Source: https://patents.google.com/patent/WO2008034005A2/en
Timestamp: 2019-04-23 18:30:26
Document Index: 235684195

Matched Legal Cases: ['Application No. 60', 'art 16', 'art 16', 'art 16', 'art 16', 'art.\n26', 'art.\n27', 'art.\n31', 'art.\n35', 'art.\n36', 'art.\n37']

WO2008034005A2 - Cardiac stimulation using leadless electrode assemblies - Google Patents
Cardiac stimulation using leadless electrode assemblies Download PDF
WO2008034005A2
WO2008034005A2 PCT/US2007/078405 US2007078405W WO2008034005A2 WO 2008034005 A2 WO2008034005 A2 WO 2008034005A2 US 2007078405 W US2007078405 W US 2007078405W WO 2008034005 A2 WO2008034005 A2 WO 2008034005A2
PCT/US2007/078405
WO2008034005A3 (en
2006-09-13 Priority to US84459906P priority Critical
2006-09-13 Priority to US60/844,599 priority
2007-09-13 Application filed by Boston Scientific Scimed, Inc. filed Critical Boston Scientific Scimed, Inc.
2008-03-20 Publication of WO2008034005A2 publication Critical patent/WO2008034005A2/en
2008-07-10 Publication of WO2008034005A3 publication Critical patent/WO2008034005A3/en
This application claims priority from U.S. Provisional Application No. 60/844,599, filed September 13, 2006, and entitled "Cardiac Stimulation System Using Leadless Electrode Assemblies," the entire contents of which are incorporated herein by reference.
Pacemakers provide electrical stimulus to heart tissue to cause the heart to contract and pump blood. Conventionally, pacemakers include a pulse generator that is implanted, typically in a patient's pectoral region just under the skin. One or more leads extend from the pulse generator and into chambers of the heart, most commonly in the right ventricle and the right atrium, although sometimes also into a vein over the left chambers of the heart. An electrode at a far end of the lead provides electrical contact to the heart tissue for delivery of the electrical pulses generated by the pulse generator and delivered to the electrode through the lead. The conventional use of leads that extend from the pulse generator and into the heart chambers has various drawbacks. For example, leads have at their far ends a mechanism, such as tines or a "j-hook," that causes the lead to be secured to a tissue region where a physician positions the lead. Over time, the heart tissue becomes intertwined with the lead to keep the lead in place. Although this is advantageous in that it ensures the tissue region selected by the physician continues to be the region that is paced even after the patient has left the hospital, it can be problematic if it becomes necessary to move or remove the lead. For example, subsequent to initial implant, it may be determined that an alternate location is preferable for pacing. Similarly, leads can fail.
Failed leads cannot always be left in the patient's body, as potential adverse reactions including infection, thrombosis, valve dysfunction, etc., may occur. As such, lead- removal procedures, which can be difficult, sometimes must be employed. The conventional use of leads also limits the number of sites of heart tissue at which electrical energy may be delivered. This is because leads are often positioned within cardiac veins, and multiple leads may block a clinically significant cross-sectional fraction of the vena cava and branching veins leading to the pacemaker implant.
There are several heart conditions that may benefit from pacing at multiple sites of heart tissue. One such condition is congestive heart failure (CHF). It has been found that CHF patients have benefited from bi- ventricular pacing - that is, pacing of both the left ventricle and the right ventricle in a timed relationship. Such therapy has been referred to as "resynchronization therapy." The conventional use of leads limits the number of sites of heart tissue at which electrical energy may be delivered. Similarly, catheters are presently used in the coronary venous system, primarily to pace the left ventricle from the veins. It is known that venous pacing is less efficient at treating CHF than is pacing from the inside wall of the left ventricle.
Wireless Pacing Electrodes (WPEs) have been proposed for the treatment of heart failure through resynchronization of contraction of the right and left ventricles, and for prevention of arrhythmias, including ventricular tachycardia and ventricular fibrillation. A significant issue to be considered in achieving a commercially practicable system is the overall energy efficiency of the implanted system. For example, the energy transfer efficiency of two inductively coupled coils decreases dramatically as the distance between the coils increases. In one example, the WPE contains a battery that is recharged from an antenna located outside the patient. In this implementation, the WPE battery stores only enough energy to pace the heart for a few days, and recharging occurs approximately daily. In another example, a battery- free WPE contains a capacitor with charge-holding capacity sufficient to pace the heart for one or several heartbeats. Energy is transmitted to the WPE from an implanted antenna located outside of the heart, and in patients where multiple WPEs are used, each WPE capacitor is recharged at each heartbeat. Because of the distance between the WPE and the antenna, the coupling between the two may be inefficient, and frequent recharging of an implanted controller that drives the antenna may be required.
This document relates to leadless electrode assemblies that may electrically stimulate cardiac tissue from distributed locations within the heart. In a first general aspect, a cardiac tissue excitation lead includes a flexible elongate lead body having a proximal end adapted to be inserted into an implantable pulse generator assembly and having a distal end adapted to be positioned within a heart. The cardiac tissue excitation lead also includes a lead conductor extending within the lead body, and a transmitter assembly located near the distal end of the lead body and electrically connected to the pulse generator assembly via the lead conductor to wirelessly transmit pacing control information and pacing energy from the transmitter assembly to an implanted leadless electrode assembly.
