Patent Application
20100100148
Subject matter presented herein relates generally to techniques to optimize timing of stimuli for cardiac pacing therapies.
Cardiac resynchronization therapy (CRT) provides an electrical solution to the symptoms and other difficulties brought on by heart failure (HF). CRT can call for delivery of electrical stimuli to the heart in a manner that synchronizes contraction and enhances performance. When CRT delivers stimuli to the right and left ventricles, this is called bi-ventricular pacing. Bi-ventricular pacing aims to improve efficiency of each contraction of the heart and the amount of blood pumped to the body. This helps to lessen the symptoms of heart failure and, in many cases, helps to stop the progression of the disease.
CRT is typically administered via an implantable device such as a pacemaker (e.g., called a CRT-P) or an ICD that has a built-in pacemaker (e.g., called a CRT-D). A CRT-D has the added ability to defibrillate the heart if a patient is at risk for life-threatening arrhythmias. Most traditional ICDs or pacemakers have either one lead placed in the heart's right upper chamber (right atrium, or RA) or the heart's RV, or two leads, placed in the heart's RA and RV. CRT devices typically have three leads: one in the RA, one in the RV, and one in the left ventricle (LV). Such a configuration allows for bi-ventricular pacing.
CRT devices typically include more features than a conventional pacing or ICD device. Some of these features require periodic execution, which can deplete a device's energy and even cause a patient to experience discomfort or sub-optimal therapy. As the number of features increase, a need exists for uncovering and capitalizing on synergies that may exist between various features. Various exemplary technologies disclosed herein aim to meet this need and/or other needs.
An exemplary method includes performing a ventricular capture assessment, determining a ventricular paced propagation delay (PPD) and/or an interventricular conduction delay (IVCD) using information acquired during the ventricular capture assessment and optimizing at least an interventricular delay (VV) based at least in part on the ventricular paced propagation delay (PPD) and/or the interventricular conduction delay (IVCD). Another exemplary method includes performing an atrial capture assessment, determining an atrial evoked response width (ΔA) and one or more atrio-ventricular intervals (AR) using information acquired during the atrial capture assessment and optimizing an atrio-ventricular (PV or AV) delay based at least in part on the atrial evoked response width (ΔA) and the one or more atrio-ventricular intervals (AR). Other exemplary methods, devices, systems, etc., are also disclosed.
In general, the various methods, devices, systems, etc., described herein, and equivalents thereof, are optionally suitable for use in a variety of pacing therapies and other cardiac related therapies.
Features and advantages of the described implementations can be more readily understood by reference to the following description taken in conjunction with the accompanying drawings.
The following description includes the best mode presently contemplated for practicing the described implementations. This description is not to be taken in a limiting sense, but rather is made merely for the purpose of describing the general principles of the implementations. The scope of the described implementations should be ascertained with reference to the issued claims. In the description that follows, like numerals or reference designators will be used to reference like parts or elements throughout.
The AutoCapture™ set of algorithms (St. Jude Medical, Inc., Sylmar, Calif.) is a leading feature in the CRMD device industry for capture assessment and the QuickOpt™ set of algorithms (St. Jude Medical, Inc., Sylmar, Calif.) is a first-to-market feature for CRT optimization. As described herein, various synergies are identified between these two technologies, which may be applied, generally, to many capture and timing assessment techniques. Synergies are described in sensing/pacing configurations and testing so that several tests can be combined, which may result in a hybrid method. Combined algorithms can help reduce clinical risks and patient symptoms, simplify load of routine tests and conserve resources.
Various examples show how information acquired during execution of capture assessment algorithms can be used to optimize timings, especially for delivery of CRT or other multisite pacing therapies (e.g., twin site left ventricular pacing).
An exemplary implantable device is described followed by a summary of capture algorithms and timing algorithms. These algorithms are then described in detail along with techniques to use information acquired during capture assessment to optimize one or more timing parameters. An exemplary system that includes an implantable device programmer is also disclosed.
The techniques described below are optionally implemented in connection with any stimulation device that is configured or configurable to stimulate and/or shock tissue. With respect to assessment of cardiac condition, an implantable device may provide for acquiring information and analyzing information to assess cardiac condition even in the instance that the device does not provide for (or is not configured/programmed for) delivery of stimulation therapy.
The right atrial lead 104, as the name implies, is positioned in and/or passes through a patient's right atrium. The right atrial lead 104 optionally senses atrial cardiac signals and/or provides for right atrial chamber stimulation therapy. The right atrial lead 104 may be used in conjunction with one or more other leads and/or electrodes to acquire cardiac electrograms and/or to delivery energy to the heart or other tissue. As shown in
To sense atrial cardiac signals, ventricular cardiac signals and/or to provide chamber pacing therapy, particularly on the left side of a patient's heart, the stimulation device 100 is coupled to a coronary sinus lead 106 designed for placement in the coronary sinus and/or tributary veins of the coronary sinus. Thus, the coronary sinus lead 106 is optionally suitable for positioning at least one distal electrode adjacent to the left ventricle and/or additional electrode(s) adjacent to the left atrium. In a normal heart, tributary veins of the coronary sinus include, but may not be limited to, the great cardiac vein, the left marginal vein, the left posterior ventricular vein, the middle cardiac vein, and the small cardiac vein.
In the example of
An exemplary coronary sinus lead 106 can be designed to receive ventricular cardiac signals (and optionally atrial signals) and to deliver left ventricular pacing therapy using, for example, at least one of the electrodes 123 and/or the tip electrode 122. The lead 106 optionally allows for left atrial pacing therapy, for example, using at least the left atrial ring electrode 124. The lead 106 optionally allows for shocking therapy, for example, using at least the left atrial coil electrode 126. For a complete description of a coronary sinus lead, the reader is directed to U.S. Pat. No. 5,466,254, “Coronary Sinus Lead with Atrial Sensing Capability” (Helland), which is incorporated herein by reference.
The coronary sinus lead 106 further optionally includes electrodes for stimulation of other tissue. Such a lead may include pacing and autonomic nerve stimulation functionality and may further include bifurcations or legs. For example, an exemplary coronary sinus lead includes pacing electrodes capable of delivering pacing pulses to a patient's left ventricle and at least one electrode capable of stimulating an autonomic nerve. An exemplary coronary sinus lead (or left ventricular lead or left atrial lead) may also include at least one electrode capable of stimulating an autonomic nerve, non-myocardial tissue, other nerves, etc., wherein such an electrode may be positioned on the lead or a bifurcation or leg of the lead.
Stimulation device 100 is also shown in electrical communication with the patient's heart 102 by way of an implantable right ventricular lead 108 having, in this exemplary implementation, a right ventricular tip electrode 128, a right ventricular ring electrode 130, a right ventricular (RV) coil electrode 132, and an SVC coil electrode 134. Typically, the right ventricular lead 108 is transvenously inserted into the heart 102 to place the right ventricular tip electrode 128 in the right ventricular apex so that the RV coil electrode 132 will be positioned in the right ventricle and the SVC coil electrode 134 will be positioned in the superior vena cava. Accordingly, the right ventricular lead 108 is capable of sensing or receiving cardiac signals, and delivering stimulation in the form of pacing and shock therapy to the right ventricle. An exemplary right ventricular lead may also include at least one electrode capable of stimulating an autonomic nerve, non-myocardial tissue, other nerves, etc., wherein such an electrode may be positioned on the lead or a bifurcation or leg of the lead. A right ventricular lead may include a series of electrodes, such as the series 123 of the left ventricular lead 106.
Housing 200 for stimulation device 100 is often referred to as the “can”, “case” or “case electrode”, and may be programmably selected to act as the return electrode for all “unipolar” modes. Housing 200 may further be used as a return electrode alone or in combination with one or more of the coil electrodes 126, 132 and 134 for shocking purposes. In general, housing 200 may be used as an electrode in any of a variety of electrode configurations. Housing 200 further includes a connector (not shown) having a plurality of terminals 201, 202, 204, 206, 208, 212, 214, 216, 218, 221, 223 (shown schematically and, for convenience, the names of the electrodes to which they are connected are shown next to the terminals).
To achieve right atrial sensing, pacing and/or autonomic stimulation, the connector includes at least a right atrial tip terminal (AR TIP) 202 adapted for connection to the atrial tip electrode 120. A right atrial ring terminal (AR RING) 201 is also shown, which is adapted for connection to the atrial ring electrode 121.
To achieve left chamber sensing, pacing, shocking, and/or autonomic stimulation, the connector includes at least a left ventricular tip terminal (VL TIP) 204, a left atrial ring terminal (AL RING) 206, and a left atrial shocking terminal (AL COIL) 208, which are adapted for connection to the left ventricular tip electrode 122, the left atrial ring electrode 124, and the left atrial coil electrode 126, respectively.
A terminal 223 allows for connection of a series of left ventricular electrodes. For example, the series of four electrodes 123 of the lead 106 may connect to the device 100 via the terminal 223. The terminal 223 and an electrode configuration switch 226 allow for selection of one or more of the series of electrodes and hence electrode configuration. In the example of
Connection to suitable autonomic nerve stimulation electrodes is also possible via aforementioned terminals and/or other terminals (e.g., via a nerve stimulation terminal S ELEC 221).
