt to measure absolute pressure and/or stroke volume. Therefore, the device may estimate the how increasing the heart rate and regurgitation will affect cardiac output and filling pressures.

For example, when filling pressures rise without a concomitant increase in stroke volume, the slope of this relationship suggests raising the filling pressure higher will contribute to shortness of breath and hyperventilation without improving forward flow. Therefore, the slope of this relationship may be used to guide heart rate and the component that influences regurgitation. In addition, the device may estimate optimal resting filling pressures to guide volume status. For example, if the device suggests the patient is volume-overloaded, the device may increase cardiac output to favor renal perfusion and diuresis. The device may simultaneously minimize how high the LVEDP may raise to limit symptoms. Alternatively, the device may communicate to the patient or patient's healthcare team that a medication adjustment should be done to help optimize patient hemodynamic status.

The device may also combine the LVEDP measurement with hemodynamic monitors during exertion, sleep, or various kinds of movement. In other embodiments, the device may use oxygen saturation, pH, respiratory rate, and/or lactate levels (or a combination) in order to determine the optimal filling pressure. For example, some patients require an LVEDP greater than 30 mmHg to maintain stroke volume. However, other patients maximize their stroke volume when the LVEDP reaches 10 mmHg. Therefore, by determine the response of stroke volume and/or cardiac output at various filling pressures (LVEDP), the device may identify the optimal LVEDP. In another embodiment, the LVEDP, where there is excess hyperventilation, acidosis, or lactate accumulation, may be identified as the maximum filling pressure to optimize patient exercise capacity.

It will be appreciated that elements or components shown with any embodiment herein are exemplary for the specific embodiment and may be used on or in combination with other embodiments disclosed herein.

While the invention is susceptible to various modifications, and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the invention is not to be limited to the particular forms or methods disclosed, but to the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the scope of the appended claims.