In another general aspect, a method of operating a cardiac pacing system includes transmitting an energy signal wirelessly from a wired lead whose distal end is positioned in first chamber of a heart. The method also includes receiving the transmitted energy signal at a wireless pacing electrode assembly positioned within a second chamber of the heart. The method further includes issuing, in response to receiving the transmitted energy signal, a pacing pulse from the wireless pacing electrode assembly to surrounding cardiac tissue unless a native cardiac electrical signal is sensed by the wireless pacing electrode assembly within a specified time period from the receipt of the transmitted signal. In selected embodiments, the energy transmission may include charging energy and pacing information. The wireless pacing electrode assembly may include sense circuitry to sense the native cardiac electrical signal. Transmitting the energy signal wirelessly from the wired lead may include generating an electric field created at the wired lead, generating a magnetic field created at the wired lead, or generating an ultrasonic beam at the wired lead implanted in the first chamber of the heart. The native cardiac electrical signal may originate at a sino-atrial node of the heart.
Advantages of the systems and techniques described herein may include any or all of the following: pacing at multiple sites may be beneficial where heart tissue through which electrical energy must propagate is scarred or dysfunctional, as this condition may halt or alter the propagation of an electrical signal through that heart tissue. In these cases, multiple-site pacing may be useful to restart the propagation of the electrical signal immediately downstream of the dead or sick tissue area. Synchronized pacing at multiple sites on the heart may inhibit the onset of fibrillation resulting from slow or aberrant conduction, which may reduce the need for implanted or external cardiac defibrillators. Additional advantages of wireless left- side pacing may include reduction of risk of stroke and improvement of left ventricle response by optimal stimulator positioning. Pacing thresholds may be reduced with distributed electrode surfaces on the seeds, left ventricle intra-wall positions, and adjacent Purkinje locations. Distributed electrode pacing sites, such as distributed left ventricle sites, may permit the heart to be defϊbrillated at lower energies than were previously realizable. The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
FIG. 9A is a diagram of an exemplary system that includes a leaded device having multiple transmitters on a single lead and multiple leadless electrode assemblies. FIG. 9B is an expanded view of a portion of FIG. 9A. FIG. 1 OA is a diagram of a heart and another exemplary cardiac stimulation system using a leadless electrode assembly implanted in or near the heart. FIG. 1OB is an expanded view of a portion of FIG. 1OA. FIG. 11 is a diagram of a leadless electrode assembly in a heart chamber and a permanent magnet positioned on an epicardial surface of the heart.
Lead 14 passes through the right atrium 22 and enters the right ventricle 23 and may include a defibrillation coil electrode 24 that may be used to sense electrical activity in the right ventricle, and to supply a defibrillation shock through the heart to pulse generator 10 and/or right atrium lead 18. A transmitter 20, at the distal end of lead 14, transmits energy or information to one or more leadless electrode assemblies, such as leadless electrode assembly 26. Herein, the leadless electrode assembly 26, or wireless electrode assembly, may be referred to simply as a "seed." In some implementations, the pacing controller may communicate with the seed 26 by transmitting charge energy, pacing information, or both, through a lead, such as lead 14, to be received by the seed 26.
In one implementation, the seed 26 has an internal receiver that may receive communications and/or energy from transmitter 20. In an implementation, the pacing controller 10 includes a pulse generator that supplies an appropriate time-varying current to the transmitter 20. The seed 26 may include an electrical charge storage that may be charged by the received energy transmission from the leaded transmitter, and may also have a triggering mechanism to deliver stored electrical charge to adjacent heart tissue. In this fashion, pacing stimuli may be delivered to cardiac tissue remote from the cardiac lead, which may advantageously permit cardiac rhythms to be more effectively managed, and may permit a level of cardiac stimulation coverage using fewer cardiac leads. In an exemplary implementation, the wireless electrode assembly 26 includes a capacitor to store received electrical charge. In another implementation, the wireless electrode assembly 26 includes a battery to store received electrical charge. Seed 26 is shown endocardially affixed via a helical tine 28 to a wall 30 of a left ventricle 32 of the heart 16. Transmitter 20 may transmit charge energy and data, such as pace trigger signals, pacing amplitude information, and pulse width information to the seed 26 via RF transmissions 34, according to some implementations. In this manner, the seed 26 may receive energy and communications from the pacing controller 10 through the transmitter 20. As just described, the transmitter 20 and the connected pacing controller 10 together, or the pacing controller 10 or transmitter 20 individually, may be referred to as a transmitter, while the wireless electrode assembly 26 may be referred to as a receiver. While only one seed 26 is shown in FIG. 1 , additional seeds 26 may be located throughout any of the chambers of the heart 16, such as the left ventricle, right ventricle, left atrium or right atrium, and each may receive energy or information from the pacing controller 10 through RF or ultrasonic transmissions, whether through transmitter 20 on lead 14, or through a transmitter attached to other leads (not shown in FIG. 1). In one implementation, the pacing controller 10 may transmit, and the seed 26 may receive, 1) a charging signal to charge an electrical charge storage device contained within the seed 26 by inductive coupling, and 2) an information signal, such as a pacing trigger signal, pacing amplitude information and/or pacing pulse width information that is communicated to a selected one or more of the seeds 26, commanding that seed to deliver its stored charge to the adjacent or surrounding cardiac tissue.