To support right chamber sensing, pacing, shocking, and/or autonomic nerve stimulation, the connector further includes a right ventricular tip terminal (VR TIP) 212, a right ventricular ring terminal (VR RING) 214, a right ventricular shocking terminal (RV COIL) 216, and a superior vena cava shocking terminal (SVC COIL) 218, which are adapted for connection to the right ventricular tip electrode 128, right ventricular ring electrode 130, the RV coil electrode 132, and the SVC coil electrode 134, respectively. Connection to suitable autonomic nerve stimulation electrodes is also possible via these and/or other terminals (e.g., via the nerve stimulation terminal S ELEC 221).
At the core of the stimulation device 100 is a programmable microcontroller 220 that controls the various modes of stimulation therapy. As is well known in the art, microcontroller 220 typically includes a microprocessor, or equivalent control circuitry, designed specifically for controlling the delivery of stimulation therapy, and may further include RAM or ROM memory, logic and timing circuitry, state machine circuitry, and I/O circuitry. Typically, microcontroller 220 includes the ability to process or monitor input signals (data or information) as controlled by a program code stored in a designated block of memory. The type of microcontroller is not critical to the described implementations. Rather, any suitable microcontroller 220 may be used that carries out the functions described herein. The use of microprocessor-based control circuits for performing timing and data analysis functions are well known in the art.
Representative types of control circuitry that may be used in connection with the described embodiments can include the microprocessor-based control system of U.S. Pat. No. 4,940,052 (Mann et al.), the state-machine of U.S. Pat. Nos. 4,712,555 (Thornander et al.) and 4,944,298 (Sholder), all of which are incorporated by reference herein. For a more detailed description of the various timing intervals used within the stimulation device and their inter-relationship, see U.S. Pat. No. 4,788,980 (Mann et al.), also incorporated herein by reference.
Microcontroller 220 further includes timing control circuitry 232 to control the timing of the stimulation pulses (e.g., pacing rate, atrio-ventricular (AV) delay, atrial interconduction (ΔA) delay, or ventricular interconduction (VV) delay, etc.) as well as to keep track of the timing of refractory periods, blanking intervals, noise detection windows, evoked response windows, alert intervals, marker channel timing, etc., which is well known in the art.
Microcontroller 220 further includes an arrhythmia detector 234, a capture assessment module 235, a morphology detector 236, and optionally an orthostatic compensator and a minute ventilation (MV) response module, the latter two are not shown in
Microcontroller 220 further includes a cardiac damage module 237 for analyzing information to determine location of one or more cardiac regions or zones, for example, as related to cardiac damage and/or health. The module 237 may use information acquired via one or more of the physiological sensor 270, information acquired via a lead (consider, e.g., leads 104, 106, 108, 110), and/or information acquired via the telemetry circuit 264 (e.g., from an external device). The module 237 may receive information from one or more modules and/or transmit information to one or more modules. The module 237 may act to control various features of the device 100 (e.g., timing of stimulation, timing of sensing, etc.). Module 237 may be implemented in hardware as part of the microcontroller 220, or as software/firmware instructions programmed into the device and executed on the microcontroller 220 during certain modes of operation.
Microcontroller 220 further includes a cardiac timing information module 238 for determining one or more cardiac timing parameters. The module 238 may include logic to determine an intrinsic conduction delay between right ventricular activation and left ventricular activation, an interval between stimulation of one ventricle and sensing of propagated electrical activity to the other ventricle, etc. Module 238 may be implemented in hardware as part of the microcontroller 220, or as software/firmware instructions programmed into the device and executed on the microcontroller 220 during certain modes of operation. The module 238 may operate based in part on analyses performed using the module 237. Further, while the modules are shown as individual modules, other arrangements are possible. The module 238 may operate based in part on information acquired using a capture algorithm or, more generally, a capture assessment method.
As described herein, the module 238 may perform a variety of tasks related to paced propagation delays (PPDs) and/or intervals. A paced propagation delay (PPD) may be considered a “travel” time for a wavefront and may be measured from a delivery time of a stimulus to a feature time as sensed on a wavefront resulting from the stimulus (e.g., a feature of an evoked response). For example, a paced propagation delay may be measured from a delivery time of a right ventricular stimulus to a maximum positive slope (e.g., repolarization) of an evoked response in the right ventricle. Such a delay may be used to help determine one or more parameters for delivery of CRT.
The electronic configuration switch 226 includes a plurality of switches for connecting the desired electrodes to the appropriate I/O circuits, thereby providing complete electrode programmability. Accordingly, switch 226, in response to a control signal 242 from the microcontroller 220, determines the polarity of the stimulation pulses (e.g., unipolar, bipolar, combipolar, etc.) by selectively closing the appropriate combination of switches (not shown) as is known in the art.
Atrial sensing circuits 244 and ventricular sensing circuits 246 may also be selectively coupled to the right atrial lead 104, coronary sinus lead 106, the right ventricular lead 108 and/or the lead 110 through the switch 226 for detecting the presence of cardiac activity in each of the four chambers of the heart. Accordingly, the atrial (ATR. SENSE) and ventricular (VTR. SENSE) sensing circuits 244 and 246 may include dedicated sense amplifiers, multiplexed amplifiers or shared amplifiers. Switch 226 can determine the “sensing polarity” of the cardiac signal by selectively closing the appropriate switches, as is also known in the art. In this way, a clinician may program the sensing polarity independent of the stimulation polarity. An exemplary method may optionally control polarity. For example, the module 237 may include control logic to select an electrode configuration with a particular polarity. The sensing circuits (e.g., 244 and 246) are optionally capable of obtaining information indicative of tissue capture for use by the capture assessment module 235. As described further below, capture information may be used to assess cardiac condition and/or to optimize delivery of a stimulation therapy.
Each sensing circuit 244 and 246 preferably employs one or more low power, precision amplifiers with programmable gain and/or automatic gain control, bandpass filtering, and a threshold detection circuit, as known in the art, to selectively sense the cardiac signal of interest. The automatic gain control enables the device 100 to deal effectively with the difficult problem of sensing the low amplitude signal characteristics of atrial or ventricular fibrillation.
The outputs of the atrial and ventricular sensing circuits 244 and 246 are connected to the microcontroller 220, which, in turn, is able to trigger or inhibit the atrial and ventricular pulse generators 222 and 224, respectively, in a demand fashion in response to the absence or presence of cardiac activity in the appropriate chambers of the heart. Furthermore, as described herein, the microcontroller 220 is also capable of analyzing information output from the sensing circuits 244 and 246 and/or the data acquisition system 252 to determine or detect whether and to what degree tissue capture has occurred and to program a pulse, or pulses, in response to such determinations. The sensing circuits 244 and 246, in turn, receive control signals over signal lines 248 and 250 from the microcontroller 220 for purposes of controlling the gain, threshold, polarization charge removal circuitry (not shown), and the timing of any blocking circuitry (not shown) coupled to the inputs of the sensing circuits 244 and 246, as is known in the art.
Information acquired by any of the sensing circuits (e.g., 244, 246, 252) is optionally used in a control scheme implemented at least in part by the microcontroller 220. For example, the module 237 may use cardiac electrograms acquired via the ventricular sensing circuitry 246 in an analysis that aims to determine location of one or more cardiac regions or zones. In turn, such an analysis may be used by the module 238 to determine timing for delivery of a pacing pulse or pulses.
For arrhythmia detection, the device 100 utilizes the atrial and ventricular sensing circuits 244 and 246 to sense cardiac signals to determine whether a rhythm is physiologic or pathologic. In reference to arrhythmias, as used herein, “sensing” is reserved for the noting of an electrical signal or obtaining data (information), and “detection” is the processing (analysis) of these sensed signals and noting the presence of an arrhythmia. In some instances, detection or detecting includes sensing and in some instances sensing of a particular signal alone is sufficient for detection (e.g., presence/absence, etc.).
The timing intervals between sensed events (e.g., P-waves, R-waves, and depolarization signals associated with fibrillation) are then classified by the arrhythmia detector 234 of the microcontroller 220 by comparing them to a predefined rate zone limit (i.e., bradycardia, normal, low rate VT, high rate VT, and fibrillation rate zones) and various other characteristics (e.g., sudden onset, stability, physiologic sensors, and morphology, etc.) in order to determine the type of remedial therapy that is needed (e.g., bradycardia pacing, anti-tachycardia pacing, cardioversion shocks or defibrillation shocks, collectively referred to as “tiered therapy”).
Cardiac signals are also applied to inputs of an analog-to-digital (A/D) data acquisition system 252. The data acquisition system 252 is configured to acquire cardiac electrogram signals (e.g., intracardiac electrograms or other), convert the raw analog data into a digital signal, and store the digital signals for later processing and/or telemetric transmission to an external device 254. The data acquisition system 252 is coupled to the right atrial lead 104, the coronary sinus lead 106, the right ventricular lead 108 and/or the lead 110 through the switch 226 to sample cardiac signals or other signals (e.g., nerves, etc.) across any pair of desired electrodes.