An external programmer (not shown) may be used to communicate with the pacing controller 10, including after the pacing controller 10 has been implanted. The external programmer may be used to program such parameters as the timing of stimulation pulses in relation to certain sensed electrical activity of the heart, the energy level of stimulation pulses, the duration of stimulation pulses (that is, pulse width), etc. Additional information such as locations of seeds 26 within heart chambers may be programmed, as well as pacing requirements involving one or more of the distributed seeds 26. The programmer may include an antenna to communicate with the pacing controller 10, using, for example, RF signals. The implantable pacing controller 10 may accordingly be equipped to communicate with the external programmer using, for example, RF signals. Similarly, the pacing controller 10 may transmit information, such as sensed cardiac patient information, system status information, warning information, and the like, to an external computing device. Physicians or care providers may then monitor the information and make changes as appropriate. Because the seed assembly 26 may receive charge energy via RF transmissions, the seed assembly 26 may be constructed without a battery in some implementations, which may permit the seed assembly 26 to be advantageously small. This may make seed implantation easier and permit pacing at sites that might not otherwise be possible with larger assemblies that include a battery. In one implementation, the seed assembly 26 includes a capacitor that may be charged by energy received from the pacing controller 10 through transmitter 20 via RF or ultrasonic transmissions. In an implementation, the pacing controller 10 may send pulses to the transmitter 20 at an RF frequency of about 150 KHz. The seed electrode assembly 26 may then provide pacing therapy to surrounding cardiac tissue using the received energy and communication information.
Referring now to FIG. 2, a third lead 50 is shown. Like the leads 12, 14 shown in FIG. 1, lead 50 is electrically connected to the pacing controller 10 at the lead's proximate end by a lead conductor that extends within a lead body. Lead 50 extends through the right atrium 22 and into a coronary sinus 52, where a transmitter 54 near a distal end 56 of the third lead 50 is positioned within the coronary sinus 52. In similar fashion to the system shown in FIG. 1 and described above, the transmitter 54 may transmit pacing energy or communication data, received from the pacing controller 10, to a left ventricle wireless electrode assembly 58 via RF or ultrasonic transmissions 60. The system shown in FIG. 3 is similar to the system of FIG. 2, but includes an alternative style wireless electrode assembly 80. Like the system shown in FIG. 1, the systems shown in FIGS. 2-3 provide efficient coupling between transmitter and receiver because of the close proximity with which transmitter and receiver are positioned. Various implementations of seed assemblies 26, including those shown in FIGS. 1-3, will now be described with reference to FIG. 4. FIG. 4 is a diagram of various exemplary implementations of leadless electrode assemblies 26 that may be used in the systems of FIGS. 1-3. The leadless electrode assemblies 26 are attached to a wall of the heart - in this example, the wall 30 of the left ventricle 32. A first leadless (or wireless) electrode assembly 26a includes a proximal electrode 121 at or near a proximal end of the assembly 26a and a distal electrode 129 at or near a distal end of the assembly 26a, according to an implementation. The proximal electrode 121 and distal electrode 129 may provide bipolar electrode capabilities for the wireless electrode assembly 26a, thereby permitting the assembly 26a to supply an electrical charge between the proximal and distal electrodes 121 and 129 (and across the nearby heart tissue). The distal end of the wireless electrode assembly 26a may also include a fixation device 130, such as a helical tine, to secure the wireless electrode assembly 26a to the heart chamber wall 30. For example, a distal tip 132 of the helical tine 130 may engage the heart chamber wall 30 and, when a torque is applied to the wireless electrode assembly 26a, the helical tine 130 may screw through the endocardium (e.g., the inner lining of the heart chamber wall) and into the myocardium. Such a configuration may permit the wireless electrode assembly 26a to be secured to the heart chamber wall 30. In some implementations, the fixation device 130 may also serve as at least a portion or all of the distal electrode 129. For example, the fixation device 130 may comprise an electrically conductive material (e.g., a metallic material or the like) and may be electrically connected to the distal electrode circuitry so as to serve as at least a portion of the distal electrode. This may permit the fixation device 130 to electrically stimulate the surrounding heart wall tissue (including the myocardium in some embodiments) when the wireless electrode assembly 26a is activated.
FIG. 4 also shows a pair of fourth wireless electrode assemblies 26d. The wireless electrode assembles 26d are mounted to the wall 30 of the left ventricle 32, one on the endocardial side (that is, inside the heart) and one on the epicardial side (that is, outside of the heart). The assemblies 26d include a "button-shaped" body 160, and are anchored to the wall 300 by helical tine fixation elements 162, which are attached to the seed body 160 at fixation point 164.