The microcontroller 220 is further coupled to a memory 260 by a suitable data/address bus 262, wherein the programmable operating parameters used by the microcontroller 220 are stored and modified, as required, in order to customize the operation of the stimulation device 100 to suit the needs of a particular patient. Such operating parameters define, for example, pacing pulse amplitude, pulse duration, electrode polarity, rate, sensitivity, automatic features, arrhythmia detection criteria, and the amplitude, waveshape, number of pulses, and vector of each shocking pulse to be delivered to the patient's heart 102 within each respective tier of therapy. The exemplary device 100 typically includes capabilities to acquire (e.g., sense or otherwise receive) and store a relatively large amount of data (e.g., from the atrial sensing circuitry 244, the ventricular sensing circuitry 246, data acquisition system 252, the one or more physiological sensors 270, the telemetry circuit 264), which data may then be used for subsequent analysis to guide operation of the device 100.
Advantageously, the operating parameters of the implantable device 100 may be non-invasively programmed into the memory 260 through a telemetry circuit 264 in telemetric communication via communication link 266 with the external device 254, such as a programmer, transtelephonic transceiver, or a diagnostic system analyzer. The microcontroller 220 activates the telemetry circuit 264 with a control signal 268. The telemetry circuit 264 advantageously allows intracardiac electrograms and status information relating to the operation of the device 100 (as contained in the microcontroller 220 or memory 260) to be sent to the external device 254 through an established communication link 266.
The stimulation device 100 can further include one or more physiological sensors 270. For example, the device 100 may include a rate-responsive sensor for use in adjusting a pacing stimulation rate according to a sensed activity state (e.g., rest, exercise, etc.) of a patient. The one or more physiological sensors 270 may be capable of acquiring information for use in detecting changes in cardiac output (see, e.g., U.S. Pat. No. 6,314,323, entitled “Heart stimulator determining cardiac output, by measuring the systolic pressure, for controlling the stimulation”, to Ekwall, issued Nov. 6, 2001, which discusses a pressure sensor adapted to sense pressure in a right ventricle and to generate an electrical pressure signal corresponding to the sensed pressure, an integrator supplied with the pressure signal which integrates the pressure signal between a start time and a stop time to produce an integration result that corresponds to cardiac output), detecting changes in the physiological condition of the heart, detecting diurnal changes in activity (e.g., detecting sleep and wake states), etc. Accordingly, the microcontroller 220 may respond by adjusting any of the various pacing parameters (such as rate, ΔA delay, AV delay, VV delay, etc.) at which the atrial and ventricular pulse generators, 222 and 224, generate stimulation pulses. As already mentioned, a device may acquire information and then use the information to assess cardiac condition, regardless of whether the device is configured or programmed to delivery a stimulation therapy.
While shown as being included within the stimulation device 100, it is to be understood that any of the one or more physiological sensors 270 may also be external to the stimulation device 100, yet implanted within or carried by a patient. Examples of physiological sensors that may be implemented in device 100 include known sensors that, for example, sense respiration rate, pH of blood, ventricular gradient, cardiac output, preload, afterload, contractility, hemodynamics, pressure, and so forth. Another sensor that may be used is one that detects activity variance, wherein an activity sensor is monitored diurnally to detect the low variance in the measurement corresponding to the sleep state. For a complete description of the activity variance sensor, the reader is directed to U.S. Pat. No. 5,476,483 (Bornzin et al.), issued Dec. 19, 1995, which patent is hereby incorporated by reference.
More specifically, the one or more physiological sensors 270 optionally include sensors for detecting movement and minute ventilation in the patient. The one or more physiological sensors 270 may include a position sensor and/or a minute ventilation (MV) sensor to sense minute ventilation, which is defined as the total volume of air that moves in and out of a patient's lungs in a minute. Signals generated by the position sensor and MV sensor are passed to the microcontroller 220 for analysis in determining whether to adjust the pacing rate, etc. The microcontroller 220 monitors the signals for indications of the patient's position and activity status, such as whether the patient is climbing upstairs or descending downstairs or whether the patient is sitting up after lying down.
The one or more physiological sensors 270 may include a pressure sensor. Pressure sensors for sensing left atrial pressure are discussed in U.S. Patent Application US2003/0055345 A1, to Eigler et al., which is incorporated by reference herein. The discussion pertains to a pressure transducer permanently implantable within the left atrium of the patient's heart and operable to generate electrical signals indicative of fluid pressures within the patient's left atrium. According to Eigler et al., the pressure transducer is connected to a flexible electrical lead, which is connected in turn to electrical circuitry, which includes digital circuitry for processing electrical signals. Noted positions of the transducer include within the left atrium, within a pulmonary vein, within the left atrial appendage and in the septal wall.
The exemplary device 100 optionally includes a connector capable of connecting a lead that includes a pressure sensor. For example, the connector 221 optionally connects to a pressure sensor capable of receiving information pertaining to chamber pressures or other pressures.
The one or more physiological sensors 270 optionally include an oxygen sensor. The companies Nellcor (Pleasanton, Calif.) and Masimo Corporation (Irvine, Calif.) market pulse oximeters that may be used externally (e.g., finger, toe, etc.). Where desired, information from such external sensors may be communicated wirelessly to the implantable device using appropriate circuitry such as that found in a programmer for an implantable device (see, e.g., the programmer 1430 of
The exemplary device 100 optionally includes a connector capable of connecting a lead that includes a sensor for sensing oxygen information. For example, the connector 221 optionally connects to a sensor for sensing information related blood oxygen concentration. Such information is optionally processed or analyzed by any of the various modules.
The stimulation device 100 optionally includes circuitry capable of sensing heart sounds and/or vibration associated with events that produce heart sounds. Such circuitry may include an accelerometer as conventionally used for patient position and/or activity determinations. Accelerometers typically include two or three sensors aligned along orthogonal axes. For example, a commercially available micro-electromechanical system (MEMS) marketed as the ADXL330 by Analog Devices, Inc. (Norwood, Mass.), is a small, thin, low power, complete three axis accelerometer with signal conditioned voltage outputs, all on a single monolithic IC. The ADXL330 product measures acceleration with a minimum full-scale range of ±3 g. It can measure the static acceleration of gravity in tilt-sensing applications, as well as dynamic acceleration resulting from motion, shock, or vibration. Bandwidths can be selected to suit the application, with a range of 0.5 Hz to 1,600 Hz for X and Y axes, and a range of 0.5 Hz to 550 Hz for the Z axis. Various heart sounds include frequency components lying in these ranges. The ADXL330 is available in a small, low-profile, 4 mm×4 mm×1.45 mm, 16-lead, plastic lead frame chip scale package (LFCSP_LQ).
While an accelerometer may be included in the case of an implantable pulse generator device, alternatively, an accelerometer communicates with such a device via a lead or through electrical signals conducted by body tissue and/or fluid. In the latter instance, the accelerometer may be positioned to advantageously sense vibrations associated with cardiac events. For example, an epicardial accelerometer may have improved signal to noise for cardiac events compared to an accelerometer housed in a case of an implanted pulse generator device.
As described herein, ischemia, injury and/or infarct may be detectable by various changes in physiology and hence by any of a variety of physiologic sensors, which can include use of aforementioned leads 104, 106, 108, 110 as electrical activity sensors. Ischemia, injury and/or infarct may be detectable based on temperature changes, decreased local myocardial pressure, decreased myocardial pH, decreased myocardial pO2, increased myocardial pCO2, increased myocardial lactate, increased ratio of lactate to pyruvate in the myocardium, increased ratio of the reduced form of nicotine amide adenine dinucleotide (NADH) to nicotine amide adenine dinucleotide (NAD+) in the myocardium, increased ratio of the reduced form of nicotinamine-adenine dinucleotide phosphate (NADPH) to nicotinamine-adenine dinucleotide phosphate (NADPH) in the myocardium, increased ST segment, decreased ST segment, ventricular tachycardia, T wave changes, QRS changes, decreased patient activity, increased respiratory rate, decreased transthoracic impedance, decreased cardiac output, increased pulmonary artery diastolic pressure, increased myocardial creatinine kinase, increased troponin, and changed myocardial wall motion. Sensed information pertaining to ischemia, injury and/or infarct as well as exemplary mechanisms for sensing such information is discussed in more detail below.
The stimulation device additionally includes a battery 276 that provides operating power to all of the circuits shown in
The stimulation device 100 can further include magnet detection circuitry (not shown), coupled to the microcontroller 220, to detect when a magnet is placed over the stimulation device 100. A magnet may be used by a clinician to perform various test functions of the stimulation device 100 and/or to signal the microcontroller 220 that the external programmer 254 is in place to receive or transmit data to the microcontroller 220 through the telemetry circuits 264.
The stimulation device 100 further includes an impedance measuring circuit 278 that is enabled by the microcontroller 220 via a control signal 280. The known uses for an impedance measuring circuit 278 include, but are not limited to, lead impedance surveillance during the 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 or minute ventilation; measuring thoracic impedance for determining shock thresholds, edema, heart failure or other indicators; detecting when the device has been implanted; measuring stroke volume; and detecting the opening of heart valves; etc. The impedance measuring circuit 278 is advantageously coupled to the switch 226 so that any desired electrode may be used.
In the case where the stimulation device 100 is intended to operate as an implantable cardioverter/defibrillator (ICD) device, it detects the occurrence of an arrhythmia, and automatically applies an appropriate therapy to the heart aimed at terminating the detected arrhythmia. To this end, the microcontroller 220 further controls a shocking circuit 282 by way of a control signal 284. The shocking circuit 282 generates shocking pulses of low (e.g., up to approximately 0.5 J), moderate (e.g., approximately 0.5 J to approximately 10 J), or high energy (e.g., approximately 11 J to approximately 40 J), as controlled by the microcontroller 220. Such shocking pulses are applied to the patient's heart 102 through at least two shocking electrodes, and as shown in this embodiment, selected from the left atrial coil electrode 126, the RV coil electrode 132, and/or the SVC coil electrode 134. As noted above, the housing 200 may act as an active electrode in combination with the RV electrode 132, or as part of a split electrical vector using the SVC coil electrode 134 or the left atrial coil electrode 126 (i.e., using the RV electrode as a common electrode). Other exemplary devices may include one or more other coil electrodes or suitable shock electrodes (e.g., a LV coil, etc.).
Cardioversion level shocks are generally considered to be of low to moderate energy level (where possible, so as to minimize pain felt by the patient), and/or synchronized with an R-wave and/or pertaining to the treatment of tachycardia. Defibrillation shocks are generally of moderate to high energy level (i.e., corresponding to thresholds in the range of approximately 5 J to approximately 40 J), delivered asynchronously (since R-waves may be too disorganized), and pertaining exclusively to the treatment of fibrillation. Accordingly, the microcontroller 220 is capable of controlling the synchronous or asynchronous delivery of the shocking pulses.
The device 100 may be configured to delivery cardiac resynchronization therapy. In general, cardiac resynchronization therapy delivers stimulation to improve overall cardiac function. This may have the additional beneficial effect of reducing the susceptibility to life-threatening tachyarrhythmias. CRT and related therapies are discussed in, for example, U.S. Pat. No. 6,643,546 (Mathis et al.), entitled “Multi-Electrode Apparatus and Method for Treatment of Congestive Heart Failure”; U.S. Pat. No. 6,628,988 (Kramer et al.) entitled “Apparatus and Method for Reversal of Myocardial Remodeling with Electrical Stimulation”; and U.S. Pat. No. 6,512,952 (Stahmann et al.), entitled “Method and Apparatus for Maintaining Synchronized Pacing,” which are incorporated by reference herein. An exemplary implantable CRT device optionally includes electrodes for epicardial placement. For example, the lead 110 may include one or more electrodes for epicardial placement.
The one or more coordination algorithms 305 may be considered as ensuring that information is used effectively, for example, to reduce test time, to reduce number of tests, to reduce energy usage, etc., as associated with various algorithms. The one or more coordination algorithms 305 may include instructions to override triggering and/or scheduling mechanisms of capture algorithms 312 and/or to override triggering and/or scheduling mechanisms of timing algorithms 362.
As described herein, an exemplary device includes one or more coordination algorithms (e.g., control logic) that allow information acquired using one or more capture algorithms to be used by one or more timing algorithms. Such a device may include the coordination algorithm(s) 305, the capture algorithms 310 and the timing algorithms 360. The one or more coordination algorithms may also allow for coordinating execution of capture algorithms and timing algorithms, especially where information acquired by a capture algorithm can assist in assessing one or more timing parameters of the timing algorithms.
As shown in the example of
An atrial capture algorithm 320 may include, for example, features of a commercially available atrial capture algorithm marketed as the ACap™ algorithm (St. Jude Medical Inc., Sylmar, Calif.). This algorithm is a confirm feature, which periodically verifies the amount of energy needed for the upper chambers of the heart (atria) to respond to stimulation pulses emitted by a pacing device. Based on the results of this periodic check, a device can automatically self-adjust the energy output required to cause capture.
The right ventricular capture algorithm 330 and the left ventricular capture algorithm 340 may include, for example, features of a commercially available set of algorithms for ventricular capture referred to as the Beat-by-Beat Ventricular AutoCapture™ algorithms (St. Jude Medical, Inc., Sylmar, Calif.). These algorithms include the following features: (a) automatic capture verification, which monitors every beat for the presence of an evoked response (e.g., the signal resulting from electrical activation of the myocardium by a delivered stimulus); (b) automatic stimulation threshold search, which measures myocardial activation thresholds on a regular basis to determine output energy level requirement to readily achieve capture; (c) loss of capture recovery, which triggers an automatic delivery of energy as a backup to ensure capture in the absence of an evoked response; and (d) automatic output regulation, which sets the output energy just above the measured threshold energy level to help ensure that a low and reliable energy level for capture is used (e.g., to help optimize battery longevity). Such algorithms may be used with any of a variety of lead configurations. For example, capabilities for unipolar leads are provided in addition to capabilities for standard bipolar leads.
As shown in the example of
The algorithms of
Various studies have related cardiac electrograms to damage. For example, subendocardial ischemia can prolong local recovery time. Since repolarization normally proceeds in an epicardial-to-endocardial direction, delayed recovery in the subendocardial region due to ischemia does not reverse the direction of repolarization but merely lengthens it. This generally results in a prolonged QT interval or increased amplitude of the T wave or both as recorded by the electrodes overlying, or otherwise sensing activity at, the subendocardial ischemic region. As described herein, a cardiac electrogram may be analyzed for evidence of myocardial damage. A long paced propagation delay, a high capture threshold, a long interventricular conduction delay, etc., can serve as indicators of myocardial damage.
The timing algorithm 360 may include, for example, features of a commercially available set of algorithms for timing of delivered stimuli to the heart are referred to as the QuickOpt™ algorithms (St. Jude Medical, Inc., Sylmar, Calif.). Such algorithms allow for clinician optimization and automatic, device triggered optimization of parameters including AV timing and VV timing. For example, the QuickOpt™ algorithms allow a clinician to program timing(s) (e.g., in about 90 s) so an implantable device can deliver optimal therapy to a patient. The QuickOpt™ algorithms also allow for timing cycle optimization to produce results clinically-proven to be comparable to echocardiography in a significantly less costly and time consuming manner. For example, a typical echocardiography procedure takes between about 30 minutes and about 120 minutes and requires interpretation by a technician; whereas, a QuickOpt™ algorithms optimization allows for frequent optimizations for patients as their needs change (e.g., event triggered, schedule-based, etc.).
Another feature referred to as the Ventricular Intrinsic Preference algorithm (VIP® algorithm, St. Jude Medical, Inc., Sylmar, Calif.) can operate in conjunction with the QuickOpt™ algorithms to reduce unnecessary ventricular pacing. The VIP® algorithm can allow a patient's heart rhythm to prevail when appropriate. The VIP® technology actively monitors the heart on a beat-by-beat basis to provide pacing only when needed, which has been shown in some studies to be better for a patient's overall heart health.
As shown, the capture assessment method 410 can optionally acquire data for one or more measurements 455 for timing optimization. For example, data acquired by the method 410 during a capture assessment may be used alternatively or additionally by the method 460. Such a scheme can alleviate one or more measurements of the method 460. In another arrangement, the capture assessment method 410 may rely on acquired data for timing optimization to thereby yield a combined or hybrid method for capture assessment and timing optimization (e.g., as outlined by dashed line).
In the example of
As indicated by the aforementioned measurements 455, where available, the method 460 may forego one or more of the measurements of the blocks 481 and 483. For example, where the atrial capture assessment block 420 provides for ARRV, ARLV or both ARRV and ARLV, then the method 460 may forego one or both measurements of the block 481. Similarly, where the RV capture assessment block 430 provides for IVCD-RL, the block 483 need not perform the IVCD-RL measurement and where the LV capture assessment block 440 provides for IVCD-LR, the block 483 need not perform the IVCD-LR measurement. As explained herein, PPDA, PPDRV and PPDLV may be used to optimize one or more timings (or other purpose).
According to the methods 410 and 460, a determination block 490 relies on the measured PRRV, PRLV, IVCD-RL and IVCD-LR values to determine an optimum PV delay (PVOpt) and an optimum VV delay (VVOpt). Such measurements may originate from capture assessment blocks of the method 410, timing optimization blocks of the method 460 or a combination of blocks from the method 410 and the method 460. An implementation block 492 implements the optimized delays PVOpt and VVOpt. In general, such timings are recorded by an implantable device (e.g., for comparison or analysis).
With respect to the method 460, as may be appreciated, if the measurement block 481 cannot measure PRRV or PRLV, the determination block 490 may not be able to determine PVOpt and/or VVOpt. Similarly, if the measurement block 483 cannot accurately measure IVCD-RL or IVCD-LR, the determination block 490 may not function or function improperly. As described herein, various cardiac conditions can confound measurements such as those presented in measurement blocks 481 and 483. In some instances, one or more alternative algorithms or techniques are available to estimate these measures or to optimize PVOpt and/or VVOpt. Some of these techniques have been explained with respect to the measurements 455. Consequently, a patient may be able to benefit from a “restricted” or alternative method to optimize one or more CRT parameters.