FIGS. 5-8 are diagrams of exemplary systems of leaded transmitter assemblies and leadless receiver electrode assemblies. The transmitters and receivers may be coupled together to permit energy transfer and information sharing, as previously described, in several different ways, including magnetic field coupling, electric field coupling, and ultrasonic coupling. While the descriptions below focus, for simplicity, on leaded transmitter assemblies and leadless receiver assemblies, in some implementations the leadless assemblies may both transmit and receive information, and similarly for the leaded assemblies. Referring first to FIG. 5, a diagram of an exemplary implementation that utilizes magnetic field coupling between a leadless electrode assembly and a leaded device is shown. For simplicity, a single lead 199 is shown attached to the pacing controller 10 in FIG. 5. Lead 199 may correspond to lead 14 of FIG. 1 or lead 50 of FIG. 2, and the distal end of lead 199 may be positioned, for example, in the right ventricle, the coronary sinus, outside of the left ventricle near an apex of the heart, or at some other appropriate location in or near the heart. As is conventional, lead 199 includes a protective and insulating shroud 206, or lead body, which may be flexible and elongate, according to an implementation. In this simplified example, lead 199 contains electrically isolated first and second lead conductors 200, 202, which are each independently electrically connected to the pacing controller 10 and also to a coil 203 near the distal end of lead
199. In an implementation, the first and second lead conductors 200, 202 may be referred to as a single lead conductor since collectively they provide a current path through the coil 203. The coil 203, in this example, is wound around a ferrite core 204, such that when time-varying current is passed from the pacing controller 10, through the first wire 200, through the coil 203, and back to the pacing controller 10 through the second wire 202, a magnetic field 214 is generated. Examples of time-varying current include alternating current (AC) or pulsed current.
The seed coil 212 may be inductively coupled to the lead coil 203 to permit transmissions from the leaded transmitter to the leadless receiver, according to an implementation. A change in current flow through the lead coil 203, as by supplying a time -varying current from pacing controller 10, may produce a magnetic field 214 that induces current flow in the seed coil 212. The efficiency of magnetic energy transmission can be relatively high if there are no absorbers of energy that compete with the seed coil 212, and if the seed coil 212 is in the near field of the lead coil 203 (e.g., within a distance equal to about a few times the linear dimensions of lead coil 203). At sufficiently low frequencies, the magnetic field energy generated when current flows into lead coil 203 is returned to the power supply when the current flows back out of the lead coil 203, minus energy absorbed by the seed coil 212. Energy coupling efficiency may generally increase with frequency. However, at frequencies higher than several megahertz, two additional losses may occur - some energy may continue out into space in the form of radiation, and some energy may be absorbed by conductive tissues of the body that surround the lead coil 203. Energy coupling efficiency may drop rapidly when seed coil 212 is in the far field of lead coil 203, because the magnetic field decreases with the cube of distance from the lead coil 203 in its far field. Energy coupling efficiency has a direct impact on the battery lifetime of pacing controller 10, and is directly proportional to battery lifetime when coupling losses dominate the controller energy budget. The geometry and magnetic properties of coils 212 and 203, as well as the operating frequency, can be tailored to optimize energy coupling efficiency for a given anticipated separation of the two coils 203 and 212. In an implementation, the two coils may be separated by a small distance (for example, a smallest distance allowable by human anatomy considerations) to optimize coupling efficiency and battery lifetime.
Similarly, a wireless electrode assembly (seed) 250 includes two conductors or wires 252, 254, each connected to one end of another ultrasonic transducer 256. Wires 252 and 254 also are connected to a seed circuit 216 within the seed 250, which may include capability for charge storage, electrical stimulation (pace) delivery, electrical sense, and information transmit, receive and storage. Seed 250 may correspond to any of the seeds shown in FIGS. 1-4 and described above. Ultrasonic coupling may provide an efficiency advantage because the beam produced upon transducer excitation may be more directed, permitting reduced loss when the receiving transducer is appropriately oriented relative to the transmitting transducer. Conversely, if the transmitted ultrasound beam only partially intersects receiver 256, the received energy may become too small to pace the tissue. The ultrasound energy transmission of FIG. 6 A may thus be more orientation- dependent than the magnetic energy transmission of FIG. 5.
In an implementation of the configuration shown in FIG. 6 A, permanent magnets 259 are included near the sites of transmitter 246 (magnet 259a) and receiver 256
(magnet 259b). The permanent magnets 259 may be aligned parallel to the lead and seed bodies, with opposite polarity on the lead and seed magnets for attraction. These magnets 259 may be placed at either end of transducers 246 and 256, or alongside the transducers. Multiple magnet configurations are possible. While the transducers 246, 256 are shown within the lead 240 and seed 250, respectively, the transducers 246, 256 (or a portion thereof, such as one or more surfaces of the transducer(s)) may be external to the lead 240 or seed 250, respectively. Seed circuit 216 may include the functionality described above with respect to the seed circuit of FIG. 5. FIG. 6B is an end view of the lead 240 and the seed 250 for an alternative implementation that includes magnets 259 on two sides of each of the transmitter 246 and receiver 256. As shown in FIG. 6B, two permanent magnets 259a are shown, each near opposite sides of the transmitter 246, and two permanent magnets 259b are similarly shown near opposite sides of the receiver 256. The configurations shown in FIG. 6A and FIG. 6B may permit the transmitter 246 and receiver 256 to be appropriately aligned, which may permit efficient energy transmission with minimal energy loss. FIGS. 7-8 are diagrams of exemplary implementations that utilize electric field coupling between a leadless electrode assembly and a leaded device. In these implementations, alternating current may be passed through the heart tissues from the lead to the seed. Since the heart may not respond to frequencies above about 100 kHz, and since radiation and absorption by the conductive tissues of the heart may not be a limiting factor at frequencies below about a few megahertz, electric field frequencies in the 100 kHz to 2 MHz range may be used in various implementations.