As described herein and shown in
With respect to parameters used in optimization or delivery of a cardiac therapy, such parameters may include:
PP, AA Interval between successive atrial events
PV Delay between an atrial event and a paced ventricular event
PVoptimal Optimal PV delay
PVRV PV delay for right ventricle
PVLV PV delay for left ventricle
AV Delay for a paced atrial event and a paced ventricular event
AVoptimal Optimal AV delay
AVRV AV delay for right ventricle
AVLV AV delay for left ventricle
Δ Estimated interventricular delay (e.g., AVLV−AVRV)
Δprogrammed Programmed interventricular delay (e.g., a programmed VV delay)
Δoptimal Optimal interventricular delay
IVCD-RL Delay between an RV event and a consequent sensed LV event
IVCD-LR Delay between an LV event and a consequent sensed RV event
ΔIVCD Difference in interventricular conduction delays (IVCD-LR−IVCD-RL)
ΔP, ΔA Width of an atrial event
According to the method 500, a determination block 502 determines ARRV and/or ARLV. In a decision block 404 a decision is made as to whether ARRV and/or ARLV have exceeded a predetermined ARmax value. If neither value exceeds ARmax, then Scenario III follows, which may disable ventricular pacing or take other appropriate therapy options per block 508. Other appropriate therapy optionally includes therapy that achieves a desirable VV delay by any of a variety of techniques. As mention with respect to
In decision block 504, if one or both values exceed ARmax, then the method 500 continues in another decision block 512. The decision block 512 decides whether ARRV and ARLV have exceeded ARmax. If both values do not exceed ARmax, then single ventricular pacing occurs, for example, per Scenario IA or Scenario IB. If both values exceed ARmax, then bi-ventricular pacing occurs, for example, Scenario II.
Scenario IA commences with a decision block 516 that decides if ARRV is greater than ARLV. If ARRV exceeds ARLV, then single ventricular pacing occurs in the right ventricle (e.g., right ventricle master). If ARRV does not exceed ARLV, then single ventricular pacing occurs in the left ventricle (e.g., left ventricle master).
For right ventricular pacing per Scenario IA, the method 500 continues in a back-up pacing block 518 where AVLV is set to ARLV plus some back-up time (e.g., ΔBU). The block 518, while optional, acts to ensure that pacing will occur in the left ventricle if no activity occurs within some given interval. The method 500 then continues in a set block 528 where the parameter ΔIVCD is used as a correction factor to set the AVRV delay to AVoptimal−(|Δ|−ΔIVCD).
For left ventricular pacing per the Scenario IA, the method 500 continues in a back-up pacing block 530 where AVRV is set to ARRV plus some back-up time (e.g., ΔBU). The block 530, while optional, acts to ensure that pacing will occur in the left ventricle if no activity occurs within some given interval. The method 500 then continues in a set block 540 where the parameter ΔIVCD is used as a correction factor to set the AVLV delay to AVoptimal−(|Δ|+ΔIVCD). The parameter ΔIVCD is calculated as the difference between IVCD-LR and IVCD-RL (e.g., IVCD-LR−IVCD-RL).
Scenario IB commences with a decision block 516′ that decides if ARRV is greater than ARLV. If ARRV exceeds ARLV, then single ventricular pacing occurs in the right ventricle (e.g., right ventricle master). If ARRV does not exceed ARLV, then single ventricular pacing occurs in the left ventricle (e.g., left ventricle master).
For right ventricular pacing per Scenario IB, the method 500 continues in a back-up pacing block 518′ where AVLV is set to ARLV plus some back-up time (e.g., ΔBU). The block 518′, while optional, acts to ensure that pacing will occur in the left ventricle if no activity occurs within some given interval. The method 500 then continues in a set block 528′ where the parameter ΔIVCD is used as a correction factor to set the AVRV delay to ARLV−(|Δ|−ΔIVCD). Hence, in this example, a pre-determined AVoptimal is not necessary.
For left ventricular pacing per the Scenario IB, the method 500 continues in a back-up pacing block 530′ where AVRV is set to ARRV plus some back-up time (e.g., ΔBU). The block 530′, while optional, acts to ensure that pacing will occur in the left ventricle if no activity occurs within some given interval. The method 500 then continues in a set block 540′ where the parameter ΔIVCD is used as a correction factor to set the AVLV delay to ARRV−(|Δ|+ΔIVCD). Again, in this example, a pre-determined AVoptimal is not necessary.
Referring again to the decision block 512, if this block decides that bi-ventricular pacing is appropriate, for example, Scenario II, then the method 500 continues in a decision block 550, which that decides if ARRV is greater than ARLV. If ARRV exceeds ARLV, then bi-ventricular pacing occurs wherein the right ventricle is the master (e.g., paced prior to the left ventricle or sometimes referred to as left ventricle slave). If ARRV does not exceed ARLV, then bi-ventricular pacing occurs wherein the left ventricle is the master (e.g., paced prior to the right ventricle or sometimes referred to as right ventricle slave).
For right ventricular master pacing, the method 500 continues in a set block 554 which sets AVLV to AVoptimal. The method 500 then uses ΔIVCD as a correction factor in a set block 566, which sets AVRV delay to AVLV−(|Δ|−ΔIVCD).
For left ventricular master pacing, the method 500 continues in a set block 572 which sets AVRV to AVoptimal. The method 500 then uses ΔIVCD as a correction factor in a set block 484, which sets AVLV delay to AVRV−(|Δ|+ΔIVCD).
A comparison between Δ and Δprogrammed or Δoptimal can indicate a difference between a current cardiac therapy or state and a potentially better cardiac therapy or state. For example, consider the following equation:
α=Δoptimal/Δ
where α is an optimization parameter. Various echocardiogram studies indicate that the parameter α is typically about 0.5. The use of such an optimization parameter is optional. The parameter α may be used as follows:
AV
RV
=AV
optimal−α|Δ| or PVRV=PVoptimal−α|Δ|
AV
LV
=AV
optimal−α(|Δ|+ΔIVCD) or
PV
LV
=PV
optimal−α(|Δ|+ΔIVCD)
If a parameter such as the aforementioned α parameter is available, then such a parameter is optionally used to further adjust and/or set one or more delays, as appropriate.
Various exemplary methods, devices, systems, etc., may consider instances where normal atrio-ventricular conduction exists for one ventricle. For example, if an atrio-ventricular conduction time for the right ventricle does not exceed one or more limits representative of normal conduction, then the atrio-ventricular time for the right ventricle may serve as a basis for determining an appropriate time for delivery of stimulation to the left ventricle (or vice versa). The following equation may be used in such a situation:
AV
LV
=AR
RV−|Δ| or PVLV=PRRV−|Δ|
This equation is similar to the equation used in blocks 528′ and 540′ of Scenario IB of
AV
RV
=AR
RV+|γ| or PVRV=PRRV+|γ|
Of course, administration of a backup pulse may occur upon one or more conditions, for example, failure to detect activity in the particular ventricle within a given period of time. In the foregoing equation, the parameter γ is a short time delay, for example, of approximately 5 ms to approximately 10 ms. This equation is similar to the equation used in blocks 518′ and 530′ of Scenario IB of
In many instances, cardiac condition will affect ARRV and ARLV, and IVCD (e.g., IVCD-RL and/or IVCD-LR), which, in turn, may affect an existing optimal VV delay setting. As explained with respect to the method 460 of
As described herein, various techniques can be used to optimize CRT, including capture assessment techniques. Optimization may, at times, rely on use of external measurement or sensing equipment (e.g., echocardiogram, etc.). Further, use of internal measurement or sensing equipment for sensing pressure or other indicators of hemodynamic performance may be optional. Adjustment and learning may rely on IEGM information and/or cardiac other rhythm information.
While not indicated in
Atrial information may include beginning of a P wave (P0) and end of a P wave (PEnd), where the duration of the P wave or P wave width (ΔP) is PEnd−P0. Atrial information may include an interval (DD) between the end of the P wave (PEnd) and the beginning of an R wave or a QRS complex, for example, as detected by a conventional algorithm or other suitable technique. While “P wave” is mentioned, similar techniques may be used to acquire “A wave” information (e.g., A0, AEnd, ΔA, AD based on AEnd and beginning of an R wave or a QRS complex).
An R wave detection technique may rely on a slope or other feature of an R wave and a time other than the “beginning” of an R wave may be used. A DD interval may rely on a detection technique used for R wave detection. As a DD interval relies on detection of an R wave or a QRS complex, an atrial to ventricular conduction pathway should exist for at least one ventricle because for patients with atrial to ventricular conduction block of both ventricles (e.g., RBBB and LBBB), a meaningful DD interval may not exist. For such patients, measurement of A wave width or P wave width may occur and such values may be used along with activity information for any of a variety of purposes (e.g., cardiac condition, pacing optimization, etc.).