Electrodes 286 and 288 are not electrically connected, but may be appropriately positioned such that when time -varying current is passed from the pacing controller 10 through the first wire 282 to the first electrode 286, the current is able to flow across the space between the electrodes to the second electrode 288, and back to the pacing controller 10 through the second wire 284. This current flow generates an electric field 290. Examples of time-varying current may include alternating current or pulsed direct current.
Similarly, a wireless electrode assembly (seed) 292 contains a first wire 294 connected to a first seed electrode 295, and a second wire 296 connected to a second seed electrode 297, where the first and second seed electrodes 295, 297 are shown encircling the seed 292 on an exterior surface of the seed 292 in FIG. 7 A. Wires 294 and 296 also are connected to a seed circuit 216 within the seed 292, which may include capability for charge storage, electrical stimulation (pace) delivery, electrical sense, and information transmit, receive and storage. Seed 292 may correspond to any of the seeds shown in FIGS. 1-4 and described above. In an implementation, the lead electrodes 286, 288 are separated by a distance greater than the distance separating the seed electrodes 295, 297. Electrodes 295 and 297 may receive energy from transmitter electrodes 286 and 288 for a majority of the cardiac cycle, in some implementations. Pacing energy may be delivered to the tissue through the same seed electrodes 295 and 297 at appropriate timing. Since a typical duration of a pacing pulse may be less than 1/1, 000th of the duration of time between pacing pulses, electrodes 295 and 297 may be connected in a "receive" mode for a vast majority of the cardiac cycle.
Electrode 354 is shown in FIG. 8 as a conventional ring electrode, but may alternatively be a tip electrode or a coil. In some implementations, electrode 354 may be only on the side of the lead that faces the seed (e.g., a pad electrode or ring electrode insulated except for a portion of the ring that faces the seed), as may be facilitated by providing orienting permanent magnets to the lead and seed. When time -varying current, such as alternating current or pulsed direct current is passed from the pacing controller 10 through the wire 352 to the lead electrode 354, current is able to flow back to the pacing controller 10, and an electric field 356 may be generated. The wireless electrode assembly (seed) 292 shown in FIG. 8 is identical to that shown in FIG. 7, and may be coupled by the electric field 356, permitting the transfer of charge energy and/or information from the leaded device to the seed 292. According to some implementations, efficient transfer of energy between lead electrode 354 and seed electrodes 295 and 297 may occur when the distance between the lead and seed conductors is an integral number of half-wavelengths of the transmitted energy. Since the exact distance between lead and seed may not be known until the seed and lead have been implanted, provisions may be made to sweep the frequency of the RF transmitter until resonant energy transfer is detected. In each of the implementations described with respect to FIGS. 5-8, the lead or catheter may be described as containing a transmitting antenna, over which data and charge energy may be transmitted. Similarly, the seed may be described as containing a receiving antenna, by which corresponding data and/or charge energy may be received. In some implementations, seeds are capable of transmitting data and catheters/leads are capable of receiving data. It will be understood that the wires shown in FIGS. 5-8 are contained within the lead or within the seed, as appropriate, despite being shown in some cases with a solid line for simplicity, and similarly for the seed circuit 216 and transmitters and receivers. In some implementations, the magnets shown in FIGS. 5-8 may be within the lead or seed, while in other implementations the magnets may be on an exterior surface of the lead or seed. Magnets may optionally be used in any of the configurations described herein.
The seed circuit 216 has been described generally with respect to FIGS. 5-8. More specifically, the seed circuit 216 may contain a bridge rectifier connected across the receiver - that is, the coil 212 (FIG. 5), ultrasonic transducer 256 (FIGS. 6A, 6B), or electrodes 295, 297 (FIGS. 7A, 7B, 8) - to rectify the AC or pulsed DC current that is induced in the receiver by the magnetic field, ultrasonic beam, or electric field. In some implementations, a filter device may be connected across the receiver, and may pass only a single frequency of communication signal that is induced in the receiver. The single frequency of the communication signal that is passed by the filter device may be unique for the particular seed as compared to other implanted seeds. In this regard, the filter may be a narrow band pass filter with a frequency unique to a particular seed, and the incoming signal may be modulated with programming information. Alternatively, the filter may consist of any type of demodulator or decoder that receives analog or digital information induced by the leaded device in the receiver, including multimode communications. The received information may contain a code unique to each seed to command discharge of stored energy, along with more elaborate instructions controlling discharge parameters such as threshold voltage for firing, duration and shape of the discharge pulse, etc.
FIGS. 1OA and 1OB are diagrams of a heart 16 and another exemplary cardiac stimulation system using a leadless electrode assembly implanted in or near the heart. Referring first to FIG. 1OA, a pacing controller 10 is shown having a lead 500 electrically connected to the pacing controller at a proximal end and extending from the pacing controller 10. Atransmitter 502 is included near the distal end of the lead 500, and is positioned near an apex 504 of the heart 16. As described above with respect to the system shown in FIG. 1, the transmitter 502 may transmit energy or information via RF transmissions to leadless electrode assemblies, such as seed electrode assembly 505. Seed 505 may correspond to any of the seeds described previously in this document, and may be inductively coupled to receive transmitted charge energy or communications from the transmitter 502. The seed 505 may contain a charge storage device and a triggering mechanism to deliver stored electrical charge to adjacent heart tissue, according to an implementation.
In this implementation, the seed 505 is affixed to the inside of the left ventricle wall 30. FIG. 1OA shows additional electrode assemblies 506, 512, which are electrically connected to the seed electrode assembly 505 via micro leads 510 and 516, respectively. As shown in FIG. 1OA, electrode assembly 506 is affixed to the left ventricle free wall 30 via a helical tine fixation element 508, and electrode assembly 512 is affixed to the septal wall 40 of the left ventricle 32 via a helical tine fixation element 514. The seed electrode assembly 505 may pass energy or communications data, such as energy or communications received from the pacing controller 10 through the transmitter 502, to the additional electrode assemblies 506 and 512 over micro leads 510 and 516, respectively, and the electrode assemblies 506, 512 may then provide pacing stimulation to surrounding cardiac tissue. For example, electrode assembly 506 may provide pacing stimulation to surrounding tissue on the left ventricle free wall 30, and electrode assembly 512 may provide pacing stimulation to surrounding tissue on the septal wall 40 of the left ventricle 32. In this manner, cardiac synchronization may be improved as additional pacing sites may be realized in a coordinated fashion. More or fewer additional electrode assemblies 506, 512 may be included in other implementations. While the additional electrode assemblies 506, 512 are shown connected to the seed electrode assembly 505 via micro leads 510, 516, in other implementations the additional electrode assemblies 506, 512 may wirelessly communicate with the seed electrode assembly 505 or with the pacing controller 10 (through transmitter 502, for example). In these implementations, micro leads 510 and 516 may be omitted. FIG. 1OB is an expanded view of a portion of FIG. 1 OA.
Turning now to FIG. 11 , permanent magnets may be advantageously utilized to position and orient leadless electrode assemblies at desirable pacing sites. In some implementations, magnets may be used to position and orient leadless electrode assemblies with respect to leaded transmitters such that more efficient field coupling may be realized. FIG. 11 is a diagram of a leadless electrode assembly 600 in a heart chamber and a permanent magnet 602 positioned on an epicardial surface of the heart. The seed 600 is held against an endocardial surface of the heart — here, against the free wall 30 of the left ventricle — by a magnetic force associated with the permanent magnet 602, which is affixed epicardially outside of the left ventricle in FIG. 11. The seed 600 may include a permanent magnet that is attracted by magnetic force to the magnet 602. Over time, fibrotic tissue growth may encroach upon the seed 600 and more permanently affix the seed to the corresponding cardiac surface. This may prevent unintended dislodgement of the seed from the wall surface.
Leads may also contain permanent magnets to orient and position seeds. For example, in the system shown in FIG. 9 A and 9B, magnets associated with coils 402 may position and orient seeds 404 using associated magnetic forces. These can be used to help align the transmitter coils 402 with the receiver coils in the seeds 404, such that more efficient and tighter coupling is possible. Alternatively, permanent magnets may also be used to position and orient catheters. In an implementation, the magnets 602 may be included in magnet assemblies, and may be utilized to advantageously position and orient seeds 26 or catheters/leads such that efficient inductive coupling between transmitter and receiver may occur.
Referring again to FIG. 11 , attractive magnetic forces between the magnet 602 and the seed 600 or catheter/lead may cause the seed 600 or catheter/lead to be held in a desired position such that unintended movement of the seed 600 or catheter/lead does not occur. Each magnet assembly may includes a permanent magnet 602 for supplying magnetic force and a fixation element (not shown in FIG. 11), such as a helical tine fixation element, for securing the magnet assembly to heart tissue.
In another implementation, four button magnets may be used, with two near the transmitter and two near the receiver. In this example, one button magnet may be placed near each end of the transmitter, and similarly one button magnet may be placed near each end of the receiver. Magnetization here may be perpendicular to the axis of the seed. This implementation may be appropriate for systems using magnetic field coupling, such as the system described above in connection with FIG. 5. FIGS. 12-13 are flow charts of exemplary operations that can be performed by the systems of FIGS. 1-3 and 5-10. Referring first to FIG. 12, a method 700 of operating a cardiac pacing system begins, at step 705, with the wireless transmission of an energy signal. The energy signal may be transmitted by a transmitter that includes a wired lead whose distal end is positioned in a first chamber of a heart, according to an implementation. The energy transmission may include pacing energy, pacing information, or both, and may be effected by a generation of an electric field, a magnetic field, or an ultrasonic beam, according to some implementations. At step 710, the transmitted energy signal may be received. In an implementation, a wireless pacing electrode assembly positioned within a second chamber of the heart may receive the energy transmission. In some implementations, more than one wireless pacing electrode assembly may receive the transmitted energy signal, which may be transmitted from a single transmitter or multiple transmitters. In an implementation, the first chamber is a right ventricle of the heart and the second chamber is a left ventricle of the heart.