As already mentioned, a PR interval typically relies on detecting P0, the beginning of a P wave. In contrast, the interval DD relies on detecting PEnd, the end of a P wave or approximate end of a P wave. Hence, the PR interval is always less than the DD interval for a particular ventricle, noting that one ventricle may have a DD interval that exceeds a PR interval of the other ventricle.
A comparison between rest state electrograms and exercise state electrograms may indicate trends in that the P or A wave duration (ΔP, ΔA) and the DD or AD interval increase with increasing activity. Under normal circumstances, while the AA interval is controlled (e.g., set to a constant or adjusted with respect to activity or other variable), the ratio of A wave duration and AD interval to AA interval or RR interval may be expected to increase.
While aforementioned atrial variables may change with respect to activity, other variables such as PR and Δ may also change with respect to activity. For example, the PR interval may increase where the increase depends on the points used to define the PR interval. However, with respect to Δ, the change may be somewhat uncertain, especially if little data exists for a patient or the patient's condition has changed.
Details of various timing algorithms have been shown in
The method 420 commences in a determination block 422 that determines an intrinsic atrial rate (e.g., P to P). An overdrive block 424 overdrives the intrinsic atrial rate by pacing faster than the intrinsic atrial rate and at an energy level sufficient to capture the atrium. Hence, an electrogram shows A waves occurring at a rate that exceeds the intrinsic rate.
A decrement block 426 decrements the energy until loss of capture (LOC) occurs. Loss of capture may be indicated by failure to detect an evoked response (A wave) and/or by presence of intrinsic activity (P wave). Once LOC occurs, an increment block 428 increments the energy to a level sufficient to regain capture and it may also optionally adjust the energy for purposes of safety (to reliably ensure capture). Further, the atrial rate may be adjusted to a therapeutic rate. For a patient that is not atrial pacing dependent, the rate may be set to a rate above an acceptable intrinsic rate for the patient.
While the method 420 has been described generally, some specifics of the ACap™ algorithm are provided below. The ACap™ algorithm includes three main steps when performing an automatic threshold test.
In a first step, the algorithm causes an implantable device to pace the atrium faster than the intrinsic atrial rate (see, e.g., block 424). Overdrive atrial pacing minimizes fusion beats and ensures atrial pacing for the threshold test. Specifically, the algorithm causes the implantable device to assess the atrial rate by passively watching for 16 beats (see, e.g., block 422); then, the device paces the atrium faster than the intrinsic rate.
In a second step, the algorithm assesses atrial threshold. Specifically, the algorithm determines where the patient loses capture (see, e.g., block 426). Atrial pacing begins at an operating voltage (high voltage) and decrements by 0.25 V until the device detects three consecutive non-captured beats at the same voltage. Backup pulses are provided during threshold searches to ensure patient safety. Starting at the voltage where capture was lost, the algorithm causes the device to increases atrial output by 0.125 V until two consecutive beats are captured. The algorithms can also call for storage of a weekly threshold trend and follow-up EGMs.
In a third step, the algorithm determines the atrial output. The algorithm sets the atrial output at a fixed voltage above the threshold ensuring an appropriate safety margin.
The ACap™ algorithms also allow for set-up and programmability of various features. For example, prior to activating the ACap™ feature a user can run an automatic ACap™ set-up test. Further, the ACap™ algorithm can be programmed to search every 8 or 24 hours. Yet further, the ACap™ algorithm's thresholds can also be checked in-clinic via an implantable device programmer.
As mentioned, a capture algorithm may provide information for use by one or more timing algorithms. To explain in more detail, exemplary information and algorithms 423 are shown in
When making determinations as to whether atrial capture occurred or not, an algorithm may rely on an integral or integrals (e.g., PDI), a slope or slopes (DMax), etc. A particular non-parametric correlation algorithm 425 relies on a nonparametric measure of association based on the number of concordances and discordances in paired observations (e.g., Kendall tau). In such a technique, concordance occurs when paired observations vary together, and discordance occurs when paired observations vary differently. The Kendall tau rank correlation coefficient (or simply the Kendall tau coefficient, Kendall's t or tau test(s)) is a non-parametric statistic used to measure the degree of correspondence between two rankings and assessing the significance of this correspondence. As indicated in
In more detail, the cardiac electrogram 701 shows timing of a pulse to a ventricle (V) and a corresponding evoked response (ER). The shape of the evoked response depends on a variety of factors, including sensing configuration. For example, sensing polarity may cause the evoked response to be inverted from the shape shown in
As described herein, in some instances paced propagation delay (PPD) may be used as a surrogate for IVCD. For example, the difference between the left and right ventricular pacing latencies (ΔPPD) may be used as an estimate for the difference between the IVCD-LR and IVCD-RL (ΔIVCD). A paced propagation delay (PPD) assessment may be used when IVCD-LR and/or IVCD-RL cannot be accurately measured (e.g., due to conduction problems). As a capture algorithm may acquire information sufficient to determine paced propagation delay, measurement of IVCD-RL and/or IVCD-LR may not be required. Or, where IVCD-RL and/or IVCD-LR cannot be measured, then paced propagation delay based on a capture assessment algorithm may be used to determine a surrogate or surrogates for use in determining one or more timings (see, e.g.,
The method 702 illustrates a basic threshold search that relies on capture detection, which may be part of a beat-to-beat or other capture detection algorithm. Again, where capture is not detected, i.e., loss of capture, corrective action is typically required, for example, a change in pulse amplitude, a change in pulse duration, etc.
The method 702 commences in a start block 704, where an implantable device may be programmed to perform capture detection and a threshold search. In some instances, a threshold search is performed on a periodic basis, whether loss of capture has been detected or not. Such a threshold search may help ensure adequate capture as well as battery life. The method 702 continues in a decision block 708 that decides if loss of capture occurred based on sensed cardiac activity. If the decision block 708 decides that loss of capture did not occur, then the method continues at the start block 704. However, if loss of capture occurred, then the method 702 continues at an adjustment block 712 that adjusts energy delivery. For example, the adjustment block 712 may increase amplitude of a stimulation pulse and/or increase duration of a stimulation pulse.
Another decision block 716 follows that decides if a pulse delivered using the adjusted energy caused capture. If the decision block decides that capture did not occur, then the method 702 returns to the adjustment block 712, or it may take other action. However, if capture did occur, then the method 702 continues at a search block 720 that seeks a capture threshold, for example, based on acquired data for prior attempts. After the threshold search 720, the method 702 may return to the decision block 708 or it may take other action as appropriate. In general, such algorithms place patient safety ahead of battery current drain; however, when the chronic threshold is low, such an algorithm may also minimize battery current drain, effectively increasing device longevity.
In addition to beat-to-beat capture verification, the AutoCapture™ algorithm runs a capture threshold assessment test once every eight hours (or other interval, as programmed). To perform this test, the paced and sensed AV delays are temporarily shortened to about 50 ms and to about 25 ms, respectively. The AutoCapture™ algorithm generally uses a bottom-up approach (also referred to as an “up threshold”) and a back-up pulse for safety when an output pulse does not result in capture. With respect to use of a back-up pulse, an output pulse of about 4.5 volts is typically sufficient to achieve capture where lead integrity is not an issue. Use of a back-up pulse may also adequately benefit certain patients that are quite sensitive to loss of capture. For example, patients having a high grade AV block may be sensitive to protracted asystole. Even if loss of capture is recognized immediately and adjustment is completed in less than about 1 second, a patient may still have been asystolic for over 2 seconds utilizing a standard capture threshold test without a back-up. A back-up pulse typically prevents occurrence of such a long asystolic period. However, most conventional automatic capture threshold/detection algorithms do not attempt to detect the evoked response directly related to capture of the back-up. Thus, the assumption that a back-up pulse resulted in capture is generally not tested. Various exemplary methods described herein optionally include evoked response detection of the back-up pulse to help determine if a back-up pulse caused an evoked response thus confirming the presence of capture associated with this stimulus. Such ER or capture detection may be implemented for a unipolar back-up pulse, a bipolar back-up pulse or other type of back-up pulse.
In general, the term “sensing” is often utilized with respect to an implantable cardiac stimulation therapy device (e.g., a pacemaker) recognizing native atrial and/or ventricular depolarizations. While technically, detection of an evoked response (ER) relies on or includes “sensing”, an implantable device often uses a separate circuit for ER detection. Throughout, the term “ER detection” or “capture detection” may be used in place of sensing when specifically concerned with, for example, a capture algorithm and recognition of capture.
With respect to ER detection, various exemplary methods may use a unipolar primary pulse with bipolar ER detection, a unipolar primary pulse with unipolar ER detection, a bipolar primary pulse with bipolar ER detection, a bipolar primary pulse with unipolar ER detection and/or no primary pulse ER detection. Various exemplary methods may use a unipolar back-up pulse with bipolar ER detection, a unipolar back-up pulse with unipolar ER detection, a bipolar back-up pulse with bipolar ER detection, a bipolar back-up pulse with unipolar ER detection and/or back-up pulse ER detection.