Turning now to FIG. 13, another method 750 of operating a cardiac pacing system is shown. An energy signal is wirelessly transmitted at step 755, and the transmitted signal is received at step 760. These two steps755, 760 may be identical to steps 705 and 710, respectively, described above with reference to FIG. 12, according to some implementations. At step 765, sense circuitry monitors for detection of a native cardiac electrical signal within a specified time period from the receipt of the transmitted signal. In an implementation, the wireless electrode assembly includes sense circuitry to sense the native cardiac electrical signal and timing circuitry to implement a monitoring period. If the patient is in normal sinus rhythm, the native cardiac electrical signal originates at the sino-atrial node of the heart, and may be sensed by controller 10 via right atrial lead 12. The controller may be programmed to deliver pacing pulses to leads in the ventricles at specific time delays relative to the sensed sinus beat (usually somewhat more than 100 msec, and may be a function of exertion sensed by an embedded accelerometer). Ventricle leads may be instructed to pace simultaneously or sequentially in a pattern that has been found to optimize cardiac hemodynamics. If the patient is being paced in the right atrium, the delays can be computed relative to the right atrium pacing pulse. If a native cardiac electrical signal is sensed at a given ventricle seed electrode before the programmed delay period has expired in step 765, the method ends. If, however, a native cardiac electrical signal is not sensed within the specified time period at step 765, a pacing pulse is issued to cardiac tissue at step 770. In an implementation, the wireless electrode assembly may issue or withhold the pacing pulse. In another implementation, the local signal sensed at the pacing site may be communicated to the controller 10, and if a native pacing signal is sensed within the delay period, the controller may not transmit pacing energy to the seed.
FIG. 14 is an exemplary block diagram of a pacing controller 10 that may be used with the systems of FIGS. 1-3 and 5-10. The exemplary pacing controller 10 includes circuits for communicating wirelessly with a wireless electrode assembly using a transmitter on an attached lead whose distal end is implanted in a chamber of the heart, or outside a chamber of the heart. In an implementation, the pacing controller 10 includes a processing unit 800, a pulse generator 805, one or more sense circuits 810, a switch matrix 815, a series of ports 820 into which leads may attach, memory 825, a telemetry circuit 830, and a battery 835. The processing unit 800 may be a programmable micro- controller or microprocessor, and may include one or more programmable logic devices (PLDs) or application specific integrated circuits (ASICs). The processing unit 800 may execute instructions and perform desired tasks as specified by the instructions. The memory 825 may include volatile and non-volatile memory, and may store the instructions that when executed by the processing unit 800 cause methods and processes to be performed by the pacing controller 10. In some implementations, the processing unit 800 may include memory as well. The memory 825 may be used to store pacing parameters and sensed information according to some implementations. The telemetry circuit 830 permits wireless RF communication with an external computing device, such as a programming device, such that information may be provided to the pacing controller 10 or supplied to the external computing device. The battery 835 supplies power to the circuits and modules of the pacing controller 10.
The pulse generator 805 may include one or more atrial pulse generator circuits 840 and one or more ventricular pulse generator circuits 845, each of which may generate pulses for transmission through the switch matrix 815 to a desired port, into which a cardiac lead may attach. Each pulse generator may include a current generation circuit, which may be capable of generating current, including time -varying current such as alternating current or pulsed direct current. The pulse generators may operate under the guidance of the processing unit 800, according to an implementation. In an implementation, the processing unit 800 directs the pulse generator 805 to generate an appropriate time -varying current that when passed through a lead conductor to a transmitter implanted in a first chamber of the heart, an electric, magnetic, or ultrasonic field is generated to couple a receiver in a wireless electrode assembly positioned in a second chamber of the heart for the transmission and reception of pacing energy, pacing information, or both.
The processing unit 800 includes a communications module 850, a timing module 855, and a stimulation control module 860, each connected by a communications bus 865. The processing unit may additionally include digital-to-analog (D/ A) converters, analog-to-digital (AJO) converters, timers, counters, filters, switches, etc. (not shown). The communications module 850, timing control module 855, and stimulation control module 860 may work individually or in concert to provide pacing stimuli to the heart and to control communication between a leaded transmitter and one or more leadless electrode assemblies. In an implementation, the processing unit 800 may encode information, such as a unique identifier, pacing threshold information, pulse width information, pacing trigger signals, demand pacing information, pace timing information, and the like, to be transmitted to the wireless electrode assemblies. The processing unit 800 may supply appropriate control signals to the pulse generator 805 to cause the pulse generator 805 to appropriately supply current to a leaded transmitter through the switch matrix 815, a corresponding port, and a lead conductor through an attached lead to cause the transmitter to emit an electric field, magnetic field, or ultrasonic beam, depending on type of transmitter utilized in the implementation. A receiver on the leadless electrode assembly may receive this information, decode and store it, and may use the information to issue pacing stimuli to surrounding cardiac tissue. The processing unit 800 may similarly control the pulse generator 805 to transmit pacing energy to the wireless electrode assembly, which may be stored and used to issue the pacing stimuli in a chamber of the heart different from the chamber in which the transmitter resides. Pacing energy may be delivered to the tissue directly upon receipt, or it may be stored until a low level communication trigger signal is received from the controller via the lead transducer.
WHAT IS CLAIMED IS: 1. A cardiac tissue excitation lead, comprising: a flexible elongate lead body having a proximal end adapted to be inserted into an implantable pulse generator assembly and having a distal end adapted to be positioned within a heart; a lead conductor extending within the lead body; and a transmitter assembly located near the distal end of the lead body and electrically connected to the pulse generator assembly via the lead conductor to wirelessly transmit pacing control information and pacing energy from the transmitter assembly to an implanted leadless electrode assembly.