Regarding AutoCapture™ algorithms, the first generation algorithm was implemented using a unipolar output configuration and a bipolar detection configuration. Where insulation and/or fracture issues arise for a proximal conductor (bipolar detection), an evoked response may not be sensed and, in turn, result in delivery of a high voltage back-up pulse and a ramping up of the primary output voltage (e.g., energy via voltage, pulse width, etc.). A capture threshold history may exhibit some information that relates to such a problem. In particular, a history may help to identify intermittent problems (e.g., sporadic increases in reported capture threshold where the actual unipolar capture threshold is relatively stable).
In clinical follow-up, a care provider may perform a threshold test to determine if the algorithm for capture is working properly and for further assessment. In systems that use the AutoCapture™ algorithm, a follow-up clinical test includes automatically and temporarily setting PV delay and AV delay intervals to about 25 ms and about 50 ms, respectively. Shortening of the AV and PV delays acts to minimize risk of fusion. Fusion (of any type) may compromise measurement and detection of an ER signal, especially ER signal amplitude. If results from the follow-up test indicate that enabling of the algorithm would not be safe due to too low an evoked response or too high a polarization signal, then the algorithm may be disabled and a particular, constant output programmed to achieve capture with a suitable safety margin. If the ER and polarization signals are appropriate to allow a capture algorithm to be enabled, an ER sensitivity will be recommended by the programmer and may then be programmed as it relates to detection of an ER signal.
The follow-up tests typically work top down. If loss of capture occurs, a first output adjustment step typically sets a high output and then decreases output by about 0.25 volts until loss of capture occurs (also referred to as a “down threshold”). At this point, output is increased in steps of a lesser amount (e.g., about 0.125 volts) until capture occurs. Once capture occurs, a working or functional margin of about 0.25 volts is added to the capture threshold output value. Hence, the final output value used is the capture threshold plus a working margin. Systems that use a fixed output use a safety margin ratio instead of an absolute added amount. The safety margin is a multiple of the measured capture threshold, commonly 2:1 or 100% to allow for fluctuations in the capture threshold between detailed evaluations at the time of office visits.
With respect to a down threshold approach, in instances where loss of capture occurs, a first output adjustment step typically increases output until capture is restored. Steps used in the AutoCapture™ algorithm are typically finer than those used in a routine follow-up capture threshold test. At times, a down threshold algorithm may result in a threshold that is as much as 1 volt lower from the result of an up threshold algorithm. This has been termed a Wedensky effect. In general, an actual output setting (e.g., including safety margin) may be adjusted to account for whether a patient is pacemaker dependent. In a patient who is not dependent on the pacing system, a narrower safety margin may be selected than would be the case for a patient whom the physician considers to be pacemaker dependent.
As already mentioned, lead instability may affect capture threshold, similarly, capture threshold history may help to identify lead instability. Lead instability includes issues germane to failure as well as issues germane to movement of a lead (e.g., to cause movement of an electrode of the lead, etc.). A stable capture threshold history may indicate normal lead function. However, marked fluctuations in capture threshold over time may indicate a lead stability problem, such as movement and variations with the degree of contact between the electrode and myocardial tissue. If the problem is associated with movement, repositioning or re-anchoring may be required. If such fluctuations occur in the early post-implant period, the problem may relate to positional instability as opposed to a marked inflammatory reaction at the electrode-tissue interface (e.g., “lead maturation”).
The method 800 includes the atrial algorithm 370 of
As described herein, an exemplary method can measure an IVCD while performing a ventricular capture assessment. For example, such a method may program a short AV (e.g., 50 ms), deliver a stimulus to one ventricle and sense activity in the other ventricle where the time between delivery of the stimulus and sensed activity responsive to the stimulus is the measured IVCD. In this example, the delivered stimulus is of sufficient energy to cause an evoked response.
With respect to the atrial information (e.g., ΔA), while not shown in the method 500 of
With respect to the paced propagation delay information (PPD), an exemplary algorithm may determine PPD for the right ventricle (for a right ventricular lead) and for the left ventricle (for a left ventricular lead) during measurement of IVCD-LR and IVCD-RL (e.g., parameters that may be used to determine VV). Alternatively, where circumstances confound measurement of IVCD-LR and/or IVCD-RL, PPD may be measured for a right ventricle and a left ventricle and the difference used as a surrogate for the parameter ΔIVCD.
While paced propagation delay can be measured from the time of delivering a pacing pulse to the time of an evoked response at the pacing lead (PPD−I), paced propagation delay may be measured alternatively from the time of the pulse to the peak of an evoked response (PPD−Peak). In either instance, such techniques may shorten block and/or discharge periods, optionally to a minimum (e.g., about 3 ms in some commercial ICDs).
The capture only branch commences in a capture only block 908. The capture only block 908 calls for implementation of the atrial capture algorithm 320 to acquire an atrial threshold, for example, for use in setting an energy level for atrial pacing.
The capture and timing branch commences in a capture and timing block 912. The capture and timing block 912 calls for implementation of the atrial capture algorithm 320 to acquire an atrial threshold (e.g., for use in setting an energy level for atrial pacing), an atrial width ΔA (e.g., for use in optimizing a timing parameter for pacing the heart) and AR times for one or both ventricles (e.g., ARRV and/or ARLV) (e.g., depending on the requirements for determination of a timing parameter value or values).
The timing only branch commences in a timing only block 916. The timing only block 916 calls for implementation of the atrial algorithm for timing 370 to acquire an atrial width ΔA (e.g., for use in optimizing a timing parameter for pacing the heart) and AR times for one or both ventricles (e.g., ARRV and/or ARLV) (e.g., depending on the requirements for determination of a timing parameter value or values).
In an exemplary method, during atrial capture assessment tests, atrial paced signals in an ER sensing window are used to test whether the atrial paces captured the atrium, for example, by PDI, a Kendall tau algorithm, etc., with minimum blocking/discharge end. The atrial paced signals can also be used to determine ΔA, which can be used for optimizing one or more timing parameters.
As described herein, an exemplary method includes performing an atrial capture assessment, determining an atrial evoked response width (ΔA) using information acquired during the atrial capture assessment and optimizing an atrio-ventricular (PV or AV) delay based at least in part on the atrial evoked response width (ΔA). In such a method the information acquired during the atrial capture assessment may be a cardiac electrogram (e.g., an IEGM). As explained below, the optimizing can optimize the atrio-ventricular delay (AV or PV) with respect to a patient activity state (AS) (see, e.g.,
The capture only branch commences in a capture only block 1008. The capture only block 1008 calls for implementation of the right ventricular capture algorithm 330 to acquire a right ventricular threshold, for example, for use in setting an energy level for right ventricular pacing.
The capture and timing branch commences in a capture and timing block 1012. The capture and timing block 1012 calls for implementation of the right ventricular capture algorithm 330 to acquire a right ventricular threshold (e.g., for use in setting an energy level for right ventricular pacing), a right ventricular to left ventricular IVCD (IVCD-RL) and/or a right ventricular paced propagation delay (PPDRV) (e.g., the latter two for use in optimizing a timing parameter for pacing the heart).
The timing only branch commences in a timing only block 1016. The timing only block 1016 calls for implementation of one or more right ventricular algorithm for timing 382 and/or 386 to acquire a right ventricular to left ventricular IVCD (IVCD-RL) and/or a right ventricular paced propagation delay (PPDRV) for use in optimizing a timing parameter for pacing the heart.
With respect to the capture scenarios of
As described herein, an exemplary method includes performing a right ventricular capture assessment, determining a right ventricular paced propagation delay (PPDRV) using information acquired during the right ventricular capture assessment and optimizing an interventricular delay (VV) based at least in part on the right ventricular paced propagation delay (PPDRV). Such a method may further include determining a left ventricular paced propagation delay (PPDLV) and optimizing the interventricular delay (VV) based at least in part on the right ventricular paced propagation delay (PPDRV) and the left ventricular paced propagation delay (PPDLV). Such a method may be embodied on one or more processor-readable media as processor-executable instructions.
As described herein, an exemplary method includes performing a right ventricular capture assessment, determining an interventricular conduction delay from the right ventricle to the left ventricle (IVCD-RL) using information acquired during the right ventricular capture assessment and optimizing an interventricular delay (VV) based at least in part on the interventricular conduction delay from the right ventricle to the left ventricle (IVCD-RL). Such a method may further include determining an interventricular conduction delay from the left ventricle to the right ventricle (IVCD-LR) and optimizing the interventricular delay (VV) based at least in part on the interventricular conduction delay from the right ventricle to the left ventricle (IVCD-RL) and the interventricular conduction delay from the left ventricle to the right ventricle (IVCD-LR). Such a method may be embodied on one or more processor-readable media as processor-executable instructions.
The capture only branch commences in a capture only block 1108. The capture only block 1108 calls for implementation of the left ventricular capture algorithm 340 to acquire a left ventricular threshold, for example, for use in setting an energy level for left ventricular pacing.
The capture and timing branch commences in a capture and timing block 1112. The capture and timing block 1112 calls for implementation of the left ventricular capture algorithm 340 to acquire a left ventricular threshold (e.g., for use in setting an energy level for left ventricular pacing), a left ventricular to right ventricular IVCD (IVCD-LR) and/or a left ventricular paced propagation delay (PPDLV) (e.g., the latter two for use in optimizing a timing parameter for pacing the heart).