2. The cardiac tissue excitation lead of claim 1 , wherein the transmitter assembly comprises a coil wound around a ferrite core
3. The cardiac tissue excitation lead of claim 2, wherein the wireless transmission of pacing control information and pacing energy occurs when the pulse generator assembly supplies a time -varying current to the coil through the lead conductor to emit a magnetic field.
4. The cardiac tissue excitation lead of claim 1 , wherein the transmitter assembly comprises an ultrasonic transducer.
6. The cardiac tissue excitation lead of claim 1 , wherein the transmitter assembly comprises a pair of separated electrodes.
9. The cardiac tissue excitation lead of claim 1 , wherein the pacing control information includes pace timing information and a pace trigger signal.
10. The cardiac tissue excitation lead of claim 1 , wherein the transmitter assembly comprises a plurality of transmitter assemblies located near the distal end of the lead body and electrically connected to the pulse generator assembly via the one or more lead conductors to wirelessly transmit pacing control information and pacing energy to a plurality of implanted leadless electrode assemblies.
12. An implantable cardiac tissue excitation system, comprising: an implantable pacing controller unit comprising a pulse generation circuit; a lead comprising a lead body extending between a proximal lead end attachable to the pacing controller unit and a distal lead end configured to be implanted within a heart, a lead conductor extending within the lead body, and a transmitter assembly located near the distal lead end, the transmitter assembly electrically connected to the pulse generation circuit through the lead conductor to wirelessly transmit pacing control information and charge energy from the transmitter assembly when the pulse generation circuit provides an electrical current to the transmitter assembly through the lead conductor; and a leadless electrode assembly configured to be implanted within the heart and comprising a receiver to receive the wireless transmission from the lead transmitter assembly, a charge storage unit to store the charge energy, and an electrical stimulation circuit to deliver an electrical stimulus to cardiac tissue using the pacing control information and the charge energy.
23. A method of operating a cardiac pacing system, the method comprising: transmitting an energy signal wirelessly from a wired lead whose distal end is positioned within a heart; receiving the transmitted energy signal at a wireless pacing electrode assembly positioned within the heart; and issuing a pacing pulse from the wireless pacing electrode assembly.
25. The method of claim 23 , wherein transmitting the energy signal wirelessly from a wired lead comprises generating an electric field created at the wired lead positioned in the first chamber of the heart.
26. The method of claim 23 , wherein transmitting the energy signal wirelessly from a wired lead comprises generating a magnetic field created at the wired lead positioned in the first chamber of the heart.
27. The method of claim 23 , wherein transmitting the energy signal wirelessly from a wired lead comprises generating an ultrasonic beam at the wired lead positioned in the first chamber of the heart.
31. A method of operating a cardiac pacing system, the method comprising: transmitting an energy signal wirelessly from a wired lead whose distal end is positioned in first chamber of a heart; receiving the transmitted energy signal at a wireless pacing electrode assembly positioned within a second chamber of the heart; and issuing, in response to receiving the transmitted energy signal, a pacing pulse from the wireless pacing electrode assembly to surrounding cardiac tissue unless a native cardiac electrical signal is sensed by the wireless pacing electrode assembly within a specified time period from the receipt of the transmitted signal.
32. The method of claim 31 , wherein the energy transmission comprises charging energy and pacing information.
33. The method of claim 31 , wherein the wireless pacing electrode assembly includes sense circuitry to sense the native cardiac electrical signal.
34. The method of claim 31 , wherein transmitting the energy signal wirelessly from a wired lead comprises generating an electric field created at the wired lead implanted in the first chamber of the heart.
35. The method of claim 31 , wherein transmitting the energy signal wirelessly from a wired lead comprises generating a magnetic field created at the wired lead implanted in the first chamber of the heart.
36. The method of claim 31 , wherein transmitting the energy signal wirelessly from a wired lead comprises generating an ultrasonic beam at the wired lead implanted in the first chamber of the heart.
37. The method of claim 31 , wherein the native cardiac electrical signal originates at a sino-atrial node of the heart.
PCT/US2007/078405 2006-09-13 2007-09-13 Cardiac stimulation using leadless electrode assemblies WO2008034005A2 (en)
US84459906P true 2006-09-13 2006-09-13
US60/844,599 2006-09-13
WO2008034005A2 true WO2008034005A2 (en) 2008-03-20
WO2008034005A3 WO2008034005A3 (en) 2008-07-10
PCT/US2007/078405 WO2008034005A2 (en) 2006-09-13 2007-09-13 Cardiac stimulation using leadless electrode assemblies
WO (1) WO2008034005A2 (en)
2007-09-13 WO PCT/US2007/078405 patent/WO2008034005A2/en active Application Filing
2007-09-13 US US11/854,844 patent/US8644934B2/en active Active
2014-01-23 US US14/162,446 patent/US9956401B2/en active Active
FR2983078A1 (en) * 2011-11-24 2013-05-31 Laurent Berneman Medical device having muscle stimulation electrodes and an electromagnetic sensor
US20140135865A1 (en) 2014-05-15
US9956401B2 (en) 2018-05-01
US20090018599A1 (en) 2009-01-15
US8644934B2 (en) 2014-02-04
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