The timing only branch commences in a timing only block 1116. The timing only block 1116 calls for implementation of one or more left ventricular algorithm for timing 384 and/or 388 to acquire a left ventricular to right ventricular IVCD (IVCD-LR) and/or a left ventricular paced propagation delay (PPDLV) for use in optimizing a timing parameter for pacing the heart.
With respect to the capture scenarios of
As described herein, an exemplary method includes performing a left ventricular capture assessment, determining a left ventricular paced propagation delay (PPDLV) using information acquired during the left ventricular capture assessment and optimizing an interventricular delay (VV) based at least in part on the left ventricular paced propagation delay (PPDLV). Such a method may be embodied on one or more processor-readable media as processor-executable instructions.
As described herein, an exemplary method includes performing a left ventricular capture assessment, determining an interventricular conduction delay from the left ventricle to the right ventricle (IVCD-LR) using information acquired during the left ventricular capture assessment and optimizing an interventricular delay (VV) based at least in part on the interventricular conduction delay from the left ventricle to the right ventricle (IVCD-LR). Such a method may be embodied on one or more processor-readable media as processor-executable instructions.
As mentioned, various techniques can be used for multisite activation or pacing of a ventricle. For example, the left ventricle may be activated at two or more sites where an optimization algorithm determines the timing of energy delivered to the sites consider, for example, AV1Opt and AV2Opt and V1V2Opt for a scheme that paces a ventricle using two sites.
In another scenario, a lead may include a series of electrodes where some of the electrodes may be better suited for delivery of energy than others for purposes of optimizing contraction of a ventricle or ventricles.
In the example of
A plot 1215 shows IVCD-LR as a time delay (ΔT) versus energy delivery/sensing configuration while a plot 1235 shows IVCD-RL as a time delay (ΔT) versus energy delivery/sensing configuration. The data of plots 1215 and 1235 may be used in a determination block 1240 to determine optimum electrode configuration for LV pacing. In the example of
In an alternative example, more than one electrode of the LV lead 1202 may be used to define a first site and a second site. Further, stimulation energy may be delivered at different times to the first site and the second site to active the myocardium in an optimal manner.
A state block 1310 defines various activity states. The activity states include a base state, for example, a rest state denoted by a subscript “0”. In other examples, the subscript “rest” is used. The activity states include at least two states, for example, a base state and another activity state. In
A PV or AV states block 1320 presents equations for the parameters β and δ as well as for a base state PV and AV and PV and AV for a state other than a base activity state, referred to as ASx, where x=1, 2, . . . N. In addition, sets of equations are presented that include a paced propagation delay term PPD. A paced propagation delay may be a pacing latency, which is generally defined as the time between delivery of a cardiac stimulus and time of an evoked response caused by the stimulus. More specifically, an implantable device may use the time of delivery of a stimulus and the time at which a sensed, evoked response signal deviates from a baseline, which is referred to herein as PPD−I (e.g., to initiation of evoked response). Such a signal is usually sensed using the lead that delivered the stimulus, however, electrode configuration may differ (e.g., unipolar delivery and bipolar sensing, bipolar delivery and unipolar sensing, etc.). In some instances, a PPD−I may exceed 100 ms due to ischemia, scarring, infarct, etc. Thus, PV or AV timing may be adjusted accordingly to call for earlier delivery of a stimulus to a ventricle or ventricles.
An exemplary algorithm may determine PPD for the right ventricle (for a right ventricular lead) and PPD for the left ventricle (for a left ventricular lead) during measurement of IVCD-LR and IVCD-RL (e.g., parameters that may be used to determine VV). While paced propagation delay can be measured from the time of delivering a pacing pulse to the time of an evoked response at the pacing lead (PPD−I), paced propagation delay may be measured alternatively, for example, from the time of the pulse to the peak of an evoked response (PPD−Peak) (noting that other possibilities exist). For purposes of measurement, techniques may shorten block and/or discharge periods, optionally to a minimum (e.g., about 3 ms in some commercial ICDs). An algorithm may also provide for detection of capture, for example, using an integral (e.g., PDI) and/or a derivative (e.g., Dmax). In general, paced propagation delays for LV and RV leads correspond to situations where capture occurs. In yet another alternative, during P wave and PR measurement, a time delay from a marker of a sensed R event to the peak of a QRS complex may be measured and used as a correction term akin to paced propagation delay.
A VV states block 1330 presents equations for the parameters α, Δ and ΔIVCD and VV for a base activity state (AS0) and another activity state (ASx). In the equations of
The block 1330 also includes equations for a paced propagation delay differential, referred to as ΔPPD. This term may be calculated, for example, as the difference between PPDRV and PPDLV, and be a surrogate for ΔIVCD. A criterion or criteria may be used to decide if a paced propagation delay correction term should be used in determining PV, AV or VV.
While various examples mention use of a “rest” state, a rest state may be a base state. Alternatively, a base state may be a state other than a rest state. For example, a base state may correspond to a low activity state where a patient performs certain low energy movements (e.g., slow walking, swaying, etc.) that may be encountered regularly throughout a patient's day. Thus, a base state may be selected as a commonly encountered state in a patient's waking day, which may act to minimize adjustments to PV, AV or VV. Further, upon entering a sleep state, a device may turn off adjustments to PV, AV or VV and assume sleep state values for PV, AV or W. Such decisions may be made according to a timer, a schedule, an activity sensor, etc.
An exemplary computing device may include control logic to assess cardiac condition based at least in part on information acquired from an implantable device where the information includes, for example, one or more CRT parameters and/or one or more rate adaptive pacing parameters or combinations thereof (e.g., α, Δ, IVCD-RL, IVCD-LR, ΔIVCD, AV, PV, VV, response time, recovery time, A-Th, RV-Th, LV-Th, PPD, ΔPPD, etc.). The computing device may be the implantable device, or in other words, an implantable device may be capable of assessing patient condition and more particularly cardiac condition.
Various exemplary methods may be implementable wholly or to varying extent using one or more computer-readable media (or processor-readable media) that include processor-executable instructions for performing one or more actions. For example, the device 100 of
As described herein, the exemplary one or more coordination algorithms 305 of
Memory 260 is shown as including the capture algorithms 310 of
The system 1400 includes a device programmer 1430 having a wand unit 1431 for communicating with the implantable device 100. The programmer 1430 may further include communication circuitry for communication with another computing device 1440, which may be a server. The computing device 1440 may be configured to access one or more data stores 1450, for example, such as a database of information germane to a patient, an implantable device, therapies, etc.
The programmer 1430 and/or the computing device 1440 may include various information such as data and modules (e.g., processor-executable instructions) for performing various actions of associated with the algorithms 310, 360 and 305, noting that a particular implementation of a method may use more than one device.
The programmer 1430 optionally includes features of the commercially available 3510 programmer and/or the MERLIN™ programmer marketed by St. Jude Medical, Sylmar, Calif. The MERLIN™ programmer includes a processor, ECC (error-correction code) memory, a touch screen, an internal printer, I/O interfaces such as a USB that allows a device to connect to the internal printer and attachment of external peripherals such as flash drives, Ethernet, modem and WiFi network interfaces connected through a PCMCIA/CardBus interface, and interfaces to ECG and RF (radio frequency) telemetry equipment.
The wand unit 1431 optionally includes features of commercially available wands. As shown, the wand unit 1431 attaches to a programmer 1430, which enables clinicians to conduct implantation testing and performance threshold testing, as well as programming and interrogation of pacemakers, implantable cardioverter defibrillators (ICDs), emerging indications devices, etc.
During implant, a system such as a pacing system analyzer (PSA) may be used to acquire information, for example, via one or more leads. A commercially available device marketed as WANDA™ (St. Jude Medical, Sylmar, Calif.) may be used in conjunction with a programmer such as the MERLIN™ programmer or other computing device (e.g., a device that includes a processor to operate according to firmware, software, etc.). Various exemplary techniques described herein may be implemented during implantation and/or after implantation of a device for delivery of electrical stimulation (e.g., leads and/or pulse generator) and the types of equipment for acquiring and/or analyzing information may be selected accordingly.
The wand unit 1431 and the programmer 1430 allow for display of atrial and ventricular electrograms simultaneously during a testing procedure. Relevant test measurements, along with customizable implant data, can be displayed, stored, and/or printed in a comprehensive summary report for the patient's medical records and physician review and/or for other purposes.
In the example of
As described herein, an exemplary implantable device includes a processor, memory and control logic to acquire information during a capture assessment and to optimize one or more cardiac resynchronization therapy (CRT) timing parameters using the acquired information. In such a device, the timing parameters can include at least one timing parameter selected from a group of atrio-ventricular timing parameters (PV or AV) and interventricular timing parameters (VV). Such a device may perform atrial capture assessment, right ventricular capture assessment and/or left ventricular capture assessment. In such a device, the control logic may include (e.g., in part) processor-executable instructions stored in the memory.
Although exemplary methods, devices, systems, etc., have been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing the claimed methods, devices, systems, etc.
